Reproduction: How Life Continues MCQs (Class 9 Science, NCERT)
155 practice questions on Reproduction: How Life Continues, a chapter in the NCERT Class 9 Science textbook, organised into 3 topics. Every question includes a written explanation. Pick a topic below, or try the samples first.
A frog may release 5,000 to 50,000 eggs at a time, while a bird lays only 1 to 15 eggs at a time. What is the main reason the frog needs so many?
AFrogs live far longer than birds and so have more time to lay eggs
BVery few of the frog's eggs survive, because they lie exposed in open water
CA bird is physically unable to produce more than 15 eggs in its whole life
DFrog eggs are much smaller, so a great many can be packed into the same space
Show answer and explanation
Correct answer: B - Very few of the frog's eggs survive, because they lie exposed in open water
Frog eggs are shed into open water, where currents and predators destroy most of them, so a very large number is needed for a few to reach adulthood. Fitting eggs into a space is not what decides the number, and lifespan is irrelevant, since the figures given are for one breeding episode. A bird lays many clutches over its life, so the last claim is simply untrue.
Q2
medium
A science club keeps one hydra in a jar of pond water. No second hydra is ever added, yet two weeks later the jar holds several small hydras. What does this best show?
AThe small hydras hatched from eggs laid earlier by two parents
BHydra can reproduce asexually, so one parent is enough
CA male hydra must already have been hidden in the pond water
DHydra splits into many individuals only when food runs out
Show answer and explanation
Correct answer: B - Hydra can reproduce asexually, so one parent is enough
New individuals appeared although only one parent was present, which is exactly what asexual reproduction means. A hidden male or eggs from two parents would both make this sexual reproduction, and nothing was added to the jar. Shortage of food is not the trigger; hydra buds most readily when conditions are good.
Q3
easy
Potato and ginger have thickened underground stems from which new shoots and roots sprout, without any seed being formed. Reproduction of this kind is called:
APollination
BVegetative propagation
CSeed dispersal
DExternal fertilisation
Show answer and explanation
Correct answer: B - Vegetative propagation
When a new plant grows from a vegetative part such as a stem, root or leaf, the process is vegetative propagation. Pollination is the transfer of pollen to a stigma, and external fertilisation is the fusion of gametes outside an animal's body, so neither fits a sprouting tuber. Seed dispersal is the scattering of seeds, and no seeds are involved here.
Q4
hard
Measurements show that a wind-pollinated grass releases about 5,00,000 to 10,00,000 pollen grains per flower but forms only about 50 to 200 seeds, while an insect-pollinated sunflower releases about 20,000 to 40,000 pollen grains and forms about 800 to 1,000 seeds. What does this comparison show?
ASunflower pollen grains must be lighter than grass pollen grains
BInsect pollination delivers pollen to stigmas far more efficiently, so far fewer grains are needed per seed formed
CWind pollination delivers pollen more efficiently, since far more pollen is released and carried to many more flowers
DWind-pollinated plants form more seeds than insect-pollinated plants do, because their pollen spreads further
Show answer and explanation
Correct answer: B - Insect pollination delivers pollen to stigmas far more efficiently, so far fewer grains are needed per seed formed
The grass spends thousands of pollen grains for each seed, while the sunflower spends only a few tens, so an insect carrying pollen straight from flower to flower wastes far less. Releasing more pollen is a sign of waste, not of efficiency. The data say nothing about pollen weight, and in fact the insect-pollinated sunflower forms the larger number of seeds.
Q5
hard
In human pregnancy the major organs begin forming during the first two months, and from about the ninth week the developing individual is given a new name. A particular pregnancy is now in its tenth week. What is the developing individual called now, and what was it called immediately after fertilisation?
AIt is a foetus now, and immediately after fertilisation it was a zygote
BIt is a zygote now, and immediately after fertilisation it was an embryo
CIt is an embryo now, and immediately after fertilisation it was a foetus
DIt is still an embryo now, and it was called a foetus only in the first two weeks
Show answer and explanation
Correct answer: A - It is a foetus now, and immediately after fertilisation it was a zygote
Fertilisation produces a zygote, which divides and implants and is then called an embryo, and from about the ninth week onwards it is called a foetus, so in the tenth week it is a foetus. Naming it an embryo now ignores the change of name at the ninth week. It cannot still be a zygote, which is a single cell, and the name foetus belongs to the later part of pregnancy, not to its first two weeks.
Q6
medium
Assertion (A): A Bryophyllum leaf that falls on moist soil can give rise to several new plants.
Reason (R): The plantlets on a Bryophyllum leaf are formed by the fusion of a male gamete and a female gamete.
ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is true, but R is false
DA is false, but R is true
Show answer and explanation
Correct answer: C - A is true, but R is false
A fallen Bryophyllum leaf really can give rise to many new plants from the plantlets on its margins, so (A) is true. (R) is false: these plantlets grow by cell division on a single parent leaf, with no gametes and no fusion, which is why they are identical to the parent. Since (R) is false, it cannot be an explanation of (A), correct or otherwise.
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