Our Environment Class 10 Notes Science chapter-15

अनुक्रम (Contents)

OUR ENVIRONMENT

Our Environment Class 10 Notes Science

Environment

Environment refers to the sum total of all external factors, substances and conditions that surround an organism and thus influence by the same without becoming its part. It includes all the physical or abiotic and biological or biotic factors.

Ecosystem

It is a structural and functional unit of biosphere. An ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals. Environmental biology is also known as ecology which is the study of relationships between all living things and their non-living components.

The ecosystems are of the following two types:

1. Natural Ecosystems: These are the ecosystems which develop in nature without human support. Depending upon the habitats, natural ecosystem may be terrestrial, i.e., present on land, e.g.. desert, grassland and forest or aquatic, ie, found in water bodies, e.g. ponds, lakes and marine.

2. Artificial Ecosystems: These are the ecosystems which have been created and are maintained by human beings. The artificial ecosystems are also called man-made or anthropogenic ecosystems, e.g., aquarium, botanical gardens, parks, etc.

The biotic components of an ecosystem are primarily made up of three kinds of organisms: (i)Producer (ii) Consumer and (iii) Decomposers.

Consumers

These are organisms which depend upon the producers for food, either directly or indirectly by feeding on other consumers for their sustenance. They are also called heterotrophs. Herbivores, carnivores, omnivores and parasites are the various types of consumers.

Herbivores– eat only plants, e.g. goat, sheep, deer, rabbit etc.
Carnivores- eat only other animals. e.g.-lion, tiger etc.
Omnivores– eat both plants and animals e.g. man, dog, bear etc.

Parasites

These are organisms that live on (ectoparasites) or in (endoparasites) the body of another organism, i.e., host from which it obtain its nutrients, e.g. parasites of man includes fleas and lice.

Decomposers

These are micro-organisms that obtain energy from the chemical break down of dead organisms or animals or plant wastes. Decomposers break down the complex organic substances into simple inorganic substances that go into the soil and are used up once more by the plants. Decomposes act as cleansing agents of environment.

Food Chain

It is a sequence of living organisms in a community in which one organism eats other and is itself eaten by another organism to transfer energy. It helps to understand the food relationship and interactions among various organisms in an ecosystem. Each step of food chain is called trophic level.

Food Web

The various food chains operating within an ecosystem cannot function in isolation. They form a network with intercrosses and linkages. A network of interconnected food chains is called a food web. It has many populations of different species.

10 Percent Law

Ten percent law states that, ‘only 10 percent of the total energy entering a particular trophic level is available for transfer to the next trophic level.’ Thus, there is a gradual decline in the amount of energy available as we move from producer level to the next trophic level.

Biomagnification

It is an increase in the concentration of harmful chemicals in the body of an organism per unit mass at each successive trophic level in a food chain.

Ozone Layer

Ozone (o₃₎ is a molecule consisting of three atoms of oxygen whereas molecules of oxygen (o₂₎ contain only two atoms. Major part of it is present in higher levels of the atmosphere (stratosphere). Ozone has a characteristic pungent smell and is deadly poisonous.

Ozone Depletion

It refers to thinning of ozone layer. Ozone layer gets depleted due to the use of chemicals called aerosol, spray propellants like chlorofluorocarbons, oxides of nitrogen, methane, carbon tetrachloride, etc.

Biodegradable Wastes

The waste materials which can be broken down to non-poisonous or harmless substances by the action of certain microorganisms (like bacteria and fungi) are called biodegradable wastes. The enzymes released by microorganisms help to break them. They are generally organic wastes, e.g., garbage, sewage, livestock waste, etc.

Non-biodegradable Wastes

The waste materials which cannot be broken down to non- poisonous substances easily are called as non-biodegradable wastes. Microorganisms like bacteria and other saprophytes cannot break down such wastes because they do not have enzymes to break these materials into non-poisonous substances.

Some non-biodegradable wastes are-plastic, polythene bags, synthetic fibres, glass, aluminium, cars, iron nails and radioactive (nuclear) wastes.

Some methods of waste disposal may be Biogas plant, sewage treat plant, land fillings, composting, recycling and reuse. Landfill and incineration (means reducing to ashes) are also the methods of waste disposal.
Planktons are microscopic organisms freely floating on the surface of water in a pond, lake, river or ocean. They are of two types- phytoplanktons (microscopic aquatic plants) and zooplanktons (microscopic aquatic animals).

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