Complete the sentences with the verb in the correct form Present Simple Passive, Past Simple Passive Tenses

Exercises

1. Complete the sentences with the verb in the correct form: Present Simple Passive Tense.

The process of taking food into the body ….. (call) ingestion. The food …..(break) into relatively small pieces in the mouth by chewing and these fragments are then …… (break) down into simpler substances by the processes of digestion. Digested food ….. (absorb) from the digestive tract by the blood and ….. (distribute) to the cells of the body. Its incorporation into the protoplasm of these cells …… (call) assimilation.

Not all the material that ….. (ingest) can be digested. So the substances, such as cellulose, cannot ….. (digest) by man and must therefore ….. (discard) as wastes. This process, involving the passage of undigested materials from the body, ….. (know) as egestion. Ingestion, digestion, and egestion are functions of specialized organs referred to collectively as the digestive system. This system ….. (make) up of the alimentary tract, that includes the mouth, teeth, tongue, pharynx, esophagus, stomach, small intestine, large intestine, and anus. The accessory organs and glands ….. (connect) with the tract or …… (locate) within its walls - the salivary glands, pancreas, liver, the glands of the stomach, and the glands of the small intestine.

The major organs of the alimentary tract lie inside the body in a tube - within-a-tube arrangement. The outer tube ….. (make) up of the skin and the muscle layers just under it. The inner tube ….. (form) by the organs of the alimentary tract, which are hollow, their walls ….. (compose) of layers of muscle. The space between the two tubes ….. (call) the coelom or body cavity and ….. (line) with a thin membrane, the peritoneum.

79) 1. All living things ….. (characterize) by the presence of a complex substance called protoplasm.

80) 2. Protoplasm first..... (recognise) as a living substance by the French zoologist Dujardin in 1835.

81) 3. All metabolic reactions are made possible by special types of proteins called enzymes.

82) 4. Many characteristics of protoplasm may..... (study) in living organisms of small size.

83) 5. The oxygen used up in the respiration of plants and animals..... (restore) through the process of photosynthesis.

84) 6. Carbon dioxide..... (absorb) from the atmosphere through the stomata of the leaves.

85) 7. Several kinds of animals...... (domesticate) by the late Stone Age.

86) 9. Snowy owls most often..... (see) along seacoasts and lake shores.

87)

Complete the sentences with the verb in the correct form: Passive or Active.

ATMOSPHERIC NITROGEN

20) The greater part of the atmosphere ….. (consist) of nitrogen, but the nitrogen, which ….. (require) by plants and animals to build up their tissues, is never available in sufficient quantities. This is due to the fact that free nitrogen cannot ….. (use) for this purpose. It can …..(assimilate) only when it ….. (combine) with other chemical elements.

21) However, the bodies of animals ….. (be) unable to make free nitrogen combine in this way. If it were not for bacteria in the soil, the world’s supply of combined nitrogen would soon …..(exhaust).

22) Certain bacteria, which ….. (find) in the roots of some varieties of plants, fix the free atmospheric nitrogen and combine it with other elements, such as carbon, oxygen and hydrogen. Plants …… (use) this combined nitrogen to build their tissues.

23) Certain other bacteria that ….. (find) in the soil combine the free atmospheric nitrogen with hydrogen to make ammonia, which they …… (use) to form their own protoplasm. When these bacteria ……. (die), the nitrogenous compounds …… (remain) in the soil and …… (be) available for the nutrition of other plants.

Дата добавления: 2014-01-04