- Life on earth depends on resources like soil, water, air and energy from the sun.
- The outer crust of the earth is called the lithosphere.
- The air that covers the earth like a blanket is called the atmosphere. It prevents the sudden increase in temperature during daytime.
- The life supporting zone on earth is known as the biosphere. Living things constitute the biotic components and non-living things constitute the abiotic components of biosphere.
- The hot air released from various biological activities consists of water vapour that can expand and cool. This cooling causes it to condense and form rain.
- When the temperature of the air is low, precipitation may occur in the form of snow, sleet or hail.
- When fossil fuels are burnt they release oxides of nitrogen and sulphur, which dissolve in rain and cause acid rain.
- Presence of high levels of hydrocarbons forms (unburnt carbon particles) increases the content of harmful substances in air is called air pollution.
- Water occupies a very large area of the earth surface. All cellular processes take place in water.
Water is one of the major resources that determines life on land. The availability of water decides the number of individuals that are able to survive in a particular area.
- Fertilizers, pesticides, sewage and chemical water released from factories and addition of undesirable substances to water can pollute it.
- Removal of useful components and addition of harmful compounds/which affect the fertility of the soil, causes soil pollution.
- Water evaporates and falls on the land as rain and later flows back into the sea via rivers. This is known as water cycle.
- Carbon dioxide is kept constant in the atmosphere by the process of photosynthesis.
- An increase in the percentage of carbon dioxide in the atmosphere increases the temperature globally. This is known as global warming.
- Oxygen is returned to the atmosphere in only one major process, i.e., photosynthesis. Ozone is present in the upper layers of the atmosphere. It prevents harmful radiations from reaching the surface of earth.
Chlorofluoro carbons or CFC react with ozone molecules and degrade it causing great harm to people on earth. We need to conserve our natural resources and use them in a sustainable manner.