Reproduction in The Animal Kingdom

Identify ways by which animal reproduce, differentiate between sexual and asexual reproduction and explain the process of fertilization.

Living things which includes people, plants and animals, can produce their own kind. The process is called reproduction. You do not see a cow give birth to a kitten, or a butterfly give birth to a duck. Just as a photocopier prints the same copy of a page, animals reproduce the same kind of animal. A cat gives birth to cats, a frog gives birth to frogs, a butterfly produces butterflies.

Reproduction is the creation of new individuals from existing individuals. The existing individuals are called parents. The new individuals are called offspring. Thus, your father and mother are your parents, and you are their offspring.

Animals are born, they grow up, and then they die. But they can live beyond time by producing offspring that they are very much like themselves. This is the benefit that living things derive from reproduction. There are two primary ways of reproduction, sexual and asexual. Sexual reproduction involves the union of two special cells called the sex cells from male and female animals. Reproduction without sex cells is called asexual reproduction. The letter “a” attached to the word sexual means “none” or “without”.

Asexual Reproduction

As mentioned, in asexual reproduction, no sex cells are involved, and only one individual produces the offspring. Many invertebrates or soft bodied animals reproduce by asexual reproduction. Four forms of asexual reproduction are described in this article, budding, and formation of gemmules, fragmentation and regeneration.

Budding

In budding, an offspring grows out of the body of a parent. An example of an animal that reproduces this way if hydra. This animal lives in water. Using a magnifying glass, you can look for hydra in a pond. You may find it clinging to a plant such as hydrilla. You can put the plant in a jar of water, and observe how hydra reproduce.

Gemmule Formation

Gemmules are internal buds. The parent animal releases a mass of special cells that can develop into an offspring. An example of an animal that reproduces this way is the sponge. Sponges also live in water.

Fragmentation

In this form of asexual reproduction, the body of the parent breaks into distinct pieces or fragments. Each piece can develop into an offspring. An example of an animal that can reproduce this way is planaria. However, planarians often undergo sexual reproduction. Planaria is one king of flatworm.

Regeneration

In regeneration, a piece of the parent animal gets detached. This piece can grow and develop into a whole new individual. It regenerates (or generates again) all the missing parts of the body. One group of invertebrates, called echinoderms, reproduces this way. An example is the sea star or star fish.

Did you know that if you try to catch a lizard by grabbing its tail, the animal will break its tail and escape? The piece of tail will be left with you. The lizard will grow another tail. This is not reproduction. Why? Because no new lizard is produced. The cut tail does not become another lizard.

Sexual Reproduction

In sexual reproduction, two individuals produce offspring that have characteristics from both parents. As mentioned earlier, this kind of reproduction involved the fusion of sex cells (also called gametes). There are two kinds, the egg cell from the female parent and the sperm cell from the male parent. When the two sex cells unite, fertilization occurs.

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