Legumes incorporate nitrogen gas into their proteins because

• A. of the presence of Azotobacter in their roots
• B. they possess root nodules containing Rhizobium
• C. they have a well developed root system
• D. they are autotrophic

In natural selection, Darwin proposed that evolution occurred because of the following conditions except

• A. food and other needs are abundant
• B. there is a fierce competition among the offsprings
• C. That the weaker offsprings are eliminated
• D. That nature selects those that will survive to reproduce their kind

Which of the following is an example of discontinuous variation?

• A. the range in height of a pea plant from 30cm to 50cm
• B. Offspring, including the two male cats and three female cats
• C. the colour of pear plants grown in the dark
• D. the adult body weight ranging from 50 kg to 95 kg

In Mendel's experiments, it was discovered that the skin of an African can be attributed to

• A. a blending of black and white genes
• B. recombination of genes
• C. loss of the epidermis
• D. mutation in the skin cells

In cold condition the mammalian body reacts in the following ways except

• A. shivering of the body
• B. dilation of the capillaries supplying blood to the skin
• C. constriction of blood capillaries in the skin
• D. increased rate of chemical changes in the body

Which of following pairs of scientists discovered the Rhesus factor in human blood?

• A. Hooke and Lavine
• B. Darwin and Landsteiner
• C. Landsteiner and Lavine
• D. Hooke and Darwin

(a) Describe the processes that occur from the time a pollen grain is deposited on the stigma of a flower to the . formation of a zygote.

(b) Explain the importance of the amniotic sac to the mammalian embryo.

(c) The following are the names of some common diseases; malaria, typhoid, amoeboid dysentry, tuberculosis, tetanus, leprosy, cholera, yellow fever, poliomyelitis, measles, common cold, small pox, influenza, chicken pox, whooping cough and trypanosomiasis. Use the format below to classify the diseases according to their causative organisms.

In an experiment, a red-flowered plant was crossed with another red-flowered plant and the following results were obtained: 448 red flowers and 154 white flowers in the F1 generation. Which of the following represents the phenotypic ratio of the above genetic cross?

• A. 1:2:1
• B. 4:1
• C. 3:1
• D. 2:2

Which of the following will have the least effect on the rate of change of the numbers in a population?

• A. food supply
• B. mutation
• C. predation
• D. disease

Good quality food will perform the following functions in humans except

• A. supplying energy
• B. providing resistance against malaria
• C. sustaining growth
• D. maintaining health