Class 10 Our Environment Notes
Our Environment Notes
Everything that surrounds us is known as environment.
Substances that are broken down by biological processes are said to be biodegradable.
Substances that are not broken down by biological processes are said
to be non-biodegradable.
All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem.
Components of Ecosystem
All the living components of the ecosystem form the biotic components.
Ex:- Plants, animals, microorganisms.
All the non-living components of the ecosystem form the biotic components.
Ex:- Temperature, rainfall, wind, soil and minerals.
Types of Ecosystem
The ecosystem which exists in nature on its own is called natural ecosystem.
Ex:- Forests, ponds and lakes.
The human-made ecosystem is known as artificial ecosystem.
Ex:- Gardens and crop-fields.
Classification of Organisms
- Producers (Autotrophs)
The organisms which can produce their own food by photosynthesis are known as producers.
Ex:- All green plants and certain blue green algae.
These organisms which consume the food produced, either directly from producers or indirectly by feeding on other organisms are known as consumers.
Types of Consumers
The organisms which obtain their food directly from the plants are known as herbivores.
Ex:- Goat, deer, cow etc.
The flesh eating organisms are called carnivores.
Ex:- Lion, tiger etc.
The organisms which feed on both plants and animals are called omnivores.
Ex:- Human beings, crow etc.
The organisms which live and feed on other organisms without killing them are called parasites.
The organism which obtains the food is called a parasite and the organism from whose body food is obtained is called the host.
Ex:- Amarbel (Cuscuta), lice etc.
The organisms which feed on and breakdown the remains of dead organisms and waste products of organisms are called decomposers.
Ex:- Fungi, bacteria
- Decomposers help in the natural replenishment of the soil and keep the environment clean.
A series of organisms in which one organism eats another organisms as food is known as food chain.
The interconnection of the food chains is called food web.
Different steps or levels of the food chain are called trophic levels.
Flow of Energy
- The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.
- 10% law:- When green plants are eaten by primary consumers, an average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.
- Some of the rest 90% energy is lost as heat to the environment, some amount goes into digestion and in doing work and some goes towards growth and reproduction.
- Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps.
- There are generally a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.
- Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.
- The flow of energy is unidirectional.
The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs.
The phenomenon of progressive accumulation of certain harmful and chemical substances at each trophic level of a food chain is called biological magnification.
- Maximum concentration of such chemicals get accumulated in human bodies as humans occupy the top level in any food chain.
- Ozone forms a protective blanket around the earth which absorbs most of the ultraviolet (UV) radiations of the sunlight, thus protecting living beings from many health hazards like skin cancer, cataract, destructions of plants etc.
- Ozone layer is present in stratosphere. It is a deadly poison at ground level.
Formation of ozone
- The high energy UV radiations breakdown the O2 molecules.
O2 O + O
- These oxygen atoms then combine with O2 molecule to form ozone molecule.
O2 + O → O3
- The decrease in the thickness of ozone layer due to excessive use of synthetic chemicals like chlorofluorocarbons (CFCs) is termed as ozone depletion.
- Chlorofluorocarbons (CFCs) are used in refrigerators, ACs, fire extinguishers, aerosol sprays etc.
- In 1987, the United Nations Environment Programme (UNEP) succeeded in forging an agreement to stop CFC production at 1986 levels