Class 8 Science chapter on Reproduction in Animals elaborates on the major forms of reproduction in different animals. The mechanism of reproducing individuals of the same species is known as reproduction. A bulk of species replicate by mating, which increases genetic diversity. Males and females have gonads, which are independent sex organs. These gonads contain gametes, which combine together to form the zygote, a single cell. Earthworms, snails, slugs, and a few other species are hermaphrodites, meaning they have both male and female reproductive organs in the same body. Read this blog to find important study notes on Reproduction in Animals Class 10.
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Table of contents
Modes of Reproduction in Animals
The first section of Reproduction in Animals Class 10 talks about the forms of animal reproduction. There are various forms of reproduction depending on the number of parents involved. There are two forms of reproduction in animals:
- Sexual Reproduction
- Asexual Reproduction
Sexual Reproduction in Animals
Sexual reproduction is the result of male and female gametes fusing together to create a new organism. Let’s take a look at the human reproductive organs and how they help in fertility as per Class 8 chapter on Reproduction in Animals.
Male Reproductive Organs
A pair of testes, two sperm ducts, and a penis are among the male reproductive organs. Sperm are male gametes formed by the testes. The testes contain millions of sperm, as shown in the illustration below of a sperm. Despite their tiny scale, sperm have a head, a middle section, and a tail. Each sperm is, in fact, a single cell with all of the normal cell components.
Female Reproductive Organs
Moving to the next topic in Class 8 Reproduction in Animals, the female reproductive organs constitute a pair of ovaries, oviducts, and the uterus. Ovary creates ova, which are feminine gametes. Per month, one of the ovaries releases a single matured egg into the oviduct in humans. The uterus is the area of the body where the baby develops. An egg is a single cell, much like sperm.
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Fertilisation is another important topic you will study in Class 8 Reproduction in Animals. There are millions of sperm in the sperm. During fertilisation, a single sperm fuses with the ova. The egg and sperm nuclei join together to create a new nucleus. As a result, a zygote is formed.
There are two methods of fertilisation:
Internal fertilisation is the process of fertilisation that takes place within the female’s body. People, pigs, dogs, and other species are examples. In terrestrial animals, this approach is more common. Some marine species, however, also use this technique. This may happen either by the male directly injecting sperm into the female reproductive tract or by the male depositing sperm in the area, which the female picks up and injects into her reproductive tract.
They are three ways by which babies are produced by internal fertilization:
- Oviparity– The fertilised eggs are laid outdoors, where the yolk provides nutrition.
- Ovoviviparity– The fertilised eggs are stored in the female’s shell, where the yolk provides nourishment. Before the eggs are hatched, they are laid.
- Viviparity– Instead of hatching from the eggs, the offspring are born alive. The mother provides them with food. Mammals are examples of this.
External fertilisation refers to fertilisation that happens outside of the person. Frogs and fish, for example. The majority of fertilisation occurs during the spawning period. Spawning is triggered by environmental signals such as water temperature.
Oviparous and viviparous animals are two separate classes of animals categorised according to how they fertilise their offspring. The main difference between oviparous and viviparous animals are listed below:
|Definition||Egg-laying animals are called Oviparous.||Animals that give birth to the young ones are called Viviparous.|
|Fertilization||Fertilization can be either internal or external.||Fertilization can only be internal.|
|Development of embryo||Nutrient is provided by the egg yolk.||Nutrient is provided by the mother through the placenta|
|Development of zygote||The embryo develops very little or not at all inside the mother.||The embryo grows completely inside the mother’s womb.|
|Chances of Survival||Since the eggs are laid outside the womb, there are less chances of survival.||Since the young one is safe within the mother, it has a better chance of surviving.|
|Examples||Insects, hens, fish, amphibians, etc.||Humans, dogs, cats, horses, etc.|
The zygote separates into a ball of cells after repeated divisions. This is known as the developing embryo. These cells differentiate into respective tissues and organs. The embryo gets implanted in the uterine wall. This process is known as implantation.
A foetus is formed when all of the embryo’s body parts become apparent. In humans, the foetus develops after nine months.
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Asexual Reproduction in Animals:
Asexual reproduction is the second most common form of reproduction in animals, after sexual reproduction. Lower species and unicellular microbes are the most common examples of this form of reproduction.
It is the mechanism by which a new entity is created without the presence of the gamete formation by a single parent. Genetically and morphologically, the individuals produced are alike. It’s found in single-celled species. There is no fertilisation and the cells separate by mitotic division. The separation happens very fast.
Types Of Asexual Reproduction
Let’s take a look at the types of asexual reproduction as elaborated in Class 8 Reproduction in Animals:
Amoeba and euglena are examples of Binary Fission. The parent cell goes through mitosis and grows in size. The nucleus separates as well. Two equivalent daughter cells, each with a nucleus, are obtained. Binary fission is the most common form of reproduction for prokaryotes including bacteria.
In this situation, the offspring emerges from the parent’s womb. When it matures, it stays bound to the parent. It separates from the parent after maturation and survives as a separate entity. Hydras use this method of reproduction the most.
When the body of an entity, such as a Planarian, splits into many parts, each piece develops into an independent offspring. Fragmentation is the term for this. It may happen as a result of predator-caused harm or as a natural form of reproduction. A fractured arm develops into a full organism in a few species, such as the sea star.
It is a form of fragmentation that is found mainly in Echinoderms. When a part of an individual, such as an arm, splits from its parent body, it transforms into a different entity. This is referred to as regeneration.
This is an asexual reproduction method in which the egg forms without being fertilised. Bees, wasps, ants, aphids, rotifers, and other insects engage in this process. Hemiploid males are produced by ants, wasps, and bees. When females were separated from males, parthenogenesis was found in a few vertebrates such as hammerhead sharks, Komodo dragons, and blacktop sharks.
We hope that this blog has provided you with a deeper understanding of Class 8 Reproduction in Animals. Check out our Class 8 study notes section to find similar material for Class 8 subjects! Don’t forget to follow Leverage Edu on Instagram, Facebook and Twitter to stay updated with the latest educational news!