Question 1

(i) Self-pollination

(ii) Cross-pollination

(iii) Fertilisation

(iv) Tissue culture

2. Arrange the following stages of sexual reproduction in plants in the correct order:

(i) Pollen germination on stigma

(ii) Fertilisation

(iii) Pollination

(iv) Formation of zygote

3. Assertion (A): The zygote formed after fertilisation immediately attaches to the uterus wall.

Reason (R): The uterus wall is always prepared to receive the zygote.

(i) Both A and R are true, and R is the correct explanation of A.

(ii) Both A and R are true, but R is not the correct explanation of A.

(iii) A is true, but R is false.

(iv) A is false, but R is true.

4. Why does asexual reproduction produce offsprings that are genetically identical to the parent?

5. Explain why the menstrual cycle stops during pregnancy.

6. Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?

7. Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?

8. If all flowers in a type of plant were only capable of self-pollination, how would it affect the genetic diversity over several generations? Explain.

9. A farmer wants to produce a large number of genetically identical plants quickly. Suggest suitable reproduction methods and explain why they are effective.

Accepted Answer

1. (i) Self-pollination: Pollination occurs within the same flower or between flowers of the same plant.
(ii) Cross-pollination: Pollination occurs between flowers of different plants of the same species.
(iii) Fertilisation: Fusion of male and female gametes to form a zygote.
(iv) Tissue culture: A method of asexual reproduction where new plants are grown from a few cells of a parent plant in a nutrient medium.

2. Correct order:
(iii) Pollination → (i) Pollen germination on stigma → (ii) Fertilisation → (iv) Formation of zygote.

3. (iv) A is false, but R is true.
Explanation: The zygote formed after fertilisation does not immediately attach to the uterus wall. It takes some time to develop into a blastocyst before implantation. The uterus wall is prepared to receive the zygote during the receptive phase.

4. Asexual reproduction produces offspring genetically identical to the parent because it involves only one parent and no fusion of gametes. The offspring inherit the exact genetic material from the parent, resulting in clones.

5. The menstrual cycle stops during pregnancy because the fertilised egg implants in the uterus and produces hormones (like hCG) that maintain the uterine lining and prevent the cycle from continuing.

6. Flowers that bloom at night are white or light-colored to attract nocturnal pollinators like moths and bats, which can see pale colors better in low light.

7. Vegetatively propagated plants are more vulnerable to diseases because they are genetically identical clones, so if one plant is susceptible to a disease, all others are equally susceptible.

8. If all flowers only self-pollinate, genetic diversity will decrease over generations, leading to inbreeding depression and reduced adaptability.

9. Methods like tissue culture and vegetative propagation (cuttings, grafting) can quickly produce many genetically identical plants. These methods are effective because they do not rely on seed formation and maintain the desired traits. — Step-by-step answers provided above explain the concepts and reasoning behind each question.

Question 2

Suresh prepares slides with pollen grains in different sugar concentrations (0%, 2.5%, 5%, 7.5%, 10%) to study the germination of pollen.

(i) What are the different hypotheses which can be tested using this set-up?

(ii) What parameters should be kept the same in this set-up?

Accepted Answer

(i) Hypotheses that can be tested:
- The effect of sugar concentration on pollen germination rate.
- The optimal sugar concentration for maximum pollen germination.
- Whether pollen grains can germinate in the absence of sugar.

(ii) Parameters to keep the same:
- Temperature during the experiment.
- Type and source of pollen grains.
- Duration of pollen exposure to sugar solutions.
- Volume of sugar solution used.
- pH of the sugar solutions if possible.
- Humidity and other environmental conditions. — The experiment aims to test how sugar concentration affects pollen germination. Controlling other variables ensures that only sugar concentration influences the results.

Question 3

Look at the picture given below and think in line with the given prompts and find out which type(s) of pollination might have been followed in these flowers —

Tomato: Stamens cover the stigma.

Wheat: Flowers open after pollination.

Papaya: Male and female flowers are often borne on different papaya trees.

Accepted Answer

Tomato: Since stamens cover the stigma, self-pollination is likely.

Wheat: Flowers open after pollination, indicating cross-pollination.

Papaya: Male and female flowers on different trees indicate cross-pollination (dioecious plants). — Tomato flowers often self-pollinate due to close proximity of stamens and stigma. Wheat is wind-pollinated and cross-pollinates after flowers open. Papaya is dioecious, requiring cross-pollination between male and female plants.

Question 4

In the lower Himalayan region of northern India, apples are an important cash crop that contribute significantly to farmer's livelihoods. The fruit yield in apple cultivation is declining continuously, associated with climate change and a significant decline in the population of natural pollinators. A researcher-farmer group set up two experimental apple orchards at two distinct locations: Places A and B. In apple orchards at Place A, they allowed natural pollinators to pollinate the flowers of the apple. In apple orchards at Place B, they applied mixed farming techniques of beekeeping. Along with honey, the farmer yielded apples. The yield of apples is depicted in Fig. 11.24, in terms of fruit setting (number of fruits/the total number of corresponding fruit-bearing branches) and fruit drop (premature falling of developing fruits) in the two types of experimental places of apple orchards.

(i) What are the hypotheses the researcher-farmers group has thought of for this investigation?

(ii) What are the different parameters in the experiment?

(iii) Compare and analyse the data of two experimental orchards Places A and B, in terms of high yields of apple fruits.

(iv) Based on your analysis, what do you infer from the data?

Accepted Answer

(i) Hypotheses:
- The presence of natural pollinators affects apple fruit yield.
- Beekeeping (managed pollinators) increases fruit setting and reduces fruit drop compared to natural pollination alone.

(ii) Parameters:
- Location of orchards (Place A and Place B).
- Pollination method (natural pollinators vs. beekeeping).
- Fruit setting rate.
- Fruit drop rate.

(iii) Analysis:
- Place B (with beekeeping) shows higher fruit setting and lower fruit drop compared to Place A.
- This indicates better pollination efficiency and fruit retention in Place B.

(iv) Inference:
- Managed pollination through beekeeping improves apple yield.
- Decline in natural pollinators negatively impacts fruit production.
- Integrating beekeeping can mitigate yield losses due to pollinator decline. — The experiment compares natural and managed pollination effects on apple yield. Data shows managed pollination improves fruit set and reduces fruit drop, supporting the hypotheses.

Question 5

A student claims, "In humans, ovulation always happens on day 14 of the menstrual cycle". Critically examine this claim and state whether the claim is correct or not. Give at least two reasons for your answer.

Accepted Answer

The claim is not entirely correct.

Reasons:
1. The menstrual cycle length varies among women and even in the same woman across cycles; it is not always 28 days, so ovulation does not always occur on day 14.
2. Ovulation typically occurs about 14 days before the start of the next menstrual period, so in shorter or longer cycles, ovulation day shifts accordingly.

Therefore, ovulation timing is variable and depends on individual cycle length. — Ovulation timing depends on the luteal phase length and total cycle length, which vary among individuals, making day 14 ovulation a general average but not a fixed rule.

Question 6

What is reproduction in living organisms?

Accepted Answer

A biological process by which living beings produce new individuals of their own kind — Reproduction is defined as the biological process by which living beings produce new individuals of their own kind, ensuring the continuity of life on Earth.

Question 7

Which of the following is an example of asexual reproduction in plants?

Accepted Answer

Potato sprouting from its underground stem — Potato reproduces asexually by sprouting new plants from its fleshy underground stem called tubers, which is an example of vegetative propagation.

Question 8

Identify the structure labelled as the tiny plantlet growing from the leaf in Fig. 11.1.

Accepted Answer

Plantlet — In Fig. 11.1, the Bryophyllum leaf is shown producing tiny plantlets at its edges, which grow into new plants. This is an example of vegetative propagation by leaf buds.

Question 9

Which of the following methods is NOT a technique of vegetative propagation?

Accepted Answer

Pollination — Cutting, grafting, and layering are methods of vegetative propagation involving parts of plants. Pollination is a sexual reproduction process involving transfer of pollen.

Question 10

In the cutting method of vegetative propagation (Fig. 11.2), at what angle are the cuttings inserted into the soil?

Accepted Answer

45–60° — In the cutting method, cuttings are inserted into the soil at an angle of about 45 to 60 degrees from the soil surface to facilitate root growth and stability.

Question 11

Arrange the steps of grafting in the correct order as shown in Fig. 11.3.

Accepted Answer

— The correct sequence is: (a) Take a healthy rooted plant (Plant A), (b) Make a slit on Plant A's stem, (c) Insert stem cutting of Plant B into the slit, (d) Secure the graft with cloth or film, (e) Cut other branches of Plant A.

Question 12

What is the main advantage of vegetative propagation in agriculture?

Accepted Answer

Vegetative propagation is helpful in agriculture because it allows farmers to produce genetically identical plants quickly and in large numbers. For example, using stem cuttings of sugarcane, farmers can cultivate crops that retain desirable traits such as high yield and disease resistance. — Vegetative propagation enables rapid multiplication of plants with desirable characteristics, ensuring uniformity and saving time compared to seed propagation. This method is widely used in horticulture and agriculture to improve crop production.

Question 13

Describe the process of budding in hydra.

Accepted Answer

Budding in hydra is an asexual reproduction process where repeated cell division at a specific site on the parent produces a small outgrowth called a bud. The bud enlarges and eventually detaches to live independently. For example, many buds can be seen growing simultaneously on the body of a hydra. — In hydra, cell division forms a bud that grows into a new individual genetically identical to the parent. This method allows rapid population increase without gamete formation.

Question 14

Identify the organism shown in Fig. 11.6 with small round outgrowths on its cells.

Accepted Answer

Yeast — Fig. 11.6 shows yeast cells with small round outgrowths called buds, which are characteristic of yeast reproduction by budding.

Question 15

Which of the following statements about spores is correct?

Accepted Answer

Spores are produced in large numbers and are lightweight to disperse easily — Spores are produced in huge numbers by fungi, are usually single-celled and lightweight, allowing them to float through air currents and germinate under favorable conditions.

Reproduction: How Life Continues

Reproduction: How Life Continues — Study Notes

Introduction

11.1 Asexual Reproduction

Asexual Reproduction in Unicellular Organisms and Fungi

Practice Questions — Reproduction: How Life Continues

All 13 Chapters in Exploration