Class 10, Science, Chapter-13, Lecture-1, Ecosystem (Notes)

POLLUTION: 

The undesirable change in physical, chemical, or biological characteristics of air, land, or water due to contamination with unwanted materials is termed as pollution.
Types of pollution

1. Air pollution
2. Water pollution
3. Land pollution

POLLUTANTS: 

The substances or agents that cause undesirable change in physical, chemical or biological characteristics of air, land or water are called pollutants.

TWO TYPES: (on the basis of their decomposition)

1. Biodegradable Pollutants:
   The pollutants which can be broken down by the action of micro-organisms and can enter the biogeochemical cycles are termed as biodegradable pollutants.
   Examples:
   domestic wastes , urine , faecal matter , sewage , agricultural residue , paper , wood , cloth.
2. Non-Biodegradable Pollutants: 
   The pollutants which cannot be broken down by the action of micro-organisms and may cause biomagnification in the food chains are termed as non-biodegradable pollutants.
   Examples: insecticides, pesticides, DDT, mercury, lead, arsenic, aluminium, plastics, radioactive wastes.

Some Substances are biodegradable while some are non-biodegradable.            
Justification:        

Compounds made of complex molecules get broken into smaller molecules (decomposed) by the action of micro-      organisms present in the atmosphere (soil, water, air) these are biodegradable compounds.

But many human-made compounds cannot be decomposed by these organisms under normal conditions.

So these compounds remain unchanged for a long period of time and are non-biodegradable compounds.        

Effects of Biodegradable substances in the environment:

(a)     Biodegradation of organic wastes produces various gases which cause suffocation and foul smell.        
(b)     It also produces methane which is a greenhouse gas and causes global-warming.        

Effects of Non-Biodegradable substance in the environment:

(a) The presence of non-biodegradable wastes such as polythene bags can cause the choking of sewage canals.        
(b) The presence of non-biodegradable chemicals can lead to biomagnifications thereby causing death of organisms of higher trophic levels.      

Ecosystem:

The structural and functional unit of the biosphere, constituting all the living and non-living components, which is capable of independent existence is called an ecosystem. 

Examples:

Natural ecosystems:    Forests, Deserts, Mountains, Lakes. 

Man-made ecosystems:    Gardens, Crop fields.

Components of an Ecosystem:

(a) Biotic components:

The living organisms of an ecosystem like plants, animals, human beings, microorganisms etc. are called biotic components.

(b) Abiotic components:

The non-living part of an ecosystem including physical environments like air, water, soil, minerals, etc and inorganic substances like oxygen, nitrogen, carbon dioxide, etc are abiotic components.    

A Garden is an Ecosystem.

Justification:

In a garden, the various biotic components such as flowers, insects, frogs etc interact with each other. The frog eats the insects. The insects feed on grass.

Also, their growth, and reproduction are affected by the abiotic components of the garden such as temperature, water, etc.

An aquarium needs to be cleaned but a pond does not.

Justification:

The microorganisms present in a pond break down the complex organic substances into simpler inorganic substances, which are then returned to the nutrient pool.

The absence of decomposers in an aquarium leads to the accumulation of harmful substances.

The absence of decomposers would affect the atmosphere.

Justification:

Decomposers break down complex organic substances into simpler inorganic substances. These inorganic substances return to the soil and are used by plants as nutrients.

In the absence of decomposers, the growth of plants will be affected and the balance between carbon dioxide and oxygen will be disturbed.