Degradation of the soil is caused by natural processes as well as by human activities. Now let us briefly study about both of these. Soil is a complex body and forms the thin outer layer of the earth. It is directly or indirectly developed from the mineral constituents of the rocks.
The oceans which cover about 71 per cent of the earth's surface are crucial to the maintenance of the environment for they contribute to the basic oxygen-carbon-dioxide balance of the biosphere, upon which the human and animal life depend.
Classification of water pollution depends on the criterion used for categorization of pollution. Based on the medium in which pollutants occur, types of water pollution may be distinguished as fresh water pollution and marine pollution.
Climate means the average pattern in which weather varies in time. The average is determined over long periods from a month up to decades.
Coin sorter is a machine with the help of which coins of different denominations are automatically sorted out at a faster speed. It consists of a box with different trays having holes on the basis of size of different coins.
The host and environment are in constant interaction and that a disease is caused by disturbance of equilibrium between agent, host and environment. The disease assumes epidemiological proportions when the environmental conditions are favorable for the disease agent and unfavourable conditions exist for man.
The main advantages of accounting machines are: (a) The work done in accounting machine is neat and accurate. (b) The entries done by this machine are legible and tidy.
Camillus Golgi in 1898 for the first time observed the structure of Golgi bodies in the nerve cells of barn own and cat. Golgi bodies are membrane-bound organelles which occur in the form of tubules, vesicles of cistern (confined spaces). They look like a network under the compound microscope.
Classification means arranging things into groups. There are many living things in surroundings. To make learning simple, we must classify them first. Scientists use similarities and differences to classify living things into groups.
The entire frame of our body is made of bones and is called the skeleton. It is the name given to the framework of bones that holds up the rest of our body. All the bones of our body are connected to each other. The places where the bones meet are called joints.