Life on the Earth

1. The study of the relation between agricultural crops and environment is called agro-ecology.
2. The physical conditions as well as the biotic communities of different croplands vary widely.
3. Since there are some common features that mark all croplands, they are generally called agro-eco systems.
4. The physical conditions of the farm depend upon latitude, overall climatic and ecological factors.
5. The type of crops depends upon the climatic season and choice of the farmer.
6. Animal population of cultivated lands comprises earth worms, nematodes, domestic animals, insects and many birds.

The fresh water bodies are lakes and ponds. They vary in size from less than a hectares to hundreds of hectares. The relatively shallow lakes called eutrophic lakes have a rich accumulation of organic products.

Streams and rivers: They differ widely in volume of water, speed of flow and oxygen content, etc. The nature and composition of flora and fauna depends on the source of the river and the land environment. Floating population of planktons are generally absent in such waters. Sediments are deposited on the river bed. The total volume of water is also larger. The surface gets more sunlight raising the temperature of water. The water often is muddy cutting down light at the river bed. Many reptiles, mammals and birds obtain their food from the water therein.