26 (A400U20-1) 26 © WJEC CBAC Ltd. 8. Graphs 8.1–8.4 show the concentrations of four hormones found in the plasma of a mature ewe (female sheep). The hormone concentrations are plotted over a time period of 16 days. The days are numbered either side of the peak concentration of LH secretion. 0 – 8 – 6 – 4 – 2 0 +2 +4 +6 +8 4 2 10 8 6 Time / days Oestrogen concentration / au Graph 8.1 0 – 8 – 6 – 4 – 2 0 +2 +4 +6 +8 4 2 10 8 6 Time / days Progesterone concentration / au Graph 8.2 0 – 8 – 6 – 4 – 2 0 +2 +4 +6 +8 4 2 10 8 6 Time / days Follicle stimulating hormone concentration / au Graph 8.3 0 – 8 – 6 – 4 – 2 0 +2 +4 +6 +8 4 2 10 8 6 Time / days Luteinising hormone concentration / au Graph 8.4 (A400U20-1) Turn over. 27 27 Examiner only © WJEC CBAC Ltd. If sheep are given progesterone for eight days and then the treatment is stopped, they will ovulate eight to twelve days later. In this way, the oestrus cycle of a flock of sheep can be synchronised. Use Graphs 8.1, 8.2, 8.3 and 8.4 to explain the role of oestrogen in the control of the timing of ovulation in the sheep. Explain why the sheep will ovulate after the doses of progesterone are stopped. Suggest why is it useful for a farmer to be able to determine when ovulation will occur and suggest why some people are against injecting reproductive hormones into sheep that are used for food. [9 QER] 28 (A400U20-1) 28 © WJEC CBAC Ltd. Examiner only (A400U20-1) Turn over. 29 29 Examiner only © WJEC CBAC Ltd. 30 (A400U20-1) 30 Examiner only © WJEC CBAC Ltd. END OF PAPER 9 (A400U20-1) Turn over. 31 31 © WJEC CBAC Ltd. Examiner only Question number Additional page, if required. Write the question number(s) in the left-hand margin. 32 (A400U20-1) 32 © WJEC CBAC Ltd. Question number Additional page, if required. Write the question number(s) in the left-hand margin. Examiner only