NCERT Notes of Ch 15 Our Environment Class 10th Science

NCERT Notes of Ch 15 Our Environment Class 10th Science 

Introduction 

* The term ecology was first used by Reiter in 1868.

* Ecology is the science that deals with reciprocal relationship of organism and the external world. 

* Ecology is the science which deals about interaction among organisms and between the organism and its physical environment. 

Substances

Biodegradable : 

These are substances that are broken down by biological processes. Means that these are decomposed due to biological action. 

Non biodegradable :

These are substances that are not broken or degrade by biological action. 

Ecosystem 

It is composed of a biological community integrated with its physical environment through the exchange of energy and recycling of nutrients 

                    

                               OR

An Ecosystem is a functional unit of nature where living organisms interact among themselves and also with the surroundings physical environment. It varies greatly in size from a small pond to a large forest or a sea. 

Components of Ecosystem :

An ecosystem is comprised of biotic and abiotic components. Abiotic component includes temperature, rainfall, wind, light, soil, minerals. Biotic components includes all living organisms like plants, animals and microorganisms. Biotic components may be grouped into three on the basis of their role in ecosystem —

(i) Producers: 

 Include green photosynthetic plants. They can trap solar energy to synthesise organic food. Hence called Autotrophs. 

(ii) Consumers:

 These are animals they cannot synthesise organic food and depend on producers. 

They are called heterotrophs. Consumers may be into four—

(a) Primary consumers  : These animals directly feed on producers. These are called herbivores. Example - Cow, Deer, etc.

(b) Secondary consumers : They are animals that feed on herbivores. Example - Toad, Spider, Lizard, Birds,etc.

(c) Tertiary consumers or secondary carnivores  : These include animals that feed on secondary consumers. Example - Snake.

(d) Top carnivores  : These are carnivores which are not eaten by others. Example - Tiger, Lion, Falcon, Peacock.

(iii) Decomposers:

They are saprophytic microorganisms deriving their food material from organic matter present in dead remains of plants and animals. They bring about cyclic exchange of materials between biotic community and environment.They are also called as reducers as they degrade complex organic matter. 

Food Chain

It is a sequence of living organisms which involves transfer of food energy from producers through a series of organisms with repeated eating and being eaten is called food chain. Each level or step in a food chain where transfer of energy takes place is called trophic level. 

          Grass — Cow — wolf — Lion

Food Web :

The network of interconnected food chains at different tropic levels in a biotic community is termed as Food web. Occurance of food web provides stability to ecosystem. 

Energy Flow in an Ecosystem

It is found that in a terrestrial ecosystem green plants captures about 1% of the energy of sunlight that falls on their leaves and convert it into food energy. When plants are eaten by primary consumers only 10% of it is turned into its own body and made available for next level of organisms. Rest energy is lost in various ways. 

Ten Percent Law of energy transfer :

Proposed by Lindema in 1942. During the transfer of energy from one trophic level to another 90% of it, is lost while only 10% is fixed in flesh. 

Pollution 

Any undesirable physical, chemical or biological change in characteristics of air, water, land or soil is called pollution. Agents that brings about such change are called as pollutants. 

Kinds of Pollution :

On the basis of origin it may be Natural or Anthropogenic. 

 Anthropogenic Pollution : It is man made pollution caused by human activities. Its magnitude is quite less than natural pollution. It accounts for only 0.05% of atmospheric pollution. Example - Noise, Pesticides,  industries,etc.

Natural Pollution : It is caused by Natural phenomenon like emission of large quantity of toxic gases and particulate matter. It accounts for 99.95% of atmospheric pollution. Example - Volcanoes, Landslides, U. V. ray, Marsh gas, Forest fires, etc. 

Ozone layer and its deplition

Ozone is Teutonic gas with formula O3. It is formed independently in the lower atmosphere. 

Types of Ozone:—

(i) Bad Ozone - It is formed in the lower atmosphere and harms plants and animals. 

(ii) Good Ozone - It is found in the upper part of atmosphere called Stratosphere and it acts as a shield absorbing Ultraviolet radiation from the sun U.V.rays are highly injurious to living organisms preferably absorbs U.V.rays and its high energy breaks the bonds within the molecules.

Ozone depletion :

The amount of ozone in the atmosphere began to drop sharply in the 1980s. This decrease has been linked to synthetic chemicals like CFCs. Which are used in refrigerators and in fire extinguishers. Chlorine atoms released from CFCs due to U.V.rays at as catalyst and react with ozone to convert it into oxygen. Although depletion is occurring widely in Stratosphere but it more over Antarctic region where a large area of thin ozone layer is formed which is called as Ozone Hole. 

Biognification

The phenomenon through which certain pollutants get accumulated in tissues in increasing concentration along the food chain is called Biomagnification. Pollutants like DDT and Mercury are non biodegradable hence they can not be matabolished in fat containing tissues of the organism. Higher concentration of these pollutants at higher level of food chain results into harmful conditions.