IGCSE · Practice questions · Asexual reproduction

Clones, for better and worse.

Six original Cambridge-style questions on asexual reproduction: the definition, examples such as runners, tubers and binary fission, and (Extended) the advantages and disadvantages to wild species and to crop production.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

One parent, no gametes.

Definition: genetically identical offspring from one parent.
Spot it: one parent, new individual grows from part of it, no gametes, no fertilisation.
Advantages (Extended): fast, one parent, good features kept, uniform crop.
Disadvantages (Extended): no variation, so disease or change can kill all; competition with parent.

Recall

[2 marks]

Describe what is meant by asexual reproduction.

A process that produces offspring from one parent (no gametes, no fertilisation). ✓
The offspring are genetically identical to the parent and to each other. ✓

Analysis

[3 marks]

Read the descriptions and state whether each is asexual or sexual reproduction. (a) A yeast cell grows a bud that separates to form a new cell. (b) Pollen from one rose plant lands on the stigma of another rose plant. (c) A gardener plants a cut piece of geranium stem, which grows roots.

(a) Asexual: one parent, no gametes (budding). ✓
(b) Sexual: pollination leads to fusion of gamete nuclei from two plants. ✓
(c) Asexual: a cutting from one parent grows into a genetically identical plant. ✓

Explain

[2 marks]

Two potato plants grown from tubers of the same parent plant reach different heights. Explain how this can happen if they are genetically identical.

Their genes are the same, so the difference is not inherited. ✓
It is caused by the environment, for example different amounts of light, water or mineral ions. ✓

Explain

[4 marks]

Extended. Discuss two advantages and two disadvantages of asexual reproduction for a crop such as bananas.

Advantage: all plants keep the desirable features of the parent, such as high yield or good flavour. ✓
Advantage: it is quicker than growing from seed and the crop is uniform, so it can be harvested at the same time. ✓
Disadvantage: there is no genetic variation, so a disease or pest that kills one plant can kill the whole crop. ✓
Disadvantage: no new varieties are produced, so the crop cannot be improved or adapt to changing conditions. ✓

Data

[3 marks]

Extended. In a model, nine plants produced by asexual reproduction and ten plants produced by sexual reproduction were exposed to a disease. None of the asexual plants survived; four of the sexual plants survived.

(a) Calculate the percentage of the sexual plants that survived. (b) Explain the difference between the two groups.

(a) 4 ÷ 10 × 100 = 40%. ✓
(b) The asexual plants are genetically identical, so none had resistance to the disease and all died. ✓
The sexual offspring show genetic variation, so some happened to be resistant and survived. ✓

Explain

[3 marks]

Extended. A single spider plant is carried to a new island. Suggest why asexual reproduction helps it to colonise the island, and one risk to the population later.

Only one parent is needed, so it can reproduce without a mate. ✓
Runners produce many new plants quickly while conditions are suitable. ✓
Risk: the whole population is genetically identical, so a change in the environment or a new disease could kill them all. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.