NCERT solutions for Science Exploration [English] Class 9 chapter 11 - Reproduction: How Life Continues [Latest edition]

• When does a farmer prefer asexual or sexual methods of reproduction for crops production?
• Why do you think most complex animals and flowering plants use sexual reproduction, while many simple organisms, like yeast and hydra mainly reproduce asexually?

In a china-rose (hibiscus or gudhal) plant, a pollen tube grows and continues through the style after pollen lands on the stigma. Which process is about to happen next?

Look at the pictures Fig. of calotropis (madar) seeds and dandelion seeds given below. Can you guess what kind of seed dispersal these seeds are adapted for?

A farmer plants two varieties of maize side by side, but notices that seeds form only when pollen from one variety reaches the stigma of the other. What type of pollination is this?

Why do animals with external fertilisation generally produce more eggs than animals with internal fertilisation?

In animals, which fertilisation method the gametes are more protected?

What determines a baby’s biological sex? So far, you have learnt that every person has two sex chromosomes. Females have XX and males have XY chromosomes. The mother always contributes an X chromosome to a baby and the father contributes either an X (Female: XX) or a Y (Male: XY) chromosome. Now, from the above information, can you predict who determines the sex of a baby?

Ravi suddenly notices that he is growing taller rapidly, his shoulders are broadening, and his voice cracks. What stage of life is he entering?

Rina’s period occurs every 28 days. Her last period was on the 5th of March. On which day is she most likely to get her next period?

A human zygote has just formed. How many chromosomes does it have?

What protective devices can be used during sexual activity to reduce the spread of STIs?

If a couple uses oral contraceptive pills but not condoms, which risks remain and why?

In many animals, the young ones can walk or find food soon after birth but human babies are completely dependent for a long time. What might be some advantages of this for humans as a species?

A flower’s anthers are removed before it matures. Later, pollen from another plant of the same species is dusted onto its stigma and seeds are produced. Which process has been ensured here? 

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

1. Pollen germination on stigma 
2. Fertilisation
3. Pollination 
4. Formation of zygote

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.

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

Explain why the menstrual cycle stops during pregnancy.

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

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

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.

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

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

1. What are the different hypotheses which can be tested using this set-up?
2. What parameters should be kept the same in this set-up?

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	Wheat	Papaya
Stamens cover the stigma.	Flowers open after pollination.	Male and female flowers are often borne on different papaya trees.

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.

1. What are the hypotheses the researcherfarmers group has thought of for this investigation?
2. What are the different parameters in the experiment?
3. Compare and analyse the data of two experimental orchards Places A and B, in terms of high yields of apple fruits.
4. Based on your analysis, what do you infer from the data?

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.

Read about the ‘Seed Village Programme’ (Beej Gram Yojana) run by the Government of India. Why is it important to save indigenous seeds?

Prepare a report on IVF, its uses and drawbacks. Discuss it with your class.

Conduct a survey on crop fields. Interact with farmers on the crops grown on their farms and farm animals based on the following points —

1. Which crops do they grow through vegetative propagation? 
2. Which crops do they grow using seeds? 
3. Which seeds do they use indigenous varieties or hybrid varieties? Why? How do they develop hybrid varieties in their fields? 
4. List the indigenous breeds and hybrid breeds of the farm animals they are using in their farming practices and how are they different from each other? 
5. Discuss in class, and make a report on how asexual and sexual methods of reproduction are useful in agriculture.

Explore the crop fields near your school and find out different pollination strategies adopted by different cereal and vegetable crop plants. Talk to farmers on the following points - 

1. Pollinators of different crops 
2. Reason for the declining population of pollinators and their solutions 

Observe the pollinators visiting your school garden. Notice and record their activity. Let each student take pictures of at least five different types of pollinators and which plants they visit. Compile the data and showcase your work to discuss how pollination occurs in different plants.

Assist your elders in cutting fruits in the kitchen. While cutting fruits like lady finger, tomato, brinjal, capsicum, papaya, orange, muskmelon and more, make your observations based on the following and draw diagrams -

• When you cut a fruit longitudinally (Longitudinal Section: L.S.)
• When you cut a fruit transversely (Transverse Section: T.S.)
• Attachment of seeds

Link your observations of the L.S. and T.S. of the fruit with the internal structure of the ovary of same species.

Does a unicellular organism like amoeba or yeast ever ‘grow old’? 

When amoeba or yeast divides, it produces almost two identical copies. So, does aging happen at all?