Class 10 Science – How Do Organisms Reproduce?
HOTS Questions – 10 Questions
A farmer wants to produce a large number of genetically identical plants in a short period. Which method of reproduction should he use? Explain why this method is more suitable than reproduction through seeds.
A plant produces flowers but does not form seeds or fruits. What could be the possible reason? Explain the role of pollination and fertilisation in seed formation.
A student says, “Asexual reproduction is always better than sexual reproduction because it is faster.” Do you agree? Give two scientific arguments to support your answer.
If a hydra is cut into several pieces, each piece may develop into a complete organism. Why is this possible in hydra but not in humans?
A woman has a normal menstrual cycle. If fertilisation does not occur during a particular cycle, why does menstruation occur? Explain the hormonal changes involved.
Two healthy parents have a son and a daughter. A relative claims that the mother is responsible for determining the sex of the child. Using genetics, explain whether this claim is scientifically correct.
A person wants to prevent both pregnancy and sexually transmitted infections (STIs). Which contraceptive method would be more appropriate? Explain your reasoning.
During sexual reproduction, the offspring is not usually identical to either parent. Explain how DNA copying and sexual reproduction together contribute to variations.
A flower is covered with a transparent bag before it opens, and later no seeds are produced. What does this experiment suggest about the importance of pollination? Explain.
Suppose humans reproduced only by asexual reproduction. Predict two major consequences this could have on the human population, especially when environmental conditions change.
Class 10 Science – How Do Organisms Reproduce?
HOTS – Answers
1. Genetically identical plants in large numbers
The farmer should use vegetative propagation such as cutting, layering, or tissue culture.
Reason: It is a form of asexual reproduction, so offspring are genetically very similar to the parent and many plants can be produced quickly.
2. Flowers produced but no seeds or fruits
The possible reason may be failure of pollination or fertilisation.
Pollination transfers pollen grains from the anther to the stigma.
After pollination, the male gamete reaches the ovule.
Fertilisation produces a zygote.
The ovule develops into a seed, and the ovary develops into a fruit.
Therefore, without successful fertilisation, seeds generally do not develop.
3. Is asexual reproduction always better?
No.
Asexual reproduction is faster and requires only one parent.
However, it produces very little genetic variation.
Sexual reproduction produces variations, which can help organisms adapt to changing environmental conditions.
Therefore, neither method is universally “better”; their advantages depend on the situation.
4. Why can hydra regenerate but humans cannot?
Hydra has many cells capable of regeneration. These cells can divide and differentiate to form different body parts.
In humans, most specialised cells have limited ability to regenerate and cannot form an entire organism.
Therefore, a piece of hydra can develop into a complete organism, whereas a piece of the human body cannot.
5. Why does menstruation occur if fertilisation does not happen?
During the menstrual cycle, the uterine lining (endometrium) becomes thick in preparation for implantation.
If fertilisation does not occur:
No embryo is formed.
Hormone levels supporting the uterine lining fall.
The thickened uterine lining breaks down and is discharged as menstrual flow.
Thus, menstruation occurs when pregnancy does not occur.
6. Who determines the sex of the child?
The claim that the mother determines the sex of the child is scientifically incorrect.
Female: XX
Male: XY
The mother always contributes an X chromosome through the egg.
The father can contribute either X or Y through the sperm:
Thus, the sperm determines whether the offspring is genetically XX or XY.
7. Preventing pregnancy and STIs
Condoms are an appropriate method because they can:
Help prevent pregnancy by preventing sperm from entering the female reproductive tract.
Reduce the risk of many sexually transmitted infections (STIs) by providing a physical barrier.
No contraceptive method provides absolute protection, but correct and consistent condom use reduces both risks.
8. Why are offspring different from their parents?
During DNA copying, small changes can occur, producing variations.
In sexual reproduction:
Genetic material comes from two parents.
The combination of genetic material creates new combinations of traits.
Therefore, DNA-copying variations plus the mixing of genetic material during sexual reproduction produce differences among offspring.
9. Flower covered before opening
The experiment suggests that pollination is necessary for normal sexual reproduction in flowering plants.
If the flower is isolated and pollen cannot reach the stigma, fertilisation may not occur, and consequently seeds may not form.
However, the exact outcome can depend on whether the plant is capable of self-pollination within the protected flower.
10. If humans reproduced only asexually
Two major consequences could be:
Very little genetic variation: Offspring would be genetically very similar to the parent.
Greater vulnerability to environmental changes and diseases: A new disease or major environmental change could affect a large proportion of the population because there would be fewer genetic differences.
Thus, sexual reproduction is important for generating genetic variation in human populations.
No comments:
Post a Comment