生物 1999 年 DSE、CE 選擇題（第 6 頁）

51.

Which of the following are genetically identical ?

52.

If untreated sewage is discharged into a river, which of the following changes would occur in the water a short distance downstream from the site of discharge ?

Bacterial population	Algal population	Dissolved oxygen level
increases	increases	increases
increases	decreases	decreases
decreases	decreases	increases
decreases	increases	decreases

53.

Which of the following is a renewable resource ?

54.

If the same kind of crop is grown in a field for many years,

55.

Directions : Questions 56 to 58 refer to the diagram below, which shows some stages of the nitrogen cycle in a maize field :

Which of the following substances in the maize plants is/are formed from compound X ?

(1)fat

(2)starch

(3)protein

56.

Directions : Questions 56 to 58 refer to the diagram below, which shows some stages of the nitrogen cycle in a maize field :

Process Y will be promoted by

57.

Directions : Questions 56 to 58 refer to the diagram below, which shows some stages of the nitrogen cycle in a maize field :

Which of the following conditions will favour process Z ?

58.

Directions : Questions 59 and 60 refer to the following food web :

Which of the following animals are tertiary consumers ?

59.

Directions : Questions 59 and 60 refer to the following food web :

What is the relationship between hawk and snake ?