Biology Past Questions and Answers

Adenine pairs with thymine because

(a) (i) What is the effect of gravity on plant growth?
(ii) Describe an experiment to demonstrate the effect of gravity on the roots of plants.
(b) Explain how bitter taste is detected in humans.
(c) Copy and complete the table below on endocrine glands and their functions.

S/N	Endocrine glands	Hormone produced	functions
1	Thyroid
2		Insulin
3			Development of secondary sexual characters of females

(a) Make a diagram 8 – 10 cm long to show the relative position of the following organs in the mammalian gut:
(i) stomach
(ii) pancreas
(iii) liver
(iv) gall bladder
(v) duodenum and label fully.
(b) (i) List two diseases of the liver.
(ii) State five effects of the diseases in (b) (i) on the human body.
(c) State the deficiency symptoms of the following vitamins:
(i) vitamin A
(ii) vitamin C
(ii) Vitamin K;

(a)State the second law of thermodynamics.
(ii) Use the second law of thermodynamics to explain the flow of energy across different trophic levels in a food chain.
(b) (I) State three factors that can likely limit the size of human populations.
(ii) Outline two ways each by which humans can overcome the factors named in (b)(i).

(a) (i) What is the difference between the genotype and phenotype of an individual?
(ii) State two factors each which determine each of the terms in (a)(i).
(b) In a breeding experiment, a homozygous dog (BB) was crossed with a homozygous white dog (bb) to produce black puppies in the first filial generation (F1) The second filial generation produced a total of two hundred and forty (240) black and white puppies. With the aid of a genetic diagram, determine:
(i) the number of white puppies
(ii) the number of black puppies in the second filial generation.