Riya conducted an experiment where she observed a drop of pond water under a microscope. She noticed a single-celled organism splitting into two identical cells. Her teacher explained that this process is called binary fission, a form of asexual reproduction in which an organism divides to form two new individuals.
(a) What is binary fission? (1 Mark)
(b) How does binary fission occur in Amoeba? (2 Marks)
(c) How is binary fission in Amoeba different from binary fission in Leishmania? (1 Mark)
OR
(c) What is multiple fission? Give an example. (1 Mark)
Ans:
(a) Binary fission is a type of asexual reproduction where a unicellular organism splits into two equal daughter cells.
(b) In Amoeba, binary fission occurs as follows:
(c) In Leishmania, binary fission occurs in a fixed orientation along the longitudinal axis, while in Amoeba, it can occur in any plane.
OR
(c) Multiple fission is when a parent cell divides into many daughter cells at the same time.
Example: Plasmodium (malarial parasite).
A farmer noticed that his mango trees produced fruits only after flowers appeared. His son asked how flowers lead to fruit formation. The farmer explained that flowers contain male and female reproductive parts, and pollen grains need to reach the female part for fertilization to occur.
(a) What is pollination? (1 Mark)
(b) Explain the process of fertilization in flowering plants. (2 Marks)
(c) What happens to the ovule and ovary after fertilization? (1 Mark)
OR
(c) How is cross-pollination different from self-pollination? (1 Mark)
Ans:
(a) Pollination is the transfer of pollen grains from the anther to the stigma of a flower. (1 Mark)
(b) Fertilization in flowering plants:
(c) After fertilization:
OR
(c) Self-pollination occurs when pollen from the same flower fertilizes the ovule, while cross-pollination happens between different flowers of the same species.
Rahul’s teacher explained how human reproduction involves both male and female reproductive systems. He was curious about how a zygote forms and what happens after fertilization.
(a) Where does fertilization occur in humans? (1 Mark)
(b) Explain the process of fertilization and zygote development in humans. (2 Marks)
(c) What is the role of the placenta in embryo development? (1 Mark)
OR
(c) What happens if fertilization does not occur? (1 Mark)
Ans:
(a) Fertilization occurs in the fallopian tube of the female reproductive system.
(b)
(c) The placenta transfers oxygen and nutrients from the mother to the foetus and removes waste products.
OR
(c) If fertilization does not occur, the uterine lining sheds, leading to menstruation.
Priya’s grandmother grew roses and potatoes in her garden. Priya was surprised to see that new rose plants grew from cut stems and potatoes sprouted from buds. Her grandmother explained that these plants reproduce by vegetative propagation.
(a) What is vegetative propagation? (1 Mark)
(b) How does vegetative propagation occur in Bryophyllum and potato? (2 Marks)
(c) Why is vegetative propagation useful in agriculture? (1 Mark)
OR
(c) Give an example of a plant that reproduces using runners. (1 Mark)
Ans:
(a) Vegetative propagation is a type of asexual reproduction where new plants grow from roots, stems, or leaves of the parent plant.
(b)
(c) Vegetative propagation allows rapid reproduction and ensures genetic similarity in crops like sugarcane and banana.
OR
(c) Example: Strawberry reproduces using runners.
During a biology class, Anjali asked about family planning methods. Her teacher explained how contraceptive methods help prevent unwanted pregnancies and protect against sexually transmitted diseases (STDs).
(a) What is contraception? (1 Mark)
(b) Explain two different methods of contraception. (2 Marks)
(c) How do hormonal contraceptives prevent pregnancy? (1 Mark)
OR
(c) Can contraceptives prevent sexually transmitted diseases? (1 Mark)
Ans:
(a) Contraception refers to methods used to prevent pregnancy.
(b)
(c) Hormonal contraceptives (e.g., pills) prevent ovulation by altering hormone levels, stopping egg release.
OR
(c) Barrier methods like condoms help prevent STDs, but other contraceptive methods do not.
During a science discussion, Aman’s teacher explained that offspring look similar to their parents but are not exactly identical. Aman wondered why there are small differences between parents and children even though they belong to the same family. His teacher explained that this happens due to DNA copying and variations during reproduction.
(a) Why is DNA copying important in reproduction? (1 Mark)
(b) How does variation occur during reproduction? (2 Marks)
(c) Why is variation beneficial to a species but not necessarily to an individual? (1 Mark)
OR
(c) How is variation responsible for the evolution of species? (1 Mark)
Ans:
(a) DNA copying is essential for passing genetic information from one generation to the next and maintaining body design.
(b) Variations occur due to:
(c) Variations help a species survive in changing environments, but they may not always be useful for an individual.
OR
(c) Over generations, useful variations accumulate, leading to the evolution of new traits and species.
During a lab activity, Anjali observed that a Planaria (flatworm) was cut into three parts, and after a few days, each part developed into a complete Planaria. Her teacher explained that this happens due to a process called regeneration.
(a) What is regeneration? (1 Mark)
(b) How does regeneration occur in Planaria? (2 Marks)
(c) Why can complex organisms like humans not reproduce through regeneration? (1 Mark)
OR
(c) Give an example of another organism that reproduces by regeneration. (1 Mark)
Ans:
(a) Regeneration is the ability of an organism to grow into a complete individual from its cut parts.
(b) In Planaria, regeneration occurs as follows:
(c) Complex organisms have specialized cells, tissues, and organs that cannot regenerate the whole body.
OR
(c) Example: Hydra can also regenerate its body parts.
Rohit was observing a Hydra under a microscope when he noticed a small outgrowth on its body. His teacher explained that Hydra reproduces asexually by budding, where new individuals grow as small buds and later detach from the parent body.
(a) What is budding? (1 Mark)
(b) Describe the process of budding in Hydra. (2 Marks)
(c) How is budding in Hydra different from binary fission in Amoeba? (1 Mark)
OR
(c) Give an example of another organism that reproduces by budding. (1 Mark)
Ans:
(a) Budding is a form of asexual reproduction where a new organism develops as an outgrowth (bud) from the parent body.
(b) In Hydra:
(c) In binary fission, the parent divides into two equal parts (Amoeba), while in budding, a small bud grows and separates (Hydra).
OR
(c) Example: Yeast also reproduces by budding.
During a biology lecture, Meera asked why women experience menstruation every month. Her teacher explained that the female reproductive system prepares for pregnancy each month, and if fertilization does not occur, the uterus sheds its lining.
(a) What is menstruation? (1 Mark)
(b) Explain what happens during the menstrual cycle. (2 Marks)
(c) Why does menstruation stop when a woman is pregnant? (1 Mark)
OR
(c) What is the average duration of the menstrual cycle? (1 Mark)
Ans:
(a) Menstruation is the monthly shedding of the uterine lining along with blood and mucus when fertilization does not occur.
(b) The menstrual cycle occurs in phases:
(c) During pregnancy, the fertilized egg implants in the uterus, and hormone levels prevent the shedding of the uterine lining.
OR
(c) The average duration of the menstrual cycle is 28 days.
During a school seminar, students were taught about sexually transmitted diseases (STDs) and the importance of contraceptive methods. The speaker emphasized that some STDs, like HIV-AIDS, can be life-threatening.
(a) Name any two sexually transmitted diseases (STDs). (1 Mark)
(b) How can the spread of sexually transmitted diseases be prevented? (2 Marks)
(c) What is the importance of using condoms during sexual intercourse? (1 Mark)
OR
(d) How do contraceptive pills prevent pregnancy? (1 Mark)
Ans:
(a) Two STDs: HIV-AIDS, Syphilis.
(b) STDs can be prevented by:
(c) Condoms act as a barrier, preventing sperm from entering the female body, thus avoiding pregnancy and reducing STD risks.
OR
(c) Contraceptive pills alter hormone levels, preventing ovulation (egg release) and making fertilization impossible.
80 videos|569 docs|80 tests
|
1. What are the two main types of reproduction in organisms? | ![]() |
2. How does asexual reproduction occur in organisms? | ![]() |
3. What are the advantages of sexual reproduction? | ![]() |
4. Can you give examples of organisms that reproduce asexually? | ![]() |
5. What role do gametes play in sexual reproduction? | ![]() |