1. 1
   Blood samples were taken daily from a woman with a regular 28-day menstrual cycle (day 1 = first day of menstruation). FSH rose slightly during days 1–5. Oestradiol stayed low until about day 8, then rose steeply to a peak on day 12. LH stayed low until day 12, then rose to about eight times its earlier level on days 13–14 before falling again. Progesterone was very low until day 14, rose to a peak around day 21 and fell to a low level by day 27.

   (a)

   What causes the sharp rise in LH on days 13–14?

   [1 mark]

   • ANegative feedback from falling progesterone on the pituitary
   • BNegative feedback from high oestradiol on the pituitary
   • CSecretion of LH by the developing follicle
   • DPositive feedback from high oestradiol on the pituitary

   (b)

   Which structure secretes most of the progesterone between days 15 and 25?

   [1 mark]

   • AThe pituitary gland
   • BThe corpus luteum
   • CThe endometrium
   • DThe developing follicle before ovulation

   (c)

   Explain the consequences of the fall in progesterone at the end of the cycle.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Sweet cherry trees have hermaphroditic, insect-pollinated flowers with white petals and nectaries at the base of each flower. When pollen lands on a stigma of the same tree, it germinates but its pollen tube stops growing part-way down the style. Pollen from a genetically different variety grows a tube all the way to an ovule. Growers therefore plant at least two compatible varieties in each orchard.

   (a)

   What is the function of the nectaries?

   [1 mark]

   • ATo produce the female gametes
   • BTo produce pollen grains
   • CTo provide a sugary reward that attracts insects, which transfer pollen between flowers
   • DTo disperse the seeds after fertilisation

   (b)

   Which term describes the mechanism that stops pollen from the same tree fertilising its ovules?

   [1 mark]

   • ASelf-incompatibility
   • BDifferent maturation times of pollen and stigma
   • CSeparate male and female flowers
   • DWind pollination

   (c)

   Explain the advantage to a plant species of this mechanism.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   The New Zealand mud snail lives in lakes and streams. In the same population, some females reproduce asexually, producing only female offspring that are genetically identical to themselves, while others reproduce sexually with males. The snails can be infected by parasitic worms that make them sterile. In a survey of many lakes, males made up about 2 % of snails in lakes where fewer than 5 % of snails were infected, and about 15 % of snails in lakes where more than 20 % were infected. Lakes with intermediate infection levels had intermediate proportions of males. In a fully sexual population, about 50 % of individuals are male.

   (a)

   Using the data, outline the relationship between parasite infection and sexual reproduction, and suggest a reason for this relationship.

   [3 marks]

   (b)

   Evaluate the claim that these data show that parasites cause the snails to reproduce sexually.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A couple are having in vitro fertilisation (IVF) treatment. First, the woman is given a drug that stops her pituitary gland from secreting FSH and LH. She then receives daily injections of FSH for about 10 days, followed by a single injection of a hormone that acts like LH. About 36 hours later, 12 eggs are collected from her ovaries and mixed with her partner's sperm in a dish. Two days later, embryos are checked and one is placed in her uterus. She is given progesterone from the time of egg collection.

   (a)

   Explain the role of each hormone treatment in this IVF procedure.

   [6 marks]

   (b)

   Describe the events of fertilisation in the dish, and explain how meiosis and fertilisation together produce genetically varied offspring.

   [6 marks]

   Total for question 4: 12 marks

End of questions