September 24, 2021
Communicable diseases spread from one person to another by the entry of pathogens (disease causing organisms). Pathogens enter our body through various means, and then multiply there. They can be transferred from one person to another by direct or indirect contact.
September 23, 2021
Acid rain is caused when nitrogen oxides, SO2 and particulate matter in the atmosphere react with H2O to produce acids. Acid rain is harmful to the environment. It affects life in water and on land. The fish cannot survive in acidic water below pH 4.5. It can also damage trees in the forests.
September 21, 2021
Greenhouse is referred to as a chamber where plants are grown in a closed warm environment as compared to the outside temperature. This is normally practised in cold region of the hills. The solar radiations bringing heat (in the form of infra-red rays from the sun) are trapped inside the chamber.
September 20, 2021
The ozone layer present in the earth's atmosphere prevents the entry of sun's harmful ultraviolet (UV) radiations reaching the Earth's surface. Industrial use of chemicals called chlorofluorocarbons (CFCs) in refrigeration, air conditioning, cleaning solvents, fire extinguishers and aerosols (spray cans of perfumes, insecticides, medicines) damage the ozone layer.
September 18, 2021
Any undesirable change in the environment due to human activity is pollution. Each activity, human or industrial, discharges some unwanted substances in the environment. The presence of unwanted substances in a concentration which can have an adverse effect on organisms and environment is called pollution.
September 12, 2021
Earthquake is a common phenomenon. It is the shaking, rolling or sudden shock of the earth’s surface. The intensity of earthquake is related to the amount of energy released when rocks give way to the forces within the earth. It is measured with the help of an instrument known as seismograph. The intensity of an earthquake is measured on the Richter scale.
September 06, 2021
There is a constant need of nutrients by the biotic community for their survival and they take these from the environment. Nutrients in the form of oxygen, carbon dioxide, nitrogen, phosphorus, sulphur or water exists in a definite amount in the environment.
September 02, 2021
All living and non-living things that occur naturally on the earth constitute the natural environment. All living organisms are dependent on the environment for their survival. Their life is regulated by the environment and in turn they influence the environment.