3rd Standard Science Term - III
Unit - 1
Our Environment
I. Environment - Introduction
(Yazhini and her friends are going to school with her friends)
Yazhini : Daddy! Look at the parrots! How beautiful they are!
Father : Yes Yazhini. They used to stay on the trees near the pond.
Fathima : Uncle! Uncle! Can you please take us there?
Stephen : Yes uncle. Shall we go and have a look at them?
Father : Oh! Yes! (They are walking towards the pond)
Yazhini : We should be quiet while walking as, ther are not only parrots on the trees but also ant, spider, Squirrel, myna and monkey.
Fathima : Oh! Oh! Look at the fish and frog in the pond. I can see a turtle too.
Father : Yes! See how they live in the same place depending on the another.
Stephen : See there, goat and cow are grazing near the pond.
Father : Children, we are getting late. We shall go to school.
Children : Yes uncle. Thank you very much for showing us this beautiful place.
II. Environmental Factors
Our environment consists of everything around us. It has living and non-living things. We are surrounded by living things such as plants and animals and non-living things such as water bodies, sunlight, air and soil.
The living and non-living things in our environment interact with one another. Our environment is a wonderful gift to us given by the nature.
Our environment has two main factors : They are
(i) Biotic factors (ii) Abiotic factors
Biotic Factors
Living things in our environment are called biotic factors. E.g., Lion, Plantain, Dove, Human beings etc.
Abiotic Factors
Non-living things in our environment are called abiotic factors, E.g., Air, Soil, Water, Sunlight, Temperature etc.
III. Interaction between biotic and abiotic factors
All biotic factors depend upon abiotic factors for their living. Biotic and abiotic factors are linked to each other by the flow of energy through food. Plants are the most important among all the living things. Because they only can produce food from abiotic factors like air, soil, water and sunlight.
A few examples for interaction between biotic and abiotic factors are given below.
IV. Balanced Ecosystem
Imagine an environment where there are only plants, deer and lions.
- What will happen to the deer, if there are no lions in an environment?
- What will happen to the plants if there are no lions to eat the deer?
- If there is no plant in an environment, what will happen to the deer?
It is important for the food chain to exist in any ecosystem to make sure that the energy flows between the biotic and abiotic factors. A balanced ecosystem supports animals, plants and microorganisms to grow in their environment. An ecosystem is balanced, when the biotic and abiotic factors are able to cycle the energy and food as per their need.
The biotic factors in an ecosystem includes producers, consumers and decomposers.
1. Producers
The living things that can prepare their own food are called producers. Green plants are the producers. They make their own food by the process of photosynthesis. Hence, they are called primary producers. Including human beings all animals depend on plants for their food.
2. Consumers
The living things that eat the food prepared by the producers are called consumers. Most of the living things depend directly or indirectly on producers for their food. Consumers can be divided into three types based on their food as herbivores (plant eating animal), carnivores (flesh eating animal), omnivores (both plant and flesh eating animal).
3. Decompposers
Organisms that feed on the wastes, dead plants and animals are called decomposers. They return the nutrients to the soil.
E.g., Bacteria, Fungi.
Benefits of Plants
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