Hello students! In this lesson we will learn about our  environment.
As we all know that our environment consist of living organisms like
plants, animals, microorganisms and human beings and non-living living
organisms around us.
All these components of our environment interact with each other.
These interactive organisms along with the non-living components
together form the ecosystem.
For example: Terrestrial ecosystem,  Aquatic ecosystem, etc.
Terrestrial ecosystem consist of all the living organism residing on land
and all the non-living thing present  around them.
Aquatic ecosystem comprises of all the aquatic organisms and their environment.
Hence, we can say that ecosystem consist of two main components,
Biotic components and Abiotic components.
Biotic components comprises of all the living organisms,
while Abiotic components comprises of all the physical factors like
temperature, wind, rainfall, soil and minerals.
Ecosystems can also be classified in natural and artificial ecosystems.
Ecosystems like forests, lakes, ponds, they all are come in natural ecosystems.
While gardens, crop fields, aquariums, they all make artificial ecosystems.
Now, lets talk about the organisms present in our ecosystem.
There are three main kind of organisms depending on the manner on which they obtain their food.
And these are producers, consumers, and decomposers.
Now, we will talk about them one by one.
Producers are the organisms that make or produce their own food by photosynthesis.
For example: green plants and blue green algae.
So, we can say that all the producers are autotrophs.
Next consumers, these are the organisms which take food from the producers.
That is, we can say that all the heterotrophic organisms are the consumers.
These consumers can further be classified into herbivores, carnivores, omnivores, and parasites.
Herbivores are the animals that only feed on plants.
For example: rabbit, deer etc. They are called the primary consumers.
Next carnivores, carnivores are the organisms that only feed on animals. For example: lion, tiger, wolf, etc.
Now, these small carnivores like wolf, dog, etc are called secondary consumers.
While large carnivores like lion, tiger etc. are called tertiary consumers,
as they feed on secondary consumers.
Now next, Omnivores,
Omnivores are the organisms which feed on both plants and animals.
For example: all the human beings.
Last parasites. Parasites also derive their food from other organisms, but the main
difference between parasites and carnivores is that
carnivores obtain their food from dead animals, while parasites obtain their food from live animals.
Next, we'll talk about the third type of organisms in our ecosystems, that is the decomposers.
These decomposers break down complex organic substances into simpler organic substances.
They mainly act on the dead and decaying materials.
For example: micro-organisms like bacteria and fungi.
As all these decomposers use organic substances for their nutrition,
so, they are also heterotrophs.
Now, we can say that producers that is, grass is eaten by rabbit that is the primary consumer,
which in turn are eaten by secondary consumers, and which further are decomposed by decomposers.
For example: grass is eaten by rabbit, which in turn is eaten by lion.
When this lion dies, it's body is decomposed by micro-organisms or the decomposers present in the environment.
This sequence of who eats whom in an ecosystem is called food chain, or
we can say that the series of organisms taking part at various biotic levels form a food chain.
Each of these steps or levels in the food chain are called trophic levels.
So, we can say that the first trophic level comprises of autotrophs or the producers.
So, in this example grass makes the first trophic level.
Now, the second trophic level, it comprises of the primary consumers.
For example deer.
Third trophic level comprises of secondary consumers. For example lion.
In simple food chains like this, decomposers form the third trophic level.
There are generally more number of individuals in the lower trophic levels than in the higher trophic levels.
It can be shown diagrammatically like this.
Let's see the chain of all these organisms in pond ecosystem.
So, here the primary producers are the plants
which are growing along the borders of the pond,
and even on the surface of the water, that is the floating plants,
and even some plants which grow under water, that is the submerged plants.
So, these plants, they make their own food and so are the producers of the food chain in pond ecosystem.
Next, these plants are then eaten by herbivores which are,
the plant eating fishes, insects, etc., and they make the second trophic level of the food chain.
Then, these herbivores are in turn eaten by larger fishes or frogs which are the carnivores,
which makes the next trophic level of the food chain,
and when all these organisms, that is both plants and animals die,
they are decomposed by numerous bacteria and fungi, which are regarded as decomposers.
Now, lets see another example which is of forest ecosystem.
Now, as we all know that forest is a large area of land with a dense growth of trees.
So, in forest ecosystem also all these trees and plants, they consist of producers which is the first trophic level.
And then, all the animals which depend on all these producers, that is the herbivores
like deers, rabbits, pigeons, parrots or even some insects like grasshoppers, butterflies, etc.,
they make the second trophic level.
And then when these herbivores are eaten by carnivores, which are the tiger, lion, wolf, lizards, snakes, etc.,
they make the third trophic level.
Now, lets see the flora and fauna of forest ecosystem.
Now, flora it means the plants which naturally occur in a particular area, and
fauna means the animals naturally living in a particular area.
Now, let's see the examples of various flora and fauna of different ecosystems in India.
First, let's see about Gir forests which are in Gujarat.
The Flora of Gir forests consist of a large variety of shady trees like peepal tree, acacia, neem tree etc.
And also some wild bushes and grasses.
And the fauna of this Gir forest, it consist of the animals like bears, dogs, cats, rats, rabbits, kites, Vulture, etc. and
and the most significant animal being 'Lion'.
Now, let's see the example of another ecosystem which is, the Jim Corbett National Park, which is present in Uttarakhand.
The flora of this Jim Corbett National Park consists of various kinds of trees, including the pine trees, shrubs and grasses.
And the fauna, it consists of various types of animals, specially the tiger.
Now, let's see about Jaladpara Sanctuary which is present in West Bengal.
The flora of this sanctuary consists of various trees including the banyan trees.
And the fauna consists of a variety of animals and birds and specially the rhinoceros.
Now, let's see the energy flow in the food chain.
As we know that autotrophs are the producers from the first trophic level in the food chain.
They make their own food and derive energy from it.
This energy then travels down to all the trophic levels. The amount of energy at each trophic level
decreases continuously.
It is found that only 1% of the solar energy that fall on the leaves of the plant is utilized to make food.
These plants are then consumed by the primary consumers. So, they get this energy.
Now, this energy is lost in the environment in the form of heat, and some of this energy is used in the vital functions
like digestion, reproduction, growth etc.
And only 10% of the energy is really utilized by the organism and so on for the next levels.
So, the secondary consumers also have only 10% of the energy to be utilized for the further trophic levels.
By this, we can say that there is a unidirectional flow of energy in food chains.
That is, the energy flows from the sun to the producer, then from the producer to the primary consumers,
then to secondary consumers and so on.
Since, very little energy is present in the next trophic level, so, a food chain generally comprises of
only 4 trophic levels.
Now, as we know that all the organisms can be eaten by many different kind of organisms,
which in turn are further eaten by many organisms.
So, we can say that all these food chains are interdependent.
So, this system of interlocking and interdependence of food chains is called food web.
For example: grass can be eaten, either by a rabbit or by a deer.
And rabbit or a deer can be eaten, either by a wolf or by a lion.
Now, as you all know that the lion can also eat the wolf.
So, this interdependence between both these food chains depict a small unit of a food web.
Now, let me tell you an interesting fact about food chain which is biological magnification.
Biological magnification is the process in which the chemicals like pesticides and heavy metals
move up to the trophic levels and get accumulated in all the organisms.
Let me explain this with an example. Farmers spray pesticides or other chemicals on the crops.
These chemicals are then washed down in the soil and in other water bodies.
From there, when plants photosynthesize, they take up these chemicals along with the water.
These chemicals are also taken up by aquatic animals. And thus, these chemicals enter the food chain.
As these chemicals are non-biodegradable, so, they get accumulated at each trophic level.
It means that these chemicals are present in the highest concentrations in the highest trophic levels.
And as we all know that human being form the highest trophic levels.
So, these chemicals are in the highest concentration in the human beings.
This phenomena is known as Biological Magnification.
Now, let's have a quick glance of the lesson.
We have studied that all the interacting organisms of an area along with the non living constituents of the environment form an ecosystem.
Ecosystem consist of two components: Biotic components and Abiotic components.
There are three kinds of organisms in the biotic component of the ecosystem.
Like producers, consumers and decomposers.
Next we studied about the food chain. The sequence of who eats whom in an ecosystem is called a food chain.
Each of the steps or levels of a food chain are called trophic levels.
Only 10% of the energy present in the first trophic level gets transfer into the next level.
Next we studied about biological magnification.
It refers to the process in which certain substances like pesticides or heavy metals move up the food chain and get accumulated in all the organisms.
