All questions of Reproduction in Animals for Class 8 Exam

The fusion of male and female gamete is called fertilization. Internal fertilization takes place in humans. Male releases sperms inside female's body. Sperms and ovum fuse together in fallopian tube, during fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus.

The two types of reproduction that occur in living organisms are sexual and asexual reproduction. Sexual reproduction occurs when the female cells of an animal are combined with the male cells of another animal of the same species. Asexual reproduction does not require the merging of cells from two animals to occur.

When sperm get fussed with ovum ,the fertilization occured and the zygote is formed..

All living animals reproduce to produce new young ones.

Reproduction is a fundamental characteristic of all living organisms, including animals. It is the biological process by which new individuals of the same species are produced, ensuring the continuation of the species over time. This process involves the production of offspring, either sexually or asexually, depending on the species.

Sexual Reproduction:
In sexual reproduction, two parents contribute genetic material to produce offspring with unique combinations of genes. This process involves the fusion of specialized cells called gametes, which are produced by the male and female individuals. The male gamete is called sperm, while the female gamete is called an egg or ovum. The fusion of the sperm and egg during fertilization forms a zygote, which develops into a new individual.

The advantages of sexual reproduction include genetic diversity, which allows for adaptation and evolution, as well as the potential for offspring with improved traits. However, sexual reproduction requires the presence of both male and female individuals, and it can be a complex and energy-intensive process.

Asexual Reproduction:
In contrast, asexual reproduction involves the production of offspring without the involvement of gametes or the fusion of genetic material from two parents. Instead, a single parent organism gives rise to genetically identical offspring through various mechanisms.

Some common forms of asexual reproduction in animals include:
1. Budding: A new individual develops as an outgrowth or bud from the parent organism.
2. Fragmentation: The parent organism breaks into fragments, and each fragment develops into a new individual.
3. Regeneration: If a part of the organism is lost or damaged, it can regenerate and develop into a complete individual.

Exceptions:
While the majority of animals reproduce to produce new young ones, there are a few exceptions. Some animals, such as certain species of ants and bees, have a reproductive division of labor, where only a few individuals (queens) are responsible for reproduction, while the majority of individuals (workers) are sterile and do not reproduce.

Additionally, some animals may undergo periods of reproductive dormancy or have reduced fertility under certain conditions. However, they still have the inherent ability to reproduce when conditions become favorable again.

In conclusion, it is true that all living animals reproduce to produce new young ones, either through sexual or asexual means. Reproduction is essential for the survival and continuation of a species, allowing for genetic diversity and adaptation to changing environments.

False....No, because cloning is an asexual method of reproduction

False: The ovary is not the main male reproductive organ. The main male reproductive organ is the testes.

The male reproductive system is responsible for producing and delivering sperm, the male reproductive cells. It consists of several organs, including the testes, epididymis, vas deferens, seminal vesicles, prostate gland, and penis.

The testes:
The testes are the main male reproductive organs. They are responsible for producing sperm and the male sex hormone testosterone. Located in the scrotum, the testes are oval-shaped organs that are responsible for the production of sperm through a process called spermatogenesis. They also produce testosterone, which is responsible for the development of secondary sexual characteristics in males, such as facial hair and a deep voice.

The epididymis:
The epididymis is a coiled tube located on the back of each testicle. It serves as a storage and maturation site for sperm. Sperm produced in the testes travel to the epididymis, where they gain the ability to swim and become motile.

The vas deferens:
The vas deferens is a muscular tube that connects the epididymis to the urethra. During ejaculation, sperm travel through the vas deferens and mix with fluids from the seminal vesicles, prostate gland, and bulbourethral glands to form semen.

The seminal vesicles, prostate gland, and bulbourethral glands:
These structures produce fluids that mix with sperm to form semen. The seminal vesicles produce a fluid rich in fructose, which provides energy for sperm. The prostate gland produces a milky fluid that helps to activate sperm and neutralize the acidity of the female reproductive tract. The bulbourethral glands produce a clear, slippery fluid that lubricates the urethra and helps to flush out any urine or remaining sperm.

The penis:
The penis is the external male reproductive organ. It serves as both a conduit for urine and semen and is also involved in sexual intercourse. During sexual arousal, the penis fills with blood and becomes erect, allowing for penetration of the vagina during intercourse.

In conclusion, the ovary is not the main male reproductive organ. The main male reproductive organ is the testes, which are responsible for producing sperm and the male sex hormone testosterone.

Oviparous animals are those that lay eggs, which then develop into young ones. Viviparous animals, on the other hand, give birth to live young ones. Metamorphosis and binary fission are different reproductive processes.

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External fertilisation is most commonly observed in amphibians and fish, where fertilisation occurs outside the female body, usually in water. Birds, mammals, and reptiles typically undergo internal fertilisation.

The fusion of these two cells is called fertilization and it produces a diploid cell with 46 chromosomes - twice the amount found in each gamete. The fertilized egg is now called a zygote and has just the right amount of DNA needed for normal human development.

 The yet-to-be born mammalian offspring following the embryonic stage, and is still going through further development prior to birth. Supplement. Following the embryonic stage, the developing young enters the fetal period, which is in the later stages of development prior to birth.

Explanation:

Testes are male reproductive organs located in the scrotum outside the body cavity. They are responsible for the production of sperm and the male sex hormone testosterone. They are critical for male fertility and sexual function.

When a boy reaches puberty, the testes start producing sperm. Sperm production takes place in the seminiferous tubules of the testes. The sperm is then transported to the epididymis, a coiled tube located above and behind each testicle, where they mature and are stored until ejaculation.

During ejaculation, the sperm travels from the epididymis through the vas deferens, a muscular tube that connects the epididymis to the urethra. The urethra is the tube that carries both semen and urine out of the body through the penis.

In summary, the testes are responsible for sperm production, which is essential for male fertility and sexual function.

In frogs, the eggs are protected by a layer of jelly that holds them together and provides some protection. Unlike bird eggs, frog eggs do not have a hard shell.

The zygote, formed by the fusion of sperm and egg, develops into a new individual. It does not remain a single cell but undergoes multiple stages of development.

Understanding External Fertilisation
External fertilisation is a reproductive strategy commonly found in aquatic organisms, such as fish and amphibians. This process involves the union of sperm and egg outside the bodies of the parents.
Key Characteristics of External Fertilisation:
- Sperms Swim Towards Eggs: In external fertilisation, male organisms release sperm into the water, where they swim in search of eggs released by female organisms. This movement is crucial for successful fertilisation.
- Aquatic Environment: The presence of water is essential for this process. It facilitates the movement of sperm and protects the gametes from desiccation.
- Mass Spawning: Many aquatic species engage in mass spawning, where multiple individuals release gametes simultaneously. This increases the chances of successful fertilisation as countless sperm are present in the water.
Contrast with Internal Fertilisation:
- Internal Fertilisation: In contrast, internal fertilisation occurs within the female’s body. Sperm is deposited inside the reproductive tract, leading to fertilisation without the need for an aquatic medium.
- Reproductive Strategies: While external fertilisation is efficient for species in water, internal fertilisation offers protection for developing embryos, which is advantageous in terrestrial environments.
Conclusion:
In summary, the correct answer to the question is option 'A' - external fertilisation. This process relies on the swimming capability of sperm in water to reach and fertilise the eggs, highlighting the adaptations of aquatic organisms to their environments.

Organism cloning. Organism cloning refers to the procedure of creating a new multicellular organism, genetically identical to another. In essence this form of cloning is an asexual method of reproduction, where fertilization or inter-gamete contact does not take place.

Understanding Viviparous Animals
Viviparous animals are those that give birth to live young instead of laying eggs. This reproductive strategy is common among mammals, including humans and dogs.
Examples of Viviparous Animals
- Dog: The correct answer is option 'C' - Dogs are viviparous, meaning they carry their young in the womb until they are fully developed and ready to be born.
- Fish and Frogs: These animals primarily reproduce through external fertilization, laying eggs in water. While some species of fish have evolved to give live birth, the majority are oviparous (egg-laying).
- Birds: Birds are also oviparous, laying eggs that develop outside the mother's body.
Key Characteristics of Viviparity
- Live Birth: Viviparous animals give birth to live young, which have developed within the mother's body.
- Nourishment: The developing embryos receive nutrients and oxygen through a placenta or similar structure.
- Parental Care: Viviparous species often show a higher degree of parental care, enhancing the survival chances of their offspring.
Conclusion
In summary, the dog is a prime example of a viviparous animal due to its method of giving birth to live young. In contrast, frogs, fish, and birds primarily reproduce by laying eggs, making them oviparous. Understanding these reproductive strategies is essential in the study of animal biology and evolution.

Understanding Asexual Reproduction Through Budding
Asexual reproduction is a mode of reproduction that does not involve the fusion of gametes, allowing organisms to produce offspring independently. One prominent form of asexual reproduction is budding.
What is Budding?
- Definition: Budding is a type of asexual reproduction where new individuals develop from outgrowths or "buds" on the parent organism.
- Process: The bud grows while attached to the parent, eventually maturing into a new individual. When it is fully developed, the bud can detach from the parent and live independently.
Examples of Organisms That Reproduce via Budding
- Hydra: A small, freshwater organism that exhibits budding prominently. It forms a bud on its body, which eventually detaches to become a new hydra.
- Yeast: Single-celled fungi like Saccharomyces cerevisiae reproduce by budding, where a small protrusion forms on the parent cell, grows, and separates.
Comparison with Other Asexual Methods
- Binary Fission: Involves the division of a single organism into two equal parts. Common in bacteria and some protozoa.
- Metamorphosis: Refers to a developmental process involving drastic changes in form, common in insects, but not a method of reproduction.
- Internal Fertilization: A method involving the fusion of male and female gametes, leading to sexual reproduction, not asexual.
In summary, the correct answer to the question is option 'C' because budding specifically describes the formation of new individuals from buds, distinguishing it from other asexual reproduction methods.

In hens, a hard shell forms around the developing embryo as a protective layer. This shell protects the embryo and provides a stable environment for its development until the chick is ready to hatch.

Tadpole: The Developing Stage of Frogs
A tadpole is the larval stage in the life cycle of frogs, which undergoes a fascinating transformation from egg to adult.
Life Cycle of Frogs
- Egg Stage: Frogs lay eggs in water, typically in clusters or strings. These eggs are fertilized externally by the male frog.
- Tadpole Stage: Once the eggs hatch, tadpoles emerge. They are aquatic and have:
- Gills for breathing underwater
- A long, finned tail for swimming
- No legs at this stage
- Metamorphosis: As tadpoles grow, they undergo metamorphosis, which includes:
- Development of legs: Hind legs appear first, followed by front legs.
- Tail absorption: The tail gradually shrinks as the tadpole transitions to a frog.
- Lungs development: Gills are replaced by lungs, enabling the frog to breathe air.
Importance of Tadpole Stage
- Feeding and Growth: Tadpoles primarily feed on algae and plant matter, playing a crucial role in aquatic ecosystems by helping control algae growth.
- Adaptation: The transformation from tadpole to frog allows for adaptation to both aquatic and terrestrial environments.
Conclusion
In summary, the tadpole is a vital and distinctive developmental stage of frogs, marking the beginning of their life cycle and showcasing the incredible process of metamorphosis. This stage differs significantly from other animals like dogs, cats, or humans, highlighting the unique reproductive strategies of amphibians.

Correct option is 'A'. Because oviparous means- animal producing eggs, and snakes are oviparous, so correct option is 'A'.

Eggs are formed in the ovary. The ovary is a female reproductive organ located in the pelvis. It produces eggs, or ova, and hormones such as estrogen and progesterone. The eggs are released from the ovary during ovulation and travel down the fallopian tube to the uterus, where they can be fertilized by sperm.

Understanding Embryonic Development
The statement that "the embryo develops into a foetus before birth" is indeed true. Let’s delve into the details of embryonic development.
Stages of Development
- Fertilization: The process begins when a sperm fertilizes an egg, resulting in a zygote.
- Embryonic Stage: The zygote undergoes multiple cell divisions and forms a blastocyst. This stage lasts for roughly the first 8 weeks of pregnancy.
- Transition to Foetal Stage: After the embryonic stage, the developing organism is referred to as a foetus. This transition occurs around 8 weeks post-fertilization.
Characteristics of the Foetal Stage
- Growth and Development: The foetus continues to grow and develop the major organs and systems necessary for survival outside the womb.
- Duration: The foetal stage lasts until birth, typically around 40 weeks of gestation.
Importance of the Foetal Stage
- Vital Processes: During this time, critical processes like organ formation and maturation occur, preparing the foetus for life after birth.
- Monitoring Development: Medical professionals monitor the foetus through ultrasounds and other tests to ensure healthy development.
Conclusion
In summary, the statement is true as the embryo indeed transitions into a foetus, marking a crucial phase in prenatal development. Understanding these stages is essential for comprehending human development and reproductive health.

The fusion of sperm and egg results in the formation of a zygote, which eventually develops into an embryo and then a new individual.

A chick takes approximately 3 weeks to develop inside the egg. The hen incubates the eggs to provide the necessary warmth for development, after which the chick hatches from the egg.

Correct option is 'B'. Because sperms are called male gametes.

Understanding the Uterus
The uterus, also known as the womb, is a vital organ in the female reproductive system. It plays a crucial role in supporting a developing baby during pregnancy. Here’s a detailed explanation of its function:
Structure of the Uterus
- The uterus is a hollow, muscular organ located in the pelvis, between the bladder and the rectum.
- It has three main layers: the endometrium (inner lining), myometrium (muscular middle layer), and perimetrium (outer lining).
Function in Pregnancy
- Upon fertilization of the egg in the oviduct (fallopian tube), the fertilized egg (zygote) travels to the uterus.
- The endometrium thickens in preparation for the implantation of the embryo, providing a rich supply of blood and nutrients.
- Once the embryo implants into the endometrium, the uterus nurtures the developing fetus throughout the pregnancy.
Protection and Support
- The muscular walls of the uterus provide protection and physical support to the growing fetus.
- The uterus expands to accommodate the growing baby, eventually reaching significant size by the end of pregnancy.
Conclusion
In summary, the uterus is the correct answer because it is the structure that holds and supports the developing baby during pregnancy. The other options, such as the oviduct, ovary, and fallopian tube, have different roles in reproduction but do not serve as the location for fetal development.

Understanding Binary Fission
Binary fission is a type of asexual reproduction prominently observed in unicellular organisms, such as Paramecium. This method allows the organism to reproduce rapidly and efficiently under favorable conditions.
What is Binary Fission?
- Binary fission is a process where a single organism divides into two identical daughter cells.
- It involves the duplication of the organism's genetic material followed by a division of the cytoplasm.
Process of Binary Fission in Paramecium
- DNA Replication: The Paramecium's nucleus duplicates its DNA to ensure that each daughter cell receives a complete set of genetic information.
- Cell Growth: The cell grows larger, preparing itself for division.
- Cytokinesis: The cytoplasm divides, and the cell membrane constricts, ultimately resulting in two separate cells.
Advantages of Binary Fission
- Rapid Population Growth: This method allows for quick increases in population size, especially in favorable conditions.
- Genetic Uniformity: Since the offspring are clones, they possess identical genetic material, which can be advantageous in stable environments.
Distinction from Other Reproductive Methods
- Budding: Involves the outgrowth of a new organism from the parent.
- Regeneration: The process where an organism regrows lost parts, not a reproductive method.
- Vegetative Propagation: A form of asexual reproduction in plants, involving the growth of new plants from parts of the parent plant.
In conclusion, the process of reproduction in Paramecium via binary fission is a crucial biological mechanism that highlights the efficiency of asexual reproduction in unicellular organisms.

The head of the sperm contains the genetic material required for fertilisation. The tail aids in movement, and the middle piece provides energy.

During binary fission in amoeba, the nucleus divides first, followed by the division of the cell into two separate individuals. This method of asexual reproduction results in two amoebae from one parent cell.