Olympiad Test: Reproduction In Animals - 2 - Class 8 MCQ

Fertilization in Humans
Fertilization is the process by which the sperm and egg combine to form a zygote, which eventually develops into an embryo. In humans, fertilization occurs in the oviduct, also known as the fallopian tube. Here's a detailed explanation:
1. Oviduct (Fallopian Tube)
- The oviduct is a tube-like structure that connects the ovary to the uterus in females.
- It is responsible for the transport of the egg from the ovary to the uterus.
- Fertilization occurs in the upper part of the oviduct, closer to the ovary.
- After ovulation, the released egg is picked up by the fimbriae, finger-like projections at the end of the oviduct, and transported towards the uterus.
- If sperm are present in the oviduct during this time, they can meet and fertilize the egg.
2. Uterus
- The uterus, or womb, is the organ where a fertilized egg implants and develops into a fetus.
- Fertilization does not occur in the uterus. Instead, the fertilized egg travels from the oviduct to the uterus for implantation.
3. Ovary
- The ovary is the reproductive organ in females that produces eggs.
- While the ovary is involved in the process of ovulation (the release of eggs), fertilization does not occur in the ovary.
4. Vagina
- The vagina is the muscular canal that connects the uterus to the external genitalia.
- Fertilization does not occur in the vagina. It is the site of sexual intercourse and serves as the birth canal during childbirth.
In conclusion, fertilization in humans occurs in the oviduct or fallopian tube, not in the uterus, ovary, or vagina.

The answer is C: endocrine glands.
Hormones are secreted by endocrine glands in the body. These glands are specialized tissues that release hormones directly into the bloodstream. The hormones then travel throughout the body to target cells where they regulate various physiological processes.
Here are some key points to explain why the answer is C:
- Endocrine glands: These glands are responsible for producing and releasing hormones into the bloodstream. They do not have ducts and their secretions are released directly into the bloodstream. Examples of endocrine glands include the pituitary gland, thyroid gland, adrenal glands, and ovaries/testes.
- Functions of hormones: Hormones act as chemical messengers that regulate various bodily functions such as growth and development, metabolism, sexual function, mood, and sleep. They help maintain homeostasis and coordinate the activities of different organs and systems in the body.
- Target cells: Once hormones are released into the bloodstream, they travel to specific target cells or tissues that have receptors for the hormone. These receptors allow the hormone to bind and initiate a cellular response. The effects of hormones can be widespread or localized, depending on the specific hormone and target cells involved.
- Exocrine glands: Exocrine glands, on the other hand, secrete their products through ducts onto a body surface or into a body cavity. Examples of exocrine glands include sweat glands, salivary glands, and mammary glands. These glands do not secrete hormones but rather substances such as sweat, saliva, and milk.
In conclusion, hormones are secreted by endocrine glands in the body. These glands release hormones into the bloodstream, which then travel to target cells to regulate various physiological processes.

Fertilization: The Fusion Process of Sperm and Ovum
Fertilization is the process in which a sperm cell and an ovum (egg cell) fuse together to form a zygote, which eventually develops into an embryo. Here is a detailed explanation of the fertilization process:
1. Introduction:
Fertilization is a crucial step in sexual reproduction, where the genetic material from both parents combines to create a unique individual.
2. Sperm Journey:
- Sperm cells are produced in the testes and stored in the epididymis until ejaculation.
- During sexual intercourse, millions of sperm are released into the female reproductive tract through the penis.
3. Ovum Release:
- Meanwhile, the female reproductive system releases a mature egg cell from the ovary during ovulation.
- The ovum travels through the fallopian tube towards the uterus.
4. Sperm-Ovum Encounter:
- The sperm cells swim through the cervix, uterus, and into the fallopian tube.
- Only a few hundred sperm cells reach the fallopian tube and encounter the ovum.
5. Acrosome Reaction:
- The acrosome, a cap-like structure on the head of the sperm, releases enzymes to penetrate the protective layers surrounding the ovum.
6. Penetration of Ovum:
- One sperm cell successfully penetrates the outer layer of the ovum, which triggers changes that prevent other sperm cells from entering.
- The sperm then enters the ovum, and their genetic material combines.
7. Zygote Formation:
- The fusion of the sperm and ovum results in the formation of a zygote.
- The zygote contains the complete set of genetic information from both parents.
8. Cell Division and Implantation:
- The zygote undergoes rapid cell division, forming an embryo.
- The embryo travels through the fallopian tube and implants into the uterine wall, where it continues to develop.
In conclusion, fertilization is the process of fusion between a sperm cell and an ovum, leading to the formation of a zygote. This process marks the beginning of the development of a new individual in sexual reproduction.

Binary fission is a method of asexual reproduction in which an organism divides into two equal parts, each of which becomes a new individual. Among the given options, the organism that reproduces by binary fission is the Amoeba.
Explanation:
Amoeba:
- Amoebas are single-celled organisms that belong to the phylum Protozoa.
- They reproduce asexually by binary fission, a process in which the nucleus divides into two, followed by the division of the cytoplasm, resulting in the formation of two identical daughter cells.
- Each daughter cell then grows and develops into an independent Amoeba.
Hydra:
- Hydras are multicellular organisms belonging to the phylum Cnidaria.
- They reproduce asexually by a process called budding, where a small outgrowth or bud develops on the parent organism and eventually detaches to form a new individual.
Yeast:
- Yeasts are single-celled fungi that reproduce both sexually and asexually.
- They primarily reproduce by budding, where a small outgrowth or bud develops on the parent cell, which then grows and detaches to form a new individual.
Sea anemone:
- Sea anemones are multicellular organisms belonging to the phylum Cnidaria.
- They reproduce both sexually and asexually.
- Asexual reproduction in sea anemones can occur through a process called pedal laceration, where a part of the foot of the anemone breaks off and develops into a new individual.
Therefore, the organism that reproduces by binary fission among the given options is the Amoeba.

Answer:
The life cycle of a mosquito:
- Egg stage: Female mosquitoes lay their eggs on the surface of standing water or in areas that are prone to flooding. The eggs are usually laid in groups called rafts.
- Larva stage: The eggs hatch into larvae within a few days. The larvae, also known as wigglers, live in the water and feed on organic matter and microorganisms. They have a distinct head and body and are equipped with mouthparts for feeding and a siphon for breathing.
- Pupa stage: After several molts, the larva enters the pupa stage. The pupa, also known as a tumbler, is comma-shaped and does not feed. It is highly active and undergoes internal changes to transform into an adult mosquito.
- Adult stage: The adult mosquito emerges from the pupa by splitting the pupal case. It takes a short time for the mosquito's wings and body to dry and harden. Once fully developed, the mosquito is capable of flight and reproduction.
In summary:
- Female mosquitoes lay eggs on the surface of standing water.
- The eggs hatch into larvae.
- The larvae live in water and feed on organic matter.
- The larvae molt several times before entering the pupa stage.
- The pupa undergoes internal changes to transform into an adult mosquito.
- The adult mosquito emerges from the pupa.
Therefore, the correct answer is:
B: Larva

Amoeba reproduction
Amoeba reproduces through binary fission
- Binary fission is a form of asexual reproduction where a single organism divides into two identical daughter cells.
- This is the primary method of reproduction in amoebas.
- The process starts when the amoeba's nucleus divides into two identical copies.
- The cytoplasm then separates, forming two separate daughter cells.
- Each daughter cell is genetically identical to the parent cell.
- This process allows amoebas to rapidly multiply and increase their population.
Advantages of binary fission in amoebas
- Rapid reproduction: Binary fission allows amoebas to reproduce quickly, leading to the rapid growth of their population.
- Genetic stability: Since the daughter cells are genetically identical to the parent cell, there is no genetic variation introduced during reproduction.
- Adaptability: Amoebas can adapt to changing environments more easily through asexual reproduction, as they do not rely on finding a mate for sexual reproduction.
Other methods of reproduction in amoebas
- While binary fission is the primary method of reproduction in amoebas, they can also reproduce through sexual reproduction under certain conditions.
- Sexual reproduction involves the fusion of two gametes (reproductive cells) to form a new organism.
- This process introduces genetic variation and allows for the exchange of genetic material between individuals.
- However, the occurrence of sexual reproduction in amoebas is relatively rare compared to binary fission.
Conclusion
Amoebas primarily reproduce through binary fission, a form of asexual reproduction. This process allows them to quickly multiply and maintain genetic stability. While they can also reproduce sexually, it is less common.

Reproduction by Budding Process
To identify which organism reproduces by budding process, let's analyze each option:
A: Hydra
- Hydra is a freshwater organism belonging to the phylum Cnidaria.
- It reproduces asexually through a process called budding, where a small outgrowth or bud forms on the body of the parent organism.
- This bud eventually separates from the parent and develops into a new individual.
B: Spirogyra
- Spirogyra is a filamentous green algae.
- It reproduces through a process called conjugation, which involves the exchange of genetic material between two adjacent filaments.
- Conjugation is not considered a budding process.
C: Sponge
- Sponges belong to the phylum Porifera.
- They reproduce sexually by releasing eggs and sperm into the water for fertilization.
- Sponges do not reproduce by budding.
D: Mushroom
- Mushrooms are part of the fungi kingdom.
- They reproduce through the release of spores, which are dispersed for reproduction.
- Mushrooms do not reproduce by budding.
Therefore, the correct answer is A: Hydra. Hydra reproduces through the process of budding, where new individuals develop as outgrowths or buds on the parent organism.

Embryonic Development in Multicellular Organisms
Introduction:
Embryonic development is a complex process that involves the growth and differentiation of cells to form a fully functional organism. In multicellular organisms, this development occurs through a combination of cell division and cell differentiation.
Cell Division:
Cell division is the process by which a single cell divides into two or more daughter cells. It is a crucial part of embryonic development as it allows for the rapid increase in cell number, leading to the formation of tissues and organs. During cell division, the genetic material is duplicated and evenly distributed to ensure that each daughter cell receives a complete set of chromosomes. This process, known as mitosis, plays a vital role in the growth and development of the embryo.
Cell Differentiation:
Cell differentiation refers to the process by which cells become specialized and acquire distinct structures and functions. As the embryo develops, cells undergo specific changes in gene expression and morphology, leading to the formation of different cell types. Differentiation is controlled by various factors, including signaling molecules and transcription factors, which regulate the activation and repression of specific genes. This process is essential for the formation of different tissues and organs in the developing embryo.
Both (a) & (b):
Embryonic development in multicellular organisms occurs through a combination of cell division and cell differentiation. These processes are interconnected and mutually dependent. While cell division allows for the rapid increase in cell number, cell differentiation ensures that the cells acquire specific structures and functions necessary for the development of different tissues and organs. Therefore, the correct answer is option C - both (a) and (b).
Conclusion:
Embryonic development in multicellular organisms involves both cell division and cell differentiation. Cell division leads to the formation of new cells, while cell differentiation ensures that these cells acquire specialized structures and functions. These processes work together to shape the developing embryo and give rise to the various tissues and organs necessary for the functioning of the organism.

Answer:

Humans start becoming sexually mature at the age of 10 - 16.

Explanation:

Sexual maturity, also known as puberty, is the stage in human development when individuals become capable of reproducing sexually. This is marked by the onset of secondary sexual characteristics and the ability to conceive or father a child.

Key Points:

- Sexual maturity usually occurs during adolescence, which is the transitional period between childhood and adulthood.
- The age at which sexual maturity begins can vary among individuals and is influenced by various factors such as genetics, nutrition, and environmental factors.
- The average age range for the onset of sexual maturity in humans is typically between 10 and 16 years old.
- Girls generally start puberty earlier than boys, with the average age of onset for girls being around 10-11 years old. Boys usually begin puberty slightly later, around 11-12 years old.
- It is important to note that while sexual maturity starts during this age range, individuals may continue to go through physical and emotional changes associated with puberty until their late teens or early twenties.
- It is essential for individuals going through puberty to receive proper education and support to navigate the physical and emotional changes that occur during this period.

In conclusion, humans generally start becoming sexually mature between the ages of 10 and 16. However, it is important to remember that every individual is unique, and the exact timing of sexual maturity can vary.

Answer:

The baby sheep DOLLY was cloned and developed from a cell taken from the Mammary gland of a female sheep, and an unfertilized egg taken from another female sheep.

Explanation:

• Cloning: The process of creating an organism that is an exact genetic copy of another organism is known as cloning.


• DOLLY: DOLLY was the first mammal to be cloned from an adult somatic cell. It was a female sheep and was created through the process of nuclear transfer.


• Cell source: The cell used to create DOLLY was taken from the Mammary gland of a female sheep. Mammary glands are responsible for producing milk in mammals.


• Unfertilized egg: The unfertilized egg used in the cloning process was taken from another female sheep. The egg provides the necessary genetic material for the cloning process.


• Process: The nucleus from the Mammary gland cell was extracted and inserted into the unfertilized egg. The egg was then stimulated to divide and develop into an embryo, which was implanted into a surrogate mother sheep to complete the cloning process.

In conclusion, DOLLY the sheep was cloned using a cell from the Mammary gland of a female sheep and an unfertilized egg from another female sheep.

Animals that show metamorphosis:
- Fish
- Silk moth
- Mosquito
Animal that does not show metamorphosis:
- Earthworm
Explanation:
Metamorphosis is a process in which an animal undergoes a dramatic change in its body structure as it grows and develops. While many animals go through metamorphosis, there are some that do not. In this case, the animal that does not show metamorphosis is the earthworm.
Reasons why the earthworm does not show metamorphosis:
- The earthworm belongs to a group of animals called annelids, which do not exhibit metamorphosis.
- Instead of undergoing a complete transformation, earthworms grow through a process called continuous growth and regeneration.
- Earthworms have a cylindrical body shape and segmented structure throughout their life cycle, without any distinct larval or pupal stages.
Conclusion:
Out of the given options, the animal that does not show metamorphosis is the earthworm. It is important to note that while fish, silk moth, and mosquito undergo metamorphosis, the earthworm follows a different growth pattern.

Answer:
The natural process of giving birth to young ones of their own kind is termed as reproduction. Here is a detailed explanation of the concept:
1. Introduction:
Reproduction is a fundamental biological process through which living organisms produce offspring of their own kind.
2. Definition:
Reproduction can be defined as the process by which organisms create new individuals of the same species.
3. Types of Reproduction:
There are two main types of reproduction:
- Sexual Reproduction: Involves the fusion of male and female gametes to form a zygote, which develops into a new individual.
- Asexual Reproduction: Involves the production of offspring without the involvement of gametes. It can occur through various mechanisms such as binary fission, budding, fragmentation, etc.
4. Importance of Reproduction:
Reproduction is essential for the survival and continuation of a species. It allows for the passing on of genetic information and ensures the diversity and adaptation of populations over time.
5. Process of Reproduction:
The process of reproduction typically involves the following steps:
- Gamete Production: Male and female individuals produce specialized reproductive cells called gametes.
- Fertilization: The fusion of male and female gametes occurs, resulting in the formation of a zygote.
- Embryonic Development: The zygote undergoes development and grows into an embryo within the female reproductive system.
- Birth or Hatching: The developed embryo is expelled or hatches from the mother's body, giving birth to a new individual.
6. Examples of Reproduction:
- In humans, sexual reproduction involves the fertilization of an egg by a sperm, leading to the development of a fetus and subsequent birth.
- In plants, reproduction can occur through various means such as pollination, seed dispersal, and germination.
In conclusion, the natural process of giving birth to young ones of their own kind is termed as reproduction. It is a vital process for the survival and continuation of species, allowing for the creation of new individuals through sexual or asexual means.

The reproductive organ in flowering plants is the Flower.
Explanation:

• Flower: The flower is the reproductive organ in flowering plants. It is responsible for producing and housing the reproductive structures necessary for sexual reproduction.


• Structure: The flower typically consists of four main parts: the sepals, petals, stamens, and pistils.


• Sepals: The sepals are usually green and protect the developing flower bud.


• Petals: The petals are often brightly colored and attract pollinators, such as bees or butterflies.


• Stamens: The stamens are the male reproductive organs of the flower. Each stamen consists of a filament and an anther, which produces pollen.


• Pistils: The pistils are the female reproductive organs of the flower. Each pistil consists of an ovary, a style, and a stigma. The ovary contains ovules, which develop into seeds after fertilization.


• Pollination and Fertilization: The flower plays a crucial role in pollination, where pollen is transferred from the anther to the stigma. Once the pollen reaches the stigma, it travels down the style to the ovary, where fertilization occurs, leading to the development of seeds.

Therefore, the correct answer is Option B: Flower.

Answer:
Definition of Hermaphrodite:
A hermaphrodite is an organism that possesses both male and female reproductive organs or characteristics.
Analysis of options:
Let's analyze each option to determine which one is a hermaphrodite:
- Flower: A flower can be considered a hermaphrodite because it usually contains both male (stamen) and female (pistil) reproductive organs within the same structure.
- Bird: Birds are typically sexually dimorphic, meaning they have distinct male and female individuals. They do not possess both male and female reproductive organs simultaneously, so they are not hermaphrodites.
- Amoeba: Amoebas are single-celled organisms that reproduce asexually through binary fission. They do not possess distinct male and female reproductive organs, so they are not hermaphrodites.
- Man: Human males have male reproductive organs, while females have female reproductive organs. They do not possess both male and female reproductive organs simultaneously, so they are not hermaphrodites.
Conclusion:
Based on the analysis, the correct answer is A: Flower. Flowers are hermaphrodites as they contain both male and female reproductive organs within the same structure.

Flower Structure:
- The flower is the reproductive structure of a plant.
- It consists of several parts, including the stamen, pistil, sepal, and petals.
Stamen:
- The stamen is the male reproductive organ of a flower.
- It is composed of two main parts: the filament and the anther.
- The filament is a long, slender stalk that supports the anther.
- The anther contains the pollen sacs, which produce and release the male gametes, known as pollen grains.
Pistil:
- The pistil is the female reproductive organ of a flower.
- It is composed of three main parts: the stigma, style, and ovary.
- The stigma is the sticky, receptive surface at the top of the pistil.
- The style is a tube-like structure that connects the stigma to the ovary.
- The ovary contains the ovules, which develop into seeds after fertilization.
Flower Reproduction:
- In most flowers, both male and female reproductive organs are present in the same flower.
- This is known as a perfect or bisexual flower.
- The stamen produces the male gametes (pollen grains) in the anther.
- The pistil produces the egg cell (ovule) in the ovary.
Answer:
- The flower has the pistil which produces the egg cell and the stamen which produces the male gamete in the same flower.
- Therefore, the correct answer is B: pistil, stamen.

Answer:
External fertilization:
External fertilization is a reproductive process where the fusion of gametes (sperm and egg) occurs outside the body of the parent organisms. This process usually occurs in aquatic environments and involves the release of eggs and sperm into the surrounding water.
Organisms that reproduce by external fertilization:
Among the given options, the organisms that reproduce by external fertilization are:
- Starfish: Starfish are marine animals that reproduce externally. They release their eggs and sperm into the water, where fertilization takes place.
- Jellyfish: Jellyfish are also marine organisms that reproduce by external fertilization. They release their eggs and sperm into the water column, and fertilization occurs externally.
- Frog: Frogs, on the other hand, do not reproduce by external fertilization. They undergo internal fertilization, where the male frog transfers sperm directly into the female's body.
Therefore, the correct answer is D: all of these.

Reproductive Methods in Different Animals:
Bird:
- Birds reproduce by internal fertilization.
- Male birds transfer sperm to the female during copulation.
- The sperm fertilizes the eggs inside the female's body.
Whale:
- Whales also reproduce by internal fertilization.
- Male whales have a specialized organ, called a penis, which is used to transfer sperm into the female's reproductive tract.
- The female whale then carries the fertilized eggs inside her body until they are ready to be born.
Human:
- Humans reproduce by internal fertilization.
- During sexual intercourse, the male's penis enters the female's vagina and deposits sperm into the reproductive tract.
- The sperm then fertilizes the egg, which is located in the female's uterus.
All of these:
- All three options, bird, whale, and human, reproduce by internal fertilization.
- They all involve the transfer of sperm from the male to the female's reproductive tract for fertilization to occur.
- The fertilized eggs develop inside the female's body until they are ready to be born.
In conclusion, all of these animals, including birds, whales, and humans, reproduce through internal fertilization.

Answer:
The correct answer is C: Snake.
Explanation:
Viviparity refers to the reproductive method in which the offspring develop inside the mother's body and are born live. In this case, the mother provides nourishment and protection to the developing embryos.
Let's examine each option to determine which one is not a viviparous animal:
A: Goat - Goats are viviparous animals. They give birth to live offspring.
B: Tiger - Tigers are also viviparous animals. They give birth to live cubs.
C: Snake - Snakes are not viviparous. They are oviparous animals, which means they lay eggs and the embryos develop outside the mother's body.
D: Dog - Dogs are viviparous animals. They give birth to live puppies.
In conclusion, the animal that is not viviparous is the snake (option C).

How long does it take for an embryo of a hen to develop into a chick?
The development of an embryo into a chick in a hen takes a specific amount of time. Let's break down the stages and timeframes involved:
1. Incubation:
- The process starts when a fertilized egg is incubated, either naturally by a hen or artificially in an incubator.
- During this stage, the embryo develops and grows inside the egg.
2. Duration:
- The incubation period for a hen's egg is typically around 21 days.
- This means that it takes approximately three weeks for the embryo to develop into a chick.
3. Factors affecting incubation:
- The incubation period can vary slightly depending on various factors such as the breed of the hen, environmental conditions, and egg fertility.
Therefore, the correct answer is C: three weeks. It takes approximately three weeks for an embryo of a hen to develop into a chick.

Reproduction System in Flowering Plants and Humans
Both flowering plants and humans have reproductive systems that allow them to produce offspring. The specific structures and processes involved in reproduction may differ between the two, but there is one common reproductive organ that exists in both:
Ovary
- The ovary is a female reproductive organ found in both flowering plants and humans.
- In flowering plants, the ovary is part of the flower's pistil and contains the ovules, which are the structures that develop into seeds after fertilization.
- In humans, the ovary is part of the female reproductive system and plays a crucial role in the production of eggs or ova.
- The ovary releases mature eggs during the menstrual cycle, which can be fertilized by sperm to initiate pregnancy.
Other reproductive structures that are specific to each organism include:
In Flowering Plants:
- Anther: The anther is the part of the flower's stamen that produces and releases pollen, which contains the plant's male gametes or sperm.
- Style: The style is the elongated portion of the pistil that connects the ovary to the stigma. It provides a pathway for pollen to reach the ovary for fertilization.
In Humans:
- Sperm Ducts: In males, the sperm ducts, also known as the vas deferens, are responsible for transporting sperm from the testes to the urethra.
- Uterus: The uterus is a muscular organ in the female reproductive system where a fertilized egg implants and develops into a fetus during pregnancy.
In conclusion, while the specific reproductive structures and processes may differ between flowering plants and humans, the ovary is a common reproductive organ found in both, playing a crucial role in the production of eggs and seeds.