Search for posts by Femosky110

BASIS OF HEREDITY

from Femosky110 on 06/11/2020 01:09 PM

Chromosomes: The basis of heredity
A chromosome is a structure that exists within cells and which possesses the cell's genetic material. That genetic material, which regulates how an organism develops, is a molecule of deoxyribonucleic acid (DNA). A molecule of DNA is an extremely long, coiled arrangement that bears numerous identifiable subunits referred to as genes.

 

In prokaryotes, or cells without a nucleus, the chromosome is simply a circle of DNA. In eukaryotes, or cells with a separate nucleus, chromosomes are much more composite in structure.

In the nucleus of every cell, the DNA molecule is packaged into thread-like structures known as chromosomes. Every chromosome is made up of DNA firmly coiled a lot of times around proteins known as histones that support its structure.

Chromosomes are not noticeable in the cell's nucleus—not even under a microscope—when the cell is not undergoing division. Nevertheless, the DNA that constitutes chromosomes becomes more closely packed during cell division and is then visible under a microscope.

The majority of what researchers know about chromosomes was discovered by observing chromosomes during cell division.

Every chromosome has a constriction point known as the centromere, which divides the chromosome into two parts, or "hands." The short hand of the chromosome is labeled the "p hand." The long hard of the chromosome is labeled the "q hand."

The location of the centromere on every chromosome offers the chromosome its characteristic shape, and can be employed to assist with the location of definite genes.

DNA and histone proteins are packaged into structures known as chromosomes.

How many chromosomes do people have?
In humans, every cell usually contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, known as autosomes, look similar in both males and females. The 23rd pair, the sex chromosomes, varies between males and females.

Females possess two copies of the X chromosome, while males possess one X and oneY chromosome.

The 22 autosomes are numbered by magnitude. The other two chromosomes, X and Y, are the sex chromosomes. This picture of the human chromosomes lined up in pairs is known as a karyotype.

Chromosome: a very long DNA molecule and linked proteins, that carry portions of the hereditary information of an organism.

Structure of a chromosome (Typical metaphase chromosome):

A chromosome is formed from a single DNA molecule that contains a lot of genes.

A chromosomal DNA molecule contains three definite nucleotide sequences which are necessary for replication: a DNA replication origin; a centromere to affix the DNA to the mitotic spindle.; a telomerelocated at each end of the linear chromosome.

The DNA molecule is highly condensed. The human DNA helixes take up a lot of space in the cell. Small proteins are accountable for packing the DNA into units known as nucleosomes.

Stained chromosomes:
Chromosomes are discolored with A-T (G bands) and G-C (R bands) base pair specific dyes. When they are stained, the mitotic chromosomes possess a banded structure that unmistakably identifies every chromosome of a karyotype.

Each band posseses millions of DNA nucleotide pairs which do not match up to any functional structure.

Karyotype of a male:
The human haploid genome possess 3,000,000,000 DNA nucleotide pairs, shared between twenty two (22) pairs of autosomes and one pair of sex chromosomes.

Biological background
The terms chromosome and gene were made use of long before biologists actually understood what these structures were.

When the Austrian monk and biologist Gregor Mendel (1822–1884) came up with the fundamentary ideas of heredity, he assumed that genetic traits were one way or another transferred from parents to offspring in some kind of minute "package."

That package was afterward given the name "gene." When the term was first recommended, no one had any idea as to what a gene might look like.

The term was employed merely to express the idea that traits are transmitted from one generation to the other in particular discrete units.

The term "chromosome" was first recommended in 1888 by the German anatomist Heinrich Wilhelm Gottfried von Waldeyer-Hartz (1836–1921). Waldeyer-Hartz made use of the term to explain particular structures that develop during the process of cell division (reproduction).

One of the top most breakthroughs in the history of biology happened in 1953 when American biologist James Watson (1928– ) and English chemist Francis Crick (1916– ) revealed the chemical structure of a class of compounds referred to as deoxyribonucleic acids (DNA).

The Watson and Crick invention made it possible to communicate biological concepts (like the gene) and structures (like the chromosome) in actual chemical terms.

The structure of chromosomes and genes
Today we know that a chromosome contains a distinct molecule of DNA along with quite a few kinds of proteins.

A molecule of DNA, in turn, is made up of thousands and thousands of subunits, referred to as nucleotides, connected to one another in extremely long chains.

A lone molecule of DNA within a chromosome may be as long as 8.5 centimeters (3.3 inches). To fit within a chromosome, the DNA molecule has to be twisted and folded into a very composite shape.

What is DNA?
DNA, or deoxyribonucleic acid, is the hereditary material in humans and roughly all other organisms. Virtually every cell in a person's body has the same DNA.

The majority of DNA is situated in the cell nucleus (where it is known as nuclear DNA), but a minute amount of DNA can as well be discovered in the mitochondria (where it is known as mitochondrial DNA or mtDNA).

The information in DNA is stored as a code consisting of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and above 99 percent of those bases are the similar in all people.

The order, or sequence, of these bases determines the information accessible for building and maintaining an organism, comparable to the way in which letters of the alphabet appear in a particular order to form words and sentences.

DNA bases pair up with one another, A with T and C with G, to form units known as base pairs. Every base is as well attached to a sugar molecule and a phosphate molecule. Jointly, a base, sugar, and phosphate are known as a nucleotide.

Nucleotides are organized in two long strands that form a spiral known as a double helix. The structure of the double helix is rather like a ladder, with the base pairs forming the ladder's rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

A significant characteristic of DNA is that it can duplicate, or make copies of itself. Every strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is significant when cells break up because every fresh cell requires to possess a precise copy of the DNA present in the old cell.

DNA is a double helix formed by base pairs affixed to a sugar-phosphate backbone.

Words to remember:
Deoxyribonucleic acid (DNA): The genetic material in the nucleus of cells that contains information for an organism's development.

Eukaryote: A cell with a distinct nucleus.

Nucleotide: The building blocks of nucleic acids.

Prokaryote: A cell without a nucleus.

Protein: Large molecules that are necessary to the structure and functioning of all living cells.

Assume that a DNA molecule is represented by a formula such as this:

-[-N1-N4-N2-N2-N2-N1-N3-N2-N3-N4-N1-N2-N3-N3-N1-N1-N2-N3-N4-]

In this formula, the abbreviations N1, N2, N3, and N4 stand for the four different nucleotides used in making DNA.

The brackets at the beginning and end of the formula indicate that the authentic formula goes on and on.

A typical molecule of DNA contains up to three billion nucleotides. The unit made known above, therefore, is no more than a small portion of the whole DNA molecule.

Every molecule of DNA can be subdivided into smaller segments consisting of a few thousand or a few tens of thousands of nucleotides. Each of these subunits is a gene. Another way to represent a DNA molecule, then, is as follows:

-[-G-D-N-E-Y-D-A-B-W-Q-X-C-R-K-S-]-

where each different letter stands for a different gene.

The function of genes and chromosomes
Every gene in a DNA molecule carries the instructions for making a single kind of protein. Proteins are highly essential molecules that carry out a lot of vital functions in living organisms.

For instance, they act as hormones, carrying messages from one part of the body to another part; they act as enzymes, making possible chemical reactions that keep the cell alive; and they function as structural materials from which cells can be made.

Each cell has definite specific functions to carry out. The purpose of a bone cell, for example, is to make more bone. The purpose of a pancreas cell, on the other hand, might be to make the compound insulin, which aids in the manufacture of glucose (blood sugar).

The job of genes in a DNA molecule, consequently, is to tell cells how to manufacture all the dissimilar chemical compounds (proteins) they require to build in order to function correctly.

The way in which they perform this function is reasonably straightforward. At one point in the cell's life, its chromosomes develop into untangled and open up to expose their genes.

The genes act as a pattern from which proteins can be built. The proteins that are constructed in the cell are determined, as pointed out above, by the instructions built into the gene.

When the proteins are constructed, they are released into the cell itself or into the environment outside the cell. They are then able to carry out the functions for which they were made.

Chromosome numbers and Xs and Ys
Every species possesses a diverse number of chromosomes in their nuclei. The mosquito, for example, has 6 chromosomes. Lilies possess 24, earthworms 36, chimps 48, and horses 64.

The biggest number of chromosomes is created in the Adder's tongue fern, which has more than 1,000 chromosomes.

The majority of species possess, on average, 10 to 50 chromosomes. With 46 chromosomes, human beings fall well within this average.

Sex determination:
The 46 human chromosomes are prearranged in 23 pairs. One pair of the 23 constitutes the sex hormones, known as the X and Y chromosomes.

Males have both an X and a Y chromosome, while females have two X chromosomes.

If a father passes on a Y chromosome, then his child will be male. If he passes on an X chromosome, then the child will be female.

The X chromosome is three times the size of the Y chromosome and carries 100 times the genetic information.

Nevertheless, in 2000, scientists announced that the X and Y chromosomes were once a pair of indistinguishable twins. These identical chromosomes were discovered a few 300 million years ago in reptiles, long before mammals arose.

The genes in these creatures did not decide sex on their own. They reacted to a few environmental cues like temperature. That still happens today in the eggs of turtles and crocodiles.

But in one animal at that time long ago, a mutation happened on one of the pair of identical chromosomes, resulting to what scientists know today as the Y chromosome—a gene that when present always produces a male.

BIOLOGY OF HEREDITY

from Femosky110 on 06/11/2020 01:07 PM

Biology Of Heredity
Biology Of Heredity (Genetics)-Transmission And Expression Of Characteristics In Organisms

 

A) Hereditary Variations: Characters that can be transferred from parents to offsprings-from generation to generation like skin colour, eye and hair, blood group, sickle cell, shape of face and nose

Genetics is the branch of biology that deals with the science of heredity. Heredity is the transfer of characteristics from one generation to the next. It is the reason why offspring resemble their parents. For instance, we know that a tall mother and a tall father are liable to have children that are tall.

It as well explains why cats constantly give birth to kittens and never puppies. Geneticists (scientists who study genetics) are interested in finding out two things regarding this observation.

First, what is there in the cells of a person's body that signals the body to become tall instead of short? Second, how are the signals for "tallness" transferred from parent to offspring, from one generation to the next?

The process of heredity takes place in the midst of every living thing including animals, plants, bacteria, protists and fungi. The study of heredity is known as genetics and scientists that learn heredity are called geneticists.

Through heredity, living things take over traits from their parents. Traits are physical characteristics. You bear a resemblance to your parents due to the fact that you inherited your hair and skin color, nose shape, height, and other traits from them.

Cells are the fundamental unit of structure and function of every living thing. Small biochemical structures inside every cell known as genes transmit traits from one generation to the other.

Genes are made of a chemical known as DNA (deoxyribonucleic acid). Genes are strung jointly to structure long chains of DNA in structures referred to as chromosomes.

Genes are similar to blueprints for building a house, apart from the fact that they bear the plans for building cells, tissues, organs, and bodies. They have the instructions for manufacturing the thousands of chemical building blocks in the body.

These building blocks are known as proteins. Proteins are made of smaller units known as amino acids. Differences in genes give rise to the building of diverse amino acids and proteins.

These differences give rise to individuals that possess various traits like hair color or blood types.

A gene offers only the prospective for the development of a trait. The way this potential is achieved depends partially on the interaction of the gene with other genes. But it as well depends partly on the environment.

For instance, a person may have a genetic tendency toward being overweight. But the person's real weight will depend on such environmental factors like the kinds of food the person eats and the amount of exercise that person does.

The history of Genetics
Humans have known about hereditary characteristics for thousands of years. That knowledge has been used for the improvement of domestic plants and animals. Until the late nineteenth century, however, that knowledge had been obtained through trial-and-error experiments.

The contemporary science of genetics started with the pioneering work of the Austrian monk and botanist Gregor Mendel (1822–1884).

Words you may come across and their meaning
DNA (deoxyribonucleic acid): Molecules that make up chromosomes and on which genes are situated.

Dominant gene: The state or genetic trait that will constantly convey itself when present as part of a pair of genes in a chromosome.

Gene: A section of a DNA molecule that carries instructions for the formation, functioning, and transmission of specific traits from one generation to another.

Heredity: The transfer of characteristics from parents to offspring.

Nucleotide: A group of atoms that exists in a DNA molecule.

Proteins: Large molecules that is crucial to the structure and functioning of all living cells.

Recessive gene: The state or genetic trait that can put across itself only when two genes, one from both parents, are available and act as a kind of code for creating the trait, but will not articulate itself when paired with a dominant gene.

Triad: This is as well referred to as codon; group of three nucleotides that carry a particular message for a cell.

Through heredity, variations demonstrated by individuals can build up and cause a number of species to evolve. The study of heredity in biology is known as genetics, which includes the field of epigenetic.

In humans, eye color is an example of an inherited characteristic: characteristics transferred from parents to offspring. An individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are restricted by genes and the complete set of genes within an organism's genome is known as its genotype.

The entire set of observable traits of the structure and behavior of an organism is called its phenotype. These traits arise from the interaction of its genotype with the environment. As a result, a lot of aspects of an organism's phenotype are not inherited.

For instance, suntanned skin comes from the interaction between a person's phenotype and sunlight; thereby, suntans are not transferred to people's children.

Nevertheless, a few people auburn more easily than others, as a result of differences in their genotype: a conspicuous example is people with the inherited trait of albinism, who do not auburn at all and are very sensitive to sunburn.

Heritable traits are transferred from one generation to the other through DNA, a molecule that encodes genetic information. DNA is a longpolymer that is made up of four types of bases, which are exchangeable.

The sequence of bases along a specific DNA molecule specifies the genetic information: this is equivalent to a sequence of letters spelling out a passage of text.

Prior to the cell division through mitosis, the DNA is copied, so that every one of the resultant two cells will inherit the DNA progression.

A segment of a DNA molecule that specifies a particular functional unit is known as a gene; different genes have different progressions of bases.

Within cells, the long strands of DNA form condensed structures known as chromosomes.

Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique amalgamation of DNA progressions that code for genes.

The definite location of a DNA sequence within a chromosome is referred to as a locus. If the DNA sequence at a specific locus varies between individuals, the diverse forms of this sequence are known as alleles.

DNA sequences can alter through mutations, giving rise to fresh alleles. If a mutation takes place within a gene, the fresh allele may have effect on the trait that the gene controls, changing the phenotype of the organism.

Although this simple correspondence between an allele and a trait works in a few cases, the majorities of traits are more compounds and are restricted by multiple interacting genes within and among organisms.

Developmental biologists recommend that composite interactions in genetic networks and communication among cells can result to heritable variations that may underlay a number of of the mechanics in developmental plasticity and canalization.

B) Mendel Works In Genetics: Mendelian Traits, Mendelian Law And Mendelian Experiment

Mendelian laws of inheritance are statements about the manner specific characteristics are transmitted from one generation to another in an organism. The laws were derived by the Austrian monk Gregor Mendel (1822–1884) as a result of experiments he carried out in the period from about 1857 to 1865.

For his experiments, Mendel made use of ordinary pea plants.

Among the traits that Mendel examined were the color of a plant's flowers, their position on the plant, the shape and color of pea pods, the shape and color of seeds, and the length of plant stems.

Mendel's experiment was to transfer pollen (which is composed of male sex cells) from the stamen (the male reproductive organ) of one pea plant to the pistil (female reproductive organ) of a second pea plant.

As a plain example of this sort of experiment, presume that one takes pollen from a pea plant with red flowers and makes use of it to fertilize a pea plant with white flowers.

What Mendel intended to find out is what color the flowers would be in the offspring of these two plants. In a second series of experiments, Mendel examined the changes that took place in the second generation.

That is, assuming two offspring of the red/white mating ("cross") are themselves mated. What color will the flowers be in this second generation of plants?

As a result of his experiments, Mendel was able to come out with three generalizations about the way characteristics or traits are transmitted from one generation to the next in pea plants.

Words you ought to Know
Allele: One of two or more forms a gene may exist in.

Dominant: An allele whose expression overshadows the effect of a second form of the same gene.

Gamete: A reproductive cell.

Heterozygous: A state in which two alleles for a given gene differ from each other.

Homozygous: A state in which two alleles for a given gene are the same.

Recessive: An allele whose effects are covered in offspring by the dominant allele in the pair.

Mendel's first law: The Law of Segregation
Mendel's law of segregation explains what occurs at the alleles that constitute a gene during formation of gametes. For instance, suppose that a pea plant is composed of a gene for flower color in which the two alleles code for red.

One way to symbolize that condition is to write RR, which indicates that both alleles (R and R) code for the color red. An additional gene might possess a diverse combination of alleles, as in Rr.

In this situation, the symbol R stands for red color and the r for "not red" or, in this situation, white. Mendel's law of segregation says that the alleles that constitute "a gene" break up from each other, or segregate, during the formation of gametes.

That law can be represented by simple equations, like:

RR → R + R or Rr → R + r
Mendel's second Law: Law of independent assortment
Mendel's second law-the law of independent assortment refers to the fact that any plant contains a lot of different kinds of genes. One gene determines the colour of the flower, a second gene determines length of stem, a third gene determines shape of pea pods, and so on.

Mendel observed that the manner in which alleles from dissimilar genes divide and then recombine is unconnected to other genes. That is, assuming that a plant contains genes for color (RR) and for shape of pod (TT).

Then Mendel's second law says that the two genes will segregate independently, as shown below:

RR → R + R and TT → T + T
Mendel's third law: Dominance
Mendel's third law takes care of issue of dominance. Assuming that a gene is composed of an allele for red color (R) and an allele for white color (r).

What colour will the flower of the final plant take? Mendel found out that in every pair of alleles, one is more likely to be expressed than the other.

In other words, one allele is dominant and the other allele is recessive.

In the example of an Rr gene, the flowers produced will be red for the fact that the allele R is dominant over the allele r.

MICRO ORAGNISM IN MAN

from Femosky110 on 06/11/2020 01:00 PM

Micro-Organism: Man And Health
A microorganism or microbe is an organism that is very small that it can only be seen by a microscope. It is not usually visible to the naked eye.

 

Microorganisms are frequently showcased with single-celled or unicellular organisms; although a few unicellular protists are visible to the naked eye, and a few multicellular species can only be seen with the aid of a microscope.

The study of microorganisms is referred to as microbiology and not unexpectedly the majority of the study is channeled to those organisms which cause human disease.

It is currently observed that microorganisms are not only responsible for causing 'infectious diseases' but they as well lead to many diseases like peptic ulcers, angina, and cervical cancer.

It is possible to discover in future that microorganisms may as well cause 'non-infectious' diseases. Nevertheless, microorganisms are as well crucial to human life.

Every square inch of our body surface is occupied by a lot of thousands of organisms which assist to safeguard the body from invasion by other possible harmful organisms.

Microorganisms are classified into bacteria, viruses, fungi, and parasites. Prions, which are considered to be infective protein particles instead of living organisms, are as well studied in microbiology. These groups are completely unconnected to one another; the only general factor among them is that they are all microscopic.

1. Bacteria
They are single-celled organisms, normally either rod-shaped or fairly spherical in shape. They are grouped based on their reaction to Gram's stain: those that go blue with this stain are referred to as being Gram positive, those staining red are referred to as Gram negative.

Bacterias are responsible for diseases that range from typhoid, plague, cholera, meningococcal meningitis, tuberculosis, tetanus, gonorrhoea, and syphilis, to the more ordinary urinary tract infections, boils, and acne.

They are killed with the use of antiseptics and by boiling, although they may manufacture toxins which are not destroyed.

A lot of them were initially sensitive to antibiotics like penicillins, but excess us of these drugs has lead to a lot of multi-resistant bacteria.

2. Viruses
These are smaller than bacteria and are not visible via a light microscope. It needs the use of electron microscope. They cannot reproduce apart from inside other living cells. They are liable to heat and to a few antiseptics.

3. Fungi
Like bacteria, microscopic fungi are ubiquitous and include yeasts or moulds. Yeasts have been utilized for centuries by peoples all over the world to ferment sugar to alcohol; the drug penicillin was created in a mould.

The most common fungal infections are vaginal thrush, which frequently occurs after a course of antibiotics has killed the normal vaginal bacteria, and nail and skin infections like 'ringworm'.

4. Parasites
They are organisms which live in or on the body of another known as the 'host'. The host may provide a source of nutrients or a safe haven in which to reproduce. They vary in size from single cells, such as the malaria parasite, to tapeworms which may be up to thirty feet in length and therefore not microscopic.

Man And Microbes
As in a lot of things in life, human beings require more than what is naturally available, not only to fight natural hazards but to as well fight things we have artificially made ourselves.

Through Biotechnology, scientists all over the world are conducting researches with viruses, bacteria, and fungi for lots and lots of reasons. These microbes are the simplest of all organisms. They can as well be the most deadly of all organisms.

That is why they are being greatly studied.

In addition to constituting a lot of harms to living organisms, these microbes can as well be beneficial in a lot of ways.

Microorganisms are very important to humans and the environment, because they take part in the Earth's element cycles like the carbon cycle and nitrogen cycle, in addition to accomplishing other crucial functions in almost all ecosystems, like in recycling other organisms' dead remains and waste products through decomposition.

Microorganisms as well have a crucial place in the majority of higher-order multicellular organisms in the form of symbionts. The majority of people blame the failure of Biosphere 2 on an inappropriate balance of microorganisms.

Uses of Micro-organism in different aspects of live have been illustrated below:

1. Uses of Microbes To Make Medicine
Scientists are making use of microbes and the compounds they produce to manufacture new medicines to save human lives. The results of those researches are why we are being vaccinated for things like pox or the flu. Such vaccinations are effective because scientists have studied those viruses to examine the way they function. They consequently came up with a way to teach our immune system to do fight. If the individual eventually took ill he or she would be able to will be able to handle the infection. Labs are as well coming up with drugs that assist to get rid of these infections after you get the disease. Medical Laboratories are as well formulating fresh and stronger antibiotics on a day to day basis.

2. Uses of Microbes In War
Even though nobody enjoys talking about it, humans have a history of making use of disease and compounds produced by microbes in warfare. Labs were constructed to produce chemical compounds that would terminate people's life.

They as well isolate diseases (viruses) that could be set free to infect a whole population of people. The majority of the world has chosen not to grow diseases to be made use of in war. They have known how dangerous and uncontrollable these diseases are. Once they release these diseases, they may not be able to stop them.

3. Uses of Microbes for cleaning The Environment
Scientists are as well working with microbes to improve the environment. In the real sense, the environment did not require help; we're merely trying to reduce the negative impact we have on the environment.

Excellent examples are the bacteria that have been formulated to break down oil in the water. If a tanker leaked and oil starts to spill into the water, these bacteria could be sent out to break down the oil. The resulting compounds would not be harmful to the environment.

Scientists are as well working with bacteria and fungi to assist breakdown garbage.

4. Oil microorganisms
The nitrogen cycle in soils relies on the fixation of atmospheric nitrogen. One way this can happen is in the root nodules of leguminous plants that is composed of symbiotic bacteria of the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium.

5. Symbiotic microorganisms
Symbiotic micro-organisms like fungi and algae form an association in lichen. A group of fungi form mycorrhizal symbioses with trees that augment the supply of nutrients to the tree.

6. Human Digestion and Microorganism
A few types of bacteria that occupy animals' stomachs assist in their digestion. For instance, cows possess a lot of different micro-organisms in their stomachs that are crucial in their digestion of grass and hay.

The gastrointestinal tract is made up of a hugely composite ecology of microorganisms. A characteristic individual bears above 500 different species of bacteria, which stands for dozens of various lifestyles and capabilities. The composition and supply of this menagerie varies with age, state of health and diet.

The number and type of bacteria in the gastrointestinal tract differ significantly by region. In healthy individuals, the stomach and proximal small intestine contain some microorganisms, mainly as a result of the bacteriocidal function of gastric acid; those that are there are aerobes and facultative anaerobes.

An attractive evidence of the capability of gastric acid to repress bacterial populations is observable in patients with achlorhydria, a genetic disorder which inhibits secretion of gastric acid.

Such patients, which are otherwise healthy, may have about 10,000 to 100,000,000 microorganisms per ml of stomach contents.

Contrary to the stomach and small intestine, the contents of the colon plainly swarm with bacteria, mainly severe anaerobes -bacteria that survive only in environments that are completely devoid of oxygen.

Amid these two extremes is a transitional zone, normally in the ileum, where reasonable numbers of both aerobic and anaerobic bacteria are established.

The gastrointestinal tract is germ-free at birth, but migration characteristically starts within a small number of hours of birth, beginning from the small intestine and advancing gradually over a period of a number of days. In the majority of circumstances, a "mature" microbial flora is recognized by 3 to 4 weeks of age.

7. Use in food
Microorganisms are made use of in brewing, wine making, baking, pickling and other food-manufacturing processes. They are as well employed in the control of the fermentation process in the manufacture of cultured dairy products like in yogurt and cheese.

The cultures as well make available flavour and aroma, and eliminate undesirable organisms.

8. Use in water treatment
The majority of all oxidative sewage treatment processes depend on a large array of microorganisms to oxidize organic components which are not agreeable to sedimentation or flotation.

Anaerobic microorganisms are as well utilized to reduce slush solids manufacturing methane gas in the midst of other gases and a germ-free mineralized residue.

In drinkable water treatment, one method, the slow sand filter, uses a complicated jellylike layer made up of an extensive array of microorganisms to take away both dissolved and particulate material from raw water.

9. Use in energy
Micro-organisms are made use of in fermentation to manufacturing ethanol, and in biogas reactors to manufacture of methane. Scientists are conducting research on the use of algae to manufacture of liquid fuels, and bacteria to change different types of agricultural and urban waste into utilizable fuels.

10. Use in production of chemicals, enzymes etc
Micro-organisms are employed for a lot of commercial and industrial manufacturing of chemicals, enzymes and other bioactive molecules.

Examples of organic acid manufacture are:

• Acetic acid: Manufactured by the bacterium Acetobacter aceti and other acetic acid bacteria (AAB)

• Butyric acid (butanoic acid): Manufactured by the bacterium Clostridium butyricum

• Lactic acid: Lactobacillus and others usually known as lactic acid bacteria (LAB)

• Citric acid: Manufactured by the fungus Aspergillus niger

11. Diseases caused by Microbes
Micro-organisms are the reason of a lot of infectious diseases.

The organisms concerned are pathogenic bacteria-they cause diseases like plague, tuberculosis and anthrax; protozoa- they cause diseases like malaria, sleeping sickness, dysentery and toxoplasmosis; and as well fungi-they cause diseases like ringworm, candidiasis or histoplasmosis.

Nevertheless, a few diseases like influenza, yellow fever or AIDS are caused by pathogenic viruses, which are not normally classified as living organisms and are not, therefore, micro-organisms by the stringent definition.

12. Use in Food in Hygiene
Hygiene is the prevention of infection or food spoiling by removing microorganisms from the surroundings. As microorganisms, in particular bacteria, are discovered practically all over the place, the levels of injurious microorganisms can be minimized to suitable levels.

Nevertheless, in a few cases, it is needed that an object or substance be entirely sterile, i.e. free of every living entities and viruses. A good instance is a hypodermic needle.

13. Active use of lactic acid bacteria
Lactic acid bacteria (LAB) are an essential class of bacteria in food production. They are vigorously made use of in the manufacture of fermented foods like cured sausages and yoghurt, and a few LAB possess probiotic properties, ie. they possess a positive effect on consumer health.

Fighting unwanted bacteria
A lot of bacteria possess a negative effect on food because they depreciate the food's consumption quality or make it unsafe for consumption. When microorganisms break down and deteriorate food, these results to an increased food waste and wastage, which in turn has crucial financial and environmental consequences.

Staying further on in knowledge of the expression, deterrence and fight against bacteria is consequently an endless battle.

PLANT NUTRITION

from Femosky110 on 06/11/2020 12:51 PM

Plant Nutrition and Photosynthesis
Plants are living organisms that need food in order to stay alive. The way they obtain their nutrients though, is totally different from that of animals.

 

Plant produces the majority of their nutrients by themselves with the aid of merely 2 raw materials; water and carbon dioxide.

The leaf of a plant is taken as its kitchen. It is where food is manufactured and transported round the plant body.

Parts of the leaf:
1. Upper Epidermis: This is a layer of cells that envelop the leaf and protect it, it is enclosed by a layer of wax known as the cuticle.

2. Mesophyll Layer:
The mesopyll layer of the leaf is further dived into:

• Palisade Mesophyll: a layer of palisade cells takes care of the majority of the function of photosynthesis in plants

• Spongy Mesophyll: a layer of spongy cells under the palisade layer which also takes part in photosynthesis and store nutrients.

3. The Vascular Bundles: These are a group of phloem and xylem vessels that transport water and minerals to and from the leaves.

3. Lower Epidermis: This is related to the upper epidermis, only that it contains a unique type of cells known as the guard cells.

Guard cells are a special type of cells that regulate the passage of carbon dioxide into the cell and the passage of oxygen out of the cell by opening and closing of the stomata.

The stomata are a hole in the leaf through which gases pass through. Therefore, guard cells are responsible for gaseous exchange in plants.

Photosynthesis:
The term photosynthesis means "producing with light". It is the process by which plants manufacture useful glucose out of the raw materials of water and carbon dioxide, with the help of the light energy from the sun.

Water is vital for photosynthesis; it is obtained from the soil by the roots and transported up the stem to the leaves where it is put into effective use.

biology
Carbon dioxide, like water is necessary for photosynthesis to occur. It travels into the leaf from the air through the process of diffusion, via the stomata which are minute holes in the leaf.

As soon as carbon dioxide and water are available in the leaf, the next condition for photosynthesis that is needed and that is light.

The two cells known as palisade cells, the rectangular one and spongy mesophyl cell -the circular one, are the cells where photosynthesis takes place.

They a structure known as chloroplasts which contain a green pigment known as chlorophyll which functions at trapping sunlight to be used as energy for the photosynthetic reaction. A large number of chloroplasts is needed for photosynthesis to occur.

How photosynthesis takes place:
• Carbon dioxide and water go into the cell

• The cell traps light energy with the use of chloroplasts

• The energy is utilized to split water (H2O) into hydrogen and oxygen

• The oxygen is expelled outside the leaf to the atmosphere as a waste product

• The hydrogen reacts with carbon dioxide to form glucose.

Overall equation for the Photosynthesis

biology
Carbon Dioxide Supply:
The carbon dioxide travels to the leaf from the atmosphere by diffusion through tiny holes in the leaf known as the stomata.

Carbon dioxide is not available in a high concentration in air, but when compared to its concentration inside the leaf, it is more concentrated in the air.

This is because the cells inside the leaf are constantly photosynthesizing during the day time converting the carbon dioxide into the glucose rapidly, therefore the concentration of it inside the leaf lessens, producing a concentration gradient for diffusion from the atmosphere to the leaf.

Water Supply:
The water for photosynthesis is absorbed by the roots of the plants and then transported upwards via a hollow tube known as the xylem vessel till it arrives at the leaf where photosynthesis occurs; it passes through the leaf through holes in the xylem.

Excess water leaves the cell via the stomata; through the process known as "transpiration"

Sunlight Supply:
The leaves are always exposed to sunlight at daytime. The sun penetrates the transparent layers on the leaf till it gets to the mesophyll layer, where photosynthesis occurs.

Palisade cells are closer to the surface of the leaf than the spongy cells, so they receive more of the light and undergo more photosynthesis.

Factors Needed For Photosynthesis:
• Water

• Carbon Dioxide

• Light

Factors Affecting The Rate Of Photosynthesis:
• Amount of water: the rate of photosynthesis increases as water increases

• Concentration of carbon dioxide: the rate of photosynthesis increases as CO2 increases

• Light intensity: the rate of photosynthesis increases as light increases

Plants at night:
At night, the plant goes through a lot of processes to convert the stored starch into numerous useful nutrients such as:

• Sugars for respiration

• Cellulose and proteins for producing cells

• Vitamins to assist in energy action

• Fats as a long term storage material

• The rest of the starch is temporarily stored.

Mechanism of Guard Cells:
At daytime, the guard cells open the stomata to permit gaseous exchange, which takes place following the processes below:

• Sunlight increases the potassium concentration in the vacuoles of the guard cells, the water latency decreases producing a gradient between the guard cells and the surrounding epidermal cells,

• Water travels through the process of osmosis into the guard cells from the epidermal cells,

• The water increases the pressure inside the guard cells,

• The cell wall adjoining the stomata is thicker and less stretchable then the cell wall on the other side,

• The pressure expand the whole cell apart from the inner cell wall adjoining the stomata by forming a curve and a pore between the two guard cells,

• The stoma opens.

At night on the other hand, the mechanism is reverse:
• Potassium level lessens in the vacuole of the guard cells,

• Water potential rises in the cell and water diffuses out of it,

• The guard cells uncurl up due to low pressure closing the stoma.

Mineral Requirements:
The plant is as well in need for mineral ions to be in charge of chemical activities, grow, and manufacture materials. The major important minerals are:

• Mg+2 (Magnesium ions): They are necessary for the production of the green pigment known as chlorophyll. Deficiency of it leads to lack of photosynthesis and wilting of the leaves,

• Nitrates: these are the sources of nitrogen; they are needed to make amino acids and proteins by combining with glucose. Deficiency of it leads to deformation of the plant structure making it small and weak.

The two mineral ions are absorbed from the soil.

Fertilisers:
Occasionally, the soil is deficient of the mineral ions necessary; this issue can be resolved by the addition of fertilizers to the soil. Fertilizers are chemical compounds rich in the mineral ions required by the plants.

They assist the plants to grow faster, increase in size and become greener; they merely make them healthier and increase the crop yield. But there are disadvantages of fertilizers, like:

• Excess minerals and chemical can pass into a nearby river polluting it and creating a layer of green algae on the surface of it, resulting to the lack of light in the river, thereby inhibiting the aqua plants photosynthesizing.

• When living organisms in the river or Lake Die, decomposers like bacteria multiply and decay, respire with the use of oxygen. Eutrophication occurs in the end.

The green House
A green house is a place sheltered by transparent polythene. In green houses, the restraining factors of photosynthesis are eradicated, and the plants are provided the most favorable conditions for a healthy, rapid growth.

The soil in green houses is fertilized and extremely rich in mineral ions, ensuring healthy, large yields. Extra carbon dioxide is supplied to the crops for faster photosynthesis.

The polythene walls and ceiling permit heat waves and light rays only to enter and stop harmful waves, thereby making available a high light intensity and most favorable temperature, occasionally a heating system is as well utilized.

A watering system is as well made available. The disadvantages of green houses are that it is too small to produce a large yield and that it is costly.

Photosynthetic organisms are known as photoautotrophs, which mean they are capable of manufacturing food directly from carbon dioxide and water using energy from light.

Nevertheless, not all organisms that make of use light as a source of energy carry out photosynthesis, since photoheterotrophs make use of organic compounds, instead of carbon dioxide, as a source of carbon. In plants, algae and cyanobacteria, photosynthesis discharges oxygen.

This process is known as oxygenic photosynthesis. Even though there are a few variations between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms.

However, there are some types of bacteria that carry out anoxygenic photosynthesis, which makes use of carbon dioxide but does not release oxygen.

Carbon dioxide is converted into sugars through a process known as carbon fixation.

Carbon fixation is an endothermic redox reaction, so photosynthesis needs to supply both a source of energy to compel this process, and the electrons required to convert carbon dioxide into carbohydrate.

This addition of the electrons is a reduction reaction. In general outline and in effect, photosynthesis is the opposite of cellular respiration, in which glucose and other compounds are oxidized to manufacture carbon dioxide and water, and to release exothermic chemical energy to propel the organism's metabolism.

Nevertheless, the two processes occur via a different sequence of chemical reactions and in dissimilar cellular compartments.

The general equation for photosynthesis is therefore:

2n CO2 + 2n DH2 + photons → 2(CH2O) n + 2n DO

Carbon dioxide + electron donor + light energy → carbohydrate + oxidized electron donor

In oxygenic photosynthesis water is the electron donor and, given that its hydrolysis expels oxygen, the general equation for this process is:

2n CO2 + 4n H2O + photons → 2(CH2O)n + 2n O2 + 2n H2O

Carbon dioxide + water + light energy → carbohydrate + oxygen + water

Over and over again 2n water molecules are cancelled on both sides, giving rise to:

2n CO2 + 2n H2O + photons → 2(CH2O)n + 2n O2

Carbon dioxide + water + light energy → carbohydrate + oxygen

Other processes replace other compounds like arsenite for water in the electron-supply role; for instance a few microbes make use of sunlight to oxidize arsenite to arsenate: The equation for this reaction is:

CO2 + (AsO33–) + photons → (AsO43–) + CO

Carbon dioxide + arsenite + light energy → arsenate + carbon monoxide (utilized to build other compounds in subsequent reactions)

Photosynthesis takes place in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of the sunlight and make use of it to manufacture the energy-storage molecules ATP and NADPH.

During the second stage, the light-independent reactions make use of these products to capture and minimize carbon dioxide concentration.

TRANSPORT SYSTEM

from Femosky110 on 06/11/2020 12:49 PM

The Need for Transport
Multicellular organisms need the transport systems to supply nutrients to their cells as well as get rid of waste products. Plants transport substances through xylem and phloem while the mammalian heart makes use of blood vessels.

 

Transport systems
An increase in the size of an organism leads to a corresponding decrease in the surface area to volume ratio.

This implies that it has comparatively less surface area on hand for substances to diffuse through, so the rate of diffusion may not be swift enough to meet up the requirements of the cells.

Big multicellular organisms therefore cannot depend on diffusion alone to provide their cells with materials like food and oxygen and to eliminate waste products.

Large sized multicellular organisms therefore need specialized transport systems.

The box on the left hand side has a surface area of 6 square units and a volume of 1 cubic unit. Its surface area to volume ratio is 6:1.

The box on the right hand side has a surface area of 24 square units and a volume of 8 square units. Its surface area to volume ratio is 24:8 which equals 3:1.

The box has two times the height, length and breadth of the smaller box, but only has half the comparative surface.

Therefore the larger SA/V ratio of the smaller box would permit more effective diffusion and exchange of materials.

Transport system in plants
Plants need transport systems to transport water, dissolved food and other substances just about their structures in order to be alive.

Plants need water for two main reasons:
• For photosynthesis. In the majority of flowering plants it occurs in mesophyll cells of the leaves.

• To transport materials, like minerals.

Water absorbed by the roots of a plant is transported from one side of the plant to the leaves where a few of it is expelled out into the air. The stages involved in the process are:

1. Soil to xylem
• Water is been drawn up by the root hair cells. These are minute hairs enveloping the tip of the ends of the smallest roots. They make available a large surface area for the absorption of water by the process of osmosis.

• Water therefore passes from cell to cell via the root cortex by osmosis down a concentration gradient. This implies that every cell possess a lower water concentration than the one it is following.

• In the centre of the root, the water sips through the xylem vessels. These are vein-like tissues that transport water and minerals up a plant.

2. Xylem to leaf to air
Water molecules creeps up the xylem vessels to the leaves where they stay and are transferred from cell to cell.

Water passes from the xylem vessels into the mesophyll cells where it can be made use of for photosynthesis.

Some of the water disappears into the surrounding air spaces at the interior part of the leaf and subsequently diffuses out through the stomata into the adjoining air.

The opening and closing of the stomata is handled by guard cells in the epidermis.

The loss of water from the leaves of a plant is known as transpiration, and the resulting flow of water via the plant is known as the transpiration stream. The transpiration stream is significant because:

• It transports water for photosynthesis to the mesophyll cells. The mesophyll cells are the upper layer of cells where photosynthesis majorly occur place in the leaves.

• The water carries vital mineral salts dissolved in solution.

The xylem transport system
Water and minerals are carried up via the stem in xylem vessels. Xylem is a tissue made up of dead, hollowed-out cells that outline a system of pipes.

The walls of xylem cells are lignified. This means that they are strengthened with a substance known as lignin which permits the xylem to withstand the changes in pressure as water passes through the plant.

The phloem transport system
Sugar manufactured through the process of photosynthesis in the leaves is transported up and down the plant to the meristems and other tissues in living phloem cells.

Companion cells make available the energy for the sieve cells. The end walls of the sieve cells possess pores through which sugar is transported from cell to cell.

Animal transport and exchange systems
In mammals, nutrients like glucose and amino acids, oxygen and carbon dioxide are transported just about the body in the blood.

Oxygen is transported in red blood cells. Red blood cells are special cells that carry oxygen because:

• They have large quantities of a protein known as hemoglobin, which can react with oxygen.

• They possess no nucleus and therefore there is more room for hemoglobin.

• They possess a biconcave disc shape, which maximizes the surface area of the cell membrane for oxygen to disperse across.

• They are minute and stretchy and therefore can press through the narrowest blood capillaries to transport oxygen.

Haemoglobin
Haemoglobin reacts with oxygen in body parts where the oxygen concentration is high -in the lungs and forms oxyhaemoglobin.

Blood with a high concentration of oxygen is termed oxygenated blood. This is illustrated in the equation below:

The presence of oxygen in the blood makes it a bright red colour.

In places where the oxygen concentration is small-body tissues, the haemoglobin gives out oxygen as illustrated in the equation below.

The oxygen then passes through into the cells. Blood that has a low oxygen concentration is dark red colour and is termed a deoxygenated blood.

Transport system In Humans
The human transport system is made up of a system of tubes with a pump and valves to make sure blood flows one way.

We require a transport system to supply oxygen, nutrients and other substances to every part of our body cells, and remove waste products from them.

The oxygenated blood ie blood that is high in oxygen, red in color enters the heart from the lungs in the pulmonary vein; the heart pumps the blood to the aorta which is an artery and from there to the entire body parts.

The deoxygenated blood goes back to the heart from the body in the vena cava which is a vein and from there the heart pumps it to the lungs to eliminate the carbon dioxide.

• Oxygenated Blood: Red color, high oxygen low Carbon dioxide.

• Deoxygenated Blood: Blue color, low oxygen high Carbon dioxide.

You would observe that during one circulation, the blood passed through the heart two times, this is why it is referred to as double circulation.

When the blood is flowing away from the heart, it has an extremely high pressure, when it is flowing towards the heart it has a lower pressure.

The Blood:
The blood is a fluid that is made up of many types of cells afloat in a liquid known as plasma.

Red Blood Cells:
These are among the tiniest cells in your body; they are round with a hollow in the center. The shape is termed a Biconcave disc.

The function of the red blood cells is to convey oxygen from the lungs to the body cells.

A red protein known as Haemoglobin, when the blood reaches the lungs, oxygen passses from the alveoli to the red blood cells and reacts with haemoglobin to form an unstable compound known as oxyhaemoglobin.

When the blood reaches the body cells, the oxyhaemoglobin is readily divided into oxygen and haemoglobin again, the oxygen passses through the blood plasma to the cells.

Red blood cells are entirely tailored to their function due to the following features it possesses:

• Biconcave disc shape offers it gives it large surface area to carry more oxygen

• Haemoglobin that combines with oxygen

• No nucleus that occupies space.

White Blood Cells:
White blood cells are one of the substances that are afloat in the blood plasma. They are entirely different in function from the red blood cells. White blood cells are part of the body's Immune System.

They are very significant and play a huge role in the body's protection usually by killing bacteria which cause disease, also referred to as pathogens.

White blood cells can be differentiated from the red blood cells quite readily because they are very much bigger than the red blood cells and possess a nucleus, and are available in fewer amounts.

Types Of White Blood Cells:
Phagocytes:
They eliminate bacteria from the body by engulfing them, taking them in the cell and subsequently kill them by digesting them through the use of enzymes; this process is known as phagocytosis.

The majority of white blood cells are the phagocyte type.

Lymphocytes:
As opposed to phagocytes, lymphocytes posses a large nucleus. They are produced in the lymph nodes-in the lymphatic system.

Lymphocytes get rid of bacteria by secreting antibodies and antitoxins which directly kill the pathogens or make it easier to get them killed.

Every one of the pathogens could be killed by a specific type of antibody.

The Platelets:
Platelets are minute cell fragments that inhibit bleeding when the skin is cut, and it prevents bacteria from passing into our systems via the wound.

This functions through blood clotting, when the skin is cut, a few reactions occur which leads to the platelets manufacturing a protein, this protein will alter the fibrinogen- another soluble protein in the plasma to insoluble fibrin.

The fibrin produces the long fibres that clot together covering the cut, thereby preventing any bleeding. This process is referred to as blood clotting.

Blood Plasma:
This makes up the majority of the blood. It is majorly water with a few substances dissolved in it; these embrace carbon dioxide, hormones, food nutrients, urea and other waste products.

The blood plasma transports substances from place to place.

Functions of the blood:
• To transport the red blood cells, white blood cells, oxygen, food nutrients, hormones, and waste products.

• Defend the body against disease, by white blood cells, a process known as phagocytosis and production of antibodies.

• Providing cells with glucose to respire and maintain a constant temperature.

Blood Vessels (Vascular System):
This is a number tubes that carry the blood away from and to the heart and other organs. The major types of are Arteries, Veins and Capillaries.

Arteries:
Their function of the arteries is to transport blood away from the heart to the lungs or other organs of the body.

The blood in the arteries always comes with a high pressure.

The heart pumps the blood swiftly into the arteries, leading in the pressure, every time the ventricle of the heart contracts, the pressure in arteries increase, when the ventricle relaxes, the pressure falls.

The lumen of arteries is as very narrow, making the pressure to be higher.

The structure is uncomplicated, apart from the narrow lumen it possesses; the arteries possess a strong thick wall to endure the pressure. Their walls are as well elastic and stretchable.

Concise explanation of characteristics of arteries:

• To carry blood away from the heart

• Blood that passes here are constantly in a high pressure

• They have rigid but stretchable walls

• Narrow lumen

The function of the veins is to transport blood to the heart from the body.

The veins always have a low blood pressure because when the blood with high pressure reaches the veins, it loses the majority of the pressure it has.

biology

REPRODUCTIVE SYSTEM

from Femosky110 on 06/11/2020 12:48 PM

Mammalian Reproductive System
Most mammal reproductive systems are alike; however, there are a few prominent differences between the "normal" mammal and humans. For example, the majorities of mammalian males have a penis which is stored internally until erect, and a few have a penis bone or baculum.

 

Furthermore, males of the majority species do not remain continually sexually fertile as humans do.

Like humans, the majority of mamalian groups have descended testicles located inside the scrotum, on the other hand, others have goes down testicles that relax on the ventral body wall, and other groups of mammals, like elephants, have undescended testicles are located deep within their body cavities close to their kidneys.

General Functions of the Female Reproductive System
The female primary reproductive organs are the ovaries. The functions of the ovaries include the production of female sex hormones and oocytes as well as secretions by glands in the reproductive system.

The accessory ducts include the uterine tubes, where fertilization takes place; the uterus, where the embryo grows; and the vagina, which serves as a birth canal and receives the penis during sexual intercourse.

In amniotes, fertilization is normally internal, with sperm transfer irregularly assisted by a male intromittent organ. In placental mammals, the reproductive structures have become well developed and specialized to make the act of giving birth possible.

Methods of Reproduction in Mammals
The three types of mammals differ in their methods of reproduction.

• Placental Mammals such as the cat are viviparous. Viviparity, or birth of live young, has separately evolved more than one hundred times in vertebrates. Nevertheless, a lot of vertebrates retain the shelled egg laying method of giving birth as a result of the nutrients made available by the shell and passed to the embyo.

• Monotremes are the most primitive types of mammals. They have maintained the reptilian oviparous method of reproduction and lay shelled eggs.

• Marsupials go through a fuzzy type of viviparity. They give birth to underdeveloped live young. When the young are born, they move to the permanent brood pouch, or marsupium. Development of the young is finished in the pouch.

Female Reproductive Structures In Mammals That Allow Viviparity
Ovary: The ovary is paired, almond-shaped organs that are propped up by the mesovarium, a part of the broad ligament. The ovary is the place of oogenesis and hormone production.

Oviducts: The oviducts are as well regarded as the uterine tubes. They receive the oocyte and make available a site for fertilization.

Infundabulum: This is the sideways part of the oviduct that lokes an open funnel. This feature is covered with ciliated and finger-like projections known as fimbrae which wrap over the ovary. The movements of the fimbrae brush the oocyte into the tube.

Ostium Tubae: The infundabulum unlocks medially through the ostium tubae.

Uterus: The oviducts come together into the bigger uterine horn. The two uterine horns mingle to form the uterine body. The entire structure is Y-shaped.

The mammalian uterus has developed a highly vascularized lining whose function is to receive, retain, and nourish a fertilized egg all through pregnancy.

During the pregnancy, the uterine horns block up the abdominal cavity. The other organs are pressed in all directions to give room to the developing fetus.

Vagina: The vagina is a thin-walled tube that is located posterior to the uterus. It makes a tube for the delivery of an offspring.

Evolution of a Secondary Sexual Characteristic
Mammary glands are unique to living mammals. They are formed from specific skin glands. Mammary glands play a role in lactating females when they produce milk for the nourishment of an offspring.

Female mammals are born with all the follicles they're ever going to have, and every one of the follicles possesses a primary oocyte. There are significant numbers of these. In humans the total number of primordial follicles present at birth can be up to 500,000 or more.

They are normally dormant until the stage of puberty. Hormonal changes that take place in the body at this stage will cause the eggs to get up from their dormant state. However, just a few among those thousands of egg would mature to the stage of ovulation.

Human beings possess a much longer reproductive life than the majority of other mammals, but even at that if a woman ovulates once every month from the ages of 12 to 50, she can only produce about 400-500 matured eggs that capable of being fertilized. That is one tenth of one percent of her total follicles.

Human Reproductive System
The human reproductive system is normally composed of internal fertilization through the process of sexual intercourse. During this process, the erect penis of the male is inserted into the female's vagina until the male ejaculates semen, which is composed of sperm, into the female's vagina.

The sperm afterwards travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the egg.

Upon successful fertilization and implantation, gestation of the fetus then occurs inside the female's uterus for just about nine months, this process is referred to as pregnancy in humans. The process of gestation comes to an end with birth. The process of giving birth is referred to as labor.

Labor results as a result of the contraction of the muscles of the uterus, the dilation of the cervix and the passage of the baby through the vagina which is the woman's reproductive organ.

Human's babies and children are almost defenseless and need and require high levels of parental care for lots of years. One major crucial type of parental care is to make use of the mammary gland to nurse the baby.

The female reproductive system has two-fold functions: To produce egg and to protect and look after the offspring until birth. The male reproductive system has one function, which is to produce and to dump sperm.

Humans have a lofty level of sexual differentiation added to the variations in roughly every reproductive organ, a lot of variation normally take place in the humans during the development of the secondary sexual characteristics.

Male Reproductive System
biology
The male reproductive system is composed of organs situated outside of the body and around the pelvis region of a male which plays a role in the reproduction process. The major express function of the male reproductive system is to make available the male sperm for fertilization of the ovum.

The major reproductive organs of the male can be classified into three categories. The first category is sperm production and storage. Production of sperm occurs in the testes which are housed in the temperature regulating scrotum, immature sperm then journey to the epididymis for development and storage.

The second category is the ejaculatory fluid producing glands which are the the seminal vesicles, prostate glands, and the vas deferens. The last category is those employed during copulation, and deposition of the spermatozoa (sperm) within the male. They include the penis, urethra, vas deferens, and Cowper's gland.

The main secondary sexual characteristics of males include: larger, extra muscular stature, deep voice, facial and body hair, broad shoulders, and development of an adam's apple. A crucial sexual hormone of males is androgen, and especially testosterone.

The testes release a hormone that regulates the development of sperm. This hormone is as well responsible for the development of physical characteristics in men like facial hair and a deep voice.

Human Female Reproductive System
biology
The human female reproductive system is a succession of organs principally situated in the interior part of the body and just about the pelvic region of a female which plays a role in the reproductive process.

The human female reproductive system is composed of three major parts: the vagina, which leads from the vulva, the vaginal opening, to the uterus; the uterus, which holds the developing fetus; and the ovaries, which produce the female's ova.

The breasts are involved during the parenting stage of reproduction, but in the majority of classifications, they are not regarded as part of the female reproductive system.

The vagina opens up on the outside through the vulva, which as well contains the labia, clitoris and urethra; during intercourse this area is greased by mucus secreted by the Bartholin's glands.

The vagina is attached to the uterus via the cervix, while the uterus is attached to the ovaries through the fallopian tubes. Each one of the ovaries possesses hundreds of egg cells or ova (singular ovum).

Roughly every 28 days, the pituitary gland releases a hormone that stimulates some of the ova to enlarge and grow. One ovum is released and it passes through the fallopian tube into the uterus.

Hormones manufactured by the ovaries get the uterus ready to receive the ovum. The lining of the uterus, known as the endometrium, and unfertilized ova discharged every cycle via the process of menstruation. If the ovum is fertilized by sperm, it attaches to the endometrium and the fetus develops.

Production of Gametes: Spermatogenesis and Oogenesis
The production of gametes takes place inside the gonads via a process referred to as gametogenesis. Gametogenesis takes place when certain types of germ cells undergo a cell division known as meiosis to divide the standard diploid number of chromosome (n=46) into haploids cells which contains only 23 chromosomes.

In males, this process of gamete production is referred to as spermatogenesis and occurs only after puberty the seminiferous tubules of the testes. The immature spermatozoon or sperm are then sent to the epididymis where they gain a tail and motility.

Each of the original diploid germs cells or primary spermatocytes forms four functional gametes which is each forever young. The production and survival of sperms require a temperature that is lower than the normal core body temperature.

Since the scrotum, where the testis is present, is situated outside the body cavity, it provides a temperature about 3°C below normal body temperature.

In females, gametogenesis is known as oogenesis which takes place in the ovarian follicles of the ovaries. This process does not generate mature ovum until puberty.

As opposed to the situation in males, every one of the new diploid germ cells or primary oocytes will form only a single mature ovum, and three polar bodies which are not able to be fertilized.

It has long been understood that in females, different from what is obtained in males, every one of the primary acolytes ever found in a female will be created before birth, and that the final stages of ova production will then not start until puberty.

However, current scientific data has challenged that hypothesis. The fresh data shows that in at least a number of species of mammal oocytes carry on replenishing in females a long time after birth.

Examples of related human reproductive organs
Male organ          Female organ            Shared function
Cowper's gland   Bartholin's glands    Lubrication secretions
Penis                    Clitoris Erectile       tissue and sensation
Testes                    Ovary                       Gamete production
Prostate gland     Skene's gland         Ejaculatory fluid and sensation

ANIMAL NUTRITION

from Femosky110 on 06/11/2020 12:45 PM

Animal Nutrition
Nutrition is defined as the process by which an organism gets food which is utilized for the provision of energy and things for its life sustaining activities. It includes ways an organism gets its food and as well the processes by which the nutrients in the food are converted to simpler molecules for use by the body.

 

Holozoic Nutrition
Animals exhibit holozoic nutrition because they are not able to manufacture their own food. Holozoic animals are roughly divided into three categories in relation to their mode of feeding. These three categories of animals are Herbivores, Omnivores, and Carnivores.

Herbivores feed on grasses, carnivores feed on animal fresh and omnivore feed on both glasses and flesh.

Digestive System in Cockroach (Invertebrates)
Nutrition in cockroach is holozoic and it is an omnivore, feeding on various types of organic matter. It eats pieces of food and grinds them before digesting them. Thus a cockroach has mouth parts that are modified accordingly for chewing the food.

Structure of the Human Digestive System
The structure of the human digestive system is tailored to the omnivorous diet. The human digestive system is made up of an alimentary canal, which is roughly 8 metres long. The alimentary canal takes care of digestion, absorption and egestion.

Mouth Cavity
The Mouth cavity is the anterior opening of the digestive system through which food is ingested. It has a muscular tongue which bears the taste buds. The human mouth is made up of two rows of teeth - upper and lower.

Pharynx
The Pharynx is the part of the alimentary canal that is located after the mouth. It is a funnel-shaped air and food passage.

Stomach
The oesophagus opens into the stomach. The stomach is situated on the left side of the abdomen. It is a sac-like organ, which is linked to the oesophagus at the anterior by a cardiac sphincter and to the small intestine at the posterior end by a pyloric sphincter.

The stomach is a flexible organ with a wall made up of folds. These folds unfasten to give room for more food.

It serves as a temporary storage organ for the food for about 4 hours. It is made up of three layers of muscles, not like the other parts of the alimentary canal, which assist in churning the food.

Small Intestine
Duodenum is a short part of the small intestine which is made up of loops and measures about 25 cm.

Large Intestine
The small intestine enlarges a little to form a tubular large intestine which is 5cm wide and 2m long.

Digestive Glands and Their Secretions
It is the largest gland and is found in the upper part of the abdomen on the right side just below the diaphragm. Its secretion is called bile juice. It is alkaline and rich in organic (steroid) salts called the bile salts.

The alkaline nature serves to neutralize the acidic pH of the gastric juice and creates the right environment for the intestinal enzymes to function.

Organ System: Gall Bladdar
This is a minute sac-like elongated organ close to the liver. The surplus bile secretion is stored in the gall bladder. It is linked with the liver by a duct known as the cystic duct. If there is no food in the intestine, the bile juice passes into the gall bladder and is stored there.

It is pumped out by the muscular contraction of the gall bladder wall when the food enters into the small intestine. The cystic duct empties into the widespread bile duct which opens into the small intestine.

Physiology of pancreas
The pancreas is located at the bend of the duodenum. It secretes pancreatic juice which possesses just about neutral pH (6 to 7). This juice is secreted into the common bile duct and subsequently into the duodenum. About 700cc of pancreatic juice is secreted daily.

Mechanism of Digestion
Renin is seen only in young children. The enzyme digests the milk protein, casein. Casein is hydrolysed into paracasein which in turn is precipitated as insoluble calcium paracaseinate. This is known as coagulation.

Renin secreted by the gastric mucosa of the calf is collected to manufacture rennet tablets used commercially to curdle milk.

Digestion Mechanism in Human
The bolus is then transported into the pharynx by an involuntary swallowing action. It is made simpler through the presence of mucus along the walls of the alimentary canal.

Hormonal Control of Digestion
Digestion is in fact carried out by enzymes but the secretion of these enzymes is regulated by the nervous system and the endocrine system.

Absorption
Digestion is as well regulated by the secretion of organic materials known as hormones by the endocrine glands. Every hormone has a particular target organ. The hormones get to the target organ via the blood stream. The hormones controlling digestion are secreted by the walls of the stomach and duodenum.

Assimilation
After the ingested food has been converted into a soluble form, the intestinal walls of ileum suck up the nutrients as well as water. Due to its larger surface area, skeletal wall lining the cavity and huge number of finger-like projections, known as the villi, the highest absorption occur in this part of the alimentary canal.

The absorbed food passes through the epithelial cells of the villi and then into the blood capillaries in the villi. From the capillaries, the fat-soluble substances move into the lymph. These materials are subsequently transported all through the body by the lymphatic system, which drains them into the blood near the heart.

The food that is digested is absorbed into the blood and lymphatic systems. The lymphatic system transports the digested fats as fatty acids and glycerol into the blood vessel going into the heart. The digested food in the blood stream reaches the liver.

In the liver excess glucose is stored as glycogen to be utilized when needed. The cells obtain the glucose they require from the blood directly for respiration. Cholesterol is produced from a few fatty acids.

The amino acids are utilized to form needed proteins. Excess amino acids are deaminated. During the process of deamination, ammonia is liberated as waste.

This ammonia is broken down into the less unsafe material known as the urea. The urea is subsequently transported through the blood stream to the kidney from where it is given out as urine.

Classification of foods
1. Carbohydrates
Carbohydrates are the main energy providers of the organism. They are composed of carbon, hydrogen and oxygen.

2. Proteins
Classification and Function of Proteins
Proteins are the main body builders of the body. They are compound molecules made up of carbon, hydrogen, oxygen and nitrogen and occasionally sulphur and phosphorus.

Proteins are used in the synthesis of enzymes (like pepsin, trypsin), hormones (like insulin, adrenaline), carrier proteins (like Haemoglobin), contractile proteins (like myosin, actin), structural proteins (like collagen) and defensive proteins or antibodies.

They as well produce skin pigments such as melanin and nucleic acids of the genetic material, DNA and RNA - purines and pyrimidines.

Fats
Fats are the major energy storers of the body. When fat is oxidized, they produce about two and a half times the energy of glucose or glycogen. This is why it majorly appropriate for energy storage.

Fat on the other hands makes use of more oxygen molecules for the oxidation process in comparison with carbohydrates which uses up less oxygen.

Fats are stored in adipose tissue in definite parts of the body like under the skin and between internal organs. As well as serving as an organ for storage, fats are also utilized to manufacture structural lipids like those of membranes.

Vitamins
Vitamins are a multifaceted group of organic compounds that are needed in small quantities for the control of different activities of the body. Although they are required in minute quantities, they are necessary for our well being.

The fact that the majority of them cannot be synthesized in the body, they ought to form a part of our diet. Deficiencies of these vitamins in the diet lead to deficiency disorders.

Minerals of Human Body
Minerals are inorganic nutrients which can be metallic and non-metallic elements that absorbed by the body in the form of salts. There are 24 elements that are utilized in our body. They possess many functions like tissue formation eg., the bone, conduction of nervous impulses, formation of RBCs, and so on.

There are eight key elements needed by man and the others are required in traces. The major elements are sodium, chlorine, potassium, calcium, phosphorus, sulphur and magnesium.

Some of the trace elements or microelements are fluorine, zinc, copper, iodine, iron, manganese, chromium, cobalt, and so on. Nevertheless all of them are crucial for the well-being of the human body. All the minerals are primarily obtained from the plants which absorb them from the soil.

Adult Balanced Nutrition
The human body needs different types of nutrients in order to keep the body healthy and fit. These nutrients ought to be taken properly in our diet. The diet that we follow ought to be balanced. Balanced diet is a diet, which contains all the nutrients required by the body in the right proportions.

Nutritional Deficiency Disorders
Nutritional disorders take place due to malnutrition. Malnutrition refers to bad nutrition and can as a result be applied to both undernourishment and overeating.

Undernourishment is a grave issue especially in the developing countries which occasionally have a large population percentage being deprived of a balanced diet or even a day of full meal. The majority of those affected are children who are below the age of five.

Undernourishment may as a result of proteins, vitamins or minerals deficiency. Deficiency of these nutrients results to diseases, time and again grave and lethal.

Vitamin Deficiency Diseases
The vitamin deficiency disease is caused by the deficiency of vitamin A, which affects the rod cells of the retina. This results to poor adaptation of eyes to dim or night light- a condition known as night blindness.

The cornea and the conjunctiva as well turn dry. This condition is known as xerophthalmia or dry eyes. Serious deficiency results in keratomalacia. In this case, ulcers develop on cornea, giving rise to eventual blindness.

Mineral Salt Deficiency Diseases
Mineral salt deficiency diseases are caused by deficiency of iron. Iron is essential for the production of haemoglobin, a protein that is an oxygen carrier in the blood.

When the level of haemoglobin in the blood drops, it results in the person feeling tired easily, loss of appetite, loss of weight and pale appearance as a result of oxygen lost in the blood.

This condition is referred to as anaemia. This condition can be averted and cured by eating food that are rich in iron like spinach, liver, milk, apple, guava, etc.

Digestive Systems
biology
Animals make use of the organs of their digestive systems to extract crucial nutrients from food they consume, which can later be assimilated.

Digestive Systems of Invertebrate
Invertebrate digestive systems are composed of a gastrovascular cavity with a single opening or an alimentary canal with a true mouth and anus.

Vertebrate Digestive Systems
Vertebrates may have one stomach, complex stomach chambers, or complementary organs that assist to break down ingested food.

Digestive System: Mouth and Stomach
Animal digestion starts in the mouth and subsequently transferred to the pharynx, into the esophagus, and after that into the stomach and small intestine.

biology
Digestive System: Small and Large Intestines
Nutrients are absorbed in the small intestine and waste is geared up for elimination in the large intestine.

Nutrition and Energy Production
Food Requirements
Essential nutrients are nutrients that cannot be manufactured by an animal's metabolism and need to be obtained from the diet.

Food Energy and ATP

ANATOMY AND SENSE ORGAN

from Femosky110 on 06/11/2020 12:42 PM

Anatomy and Structure of Human Sense Organs
The human sense organs are classified into 5: the organ of sight, organ of smell, organ of taste, organ of touch and organ of hearing. Each of the 5 senses is made up of an organ that has specific cellular structures that have receptors for specific stimuli.

 

These cells have links to the nervous system and therefore to the brain. Sensing is done at primordial levels in the cells and incorporated into sensations in the nervous system.

Sight is in all probability the main developed sense organ in humans, followed narrowly by organ of hearing.

biology
The Sense Organ of Sight
The eye is the organ of vision. It has a composite structure made up of a transparent lens that focuses light on the retina. The retina is enclosed with two essential types of light-sensitive cells-rods and cones.

The cone cells are sensitive to color and are situated in the part of the retina known as the fovea, where the light is focused by the lens. The rod cells on the other hand are not sensitive to color, but possess greater sensitivity to light than the cone cells.

These cells are found around the fovea and are in charge of peripheral vision and night vision. The eye is joined to the brain through the optic nerve. The point of this connection is known as the "blind spot" due to the fact that it is insensitive to light.

The brain joins the input of our two eyes into a distinct three-dimensional image. Again, even though the image on the retina is upturned due to the focusing action of the lens, the brain recompenses and provides the upright-side image perception.

Experiments have been conducted with subjects built-in with prisms that invert the images. The subjects pass through a preliminary period of immense confusion, but afterward they identify the images as upright.

The range of perception of the eye is extraordinary. In the dark, a substance formed by the rod cells increases the sensitivity of the eye so that it is possible to sense extremely dim light. In well-built light, the iris contracts minimizing the size of the aperture that admits light into the eye and a defensive ambiguous substance minimizes the exposure of the light-sensitive cells.

The range of light to which the eye is sensitive differs from the red to the violet. Lesser electromagnetic frequencies in the infrared are detected as heat, but cannot be seen. Elevated frequencies in the ultraviolet and beyond cannot be seen either, but can be detected as tingling of the skin or eyes depending on the frequency.

The human eye is not sensitive to the polarization of light- light that move back and forth on a definite plane.

Bees, on the contrary are sensitive to polarized light, and possess an image range that expands into the ultraviolet.

A few types of snakes possess specific infrared sensors that allow them to hunt in complete darkness merely with the help of the heat given out by their prey.

Birds possess an advanced concentration of light-sensing cells than humans have in their retinas, and as a result, have a more advanced visual acuity.

Color blindness or "Daltonism" is a widespread anomaly in human vision that makes it impractical to distinguish colors correctly. One type of color blindness results in the incapability of differentiating red from green.

This can be actual handicap for definite types of occupations. To a colorblind individual, a person with standard color vision would seem to possess an extrasensory perception.

Nevertheless, we want to put to one side the term "extrasensory perception" for perception that is ahead of the range of the normal.

biology
The Organ of Hearing
The ear is the sense organ of hearing. The outer ear sticks out away from the head and is shaped like a cup to guide sounds in the direction of the tympanic membrane, which transmits vibrations to the inner ear via a series of small bones in the middle ear known as the malleus, incus and stapes.

The inner ear, or cochlea, is a spiral-shaped cavity enclosed within by nerve fibers that respond to the vibrations and transfer impulses to the brain through the auditory nerve.

The brain joins the input of our two ears to establish the direction and distance of sounds.

The inner ear possess a vestibular system produced by three semicircular canals that are roughly at right angles to each other and which are answerable for the sense of balance and spatial direction.

The inner ear possess chambers overflowing with a viscous fluid and small particles (otoliths) consisting calcium carbonate. The association of these particles over tiny hair cells in the inner ear transmits signals to the brain that are interpreted as movement and speeding up.

The human ear can pick out frequencies from 16 cycles per second, which is an extremely deep bass, to 28,000 cycles per second, which is a very high pitch. Bats and dolphins can detect frequencies above 100,000 cycles per second.

The human ear can sense pitch alterations as minute as 3 hundredths of one percent of the original frequency in a few frequency ranges. A few individuals possess "perfect pitch", which is the capability to chart a tone accurately on the musical scale without indication to an exterior standard.

It is projected that less than one in ten thousand people possess perfect pitch, but speakers of tonal languages such as Vietnamese and Mandarin exhibits amazingly clear-cut absolute pitch in reading out collection of words due to the fact that pitch is a crucial aspect of passing on the meaning of words in tone languages.

The Organ of Taste
The receptors for taste, known as the taste buds, are located mainly in the tongue, but they are as well situated in the roof of the mouth and close to the pharynx. They are capable of detecting four basic tastes: salty, sweet, bitter, and sour.

The tongue as well can detect a sensation known as "umami" from taste receptors responsive to amino acids. By and large, the taste buds located near the tip of the tongue are sensitive to sweet tastes, while those in the backside of the tongue are sensitive to bitter tastes.

The taste buds on apex and on the side of the tongue are sensitive to salty and sour tastes. At the bottom of every taste bud there is a nerve that transmits the sensations to the brain.

The sense of taste works in coordination with the sense of smell. The number of taste buds differs considerably from person to person, but higher numbers add to sensitivity. Women, commonly possess a higher number of taste buds than men. As in the case of color blindness, a number of people are numb to a few tastes.

The Sense of Smell:
The nose is the organ in charge of the sense of smell. The cavity of the nose is covered with mucous membranes that possess smell receptors linked to the olfactory nerve. The smells themselves are composed of vapors of different substances.

The smell receptors interrelate with the molecules of these vapors and send out the sensations to the brain.

The nose as well has a structure known as the vomeronasal organ whose function has not been discovered, but which is suspected to be sensitive to pheromones that manipulate the reproductive cycle. The smell receptors are responsive to seven types of sensations that can be described as camphor, musk, flower, mint, ether, acrid, or putrid.

The sense of smell is sometimes momentarily lost when a person has caught a cold. Dogs possess a sense of smell that is a lot of times additionally sensitive than man's.

biology
The Sense of Touch
The sense of touch is dispersed all through the body. Nerve endings in the skin and other parts of the body send out sensations to the brain. A few parts of the body possess a larger number of nerve endings and, consequently, are more sensitive.

Four kinds of touch sensations can be recognized: cold, heat, contact, and pain. Hairs on the skin magnify the sensitivity and act as an early warning system for the body.

The fingertips and the sexual organs have the greatest concentration of nerve endings. The sexual organs have "erogenous zones" that when stimulated start a series of endocrine reactions and motor responses resulting in orgasm.

Away from the five sense organs
Apart from the 5 generally accepted and recognized sense organs of sight, smell, taste, touch, and hearing, human beings as well possess sense of consciousness of balance known as equilibrioception, pressure, temperature also known as thermoception sense of pain as well known as nociception, and motion all of which might involve the coordinated use of several sensory organs.

The sense of balance is regulated by a complex communication of visual inputs, the proprioceptive sensors which are controlled by gravity and stretch sensors located in the muscles, skin, and joints, the inner ear vestibular system, and the central nervous system.

Disturbances occurring in any part of the balance system, or even within the brain's integration of inputs, can cause the feeling of dizziness or unsteadiness.

Kinesthesia
Kinesthesia is the accurate responsiveness of muscle and joint action which permits us to coordinate our muscles when we walk, talk, and make use of our hands.

It is the sense of kinesthesia that allows us to touch the tip of our nose with our eyes shut or to become aware of which part of the body we need to scratch when we are experiencing itching.

Synesthesia
A few individual experiences a phenomenon known as synesthesia in which a single type of stimulus leads to the sensation of another. For instance, the hearing of a sound may lead to the sensation of the visualization of a color, or a shape may be sensed as a smell.

Synesthesia is hereditary and it is likely to take place or exist in 1 out of 1000 people with variations of form and intensity. The most widespread forms of synesthesia connect numbers or letters with colors.

Path of Sensory Impulses
The following is the part a sensory impulse takes before they are finally translated to the individual. The impulse from the receptors are transmitted through the nerve to the brain which translates it and send back the message through nerves to the effectors which would now react or respond accordingly.

Receptors > Nerves > Brain > Nerves > Effectors (such as muscles)> response

As illustrated above, our sensory organs first receives the stimuli transmits the nervous impulse to the brain which interprets it and take decision of what would be the best thing to do. The brain would then send the nerve impulses to the associated effectors or effectors muscle which would then respond accordingly.

A table illustrating he five human sense organs and their related sensory organs and stimuli

Action Senses Sensory Organs Stimulus
Eating Sense of Taste Tongue Taste
Listening Sense of Hearing Ear Light
Looking Sense of Sight Eyes Light
Touching Sense of Touch Skin Touch
Smelling Sense of Smell Nose Smell

CENTRAL NERVOUS SYSTEM

from Femosky110 on 06/11/2020 12:41 PM

Nervous Co-ordination and the Central Nervous System
The nervous system is composed of two major categories or types of cells: the neurons and glial cells.

 

Neurons
The nervous system is composed of a specific types of cell known as the neuron ("neurone" or "nerve cell"). The nervous system of all animals is made up of extremely specialised cells known as neurons which can detect, receive and transfer various kinds of stimuli.

Neurons are different from other cells in many ways, but their major basic function is that they interact with other cells through synapses, which are membrane-to-membrane junctions that contain molecular mechanism that permits speedy transmission of signals, both electrical and chemical.

Numerous types of neuron have an axon, a protoplasmic projection that can expand to far-away parts of the body and make thousands of synaptic contacts. Axons regularly move through the body in bundles known as nerves.

Even in the nervous system of a single species like humans, hundreds of various types of neurons are present, with a broad variety of morphologies and roles.

These consist of sensory neurons that transform physical stimuli like light and sound into neural signals, and motor neurons that transform neural signals into activation of muscles or glands; conversely in a lot of species the great majority of neurons obtain all their contribution from other neurons and transfer their output to other neurons.

Glial cells
Glial cells are non-neuronal cells that offer support and nutrition, sustain homeostasis, form myelin, and take part in the transmission of signal in the nervous system. In the human brain, it is projected that the total number of glia approximately equals the number of neurons, even though the proportions differ in various portions of the brain.

Among the majorly crucial role played by glial cells are to support neurons and clutch them in place; to provide nutrients to neurons; to electrically insulate neurons; to annihilate pathogens and get rid of dead neurons; and to make available guidance cues directing the axons of neurons to their targets.

A very crucial type of glial cell oligodendrocytesin the central nervous system and Schwann cells in the peripheral nervous system produces layers of a fatty substance known as myelin that enfolds around axons and makes electrical insulation which permits them to put out action potentials much more hastily and competently.

biology
Diagram showing the major divisions of the vertebrate nervous system

The nervous system of vertebrates humans inclusive is divided into the central nervous system(CNS) and the peripheral nervous system (PNS).

The (CNS) is the main division, and is made up of the brain and the spinal cord. The spinal canal possesses the spinal cord, whereas the head caries the brain.

The CNS is cased and shielded by the meninges, a three-layered system of membranes which include a tough, fibrous outer layer known as the dura mater. The brain is as well covered by the skull, and the spinal cord by the vertebral column.

The peripheral nervous system (PNS) is a combined name for all the nervous system structures that do not fall within the CNS.

The large majority of the axon bundles known as nerves are well thought-out to fit into the PNS, even while the cell bodies of the neurons to which they fit in exist in the brain or spinal cord. The PNS is somatic and visceral parts.

The somatic part is composed of the nerves that innervate the skin, joints, and muscles. The cell bodies of somatic sensory neurons are situated in dorsal root ganglia of the spinal cord.

The visceral part, as well known as the autonomic nervous system, possesses neurons that permeate the internal organs, blood vessels, and glands. The autonomic nervous system itself is composed of two parts: the sympathetic nervous system and the parasympathetic nervous system.

A few scientists as well include sensory neurons whose cell bodies is situated in the periphery for senses such as sense of hearing as part of the PNS; while others nonetheless omit them.

The vertebrate nervous system can as well be divided into areas known as grey matter and white matter. Grey matter which is merely grey in conserved tissue, and is better regarded as pink or light brown in living tissue possesses a high quantity of cell bodies of neurons.

White matter is mainly made up of myelinated axons, and takes its color from the myelin. White matter consists of all the nerves, and the majority of the interior of the brain and spinal cord.

Grey matter is created in clusters of neurons in the brain and spinal cord, and in cortical layers that line the surfaces of the brain and the spinal cord.

There is an anatomical rule which states that a cluster of neurons in the brain or spinal cord is known as a nucleus, while a cluster of neurons in the periphery is known as a ganglion. There are, nevertheless, a few exceptions to this rule, remarkably including the part of the forebrain known as the basal ganglia.

The Human Nervous System:-
The human nervous system is divided into two parts:

(i) Central Nervous System (CNS)

(ii) Peripheral Nervous System (PNS)

The CNS is composed of the brain and the spinal cord and is the location for information processing and control. The PNS is composed of all the nerves of the body that are connected with the CNS – the brain and spinal cord. The nerve fibres of the PNS are divided into two:

(a) Afferent Fibres

(b) Efferent Fibres

The afferent nerve fibres transmit impulses from tissues/organs to the CNS and the efferent fibres transmit regulatory impulses from the CNS to the particular peripheral tissues/organs.

The PNS is classified into two:

The somatic nervous system and autonomic nervous system

The somatic nervous system conveys impulses from the CNS to skeletal muscles whereas the autonomic nervous system conveys impulses from the CNS to the involuntary organs and smooth muscles of the body. The autonomic nervous system is again classified into sympathetic nervous system and parasympathetic nervous system.

The neuron as structural and functional unit of nervous system
A neuron is a tiny structure made up of three main parts, specifically, cell body, dendrites and axon.

Cell Body: The cell body possesses the cytoplasm with characteristic cell organelles and definite granular bodies known as Nissl's granules.

Dendrites: Dendrites are short fibres that branch repetitively and protrude out of the cell body. It is as well made up of Nissl's granules and is known as dendrites. These fibres transmit impulses towards the cell body.

Axon: The axon is an enlongated fibre, which is subdivided repeatedly at the distal end. Every branch ends like a bulb-like structure known as synaptic knob which contain synaptic vesicles bearing chemicals refered to as neurotransmitters. The axons convey nerve impulses away from the cell body to a synapse or to a neuro-muscular junction.

In respect of the number of axon and dendrites, the neurons are separated into three types:

(a) Multipolar: A neuron that contains one axon and two or more dendrites; located in the cerebral cortex,

(b) Bipolar: A neuron that contains one axon and one dendrite, located in the retina of eye and

(c) Unipolar : A neuron with cell body and one axon only; usually visible in the embryonic stage).

biology
The axon is made up of two types, namely, myelinated and nonmyelinated axon. The myelinated nerve fibres are covered with Schwann cells, which develop into a myelin sheath about the axon.

The gaps connecting two adjacent myelin sheaths are known as nodes of Ranvier. Myelinated nerve fibres are located in the spinal and cranial nerves.

Unmyelinated nerve fibre is covered by a Schwann cell that does not develop into a myelin sheath about the axon, and is frequently created in autonomous and the somatic nervous systems.

The human central nervous system
biology
The brain is the central information processing organ of our body, and functions as the 'command and control system'.

It regulates the voluntary movements, balance of the body, performance of vital involuntary organs like the lungs, heart, kidneys, etc., thermoregulation, hunger and thirst, circadian (24-hour) rhythms of our body, actions of quite a lot of endocrine glands and human actions.

It is as well the site for processing of vision, hearing, speech, memory, intelligence, emotions and thoughts.

The human brain is well sheltered by the skull. Inside the skull, the brain is enveloped and shielded by cranial meninges made up of an outer layer called dura mater, a very thin middle layer known as arachnoid and an inner layer touches the brain tissue known as the pia mater. The brain can be classified into three major parts:

(i) The Forebrain,

(ii)The Midbrain, and

(iii) The Hindbrain

biology
Forebrain
The forebrain is made up of the cerebrum, thalamus and hypothalamus. Cerebrum consists of the greater part of the human brain. A profound cleft splits the cerebrum longitudinally into two halves. These two halves are known as the left and right cerebral hemispheres.

The hemispheres are linked by a tract of nerve fibres known as corpus callosum.

The layer of cells which envelops the cerebral hemisphere is known as the cerebral cortex and is made up of high up folds. The cerebral cortex is known as the grey matter as a result of its greyish appearance. The neuron cell bodies are intense here resulting to that colour.

The cerebral cortex is composed of motor areas, sensory areas and large regions that are not classified as sensory or motor in function. These regions are known as the association areas. They are responsible for intricate functions such as intersensory associations, memory and communication.

Fibres of the ducts are covered with the myelin sheath, which makes up the inner part of cerebral hemisphere. They offer an opaque white look to the layer and, therefore are known as the white matter.

The cerebrum wraps just about a structure known as thalamus, which is the main coordinating centre for sensory and motor signals. An additional highly essential part of the brain –the hypothalamus is found at the base of the thalamus.

The hypothalamus has some centres which regulate the body temperature, desire for eating and drinking. It as well possesses many groups of neurosecretory cells, which secrete hormonesknown as the hypothalamic hormones.

The Midbrain
The midbrain lies between the thalamus/hypothalamus of the forebrain and pons of the hindbrain. A canal known as the cerebral aqueduct passes via the midbrain. The dorsal part of the midbrain made up of mainly four round protrusions or lobes known as corpora quadrigemina. Midbrain and hindbrain together act as the stem of the brain.

Hindbrain
The hindbrain is made up of the pons, cerebellum and medulla which as well known as the medulla oblongata. Pons is made up of fibre ducts that can be integrated to different parts of the brain.

Cerebellum has extremely complicated surface which enable it to provide the extra space needed for a lot of neurons. The medulla of the brain is linked to the spinal cord. The medulla contains centres which control respiration, cardiovascular reflexes and gastric secretions.

BIOLOGY: HORMONAL COORDINATION

from Femosky110 on 06/11/2020 12:09 PM

Hormonal coordination
All animals are made up of chemical components formed by exocrine or endocrine glands. Exocrine glands discharge their chemicals into ducts. The endocrine glands discharge their secretions, the hormones, openly into the blood-stream.

 

These hormones are afterward carried to other parts of the body known as target organs, where in very minute quantities, they bring out cellular responses.

Hormones are specifically-acting organic compounds with changeable chemical compositions, frequently steroids, proteins, peptides or amino acids. Based on their common roles, hormones are metabolic.

They either stimulate or retard metabolic activities. They are trophic-they regulate rate and secretion of other endocrine glands and morphogenetic –they influence rate and development of assorted parts.

Hormones are an additional means of coordination and communication. Together with the nervous system, the endocrine system forms a combined neuro-endocrine system. The hormone pathway is by the blood stream, while nervous pathway is by the neuron-reflex arc.

Glands are classified into two:
• Exocrine glands

• Endocrine glands

biology
The diagram of Exocrine and Endocrine Gland Showing Release of Secretion

Exocrine glands are those glands which pour their secretions into a duct. For instance, sweat glands, tear glands, and so on.

Endocrine glands are those glands which are abundantly filled with blood vessels and discharge their secretions directly into the blood vessels. The secretions get to their target through blood. These glands are known as the ductless glands as they do not possess ducts. Examples of ductless glands are: thyroid, adrenal, etc.

The control and coordination of the various bodily functions is as well done with the assistance of the endocrine system. The endocrine system exerts chemical power over the activities. These chemicals are secreted from organs known as endocrine glands.

The secretions of the endocrine glands are known as hormones. Hormones possess the following characteristics:

• they may be proteinaceous or non-proteinaceous -amino acids or steroids

• they are secreted as per requirement and not stored, only excreted

• their secretion may be controlled by nerves or by feedback effect

• they are transported through the blood

• they mainly give rise to long-term effects like growth, alteration in behaviour, etc.

• they do not catalyze or speed up any reactions

• they function by motivating or inhibiting the target organs.

Hormones can be defined as secretions that are discharged into blood in order to get to a particular target organ.

The human endocrine system is composed of the following glands:

• Hypothalamus

• Pineal

• Thyroid

• Parathyroid

• Pituitary

• Thymus

• Adrenal

• Pancreas

• Ovary in female

• Testes in male

biology
Position of Various Endocrine glands in the Human Body
Pituitary Gland
The pituitary gland also known as hypophysis is about the size of a large pea, situated beneath the brain, at the back the nasal cavity on the floor of the cranium. It is affixed by a stalk to the hypothalamus part of the brain on the undersurface of the cerebrum.

It is positioned in the sphenoid bone of the skull and is strictly invested by a connective tissue capsule.

biology
The location of Pituitary gland
The pituitary gland is referred to as the master endocrine gland due to its control over quite a few other endocrine glands.

Nevertheless, the body's actual master gland is the hypothalamus of the brain which takes charge of the secretions of the anterior pituitary by discharging and inhibiting hormones. Also, the pituitary itself is as well regulated by feedback from other glands.

The anterior lobe of the pituitary gland manufactures six dissimilar hormones. Among them, two function directly on body tissue (somatotrophic) and the other four controls the action of other endocrine organs.

The middle lobe known as pars intermedia discharges only one hormone known as intermedin. This hormone is in charge of the control of skin colors in lower vertebrates, but is vestigial in mammals, and has no function in humans.

The posterior lobe purpose is for storage and discharge point for two hormones secreted by the hypothalamus-neurosecretory cells and carried to the lobe via a linking duct referred to as the neurohypophysis).

The hormones of the Pituitary gland
The anterior lobe of the pituitary gland secretes six hormones. They are:

1. Thyroid stimulating hormone (TSH) or thyrotropin:
This hormone stimulates the secretion of thyroxin from the thyroid glands.

2. Somototropic or growth hormone:
This hormone controls growth of tissue, bone, muscles and internal organs, and as well influences metabolic processes. Hyper secretion in early on of life gives rise to a condition known as gigantism, and after the growth period in adult life it leads to acromegaly.

In acromegaly, excess secretion becomes visible after long bones have become hardened and the growth continues alone in certain bones, leading to lengthening of forelimbs, hindlimbs, and enlarged jaw and face.

Hypo secretion during growth years leads to pituitary infantilism, a kind of dwarfism, in which an adult is not above three or four feet tall, and is typically sexually immature.

3. Follicle stimulating hormone (FSH):
The follicle stimulating hormone excites the ovaries and testes. In females, it controls the development of grafian follicles or ova. In males, FSH influences spermatogenesis. That is the production of sperm by the seminiferous tubules of the testes.

4. Adrenocorticotropic hormone (ACTH):
This hormone motivates the adrenal cortex and controls the secretion from the adrenal glands.

5. Luteinizing hormone (LH) along with FSH:
This hormone in addition to FSH is responsible for the growth of ovarian follicles, release of mature ova or egg, development of the corpus luteum, production of progesterone and regulation of menstrual cycle in females. In males, LH stirs the testes to secrete testosterone or ICSH- interestitial cell stimulating hormone.

6. Prolactin kicks off the secretion of milk by the mammary glands after the birth of a baby. In the nonexistence of prolactin, milk secretion is put to a stop.

biology
Relationship between the pituitary and other endocrine glands

(---------In charge of feed back or inhibition)

(---------Pituitary Hormones that stimulate other glands)

The intermediate lobe of the pituitary gland:
The intermediate lobe secretes only one hormone, Melanophore Stimulating Hormone (MSH), or intermedin, which regulates the pigmentation of the skin in varieties of vertebrates. It darkens the color of the skin. Nevertheless it is of no significant purpose in humans.

The posterior lobe of the pituitary gland

The posterior lobe secretes the following hormones:

1. Oxytocin: This hormone is responsible for the contraction of the uterus in females during childbirth and also controls lactation or the release of milk.

2. Antidiuretic hormone (ADH) or Vasopressin: This hormone stimulates the kidneys to reabsorb more water, preventing too much water loss by urination. Chronic deficiency of ADH causes diabetes insipidus (polyuria), in which the patient feels extremely thirsty and passes a large amount of dilute urine.

The Thyroid Gland
biology
Position and Structure of thyroid gland:
All vertebrates have a pair of thyroid glands, situated in the neck just beneath the larynx or Adams apple. In human being, the thyroid gland is made up of two lobes-H-shaped that is positioned on either side of the trachea.

The two lobes are linked by a narrow isthmus that passes in front of the trachea. The gland differs in size with the variation in sexual development, diet and age.

The histology of the thyroid gland:
The thyroid gland is made up of a large number of round or oval follicles enclosed by connective tissue with a large number of blood vessels. Every one of the follicle is lined by one-cell thickcuboidal epithelial cells.

The cavities of the follicles are packed with viscous protein material known as colloid. The thyroid hormone, thyroxine contains iodine atoms. It is not stored in the cells of the thyroid, but in the colloid enriching the follicles.

The function of thyroid cells is to pull iodine out of the blood. This is then integrated into the protein thyroglobulin, which is subsequently hydrolyzed into the energetic hormone thyroxine.

Transverse section through the thyroid gland
The hormones of the Thyroid Hormones
Thyroid glands manufacture a hormone known as thyroxine. The secretion of thyroxin is restricted by TSH which is manufactured in the the pituitary. The hypo secretion or under secretion of thyroxine in a child leads to a condition known as cretinism.

This condition exhibits itself by retarded growth and development (dwarfism), a overhanging abdomen, mental retardation, puffy skin and stumpy metabolic rate.

In adults hypo function results in myxedema; the symptoms are a low metabolic rate, reduction in mental and physical activity, and increase in weight, puffy skin, a decrease in heart beat and body temperature, and loss of hair.

When hypofunction or under secretion leads to a deficiency of iodine in diet, swelling of the thyroid which leads to a condition known as simple goiter.

In a bid to grab more iodine from the blood, the gland enlarges follicles and grows excessively. Hypofunction can be cured with a supply of iodized salt, sea food, and by surgery foods with the aim of getting rid of excess thyroid tissue.

In amphibians, thyroxine plays a vital role during metamorphosis. If thyroid function of an embryo or young tadpole is repressed for instance by removing the thyroid gland, then the animal remains a tadpole permanently.

On the contrary, if a young tadpole is offered an excess of thyroxin, the larva metamorphoses ahead of time into a miniature froglet.

Hyperfunction leads to a boost on the rate of metabolism of about 40%, abundant sweating, augmented food intake but loss of weight, high blood pressure, nervous tension and muscular weakness.

Some patients with hyperthyroidism possess protruding eyeballs, a condition known as exophthalmos. The swelling of thyroid gland as a result of hypersecretion gives rise to exophthalmic goiter.

Another hormone manufactured by the thyroid gland is calcitonin. It regulates the level of blood calcium. Calcitonin is discharged by the thyroid when there is an elevated level of calcium in the blood. The surplus Calcium is next reduced and dropped in bones.

To summarize all we have discussed:
• The chemicals controlling the majority systems of vertebrates are made up of secretory cells, which are structured into exocrine and endocrine glands. Endocrine glands function is to secrete hormone into the blood. A hormone is a biological molecule (chemical transmitter) which works on target organs and elicits a lot of cellular activities.

• The key endocrine organs are the hypothalamus, pituitary gland, thyroid gland, parathyroids, adrenal glands, islets of Langerhans, testis and ovary.

• The pituitary gland is referred to as the master endocrine gland. It is positioned beneath the brain, and posseses three divisions-the anterior lobe, middle lobe and posterior lobe.

• The anterior lobe secretes six hormones-the TSH, somatotrophic hormone, FSH, ACTH, LH and prolactin, whereas the posterior lobe secretes oxytocin and antidiuretic hormone (ADH). Middle lobe has no function in humans.

• The malfunctions of the pituitary cause various conditions like gigantism, acromegaly, pituitary infantilism, and diabetes insipidus and so on

• The thyroid gland is situated in the neck and is made up of thyroid follicles which contain colloid.

• The Thyroid gland secretes the hormone thyroxin; hypofunctin Hyperthyroidism leads to exophthalmos and exophthalmic goiter.

• The hormone calcitonin regulates the blood calcium level.

• The majority of biological or chemical control systems function on feed back