The world of living

Learn about living beings, their life processes, and reproduction.

Insulin: Maintaining glucose homeostasis

Insulin is a hormone produced by the beta cells of the pancreas. This hormone is primarily responsible for maintaining glucose homoeostasis in the human body.

The human body depends on glucose for most of its energy needs. In fact, glucose is the primary source of energy for all living cells. However, most human tissues cannot utilise glucose in the absence of insulin. The brain is an exception. The brain can use glucose even in the absence of insulin.

Let us briefly discuss human digestion. The food we eat consists of carbohydrates, proteins and fats. The amylase present in saliva starts the digestion of carbohydrates in food. The pancreatic amylase completes the process of digestion of carbohydrates in the small intestine. The pancreatic amylase completely breaks down the carbohydrates into glucose and fructose. Glucose and fructose are six carbon molecules that are the simplest of the sugars. Glucose enters the bloodstream after absorption from the small intestine.?

Blood then supplies glucose to tissues, and the excess glucose is converted into glycogen in the liver. Glycogen is the energy reserve of the body. When the body is fasting, glycogen is degraded into glucose and utilised by the cells.

As soon as glucose enters the bloodstream, it stimulates the release of insulin from the beta cells of the pancreas.Amino acids also stimulate the release of this hormone from the pancreas (in fact, amino acids are a more potent stimulus).

The insulin acts primarily on the liver, muscle and adipose tissues. Other tissues are not dependent?on this hormone to utilise glucose.

Structure

Insulin is a peptide hormone consisting of two polypeptide chains- A & B. A disulphide bond links the two chains. It is first synthesised as a single polypeptide chain- preproinsulin. This polypeptide chain is processed by the endoplasmic reticulum to produce a 39 amino acid residue. During this process, a polypeptide chain called C-peptide is released. We can check the functioning of the pancreas by checking the level of C-peptide in the blood.

The synthesis and release of this hormone are regulated at several levels- transcription of the gene, translation and post-translational modifications.

Effects

Insulin is an anabolic hormone. It induces the synthesis of many substances. It also regulates growth. The following effects are known:-

  1. Glycogen synthesis- The cells of the liver and the muscles are the primary targets of insulin. Insulin promotes uptake of glucose by the hepatocytes and myocytes. It also promotes synthesis of glycogen in the liver and muscle. When the body is fasting, the blood level of insulin decreases and this promotes degradation of glycogen. The degradation of glycogen maintains blood glucose at a constant level.

  2. Lipid synthesis- This hormone acts on the adipocytes or fat cells and promotes synthesis of triglycerides and fatty acids. Treatment with insulin leads to weight gain due to increased production of fat by adipose tissue (apart fro fluid retention). It also promotes esterification of fatty acids.

  3. Decreases the degradation of proteins

  4. Decreased degradation of fats

  5. Decreases production of glucose- Apart from degradation of glycogen, the human body has mechanisms to produce glucose (gluconeogenesis) from amino acids. Gluconeogenesis helps maintain blood glucose levels when the body is fasting, and the glycogen stores are depleted.?

  6. Increases uptake of amino acids. Also promotes the production of proteins.

  7. Increased potassium uptake by cells- Insulin promotes uptake of potassium by the cells. Therefore, serum potassium levels can fall following treatment with insulin. The ability to reduce serum potassium levels is harnessed therapeutically to reduce elevated serum potassium. This hormone increases uptake of potassium by increasing the concentration of Na-K ATAase on the cell surface by translocation of the receptors from the cytosol to the cell membrane.

  8. Effect on arterial muscles ? Has a significant impact on the arterial muscles. This hormone causes relaxation of the arterial muscles, thus, reducing arterial tone. The reduction in the arterial tone improves microcirculation.

  9. Increases secretion of hydrochloric acid in the stomach

  10. Reduces sodium excretion by the kidneys. Therefore, treatment with insulin can lead to fluid retention.

Disorders due to over or underproduction of insulin

Insulin plays a critical role in glucose homoeostasis. Therefore, over or underproduction can result in many disorders. Diabetes Mellitus is a disorder caused by underproduction. Lack of insulin leads to impaired utilisation of glucose by body tissues. Therefore, blood glucose levels rise and result in some problems- kidney damage, damage to blood vessels and nerves, etc.?

Until the development of injectable insulin, diabetes was a disease with high morbidity and mortality. In 1920. Scientists Banting and Best purified insulin and postulated that injections can be used to treat diabetes. Use of insulin to treat diabetes has revolutionised the management of this chronic disorder. For their work, Banting and Best were awarded the Nobel Prize in Physiology in 1923.

Overproduction leads to dropping in blood glucose levels. When blood glucose level drops (hypoglycaemia) below a specified threshold symptoms like weakness, dizziness, palpitations, sweating and seizures can occur. Overproduction is the hallmark?of a disorder?called insulinoma.

Sense of smell: Dogs Vs. Humans

The sense of smell is one of the five senses. The sense of smell is an essential feeling and without it life would be difficult for humans. Can you think of what would happen if humans lost the sense of smell?

What happens when your nose is blocked due to cold? You lose the feeling of smell. Loss of sense of smell also leads to altered taste. Food that used to feel good to you no longer feels as good! So, the feeling of smell is necessary for the sense of taste as well.

So, which animal has the best sense of smell?

I am sure you have heard this phrase before- sniff like a bloodhound. Dogs have been used for many centuries as a hunting aid. Dogs are used to sniff out drugs, explosives and humans. So, what is so special about dogs that make them suitable for these duties?

Dogs have an incredible sense of smell. A dog has over 220 million smells receptors. In contrast, humans only have five million olfactory receptors. The bloodhound has as many as three hundred million receptors for smell.

The dog’s olfactory comprises of two nares, nasal cavity, a specialised layer of olfactory epithelium and a specialised organ- the vomeronasal organ.?

sense of smell

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Air enters through the nares. Odours in the inspired air are ascertained by the olfactory receptors in the specialised olfactory epithelium lining the nasal cavity. Each olfactory receptor stimulates an olfactory nerve. The odours then reach the olfactory lobe by travelling through the olfactory nerve.

The vomeronasal organ is a pair of elongated fluid-filled sac that opens into the mouth or the nose. The olfactory receptors in the vomeronasal organ are different from those in the nasal cavity. The olfactory neurones in the nasal cavity have cilia while those (Neurones) in the vomeronasal cavity usually have microvilli. Also, the neurones in the vomeronasal organ are specialised structures that are necessary for detection of pheromones. The vomeronasal organ is connected to the hypothalamus in the dog’s brain. The hypothalamus regulates many sexual and social behaviours.

So, have you seen a dog sniff? Sniffing is a technique that dogs use to maximise the detection of odours. Sniffing is a series of rapid inhalation and exhalation that is a disruption of the normal breathing pattern. Sniffing creates a pocket within the nasal cavity. This pocket allows accumulation of odour molecules and improves recognition of odours.

Difference between human and canine olfaction

There are many differences between humans and dogs when it comes to the sense of smell. As discussed before, the number of olfactory receptors is huge in dogs when compared to humans. Dogs are also more proficient in detecting pheromones.

Also, dogs have a very well developed olfactory lobe that helps with recognition of smells.

Therefore, your dog is far more proficient in recognising smells than you. However, recent research suggests that human sense of smell is better than we imagined. Although the number of olfactory receptors is lesser than that of a dog, we humans have a greater variety in terms of olfactory receptors. Recent studies suggest that there are over four hundred types of smell receptors in the humans. These (receptor) acting in various permutations and combinations can detect as many as one trillion smells (Nature.?doi:10.1038/nature.2014.14904 ).

Fungi: The scavengers of the natural world

Fungi are a group of organisms that play a vital role in the natural world. Fungi are the scavengers of the natural world. They (fungi) range in complexity from simple single-celled organisms like yeast to complex multi-cellular organisms like mushrooms.

The fungus is abundant and omnipresent in the natural world. The air we breathe, the water we drink and the soil, all contain fungus. Apart from being natural scavengers, the fungus is also important in medicine. Fungus cause many diseases. The most common infections caused by fungus include skin and hair infections. However, the fungus can also cause serious infections like pneumonia and bloodstream infections, especially in persons with compromised immunity.

What is unique about fungus?

Till 1969, fungi were considered to be a part of the plant kingdom. However, research showed that fungi are different from other animals and plants. The cell walls of fungi contain a substance- chitin. The cell wall or membrane of plants and animals does not contain chitin. Therefore, fungi are now a separate kingdom.

How do fungi derive their nutrition?

Like other animals, fungi are also heterotrophs. That means that they (fungi) derive their nutrition from the natural world. As discussed before, a fungus is the first scavengers of the natural world. Therefore, you are likely to see them near rotting organic matter, like waste dumps or even in your garden.

What are the types of fungi?

There are three major types:-

  1. Single-celled yeasts

  2. Filamentous Multicellular moulds like Aspergillus or Rhizopus: – The basic unit of moulds is the hyphae. The hypha is a long filament that grows and repeatedly divides, forming a bunch of intervened filaments- the mycelium.

  3. Mushrooms- multicellular, filamentous fungus that form large fruiting bodies: – Mushrooms are also made up of hyphae. The body of the mushrooms contains many hyphae that are tightly packed to form the umbrella-like structure that grows overground.

Most of the medically important fungus belong to the category of yeasts or moulds. On the other hand, the commercially important fungus belongs to the class of mushrooms (not in the strictest sense, fungi like yeast are also important commercially, like in bakeries and breweries).

fungi

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How do fungi reproduce?

Fungus reproduces by spore formation. Spore formation is a method of asexual reproduction. Spores are specialised structures that are resistant to sunlight and drying. Therefore, they can persist in the environment for many days or even months. These spores can germinate when the condition is favourable to produce a daughter fungus. You must have seen a powdery substance that sticks to all surfaces during the rainy season. The powdery substance is a fungus. During rains, the atmosphere is high in moisture. Therefore, this is a favourable time for fungal spores to germinate. The fungal spores that are present in the air settle on moist surfaces and then germinate, thus forming the powdery substance. The same principle is true for mushrooms as well.

Thus, the fungus is a ubiquitous organism that play a vital role in the natural world. The fungus has many important roles in medicine, everyday life and many commercial applications. Mycology is the study of fungus.

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Mitochondria- The powerhouse of the cell

Mitochondria are cellular structures that generate the energy required by cells for life processes. These organelles are mostly found in Eukaryotic cells. Their name comes from the Greek word- ????? (mitos or thread) and ???????? (chondrion or granular).

The number of mitochondria can vary from a few hundred to more than 2000/per cell (hepatocytes). The number and distribution of mitochondria are proportional to the energy requirement of the cells. Cells like red muscles that do sustained work are abundant in mitochondria. Similarly, the liver has high energy demand. Therefore, each hepatocyte can have in excess of 2000 . On the other hand, the white muscles have a small number of these organelles despite consuming a large amount of energy. Most of the energy used by the white muscles comes from anaerobic metabolism of glycogen. Therefore, the number of mitochondria is also small. Some cells like the red blood cells do not contain any mitochondria.

We have previously learned about aerobic and anaerobic metabolism. Mitochondria are exclusively involved in aerobic metabolism.

These organelles are 0.5 to 1.0 micrometres in size. They have a double layer of lipid membrane and the proteins and enzymes of the mitochondrial electron transport system are embedded within the two layers of the mitochondrial membrane.

mitochondria

Glucose, the principal source of energy for the cell is degraded in the cytosol by anaerobic metabolism to produce pyruvate. The pyruvate is taken up by the mitochondrial membrane by an active process and this (pyruvate) is further degraded by the enzymes in the mitochondrial matrix. The process of degradation of pyruvate results in the production of water, carbon dioxide and energy. The energy released by the breakdown of glucose is captured in the phosphate bonds of Adenosine triphosphate (ATP). ATP is used by the cell for its energy requirements. As oxygen is required for this process, this (breakdown of glucose) is called as aerobic metabolism or respiration.

Mitochondria are unique in many aspects. They can replicate, i.e. it can divide and reproduce in response to increasing energy demand. They also contain DNA, the genetic code of life. Defects or problems in the mitochondrial DNA can cause many diseases- mitochondrial disease. The musculoskeletal system is commonly involved by disorders of the mitochondria. These disorders are called mitochondrial myopathies. The pattern of inheritance of mitochondrial disorders is also unique. As the zygote (the fertilised ovum) receives all its mitochondria from the mother, all mitochondrial disorders are transferred from the mother to the offspring.

In addition to generating energy, these organelles also regulate many cellular functions like cell signalling, differentiation, control of cell cycle and apoptosis.

In conclusion, mitochondria are vital organelles that generate energy for maintenance of life processes.

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Heredity- Mendelian Genetics

Do you know what is heredity? We have heard of the word hereditary. What does this word mean? The word hereditary is derived from the word heredity. The word hereditary refers to some trait or characteristic or even an item that is inherited from our parents.

In the article on reproduction, we had learned that both the parents contribute an equal amount of genetic material to the offspring. Thus, for each trait, we inherit one copy from our mother and one from our father. So, which trait will be expressed in the offspring? Are there any rules that determine which character is expressed and to what extent?

These were some of the questions on heredity that were answered by Gregor Mendel, an Austrian scientist. Mendel is often hailed as the father of modern genetics. He performed many experiments to elucidate the nature of heredity. He took pea plants with many different characteristics like round/wrinkled seeds, tall/short plants, white/violet flowers, etc. He cross-bred these plants and noted the features of the offspring.

In the first generation offspring, he noted that there were no midway characteristics. For e.g. when a tall plant was bred with a short plant, the offspring was all tall. When this offspring was allowed to produce by self-pollination, Mendel noted that a quarter of the offspring was short while ? of the offspring were tall in character. Therefore, he inferred that that the 1st generation offspring or F1 had inherited the tall and short trait from its parents, but only the tall character was manifest in the 1st generation of offspring. He called the tall trait as dominant trait while the short characteristic was the recessive trait.

heredity

Mendelian inheritance

A question naturally arises- why were a quarter of plants in the 2nd generation short?

Mendel postulated that the 1st generation offspring would have inherited both traits (tall and short) from its parents. We shall call these traits T & t. So, the tall parent is TT, and the short parent is tt.

The first generation offspring is Tt. When this plant reproduces by self-pollination, then there are four possible combinations that can be produced- TT, Tt, Tt and tt. Therefore, ? of the 2nd generation of plants are short. The characteristic T & t are now referred to as genes.

Based on his experiments with peas, Mendel proposed a set of rules of heredity. Organisms that reproduce by these rules of heredity are said to follow Mendelian genetics. However, not all traits are inherited in accordance with Mendel?s laws. We will learn about non-Mendelian inheritance in another article.

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The human eye

The human eye is one of the five sense organs. It perceives the meaning of light. It is because of the human eye that we can see the varied and beautiful world around us. There are two eyes, located within a bony socket called the orbit. The bones of the skull and face form the boundaries of the orbital cavity. Within the orbital cavity, lies the eye, the extra-ocular muscles, loose connective tissue, blood vessels, nerves and the optic nerve.

The outermost covering of the human eyes is sclera, a thick, fibrous sheath. It functions to protect the eyeball from injury. The white colour of the eye is because of the sclera.

The cornea is the transparent portion of the eye that light to enter the eye. ?In previous chapters, we have learned about refraction. The cornea can be considered to be a refractive medium that brings the light rays to focus. Most of the refraction occurs at the out surface of the cornea.

human eye

Human eye: A cross-section.

The Iris, a muscular diaphragm, controls the entry of light into the human eye. How does the Iris monitor the entry of light into the human eye? Iris does so by controlling the size of the pupil, a small aperture. Have you noted what happens when you shine a torch into the eye? The pupil constricts, thus reducing the amount of light entering the human eye.

Immediately behind the Iris, lies the lens. The lens is flattened towards the front and it is suspended in the eye by muscles called the ciliary muscles. These muscles help with the process of adaptation. The ciliary muscles can increase or decrease the focal length of the lens to enable the eye to focus on objects across a broad range of focal lengths.

The light from a source is refracted by the cornea and the lens and is brought to focus on the light sensitive layer of the human eye- the retina.The retina contains two types light sensitive cells- the rods and cones. The rods, numbering 120 million are more numerous and are more sensitive to light. On the other hand, cones, numbering 6-7 million sense colour. The cones are concentrated around the centre of the retina, an area called the optic disc. Within the optic disc lies the fovea. Cones are present in the highest concentration in the fovea. Therefore, colour perception is best at the fovea.

The light that is refracted by the cornea and the lens forms an inverted real image over the retina. The image is transmitted to the occipital lobe of the brain by the visual pathways comprising the two optic nerves, optic tracts and their projections. The human brain processes the signals. Therefore, we only see the erect images.

Thus, the human eye behaves like a camera for all purposes. There is one difference though- the human eye can appreciate the depth of field, which a camera sorely lacks.

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Nine cool facts about the Human Brain

The human brain is the heaviest organ in the human body. It is one of the most complex and least understood parts of the human body. Here are a few cool?facts that we do know about the human brain:-

  1. What happens when you touch a hot object? You will reflexly withdraw your hands, and it takes a split second for you to do this action. But in this split second, information about the hot object is first sent to the spinal cord. The spinal cord processes this information and returns a set of instructions to the muscles in your hands. So, how fast do these impulses travel? In some conducting nerve fibres, the electrical impulses can travel at speeds as fast as 170 miles/sec. Thus, the human nervous system is as fast as a high-end luxury car! However, not all nerves carry impulses at such high speeds. The unmyelinated neurons (myelin is a thin coating over the axons) conduct impulses are very slow speeds (0.5 m/sec). These neurons predominantly conduct pain impulses.

  2. The human brain is always active. It is functioning even when we sleep. The electrical energy generated by the human brain is enough to light up a 10-watt bulb. Thus, the image of a bulb lighting up when we think is not far off the mark!

  3. The human brain is a vast storehouse of information. The estimated storage capacity of the human mind is between 3 to 1000 terabytes (nobody knows). This storage capacity is five times the information contained in the Encyclopedia Britannica. The National Archives of UK, which stores over 900 years of historical records only occupies seventy terabytes of space. Therefore, there is no such thing as overloading the human brain!

  4. The human brain is the most active organ in the human body. It receives 20% of the cardiac output, and it consumes nearly 20% of the oxygen taken in by the body. The human brain is extremely sensitive to oxygen deprivation. The neurons in the brain will start dying after four minutes of oxygen deprivation. You will now appreciate why deep breathing is so refreshing to the mind!

  5. At what time of the day is the brain most active? Most of us would say- when we are awake. But, this is not true. The human brain is more active when we sleep than when awake. We do not know the exact reason, but research has shown that short-term memory is converted to long-term memory during sleep. Also, the neurons repair themselves when we are sleeping. That is why a good night sleep is recommended for students.

  6. All people have dreams, but only a few can recollect their thoughts. There is nothing unusual about this as the average duration of a dream is about 2-3 seconds only. We can have hundreds of dreams in one night. Research has also shown that people with higher I.Q. Tend to have more dreams.

  7. For many years, we believed that neurons cannot regenerate. Recent research has shown that this may not be entirely accurate. While neurons do not regenerate like other tissues, they have the capacity to take over the function of damaged neurons. This feature is called as neural plasticity.

  8. All pain impulses converge at the brain, but the majority of the brain parenchyma does not feel pain. That is why it is possible to perform brain surgery without anaesthesia. The only pain-sensitive structures in the brain are the blood vessels and the dura (a thick fibrous sheet that covers the brain and protects it).

  9. Over 80% of the brain is composed of water. The living brain has jelly like consistency. When we do not drink enough water, the brain gets dehydrated. We can then suffer from headaches and inability to concentrate. Therefore, it is important to drink enough water.

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Sexual reproduction in plants.

We have learned in previous articles about asexual reproduction in plants. We shall learn about sexual reproduction in plants.

What do you know about sexual reproduction in plants?

Plants reproduce sexually for the same reasons as any other organism- to maintain genetic diversity. Sexual reproduction in plants is limited to flowering plants. Flowering plants are those plants that produce flowers. Have you ever wondered why flowers are so colourful or smell so good?

Plants invest a lot of energy in producing flowers. The flowers are bright to attract insects and bees. These insects and bees transport the pollen from one flower to another, thus, helping with the process of sexual reproduction in plants.

Flowers have only one role- sexual reproduction in plants. We have studied about the parts of a flower previously. Can you recollect the parts of a flower?

sexual reproduction in plants

Flowers are composed of sepals, petals, stamens and carpels. The sepals and petals protect the stamens and carpels. The stamens and carpels are the reproductive organs of the plant. The stamens are the male reproductive organs and the carpel is the female reproductive organ of a plant.

Plants are of two types- unisexual and bisexual.

Unisexual Plants– These plants have flowers that comprise only of stamens or carpels. Examples include papaya and watermelon. Therefore, these plants can only be fertilised by pollen from another plant.

Bisexual plants- Flowers of these plants contain both stamens and carpels. Thus, these plants can be fertilised by pollen from the same plant or another plant. Examples include Hibiscus and mustard.

sexual reproduction in plants

Stamens produce pollen. Pollen is the sticky, yellow powder that sticks to our hands if we touch it. The powder corresponds to the male gamete of the plant. When bees and other insects come in contact with the pollen, the pollen sticks to their feet and are transported to other flowers. This process is called pollination. Bees play a critical role in pollination. We will discuss the role of bees in agriculture in another article.

The carpel is the female reproductive organ of the plant. The carpel comprises of the ovary, the style and the stigma. The ovary is the bottom, swollen part of the carpel. The style is an elongated tube that functions to transport the pollen and the stigma is the sticky top part of the carpel. Pollen is deposited on the stigma and it travels through the style to reach the ovary. Here, it fuses with the female gamete to produce seeds. Once a flower is pollinated, the rest of the parts of the flower shrivel and fall off.

There are two terms one usually comes across about pollination:-

Self-pollination- Pollen from the same plant fertilise the ovule.

Cross-pollination– Pollen from another plant fertilises the ovule.

To summarise, sexual reproduction in plants is vital for maintaining genetic diversity and forms the basis of most agricultural innovation. Flowers are the reproductive organs of the plants and these flowers can either be fertilised by pollen from the same plant or another plant.

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Sexual Reproduction : Why and how!

What is the significance of sexual reproduction?

In the previous article on breeding we learned about the various methods of asexual reproduction. So, what are the limitations of asexual reproduction?

During the process of reproduction, the genetic code present in the DNA is copied. This process is quite efficient with a tiny margin of error. However, errors do happen, and these mistakes are the source of genetic variation in nature. Genetic variation is necessary for propagation and survival of the species. In asexual reproduction, as each progeny is an exact copy of the parent, the scope of genetic variation is quite limited. Therefore, to ensure genetic variation, organisms have developed the sexual form of reproduction.

Apart from the most primitive form of life like eukaryotes and prokaryotes, most plants and animals reproduce sexually. So, what does sexual reproduction mean?

Can a hen produce a chick by herself? No, the chicken needs the rooster to produce a chick. Similarly, a cow cannot produce a calf by herself. She needs a bull to produce progeny. Thus, in sexual reproduction, both males and females are required to produce an offspring.

The male and female of a species produce gametes. Gametes are specialised cells that combine to produce progeny. The male gamete is usually mobile while the female gamete is stationary and has stores of energy. The male gamete is also called sperm, and the female gamete is called ova or ovum.

In sexual reproduction, the male and female gamete combine to produce a zygote. However, this creates a unique problem. Each time the gametes fuse, the amount of DNA would double. If this process continues, then the amount of DNA will grow exponentially and over a period there will only be DNA on earth.

So, how does nature work around this problem?

Simple, nature keeps the amount of DNA constant across generations by halving the amount of DNA present in gametes. For example, all human cells contain 46 chromosomes. However, the gametes i.e. Sperm and Ova contain only 23 chromosomes.

When the sperm combines with the Ovum, the number of chromosomes is restored back to 46. Thus, the amount of DNA is preserved across generations.

Thus, the non-reproductive cells have twice the amount of DNA as compared with gametes. The non-reproductive cells are diploid, and the gametes are haploid.

As sexual reproduction requires the presence of male and female gametes, organisms have well developed male and female reproductive organs. The male and female reproductive organs are the cause of the differences in the bodies of the male and female organisms.

We shall learn more about sexual reproduction in plants and humans in another article.

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Modes of Asexual Reproduction

In asexual reproduction, the offspring inherits its genetic material from a single parent. Asexual reproduction is the most common method of reproduction. This method of reproduction is primarily seen in the less evolved organisms like bacteria, fungi and protozoa. However, many plants also reproduce by asexual means. In the previous article on modes of reproduction, we had learned about the different types of reproduction. We learned that sexual reproduction maintains genetic diversity, while asexual reproduction is useful for rapid growth in population. In this article, I shall discuss the various types of asexual reproduction.

Fission

We had learned about nuclear fission in the article on nuclear energy. Can you recollect what a nuclear fission is? Nuclear fission is the process by which an atom splits into two atoms. Asexual reproduction by fission is similar to a nuclear fission. However, unlike nuclear fission, where the daughter atoms are different to the parent molecule, the daughter cells are entirely analogous to the parent cell. Bacteria and amoeba are some of the organisms that reproduce through fission. Fission is of two types- binary and multiple. Organisms like Leishmania (the causative agent of Kala-Azar) split into two exact halves while the malarial parasite splits into multiple daughter cells. The former is binary fission and the latter is multiple fission.

Budding

Have you seen how a hydra reproduces? Hydra reproduces by budding. There is initially a small outgrowth from the body of the hydra that grows into a little hydra. When the daughter hydra is fully developed, it detaches from the parent and becomes an independent individual.

Vegetative Propagation

How many of you have a garden at home? If not a garden, many of us would have grown plants in pots. My favourite flower is the rose. Do you know how the rose is cultivated? You can just cut a twig from a rose plant, plant it in soil and it will grow into another rose plant. Can you think of any other plant that can be grown this way? Banana, jasmine and oranges can all be grown through this method. Vegetative propagation is the method by which the various parts of an individual plant- roots, shoots, and leaves, under proper conditions, can grow into an independent organism.

Spore formation

The Rhizopus is a species of fungi that reproduces by spore formation. The spores are blob-like structures present at the tip of the Rhizopus. These spores contain sporangia; cells that are capable of producing new rhizopus. These spores are shed in the atmosphere and winds carry these spores to distant areas where the sporangia can grow into new rhizopus.

So, how have we adapted asexual reproduction to fulfil our requirements? We have harnessed technologies like tissue culture; where cells from one plant can be grown in artificial media under disease-free conditions. It is now very easy to produce a large number of saplings with minimum effort using tissue culture. We can also improve the yield of crops by a technique of grafting.

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