Exercise 17. Define the tense of the predicate and make the following sentences interrogative and negative

Ecosystems may be further subdivided into smaller biotic units

Called communities. 2. The living portion includes three general categories of organisms based on their methods of acquiring energy. 3. At first, the oceans and the lands were teeming with large numbers of a few kinds of simple single-celled organisms. 4 The Earth was a bleak place before the coming of life. 5. This strictly inorganic state of the Earth is called the geosphere. 6. The geosphere consists of the lithosphere, the hydrosphere, and the atmosphere. 7. Energy from the Sun bombarded the surface of the primitive Earth. 8. The generation of life in the thin outer layer of the geosphere established the biosphere.

Exercise 18. Put all types of questions to the following sentences:

This article focuses on the makeup of the biosphere. 2. The characteristics and dynamics of biological populations are dealt with in this article. 3. Due attention was also given to the processes that produced such patterns. 4. Other points included the cyclic flow of materials needed for life. 5. Ecology deals with the interrelations of organisms with their environment and each other. 6. Further treatment of the various aquatic environments is provided in ocean, lake and river