CBSE Class 9 Science Chapter 11 Reproduction How Life Continues MCQs Set 01

Answer: (B) Asexual reproduction through vegetative propagation

Explanation:
Potato plants sprout new individuals from their fleshy underground stems without seeds, which is a form of asexual reproduction called vegetative propagation. This process involves only one parent and produces genetically identical offspring.

Answer: (B) It allows farmers to cultivate desirable crop varieties on a large scale by combining traits from different plants

Explanation:
Grafting enables horticulturists to propagate plants with specific desirable characteristics efficiently. By joining a stem from one plant variety onto the roots of another, it allows rapid and large-scale cultivation of plants with preferred traits.

Answer: (B) Buds

Explanation:
Yeast reproduces asexually through budding, where small round outgrowths emerge from parent yeast cells, enlarge, and then separate to live independently. This is a common form of asexual reproduction in unicellular organisms.

Answer: (A) It produces gametes with half the chromosome number to prevent doubling when gametes fuse

Explanation:
• Meiosis reduces chromosome number from diploid (full set) to haploid (half set)
• When sperm and egg fuse during fertilisation, the chromosome number is restored
• This prevents chromosome doubling in each successive generation
• The process maintains species chromosome stability across generations

Answer: (D) Eight

Explanation:
The activity demonstrates that with three independent pairs of characters, each with two possible options, the total combinations are 2 × 2 × 2 = 8. This illustrates how genetic variation arises from random assortment of chromosomes during meiosis.

Answer: (B) To protect flower parts in the bud stage

Explanation:
Sepals form the outermost whorl of a flower and are typically green. They protect the flower and its developing parts while the flower is still in the bud stage, before it blooms.

Answer: (C) The unopened flower bud with stamens removed and wrapped

Explanation:
When stamens are removed from an unopened flower bud and it is wrapped to prevent outside pollination, no fruit develops. This demonstrates that pollen transfer from stamens is necessary for fruit formation even in developing buds.

Answer: (B) Self-pollination involves pollen from the same flower or plant, while cross-pollination involves pollen from a different plant of the same species

Explanation:
Self-pollination occurs when pollen transfers within the same flower or between flowers of the same plant. Cross-pollination occurs when pollen transfers between flowers on different plants of the same type. This distinction determines the level of genetic variation in offspring.

Answer: (B) Because most pollen grains fail to reach a compatible stigma and are wasted

Explanation:
Wind pollination is inefficient because pollen grains are carried randomly by air currents and most never reach their target stigmas. Producing millions of pollen grains (5,00,000 to 10,00,000 per flower) compensates for this waste and ensures enough reach compatible stigmas to produce seeds.

Answer: (B) Zygote

Explanation:
The zygote is the fertilised egg formed when a sperm nucleus fuses with an egg cell nucleus. This zygote then undergoes cell divisions to eventually develop into an embryo that grows inside the seed.

Answer: (B) It transforms into a fruit containing seeds

Explanation:
Following fertilisation, the ovary surrounding the ovules undergoes changes—its wall enlarges and develops into the fruit, while the ovules inside become seeds. This transformation is crucial for seed dispersal and plant reproduction.

Answer: (B) To compensate for the low survival rate due to water currents, predators, and other environmental hazards

Explanation:
External fertilisation is a risky reproductive strategy because eggs and developing young are exposed to water currents and predation. Producing huge numbers of eggs dramatically increases the probability that at least some will survive to maturity, offsetting the high mortality rate of offspring.

Answer: (B) The seminal vesicles and prostate gland

Explanation:
The seminal vesicles and prostate gland secrete fluids that combine with sperm to form semen. These fluids provide nutrients to keep sperm active and help them move through the reproductive tract toward the female reproductive system.

Answer: (B) Ovulation

Explanation:
Ovulation is the release of a mature egg from one of the ovaries. This typically occurs around day 14 of a 28-day menstrual cycle and is the critical event that allows fertilisation to occur if sperm are present in the female reproductive tract.

Answer: (B) Menstruation, during which the thickened uterine lining sheds

Explanation:
When fertilisation does not occur or the zygote fails to implant, the thick uterine lining is no longer needed. The lining sheds along with some blood through the vagina in a process called menstruation, which typically lasts three to seven days before the cycle repeats.

Answer: (B) Vegetative propagation through leaf tissue differentiation

Explanation:
Bryophyllum leaves sprouting plantlets is a classic example of vegetative propagation, where new plants arise directly from the vegetative parts of an existing plant without seed production.

Answer: (B) Cut the twig from the parent plant so it can grow separately

Explanation:
Once roots have formed in the buried portion of the twig, separating it from the parent plant allows it to function independently as a new plant.

Answer: (B) Lightweight nature, huge production numbers, and ability to float through air

Explanation:
• Spores are lightweight and travel easily through air currents
• Produced in millions from a single mould colony
• Float until moisture and nutrients allow them to germinate quickly into new individuals
• This combination enables rapid population spread and colonisation.

Answer: (C) 23 chromosomes (half the parent)

Explanation:
Meiosis reduces the chromosome number by half, so gametes have 23 chromosomes instead of 46, ensuring that when sperm and egg fuse during fertilisation, the zygote has the normal diploid number.

Answer: (B) Each child receives a unique combination of chromosomes different from siblings

Explanation:
Random segregation of chromosome pairs during meiosis produces vast numbers of possible combinations, making each child genetically different from their siblings despite sharing the same parents.

Answer: (B) The filament provides support and the anther produces pollen grains

Explanation:
The stamen consists of a filament (a thin stalk) that supports the anther, which is the structure that produces and releases pollen grains containing male gametes.

Answer: (B) To test whether pollen needs to reach the stigma for fruit formation to occur

Explanation:
By preventing pollen access to the stigma using bags, the experiment demonstrated that pollination (pollen transfer to the stigma) is necessary for fruits to develop, showing cause-and-effect between pollination and fruit formation.

Answer: (B) The male gamete fuses with the egg cell in a process called fertilisation

Explanation:
Fertilisation occurs when the male gamete travels through the pollen tube and fuses with the egg cell in the ovule, creating a zygote that marks the beginning of a new plant.

Answer: (C) External fertilisation organisms produce many more eggs but lower survival rates

Explanation:
External fertilisation in fish and frogs results in production of hundreds to thousands of eggs at a time but with low survival rates because many are destroyed or eaten, whereas internal fertilisation organisms produce fewer eggs with higher protection and survival chances.

Answer: (C) The prepared lining sheds along with blood through the vagina in a process called menstruation

Explanation:
When no fertilisation takes place, the thick vascular uterine lining is no longer needed, so it breaks down and is shed through the vagina as menstruation, which typically lasts 3 to 7 days and marks the beginning of the next cycle.