CBSE Class 10 Science Chapter 15 Our Environment

Class Notes of Ch 15 : Our Environment

Class 10th Science

Our Environment

      Topics: 

• Introduction
• Biodegradable and Non-Biodegradable Substances
• Ecosystem
• Producers, Consumers and Decomposers
• Food Chains
• Food Web
• Effect of Depletion of Ozone Layer and Waste disposal to the Environment

Introduction

Environment is the sum total of all plants, animals and microorganisms (biotic factors) with all non-living factors(abiotic components).

Living beings always interact with each other as well as with the non-living things in the environment.

Environment consists of mixture of gases and particles, including nitrogen, carbon, oxygen, water.

Nitrogen, carbon, oxygen, water are changed from one form to another in separate biogeochemical cycles.

Biogeochemical cycle is the pathway by which a chemical substance moves through biotic and abiotic components of environment.

Biodegradable and Non-Biodegradable Substances

Biodegradable Substances

• The waste materials released from our daily activities are thrown in the environment.
• Some substances are broken down by biological processes are said to be biodegradable substances. Example – organic matter of plants and animals.

Non-Biodegradable Substances

• Some substances are not broken down by the bacteria or saprophytes are called non-biodegradable substances. Example- plastics.

• Enzymes which are used in the degradation of the substances are specific in their action and specific enzymes are needed for the breakdown of a particular substrate and that is why all bacteria cannot decompose all kinds of waste.
• The non-biodegradable substances are acted upon by physical processes like heat and pressure.
• Non-biodegradable substances are inert.
• Under certain conditions, the non-biodegradable substances can persist for long time and can also harm the various members of ecosystem.

Ecosystem

All organisms such as plants, animals, microorganisms and human beings interact with the non-living physical surroundings in an area called as the ecosystem.

The abiotic components of ecosystem are light, temperature, rainfall, wind, soil etc.

Various examples of ecosystem are forests, ponds, gardens, crop fields.

An ecosystem which is formed due to the result of interactions between organisms and the environment is natural ecosystem.

An ecosystem which is created by human beings and did not exist naturally is artificial ecosystem.

Example- Forests, ponds are natural ecosystem and gardens, crop fields are artificial ecosystem.

Producers, Consumers and Decomposers

Organisms are grouped as producers, consumers and decomposers based on the manner in which they obtain their sustenance from the environment.

Producers

• All organisms which can prepare their own food by photosynthesis using the radiant energy of the sun absorbed by the chlorophyll of the leaves are called producers.

Consumers

• The organisms which consume the food produced either directly or indirectly are called consumers.
• Consumers can be classified into primary, secondary and tertiary consumers based on their mode of nutrition.
• All herbivores and some parasites are primary consumers. Example- rabbit, which eats grass.
• Many small carnivores and some parasites are secondary consumers. Example- snake, which eats rabbits.
• Larger carnivores and omnivores are tertiary consumers. Example- owl, which eats snakes.

Decomposers 

• The organisms which break down the dead remains and waste products of organisms are called decomposers.
• Decomposers break down the complex organic substances into simple inorganic substances in the soil which is used by the plants.

Food Chains

A food chain is a series of organisms where all the organismsare dependent on next organism as a source of food.

The series of organism take part at various biotic levels to form a food chain.

Each step of the food chain forms a tropic level.

The producers (green plants) are at the first tropic level.

Primary consumers (herbivores) are at the second tropic level.

Secondary consumers (small carnivores) constitute the third tropic level.

Tertiary consumers (larger carnivores) form the fourth tropic level.

Producers have the greatest number of individuals

Grass is eaten by insects and frogs eat the insects which in turn are eaten by the snakes and eagles eat the snakes.

Flow of energy takes place from one component of the food chain to another.

The autotrophs capture 1% of energy present in sunlight and convert it into chemical energy, the chemical energy then flows to heterotrophs and decomposers.

When green plants are consumed by the primary consumers a great amount of energy is lost as heat to the environment and rest of the energy is used up by the body of consumers for digestion, growth, reproduction.

An average of 10% of food is turned into its own body which is again consumed by the secondary consumers.

At the fourth tropic level very less mount of usable energy remains as the energy which flows from one level to another is very little.Chemicals may enter our bodies through food chains.

Bio magnification is the process in which maximum concentration of chemicals get accumulated in the body organisms of fourth tropic level.

Pesticides used to protect the crop from pests are washed away in the water bodies or into the soil.

Plants and aquatic animals absorb the chemicals from soil and water bodies respectively which then accumulate in the body of tertiary consumers.

Human beings occupy the top tropic level hence maximum amount of chemicals accumulates in the body of human beings.

Food Web

Food web is a network of food chains where all the chains are naturally interconnected.

Each organism is generally eaten by two or more kinds or organisms which are again eaten by several other organisms and so instead of straight line food chain, the series of organisms dependent on one another food can be shown by branched lines which is called as a food web.

Flow of energy in a food chain is unidirectional, once it reaches the next tropic level it does not come back again.

For example- energy which passes to the herbivores does not come back again to autotrophs.

Effect of Depletion of Ozone Layer and Waste Disposal to the Environment

Ozone is a molecule formed by three atoms of oxygen.

Oxygen is essential for all life processes whereas ozone is a deadly poison.

At the higher levels of the atmosphere, it shields the surface of the earth from ultraviolet radiation of the sun which is highly dangerous to organisms as it can cause skin cancer.

The UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms which then combine with the molecular oxygen (O2) to form ozone (O3).

O2   -->O + O

O + O2 --> O3 (ozone).

Chlorofluorocarbon (CFCs) a synthetic chemical which is used as refrigerants and fire extinguisher has been linked for sharp drop of ozone in the atmosphere.

Heaps of garbage is heaped all over the places in towns, cities which can affect the environment badly.

Garbage causes damage to the local ecosystem.

Garbage if tossed into water it travels long distances with water current and wind which can directly affect aquatic life.

In land garbage can cause land pollution and can harm or kill animals, serves as a house of bacteria and also can start fire.

SCIENCE Revision Notes

Chapter:01  Chemical Reaction & Equation
Chapter:02  Acid Base & Salt
Chapter:03  Metals & Non Metals
Chapter:04  Carbon & its Components
Chapter:05  Periodic Classification of Elements
Chapter:06  Life Processes
Chapter:07  Control & Coordinates
Chapter:08  How do Organisms Reproduce
Chapter:09  Heridity & Evolution
Chapter:10  Light Reflection Refraction
Chapter:11  The Human Eye & the Colourful World
Chapter:12  Electricity
Chapter:13  Magnetic Effect of Electric Current
Chapter:14  Source Of Energy
Chapter:15  Our Environment
Chapter:16  Management of Natural Resource

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