Sexual vs asexual reproduction and reproduction in plants – IGCSE Biology exam questions with mark scheme

1Grade 1–33 marks

(a) Give two differences between sexual and asexual reproduction. [2]

(b) Name the type of cell division that produces gametes. [1]

(a) any two comparative differences from: sexual involves two parents, asexual one parent; sexual involves gametes / fertilisation / fusion of gametes, asexual does not; sexual offspring genetically different / show variation, asexual offspring genetically identical / clones; sexual involves meiosis, asexual only mitosis; allow asexual is quicker / produces many offspring quickly, sexual is slower; ORA — first difference(1)
(a) second difference (must be a different idea from the first)(1)
(b) meiosis; reject mitosis; reject spellings that could be read as mitosis (e.g. 'miosis', 'meitosis')(1)
Answer: (a) e.g. two parents vs one; variation vs genetically identical (b) meiosis
Examiner tip: Make each difference a comparison — say what happens in BOTH types (e.g. 'two parents, but asexual needs only one').

2Grade 4–54 marks

(a) Define the term pollination. [1]

(b) Give three ways the structure of a wind-pollinated flower differs from an insect-pollinated flower. [3]

(a) transfer of pollen from an anther to a stigma; allow from stamen to stigma; reject 'fusion of pollen and ovule' / any reference to fertilisation as the definition(1)
(b) any three from (wind-pollinated compared with insect-pollinated; ORA): small / dull / green / no petals; no scent; no nectar / nectaries; anthers hang outside the flower / on long filaments; large / feathery stigmas hanging outside the flower; large amounts of pollen; small / light / smooth pollen — first difference(1)
(b) second difference(1)
(b) third difference(1)
Answer: (a) transfer of pollen from anther to stigma (b) e.g. no petals/scent/nectar; anthers and feathery stigmas outside; lots of light pollen
Examiner tip: Pollination is not fertilisation — mentioning gamete fusion in (a) loses the mark.

3Grade 6–74 marks

A student set up four tubes, each with 10 cress seeds, to find the conditions needed for germination. All four tubes were kept in the dark.

Tube	Conditions	Seeds germinated after 5 days
A	dry cotton wool, 20 °C	0
B	moist cotton wool, 20 °C	9
C	moist cotton wool, 4 °C (fridge)	0
D	seeds under boiled and cooled water, covered with a layer of oil, 20 °C	0

(a) Deduce three conditions needed for germination. For each condition, give the two tubes you compared. [3]

(b) Suggest why one seed in tube B did not germinate. [1]

(a) water is needed — tubes A and B(1)
(a) warmth / a suitable temperature is needed — tubes B and C; allow 'heat'(1)
(a) oxygen / air is needed — tubes B and D (boiling removes dissolved oxygen, oil stops it re-entering); condition without a correct pair of tubes scores 0 for that point(1)
(b) seed was not viable / dead / damaged / dormant / embryo damaged; allow seed had no embryo / was not fertilised / had too little food store; ignore 'not enough water / warmth / oxygen' unqualified (conditions the same for all seeds)(1)
Answer: (a) water (A and B); warmth (B and C); oxygen (B and D) (b) seed not viable / dead / dormant
Examiner tip: Each conclusion must come from comparing tube B (all conditions) with ONE other tube.

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