Reproduction Questions and Answers

Answer: B

The words in order are zygote, embryo, uterus, foetus.

Fertilisation of the egg by the sperm forms a single cell, the zygote (W), which divides repeatedly into a ball of cells. As the cells begin to form tissues and organs, the developing structure is called the embryo (X), and it becomes embedded in the wall of the uterus (Y). Once all the body parts can be identified, the embryo is called a foetus (Z).

Option 1 swaps embryo and foetus. Options naming the fallopian tube are wrong because fertilisation happens there, but implantation takes place in the uterus, and option 3 also puts embryo before zygote.

Answer: B

All three plants produce bisexual flowers in Mustard, Rose, Petunia.

A bisexual flower has both stamens and pistil. Mustard, rose and petunia, like hibiscus, have such flowers, which is why they are the standard textbook examples of bisexual flowers.

Each other set includes a plant with unisexual flowers: cucumber has separate male and female flowers on the same plant, papaya usually bears male and female flowers on separate plants, and maize (corn) has a male tassel and female ears.

Answer: A

(A) and (B) are Layering, Jasmine.

In layering, a branch is bent down and covered with moist soil while still attached to the parent plant; once roots form, it is cut off as a new plant. Jasmine is a common example.

Cutting uses a piece of stem detached from the plant, and potato is grown from tubers, not cuttings. Grafting joins a cutting to a rooted plant, and budding in Hydra is asexual reproduction in an animal, not vegetative propagation of a plant.

Answer: D

S1 is true and S2 is false, so the answer is S1 is true and S2 is false.

In school science, self-pollination is the transfer of pollen from the anther to the stigma of the same flower. That needs one flower to carry both stamens and carpels, that is, a bisexual flower, so S1 is true. A unisexual flower has only one of the two parts and cannot pollinate itself in this sense.

S2 says cross-pollination happens only in unisexual flowers. Cross-pollination is the transfer of pollen to the stigma of another flower, on the same plant or a different one. It occurs in bisexual flowers too (a bisexual flower can receive pollen from another plant's flower, and many bisexual flowers are built to avoid self-pollination), so 'only in unisexual flowers' is false.

The other options each mark S1 or S2 wrongly. A later, finer classification calls pollen moving between two flowers of one plant geitonogamy and treats it separately from self-pollination, but that does not make self-pollination possible in unisexual flowers, so the keyed reading holds.

Answer: C

The correct statement is Seedlings are formed after pollination and development of embryo.

In a flower, events follow this order: pollination (pollen reaches the stigma), fertilisation (a male gamete fuses with the egg in the ovule), formation of the zygote and its development into an embryo inside the seed, and finally germination of the seed into a seedling.

Seedlings cannot form before the embryo (A), since the embryo is what grows into the seedling. The embryo forms after pollination, not before it (B). The embryo forms before the seedling, not after it (D).

Answer: D

The blanks are: ovaries enlarge, they produce estrogen, the testes produce testosterone, and production is controlled by the pituitary gland.

At puberty the ovaries enlarge, eggs begin to mature and the ovaries secrete the female sex hormone estrogen. The testes secrete the male sex hormone testosterone. The release of these hormones is controlled by hormones from the pituitary gland, which stimulate the ovaries and testes.

The ovaries do not reduce in size, which rules out two options. Thyroxine is made by the thyroid gland and is not a sex hormone, and the adrenal gland does not control the production of the sex hormones, which rules out the others.

Answer: C

X, Y, Z and W are anther, ovary, stigma, petals.

Pollen grains are produced in the anther (X). The female gamete, the egg, is formed inside the ovule within the ovary (Y). Pollen grains land and germinate on the stigma (Z). Brightly coloured petals attract insects for pollination (W).

The pistil is the whole female organ, not the part that makes pollen, and sepals protect the bud rather than attract insects, which rules out the first two options. The last option names the stamen for X and the ovule for Z, but pollen germinates on the stigma, not on the ovule.

Answer: A

The common method is Spore formation.

Fungi such as bread mould (Rhizopus) produce spores in sporangia. Mosses and ferns are non-flowering plants that also reproduce by spores, released from the capsule of a moss and from the sori on the underside of fern leaves.

Regeneration is typical of animals like Planaria and Hydra. Budding is seen in yeast and Hydra, not in mosses and ferns. Fragmentation is typical of filamentous algae such as Spirogyra, and is not the method these three groups share.

Answer: D

The set in which all show external fertilisation is Frogs, fish, starfish.

In external fertilisation eggs and sperm are released into water and fuse outside the body. Frogs and most fish release eggs and sperm in water, and starfish shed their gametes into the sea.

Hens, lizards and butterflies all have internal fertilisation, so any set containing one of them fails.

Answer: A

The correct matching is (a)-(v), (b)-(i), (c)-(ii), (d)-(iii).

• Rose: vegetative propagation, by stem cuttings.
• Yeast: budding, a small bud growing from the parent cell.
• Ferns: spore formation.
• Spirogyra: fragmentation, the filament breaking into pieces that each grow.

Pollination is not a mode of asexual reproduction at all; it is a step in sexual reproduction, so options matching any plant to pollination are wrong, and option C swaps the yeast and Spirogyra methods.