Environment:
All the physical surroundings on the earth are called environment.
It includes everything living and non-living things. It covers every part of the earth like atmosphere, lithosphere, hydrosphere etc.
Ecosystem:
The interaction of all the living organisms and non-living constituents in a particular place is called ecosystem.
Types of ecosystems:
Two types- (examples; Board 2025)
1). Natural Ecosystem:
Natural ecosystem is also two types.
a). Terrestrial ecosystem: Mountain, grassland, desert, coastal and forest ecosystem.
b). Aquatic ecosystem: Oceans, ponds, lakes, marshy, rivers etc.
*Don’t be confused If ponds or lakes are artificial ecosystem? They are considered natural ecosystem.
Reason: They are self-regulating and can sustain themselves without human intervention.
2). Artificial ecosystems or Man-made ecosystems:
These are made by man for his benefits or his recreational.
Ex. Gardens, crop fields, aquarium etc.
Reason: All these ecosystems are regulated by human.
Components of an Ecosystem:
An ecosystem consists of biotic components and abiotic components.
Biotic components:
The living things of an ecosystem is called biotic ecosystem.
Ex. Plants, animals and micro-organisms.
Abiotic components:
The non-living things are called abiotic components.
Abiotic components consist physical factors.
Ex. Temperature, rainfall, wind, soil, minerals etc.
Food Chain:
A series of organisms feeding on one another at various biotic levels is known as food chain.
OR
Food chain is the simpler and linear relationship between the producer and the consumers of different trophic levels.
Sun is the source of energy in the ecosystem.
A generalised food chain:
Sun→Producers→Consumer 1→Consumer 2→Consumer 3
Ex.
Grass→Rabbit→Hawk
Grasses→Grasshopper→Frog→Snake→Hawk
Green plants/grasses→Deer→Lion
Examples of some Aquatic food chains:
Phytoplanktons→Zooplanktons→Small fish→Large fish→Shark
Phytoplanktons→Zooplanktons→Small fish→Large fish
Food Web:
A food web is a network of food chains which establish a network of relationships between various species.
OR
The network of several interlinked food chains is known as food web.
A food web consists more than two food chains. A healthy food web lies in the length and complexity of food chains. Each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms.
Difference between food chain and food web:
Fig: Food web, containing of many food chains
All the biotic components can be categorised as follows:
a). Producers:
The living organisms which produce their own food are called producers. These are also known as autotrophs.
Ex. All green plants and Blue-green algae etc.
Producers produce their own food by photosynthesis process. These absorbs the water and minerals from the soil while takes carbon dioxide gas from the atmosphere. All the consumers are depended on producers directly or indirectly.
b). Consumers:
Those organisms which depend directly or indirectly on producers for their food are called consumers.
Types of consumers:
As per their feeding habits these are four types-Herbivores, Carnivores, Omnivores, parasites etc.
But as per the level in food chain, they are three categories- Primary consumers, secondary consumers, tertiary consumers.
Primary consumers (herbivores): Those organisms which eat plants are called herbivores. These are first organisms which eat the plants, so these are also known as primary consumers.
Ex. Goat, sheep, horse, cow, elephant, deer, grasshopper, seed eating birds (dove, pigeon, parrot), butterfly, rabbit, giraffe etc.
Secondary consumers (Primary carnivores): Those organisms which eat the herbivorous are called secondary consumers.
Ex. Lion, tiger, crocodile, peacock, eagle etc.
Tertiary consumers (Secondary carnivores): Those organisms which eat other carnivores are called tertiary consumers.
Ex. Snake, big fish, eagle, peacock etc.
Small carnivores: The small animals which eat herbivores are called small carnivores.
Ex. Lizards, frog etc.
Big or top carnivores: These eat the small carnivores. These are also called tertiary consumers.
Omnivores: Those organisms which can eat the plants or plant products and herbivores are called omnivores.
Ex. Cat, dogs, bear, human etc.
Parasites: Those organisms which live on the body of host and take food from it are called parasites.
These are two types-External parasites or internal parasites.
Ex. Lice, cuscuta (amar-bel), virus, bacteria etc.
Decomposers: Those organisms which convert the dead remains of the plants and animals into simpler substances are called decomposers.
Ex. Bacteria, fungi, earthworms etc.
Decomposers break down the complex organic substances to simple inorganic substances that go into the soil and are used up once more by the plants. These help in the replenishment of natural reservoirs and for cleaning environment. They also increase the fertility through this process.
Q. What will happen if decomposers are not there?
A. Decomposers play a very important role in the ecosystem. They help to clean the environment. The also helps to replenishment of the nutrients in the ecosystem. They break down the complex organic substances (organic wastes) into simpler inorganic substances (compost). By this way they help to increase the soil fertility.
Trophic level: Each step or level of the food chain is known as trophic level.
Trophic level 1: Producers (green plants and blue-green algae) are come the first trophic level.
Trophic level 2: Herbivores come in the second trophic level.
Trophic level 3: Small carnivores that eat the herbivores are come in the third trophic level.
Trophic level 4: Big carnivores that eat other carnivores are come in the fourth trophic level.
Energy Flow in the ecosystem and food chain:
10% law of energy:
According this law, only 10% of the energy is passed on to the next trophic level from one trophic level.
Rest of energy is either utilized for its own metabolic activities or is lost in the environment as heat.
Some important points:
Sun is the ultimate source of energy on the earth. Green plants capture about 1% of the energy of sunlight and convert it into food energy through photosynthesis.
When green plants are eaten by primary consumers, they get only 10% of the energy of green plants. Other 90% of the energy is lost as heat to the environment. Some amount of energy goes into digestion and in doing work, growth and reproduction.
An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.
The highest energy is got by herbivores because they feed upon the green plants. The loss of energy in each step is so great that very little usable energy remains after four trophic level or to the higher-level consumers. That’s why a food chain is found only till fourth trophic level.
The flow of energy in the ecosystem:
The transfer of energy is unidirectional. (Why? Board 2022; 2025)
The energy that captured by the green plants (autotrophs) does not revert back to the sun.
The energy which passes to the consumers does not come back to the back
to the plants.
Fig: The flow of energy in an ecosystem Fig: An example of 10% transfer of
energy in a food chain
Bio-Magnification (Biological Magnification):
The process of accumulation of chemicals in the individuals of higher trophic level is called bio-magnification.
Human is situated on the top of food chain. So, he receives higher concentration of these harmful chemicals. The result of this, human affects by various health problems.
Ex. The using of pesticides, insecticides and other chemicals to protect the crops from diseases and pests. These are harmful to other organisms and affects through ground water, plant produces like fruits, vegetables. These transfer one organism to other through food chain. Because these are non-biodegradable and these get accumulated progressively at each trophic level. The organism (like human) which is situated at higher level, affect most by these chemicals. This phenomenon is known as bio-magnification.
We affect to our Environment:
We affect to our environment through our activities. These activities change the environment around us.
Two environmental problems which are affected by our activities.
A). Ozone depletion
B). Waste disposal
(A). The depletion of ozone layer:
Ozone (O3) is a gas which found in the stratosphere of atmosphere. Mainly it occurs height between 15 to 37 km. Its high concentration is found between 25 to 37 km above the earth. This layer is also known as ozone layer.
It is known as earth’s protective umbrella. It supports the life on the earth.
Nature of Ozone gas:
Fig: Ozone layer
Formation of Ozone gas:
It is formed by three atoms of oxygen. The formation of ozone gas by two stages.
a). UV radiation reacts on oxygen (O2) and breaks it into free oxygen (O).
O2 UV→ O+O
b). These free oxygens then combine with oxygen gas to form ozone.
O2+O O3(Ozone)
Functions of Ozone gas:
It protects the earth from the harmful UV radiation coming from the sun. These UV rays are highly damaging to organisms. So, it is known as life supporter of the Earth.
Ozone Depletion:
The decreasing of amount of ozone in the atmosphere is known as ozone depletion.
Depletion of the ozone is also known as ozone hole.
It began to drop sharply in 1980s due to increasing of using CFC (Chlorofluorocarbons) which are used in refrigerators and in fire extinguishers.
The substances which deplete the ozone gas are called ozone depleting substances (ODS).
Ex. CFCs, HCFCs, Halons etc.
One molecule of chlorine breaks down the ozone gas for 115 years.
Effects of ozone depletion:
a). Skin cancer in human being
b). Cataract
c). Many diseases in plants
Prevention of ozone depletion:
In 1987, the UNEP (The United Nations Environmental Programme) succeeded an agreement to freeze CFCs production at 1986 levels.
(B). Waste disposal:
Increasing of waste problem is one of the biggest problems in the world. Every day the waste materials are increasing around us.
Reasons of the increasing of waste materials:
a). Increasing of the population and improvements in our life-style:
We generated the high amount of waste material around us.
b). Changes in attitude also have a role to play with more and more things we use becoming disposable.
What can we do?
The biodegradable waste is not a problem, but the actual problem from the non-biodegradable waste. Because it cannot be degraded by the natural process.
It affects us and environment.
It can pollute the air if we burn it,
It pollutes the water and aquatic animals if we throw it in water bodies,
It pollutes the ground water if we landfill it.
It also pollutes the soil and its fertility.
Solutions of waste disposal:
a). By preventing the above activities.
b). Stop using single use plastic and say no to use polythene/plastic bags.
c). By using clothes, paper and jute bags while shopping.
d). Through awareness about environment, scientific attitude, concern for community health and personal health.
e). Other solutions- by follow the 5Rs. Recycle, reuse, refuse, reduce, recover.
f). Changes in packaging (environmental-friendly) have resulted in much of our waste becoming non-degradable.
Differences between Biodegradable and non-biodegradable wastes:
