iGCSE Biology (0610)-16.3 Sexual reproduction in plants

Question

The diagram shows parts of two different plants, $1$ and $2$, of the same species. The transfer of pollen between the flowers of these two plants is shown by the arrows labelled $P$ and $Q$.

Which arrows show cross-pollination, and which transfer of pollen would produce the most variation in the offspring?

▶️ Answer/Explanation

Cross-pollination occurs when pollen is transferred from the anther of a flower on one plant to the stigma of a flower on a different plant of the same species. In the diagram, arrow $P$ represents cross-pollination, while arrow $Q$ represents self-pollination (transfer between flowers on the same plant). Since cross-pollination combines genetic material from two genetically distinct parents, it results in greater genetic variation among the offspring compared to self-pollination. Therefore, transfer $P$ is both the only instance of cross-pollination and the one that produces the most variation.
✅ Answer: (A)

Question

The diagram shows two methods of pollination, $V$ and $W$. The two flowers are on different plants of the same species.

A student made three conclusions about these two methods of pollination.

Method $V$ will produce genetically identical offspring.
Method $W$ will produce genetically different offspring.
Method $W$ increases the ability of the species to adapt to its surroundings.

Which conclusions are correct?

(A) $1$, $2$ and $3$
(B) $1$ and $2$ only
(C) $1$ and $3$ only
(D) $2$ and $3$ only

▶️ Answer/Explanation

Method $V$ is self-pollination, which still involves meiosis and the fusion of gametes; therefore, the offspring are not genetically identical (clones), making conclusion $1$ incorrect. Method $W$ is cross-pollination between two different plants, which significantly increases genetic variation by combining alleles from two distinct parents. This increased genetic diversity ensures that offspring are genetically different (conclusion $2$) and provides a larger gene pool for natural selection to act upon. Consequently, the species has a better chance of adapting to environmental changes (conclusion $3$). Since only statements $2$ and $3$ are valid, the correct option is $D$.
✅ Answer: (D)

Question

Which statement about pollination is correct?

(A) Self-pollination increases the ability of the population to respond to changes in the environment by increasing variation.
(B) Self-pollination increases the ability of the population to respond to changes in the environment by reducing variation.
(C) Self-pollination reduces the ability of the population to respond to changes in the environment by increasing variation.
(D) Self-pollination reduces the ability of the population to respond to changes in the environment by reducing variation.

▶️ Answer/Explanation

Self-pollination involves the transfer of pollen within the same plant, which leads to a high degree of genetic uniformity. Because the offspring are genetically similar to the parent, there is reduced genetic variation within the population. Genetic variation is the raw material for natural selection; without it, a population lacks the diverse traits needed to adapt to new selection pressures, such as climate change or disease. Consequently, a lack of variation reduces the ability of the population to respond or adapt to environmental changes. This makes the population more vulnerable to extinction if conditions shift.

✅ Answer: (D)

iGCSE Biology (0610)-16.3 Sexual reproduction in plants – iGCSE Style Questions Paper 2

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