reproduction in animals class 8 questions and answers
Reproduction in Animals: Questions and Answers for Class 8
1. What do we mean by reproduction in animals?
Reproduction in animals refers to the biological process by which new individual organisms are produced. It ensures the continuation of a species by passing genetic material from parents to offspring.
2. What are the two main types of reproduction in animals?
Animals reproduce in two main ways: asexual reproduction and sexual reproduction.
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Asexual Reproduction: In this type, a single organism can reproduce without the involvement of another organism. There are no gametes involved, and the offspring are genetically identical to the parent, known as clones.
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Sexual Reproduction: This involves two organisms, typically a male and a female. The male provides sperm, and the female provides eggs, which combine to form offspring with genetic material contributed by both parents.
3. Can you give examples of animals that reproduce asexually?
Sure! Here are a few examples:
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Amoeba: Reproduces by binary fission, where the nucleus divides, followed by the division of the cytoplasm, resulting in two identical cells.
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Hydra: Uses budding, where a new organism grows out of the body of the parent, eventually detaching and living independently.
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Starfish: Capable of regeneration, particularly when parts like arms are cut off. Each severed arm can grow into a new individual.
4. What are the advantages and disadvantages of asexual reproduction?
Advantages:
- Requires only one parent, so it saves time and energy compared to finding a mate.
- If the environmental conditions are stable, asexual reproduction is efficient for producing many offspring quickly.
Disadvantages:
- All offspring are genetic clones of the parent, leading to less genetic diversity.
- Higher susceptibility to diseases and changes in the environment, as all individuals are genetically similar.
5. How does sexual reproduction create genetic diversity?
In sexual reproduction, genetic material from two parents is combined through the fusion of sperm and egg cells. This process, known as fertilization, mixes the genetic information, resulting in offspring that are genetically different from their parents and each other. This diversity is crucial for survival in changing environments as it increases the likelihood of having individuals with beneficial traits.
6. What is the role of gametes in sexual reproduction?
Gametes are specialized cells involved in sexual reproduction. In animals:
- Sperm: The male gamete, typically smaller, mobile, and designed to travel towards the egg for fertilization.
- Egg (Ovum): The female gamete, larger than the sperm, contains nutrients necessary for the developing embryo post-fertilization.
Gametes are haploid, meaning they contain half the number of chromosomes found in regular body cells. When a sperm and an egg fuse, they form a diploid zygote, restoring the normal chromosome number and initiating the development of a new individual.
7. Explain the process of external fertilization with examples.
External fertilization occurs outside the body of the organism, commonly seen in aquatic animals. Here, females release eggs into the water, and males release sperm nearby to fertilize the eggs. This process requires water to enable the sperm to swim towards the eggs.
Examples:
- Fish: Most species release eggs and sperm into the water where fertilization occurs.
- Frogs: Engage in external fertilization during which male frogs release sperm over eggs laid by females in water.
8. What is internal fertilization and in which animals does it occur?
Internal fertilization takes place inside the body of the female. The male typically introduces sperm into the female’s reproductive tract, where fertilization of the egg occurs. This type of fertilization is more common in terrestrial animals.
Examples:
- Mammals: Including humans and other animals like elephants and whales, exhibit internal fertilization.
- Birds and Reptiles: Also employ internal fertilization, laying fertilized eggs outside their bodies.
9. Compare and contrast oviparous and viviparous animals.
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Oviparous Animals: Lay eggs that develop and hatch outside the mother’s body. Examples include birds, reptiles, and most fish. Eggs are usually covered with a protective shell to prevent damage and desiccation.
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Viviparous Animals: Give birth to live young ones that have developed inside the mother’s body. Nutrients are provided to the growing embryo through specialized structures like the placenta. Examples include most mammals.
10. How do marsupials differ from placental mammals in terms of reproduction?
Marsupials, like kangaroos and koalas, give birth to relatively undeveloped young. After birth, these young immediately latch onto nipples within a pouch on the mother’s body, where they continue their development.
Placental mammals, on the other hand, nourish their young via a placenta for a longer period before birth, resulting in more developed offspring at birth.
11. Describe the process of metamorphosis in amphibians.
Amphibians like frogs undergo metamorphosis, a developmental transformation:
- Egg Stage: Fertilized eggs hatch into larvae called tadpoles.
- Larval Stage (Tadpoles): Aquatic and have gills for breathing underwater. Tadpoles feed and grow longer as they undergo changes.
- Transformation: Tadpoles gradually develop legs, lungs replace gills, and they start losing their tails.
- Adult Stage: Fully transformed into adult frogs, now capable of living both in water and on land, ready to reproduce.
Each step of metamorphosis is crucial for the amphibian’s ability to survive in varied environments.
12. What hormones regulate animal reproduction?
Animal reproduction is regulated by hormones, which are chemical messengers:
- In Vertebrates: Key hormones include testosterone in males and estrogen and progesterone in females. These hormones control the development of reproductive organs, production of gametes, and secondary sexual characteristics.
- In Invertebrates: Hormones like ecdysteroids play a role in reproductive functions and metamorphosis in insects.
Hormones ensure the timely development of reproductive capabilities and successful reproduction.
13. How does parental care vary among different animal species?
Parental care can greatly vary:
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Minimal Care: Some animals, like sea turtles, lay eggs and provide no further care. They rely on the environment to nurture their young.
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Moderate Care: Species like fish may guard their eggs until they hatch.
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Intensive Care: Many birds feed and protect their young until they can fend for themselves. Mammals, including humans, show extended care by nurturing their young through infancy and beyond.
The degree of parental care often correlates with offspring survival rates and environmental conditions.
14. What is the significance of reproduction for a species’ survival?
Reproduction is crucial for a species’ survival because:
- Genetic Continuity: Allows the continuation of a species by passing genes to successive generations.
- Population Maintenance: Ensures that a population can withstand failures or disasters, maintaining stable numbers.
- Adaptation: Through genetic variation, reproduction allows populations to adapt to environmental changes over time, increasing survival chances.
Reproductive success is a fundamental aspect of evolutionary processes, as it drives natural selection.
15. How does environmental change influence reproductive strategies?
Environmental changes can influence reproductive strategies:
- Stable Environments: Species in stable conditions might reproduce in a way that emphasizes quantity over quality (e.g., many offspring with little care).
- Unstable or Variable Environments: Encourage reproductive strategies focusing on fewer offspring with higher parental investment to ensure survival (e.g., mammals and birds).
Such adaptability in reproductive strategies helps species thrive despite challenges in their surroundings.
Overall, understanding reproduction in animals provides insight into the incredible diversity of life and the complex mechanisms developed over millions of years to ensure survival and adaptation. Keep exploring, asking questions, and never hesitate to delve deeper into the wonders of biology. You’re on a great path, and learning about such fascinating topics opens the door to endless possibilities! @Genom3