Reproduction: How Life Continues - Chapter 11 Class 9 Exploration

Question 1
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? (i) Self-pollination (ii) Cross-pollination (iii) Fertilisation (iv) Tissue culture
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Answer: (ii) Cross-pollination
The anthers are removed before maturing, so the flower cannot self-pollinate.
Pollen comes from
another plant of the same species
and lands on the stigma — this is
cross-pollination
(which then leads to fertilisation).
Option
Verdict & why
(i)
Self-pollination
Wrong
— the anthers were removed, so no pollen from the same flower or plant could reach the stigma.
(ii)
Cross-pollination
Correct
— pollen came from
another plant
of the same species onto this stigma.
(iii)
Fertilisation
Wrong
— fertilisation follows later, when the male gamete fuses with the egg. The step
ensured
here is the pollen transfer.
(iv)
Tissue culture
Wrong
— that is an asexual, laboratory method. No pollen or seeds are involved.
Back to: 11.2.3 How does the process of pollination occur in flowers?

Question 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
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Answer: (iii) → (i) → (ii) → (iv)
Pollination
(pollen reaches the stigma) →
Pollen germination on stigma
(pollen tube grows).
→
Fertilisation
(gametes fuse) →
Formation of zygote
.
Correct Order
Step 1
Pollination — pollen reaches the stigma
↓
Step 2
Pollen germinates on the stigma
↓
Step 3
Fertilisation — the gametes fuse
↓
Step 4
Formation of the zygote
↓
Order: (iii) → (i) → (ii) → (iv)
Back to: 11.2.5 Fertilisation and seed formation

Question 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.
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Answer: (iv) A is false, but R is (treated as) true
A is false:
the zygote does not attach immediately — it undergoes mitotic divisions while travelling to the uterus and only then implants.
The uterine lining is prepared to receive a zygote (though it is prepared cyclically, not literally “always”), so R is taken as the true statement; since A is false, option (iv) fits best.
Option
Verdict & why
(i)
Both A and R are true, and R is the correct explanation of A.
Wrong
— A is false, so this cannot hold.
(ii)
Both A and R are true, but R is not the correct explanation of A.
Wrong
— A is false.
(iii)
A is true, but R is false.
Wrong
— it is the other way round.
(iv)
A is false, but R is true.
Correct answer.
A is false
— the zygote divides by mitosis while travelling down the oviduct, and only then implants.
R is true
— the uterine lining thickens each cycle, ready to receive a zygote.
Back to: 11.5.6 What happens when an egg is not fertilised?

Question 4
Why does asexual reproduction produce offsprings that are genetically identical to the parent?
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Asexual reproduction involves a
single parent
and occurs by
mitosis
.
Mitosis makes daughter cells with the
same chromosomes
as the parent, so the offspring are genetically identical clones.
Genetically Identical
One parent, reproduction
by mitosis
Mitosis copies the same
chromosomes
Offspring are identical
clones
Back to: 11.1 Asexual Reproduction

Question 5
Explain why the menstrual cycle stops during pregnancy.
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During pregnancy, a zygote
implants
in the thick uterine lining, which is needed to nourish the embryo.
Since the lining is not shed and no new egg is prepared for release,
menstruation stops
until after the baby is born.
No Cycle in Pregnancy
A zygote implants in the
thick lining
The lining nourishes the
embryo
So it is not shed →
menstruation stops
Back to: 11.5.6 What happens when an egg is not fertilised?

Question 6
Why are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?
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Night-blooming flowers are pollinated by night visitors like moths and bats rather than by sight-hunting day insects.
White or light petals reflect the little available light
, making the flowers easy to locate in the dark, which improves pollination.
Night-Blooming Flowers
Pollinated by moths and
bats, not by sight
Pale petals reflect the little
light
Easier to find in the dark →
pollination
Back to: 11.2.4 Pollination strategies and reproductive success

Question 7
Why do vegetatively propagated plants tend to be more vulnerable to diseases than sexually reproduced plants?
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Vegetatively propagated plants are
genetically identical clones
with no variation.
Because they all share the same weaknesses, a single disease can spread through and destroy the whole crop, unlike varied sexually reproduced plants.
Vulnerable to Disease
Vegetative plants are
identical clones
No genetic variation among
them
One disease can wipe out
the whole crop
Back to: 11.1.1 How is vegetative propagation in plants helpful in agriculture?

Question 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.
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Self-pollination mixes genes only from the
same plant
, so little new variation is introduced.
Over several generations the
genetic diversity falls
, leaving the plants less able to adapt to new conditions or resist disease.
Only Self-Pollination
Genes mix within the same
plant only
Little new variation is
introduced
Genetic diversity falls over
generations
Back to: 11.2.3 How does the process of pollination occur in flowers?

Question 9
A farmer wants to produce a large number of genetically identical plants quickly. Suggest suitable reproduction methods and explain why they are effective.
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Use
vegetative propagation
(cutting, grafting, layering) or
tissue culture
.
These use a single parent and mitosis, so they quickly produce a large number of
genetically identical
plants with the desired qualities.
Fast Identical Plants
Step 1
Use cutting, grafting or layering
↓
Step 2
Or tissue culture from shoot-tip cells
↓
Step 3
All offspring are clones of the parent
↓
Quick, large-scale, identical plants
Back to: 11.1.1 How is vegetative propagation in plants helpful in agriculture?

Question 10
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?
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(i) Hypotheses:
e.g. pollen germinates best at a particular sugar concentration; too little or too much sugar reduces germination.
(ii) Kept the same:
temperature, type/age of pollen, amount of pollen, time allowed, humidity and light — only the sugar % is varied.
Pollen Germination
Study
Hypothesis: sugar percent
affects germination
Keep same: temperature,
pollen, time
Vary only the sugar
concentration
Back to: 11.2.3 How does the process of pollination occur in flowers?

Question 11
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.
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Tomato:
stamens cover the stigma →
self-pollination
.
Wheat:
flowers open after pollination →
self-pollination
(and wind).
Papaya:
male and female flowers on different trees →
cross-pollination
.
Types of Pollination
Tomato — Wheat — Papaya — stamens opens after sexes on cover pollination different stigma → → trees → self cross self/wind
Back to: 11.2.3 How does the process of pollination occur in flowers?

Question 12
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?
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(i)
Hypothesis: adding a bee colony (extra pollinators) increases fruit set and reduces fruit drop, raising yield.
(ii)
Parameters: pollination method (natural vs bee colony), fruit set %, fruit drop %.
(iii)–(iv)
Place B (with bee colony) shows
higher fruit set and lower fruit drop
than Place A, so
more pollinators give higher apple yield
.
Apple Orchard Data
Place B (bee colony) has
higher fruit set
Place B has lower fruit drop
More pollinators → higher
apple yield
Back to: 11.2.4 Pollination strategies and reproductive success

Question 13
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.
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The claim is
not fully correct
. Day 14 ovulation is only an average for a typical
28-day
cycle.
Reason 1:
cycle length varies from
21–35 days
between people.
Reason 2:
ovulation day shifts with cycle length, stress, health and hormones — so it does not always fall on day 14.
Ovulation on Day 14?
Day 14 fits only an average
28-day cycle
Cycles vary from 21 to 35
days
So it is not always day 14 →
claim is wrong
Back to: 11.5.6 What happens when an egg is not fertilised?

Project 1
Read about the ‘Seed Village Programme’ (Beej Gram Yojana) run by the Government of India. Why is it important to save indigenous seeds?
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The Seed Village Programme helps farmers produce and store good-quality seed locally. Saving indigenous seeds preserves genetic diversity, keeps locally-adapted, hardy varieties alive, reduces dependence on bought seed, and protects crops against pests, disease and climate stress.

Project 2
Prepare a report on IVF, its uses and drawbacks. Discuss it with your class.
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Cover what IVF is (combining egg and sperm outside the body), its uses (helping couples facing infertility) and drawbacks (cost, low success rate per cycle, emotional and physical stress, multiple-pregnancy risk). Mention India’s role — Subhash Mukhopadhyay’s pioneering work in 1978.

Project 3
Conduct a survey on crop fields. Interact with farmers on the crops grown on their farms and farm animals based on the following points — (i) Which crops do they grow through vegetative propagation? (ii) Which crops do they grow using seeds? (iii) Which seeds do they use — indigenous or hybrid varieties? Why? (iv) List the indigenous and hybrid breeds of farm animals they use and how they differ. (v) Discuss in class and make a report on how asexual and sexual methods of reproduction are useful in agriculture.
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Prepare a questionnaire, interview local farmers, and tabulate which crops are grown vegetatively (e.g. sugarcane, potato, banana) versus from seed (e.g. wheat, rice). Note their choice of indigenous vs hybrid varieties and breeds, then write a report linking both reproduction methods to agricultural benefits.

Project 4
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 — (i) Pollinators of different crops (ii) Reason for the declining population of pollinators and their solutions. Observe the pollinators visiting your school garden, record their activity, and compile pictures of at least five different pollinators and the plants they visit.
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Identify wind-pollinated cereals (wheat, maize) and insect-pollinated vegetables (pumpkin, brinjal). Discuss why pollinators are declining (pesticides, habitat loss, climate change) and solutions (fewer chemicals, pollinator-friendly plants). Photograph and tabulate at least five pollinators and their host plants.

Project 5
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 — (i) When you cut a fruit longitudinally (L.S.) (ii) When you cut a fruit transversely (T.S.) (iii) Attachment of seeds. Link your observations of the L.S. and T.S. of the fruit with the internal structure of the ovary of the same species.
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Cut each fruit in both directions and draw its L.S. and T.S., marking the seeds and how they attach. Relate what you see to the ovary structure — the fruit is the matured ovary and the seeds are the matured ovules, arranged as they were inside the ovary.
🔑 The Quest Continues…
Does an amoeba or a yeast cell ever ‘grow old’?
When it divides, it makes two almost identical copies.
Neither copy is clearly the older parent.
So does ageing happen at all in such organisms?
Keep observing, and keep questioning!