Cameroon gce Biology 2017 A level paper 2

• When a pepper plant with long and yellow seeds was crossed with one with round and red seeds all the offspring hand long yellow seeds in the Fl.
• A majority of the F1, pepper plants when crossed with a double recessive for both traits gave an equal
• number of pepper plants with long yellow and round red seeds in the F2

C:       A few pepper plants from among the Fl when crossed with a double recessive gave in the F2, the
following phenotypic numbers

• 890 long yellow seeds 900 round red seeds 104 long red seeds 110 round yellow seeds..
• State the dominant and recessive traits in these crosses
• What,can you suggest is responsible for the different phenotypic numbers of B and C?
• Using appropriate symbols show the crosses of the findings in A, B and Your crosses should show all
  the necessary steps.

(2, 3, 15 marks) (Total = 20 marks)

4. Describe how: .

• A stomach of a ruminant herbivore is adapted to carry.out.its functions.
• The nervous and hormonal systems control digestive secretions in the human gut.
• , Auto digestion is prevented in the human gut.

(6, 10, 4 marks) (Total = 20 marks)

5. (a) Define tropic and nastic responses stating one example in each case.

(ii)        List the differences between tropic and nastic responses.     •

(b)      Explain why phytochromes are involved in detecting photoperiods in flowering plants?

(e)       List 5 uses of auxins in agriculture.

(10, 5, 5 marks) (Total = 20 marks)

6. (a) Define a food web. Use organisms in a named ecosystem to illustrate the principle of a food web.

(b)         Briefly explain the following:

• Ozone layer depletion;
• Global warming and –
• Eutrophication
• (8, 12 marks)

(Total = 20 marks)

7. (a) What is:

• Growth and
• Cell differentiation?

(b)                 Discuss five factors: three external and two internal that affect growth in plants.

(5, 15 marks)

(Total = 20 marks)

8. (a) Describe Biotechnology.

List the steps involved in a Biotechnological process.

(c)           .Describe each of the following:

• Cheese production;
• Yogurt production and
• Production of the antibiotic penicillin

(3, 5, 12 marks) (Total =20 marks)