O-LevelBiologyGenetics & Variation5090/22 · Oct/Nov 2015 · Q18 Marks

Fig. 1.1 shows a carpel of a flower with two pollen grains on top. [Figure 1.1]

(a)(i)the process that has brought the pollen grains to the carpel[1]
(a)(ii)the part of the carpel to which the pollen grains are attached.[1]
(b)On Fig. 1.1, draw a line to show the route taken by the pollen tube up to the point at which male and female gametes fuse.[3]
(c)(i)a part of the carpel where the nuclei are all diploid[1]
(c)(ii)a part of the carpel that contains haploid nuclei.[1]
(d)Suggest why pollen grain A has not developed a pollen tube.[1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2015). The mark or mark type is shown in brackets.

[1] pollination;
[1] stigma;
[3] line (continuing) down style ; entering micropyle ; touching/entering embryo sac ;
[1] stigma/style/ovary wall ;
[1] ovary/ovule/embryo sac/ovum/ova/egg (cell)/gamete;
[max 1] from a different species/type/kind of plant; ref. chemicals on stigma unsuitable ; couldn't germinate/not viable/infertile AW ; not there long enough/grain immature/wrong enzymes ;

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