Question
The image shows a cell in the anther of a lily (Lilium sp.) plant during the first division of meiosis.
(a) (i) Identify the stage of meiosis shown in the image
(ii) State where in the lily flower pollen would be formed.
(b) Distinguish between plant pollination and fertilization.
(c) The diagram shows a cross section through a broad bean (Vicia faba) seed.
(i) On the diagram, label the cotyledon.
(ii) Outline the function of the cotyledon.
▶️Answer/Explanation
(a) (i) anaphase / anaphase I;
(ii) anther/stamen;
(b) a. pollination is the transfer of pollen from anther/stamen to stigma;
b. fertilization is the fusion of male and female gametes / fusion of gametes to form a zygote/diploid cell;
(i) 
(ii) a. contains food reserves/food store/nutrients/protein/carbohydrate;
b. used during germination;
c. used for growth of the embryo (plant) / for root development / for shoot development;
Question
Multicellular organisms benefit from cell specialization and division of labour.
(a) Outline the processes occurring during interphase in the cell cycle.[4]
(b) Describe what occurs in a neuron when an action potential is propagated along the axon. [4]
(c) Explain how cells in the bloodstream cause a specific immune response.[7]
Answer/Explanation
a a. growth/increase in cell size;
b. division of mitochondria/chloroplasts/production of more organelles/number of organelles doubled;
c. replication of DNA/amount of DNA is doubled;
d. transcription of genes/production of mRNA;
e. protein synthesis;
f. cell respiration/production of ATP;
b a. sodium ions/Na+ enter/diffuse in;
b. depolarization/membrane potential/voltage changes from negative to positive;
c. potassium channels open AND potassium ions/K+ exit/diffuse out;
d. repolarization/membrane potential/voltage changes back from positive to negative;
e. local current due to diffusion of sodium ions along the neuron;
f. (local currents) cause next sodium channels to open/next part of axon to depolarize;
g. opening of sodium channels triggered when threshold potential/-50mV reached;
c a. (specific immune response is) production of antibodies in response to a particular pathogen;
b. antibody is specific to/binds to a specific antigen;
c. macrophages/phagocytes engulf/present antigens from pathogens/viruses/bacteria;
d. T lymphocytes activated by antigens/antigen presentation/antigens presented by macrophage;
e. (activated) T lymphocytes activate B lymphocytes;
f. only B lymphocytes that produce antibodies against the antigen/pathogen are activated;
g. (activated) B lymphocytes clone/divide by mitosis to form plasma cells;
h. plasma cells then secrete (large quantity) of an antibody/secrete antibodies of same type;
i. some B lymphocytes/plasma cells form memory cells;
j. memory cells give long lasting immunity/faster response to a disease/pathogen;