All questions of Animal Body Plans for Grade 9 Exam

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.

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.

No it's option b as urethra is also there in male reproductive system so in my opinion it's wrong fix the mistake

Protection for Frog Eggs
Frog eggs are typically laid in water, and their protection is crucial for the survival of the developing embryos. The correct answer to the question about what provides this protection is option 'B': a layer of jelly.
Structure and Composition
- Frog eggs are surrounded by a gelatinous layer, commonly referred to as jelly.
- This jelly layer is composed of water and proteins, which serve multiple protective functions.
Functions of the Jelly Layer
- Physical Barrier: The jelly provides a soft yet firm shield against physical disturbances and predators. It helps to absorb shocks, protecting the delicate eggs inside.
- Hydration: The jelly is primarily composed of water, which helps keep the eggs hydrated. This is vital for their development, as the embryos need a moist environment to grow.
- Chemical Defense: The jelly can contain chemicals that deter predators and parasites, making it less appealing to potential threats.
- Oxygen Supply: The gelatinous layer allows for gas exchange, ensuring that the developing embryos receive enough oxygen while still being protected.
Conclusion
In summary, the jelly layer around frog eggs serves as a crucial protective mechanism that ensures the survival and development of the embryos. Its physical, chemical, and biological properties make it an essential feature of amphibian reproduction in aquatic environments.

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.

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.

The Role of Sperm Structure in Genetic Transmission
Sperm cells are specialized reproductive cells that play a crucial role in fertilization. Understanding their anatomy is essential for recognizing how genetic material is transferred during reproduction.
Components of a Sperm Cell
- Head: The head of the sperm is the most critical component in terms of genetics. It contains the nucleus, which houses the genetic material (DNA). This DNA is a combination of genetic information from the male parent.
- Middle Piece: This section contains mitochondria that provide the energy necessary for the sperm to swim towards the egg. While it is vital for mobility, it does not contain genetic material.
- Tail: The tail is responsible for the locomotion of the sperm. It propels the sperm towards the egg but does not play any role in carrying genetic information.
Significance of the Head
- Nucleus: The nucleus within the head is packed with tightly coiled DNA. This DNA is critical because it determines the genetic traits that will be passed on to the offspring when the sperm fertilizes an egg.
- Acrosome: The head also contains an acrosome, which is a cap-like structure filled with enzymes. These enzymes help the sperm penetrate the outer layers of the egg during fertilization.
Conclusion
In summary, the head of the sperm is where the genetic material is stored, making it the primary carrier of genetic information during reproduction. Understanding this structure is vital in fields such as genetics, reproductive biology, and medicine.

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.

Understanding the Stages of Embryonic Development
In the development of a human embryo, there are several critical stages. The correct answer to the question about the stage where all body parts can be identified is the "Fetus."
Stages of Embryonic Development:
- Zygote:
- This is the earliest stage of development, occurring right after fertilization when the sperm and egg unite.
- At this point, the zygote is a single cell and does not yet exhibit distinct body parts.
- Embryo:
- This stage follows the zygote and lasts until the end of the eighth week of gestation.
- While the embryo begins to develop basic structures, significant features like hands, legs, and facial features are not yet fully formed.
- Fetus:
- This stage begins at the ninth week of gestation and continues until birth.
- By this time, major body parts such as hands, legs, head, eyes, and ears can be distinctly identified.
- The fetus undergoes rapid growth and development, refining its features and systems.
Conclusion:
The correct answer is b) Fetus because it is during this stage that all major body structures become recognizable. Understanding the progression from zygote to embryo and finally to fetus is essential in comprehending human development.

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 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.

Protective Layer Around the Developing Embryo in Hens
The correct answer is the egg shell, which serves as a vital protective layer for the developing embryo in hens. Here’s a detailed explanation:
Structure of the Egg
- The hen's egg consists of several key components, with the egg shell being the outermost layer.
- The egg shell is primarily made of calcium carbonate, giving it strength and rigidity.
Functions of the Egg Shell
- Protection: The egg shell acts as a barrier against physical damage and environmental threats, such as bacteria and pathogens.
- Gas Exchange: Tiny pores in the shell allow for the exchange of gases, enabling the developing embryo to receive oxygen and expel carbon dioxide.
- Moisture Regulation: The shell helps to retain moisture, crucial for the embryo's development, while still allowing for necessary gas exchange.
Comparison with Other Options
- Amniotic Sac: This structure is found in mammals, providing cushioning and a fluid environment, but it is not present in birds.
- Placenta: This is a mammalian feature that facilitates nutrient and waste exchange between mother and embryo, absent in bird reproduction.
- Uterine Lining: Relevant to mammals, this structure supports embryo implantation and nourishment, which does not apply to avian reproductive processes.
Conclusion
The egg shell is essential for the survival and development of the embryo in hens, offering protection, facilitating gas exchange, and maintaining moisture, which are all critical for successful incubation and growth.

Understanding Fertilization
The fusion of a sperm and an egg is a fundamental biological process that leads to the formation of a new organism.
What is Created?
- When a sperm cell successfully fertilizes an egg cell, the result is a zygote.
- The zygote is the first cell that forms after fertilization and contains a complete set of chromosomes, half from the mother (egg) and half from the father (sperm).
Key Points about the Zygote
- Diploid Cell: The zygote is diploid, meaning it has two sets of chromosomes, one from each parent.
- Development: The zygote undergoes multiple rounds of cell division (cleavage) and eventually develops into an embryo.
- Genetic Makeup: The zygote carries a unique genetic combination that contributes to the traits of the future organism.
Why Not Other Options?
- Embryo: This term refers to the developmental stage that follows the zygote stage. The zygote becomes an embryo as it continues to divide and develop.
- Gamete: Gametes are the reproductive cells (sperm and egg) themselves, which fuse to form the zygote.
- Sperm Cell: This is the male gamete involved in fertilization, not the result of the fusion.
Conclusion
In summary, the correct answer to the question of what the fusion of sperm and egg creates is option B: Zygote. The zygote is the initial cell that marks the beginning of a new organism’s development.

Cloning means making a copy of a living thing. It's like making an exact twin of a plant, animal, or any living part. Just like when you have a toy and you make another toy that looks exactly the same, that's what cloning is - making a copy.

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.