51.
Consider the following statements and choose the correct answer:
1. The effects of biotic factors include interactions amongst plants growing in a community, between plants and animals including man and between plants and soil-microorganisms
2. In a densly populated area, one of the most important types of biotic factors influencing vegetation is due to man's multifarious activities - this is noted in farming operations
3. Change or destruction of vegetation by fire is a direct biotic effect due to man's activities
4. In many cases different plant groups, plants and bacteria live in mutual benefit - this is called symbiosis in which each partner derives some benefit from the other

52.
The leaves of Ficus religiosa are provided with drip tips to adapt for

53.
Lighter rainfall, where rainfall is heavy during summer but low during winter, is responsible for the formation of

54.
Consider the following statements and choose the correct answer:
1. The density of water varies inversely with temperature
2. The density of water varies inversely with the concentration of dissolved substances
3. Water is more dense at approximately 4° C and becomes progressively less dense as it is cooled below +4° C
4. When great evaporation occurs in a lake having no outlet, the lake may come to contain a higher percentage of salts than the ocear

55.
According to Maximov (1929),

58.
Which of the following compounds acts as a source of electrons for purple sulphur bacteria?

60.
The amount by which respiration is increased over normal or ground respiration by the transfer of a plant or tissue from water to a salt solution is known as