Maharashtra Board Class 8 Science Chapter 18 Ecosystems PDF Download

18. Ecosystems

Can You Recall?

1. Which factors do you found in your surrounding?

2. Are these factors directly or indirectly related to you?

Classify the following into living and non-living factors.

Sunlight, sunflower, elephant, lotus, algae, stone, grass, water, ant, soil, cat, fern, air, lion.

Ecosystem

The world around us is made up of living and non living factors. Living are called biotic factors while non living are called abiotic factors. There is a continuous interaction between these living and non living factors. Living organisms and their habitat, environment are corelated with each other.

The structure which is formed due to these reciprocal relationships is called an ecosystem. Biotic and abiotic factors and their interactions form an ecosystem.

18.1 Components Of Ecosystem

Living organisms need different types of abiotic factors and they have different capacities to adapt with those abiotic factors. Some microbes need oxygen, while others don't. Some plants need more sunlight, while others grow well in shade.

The organic substances (carbohydrates, proteins and lipids) from dead bodies of plants and animals are converted into inorganic substances (hydrogen, oxygen, calcium, iron, sodium, potassium etc.) by microorganisms. Therefore, microbes are said to be 'Decomposers'.

Teacher's Note

An ecosystem is like a family. Every member has a job to do. For example, in your school garden, plants make food, insects eat the plants, and birds eat the insects.

Exam Trick

Remember: Biotic = living (Bio = life). Abiotic = non-living (A = no). Just like "airplane" has no car, abiotic has no life!

Points To Remember

Biotic factors are all living things in an ecosystem.
Abiotic factors are non-living things like air, water, and sunlight.
Decomposers break down dead plants and animals.
Every ecosystem has producers, consumers, and decomposers.
All parts of an ecosystem depend on each other.

18.2 Interactions Among Factors Of An Ecosystem

Each and every abiotic factor (air, water, soil, sunlight, temperature, humidity) affects the biotic factors in the ecosystem. The abiotic factors in an ecosystem decide which biotic factors will survive in it and what will be their number. The proportion of abiotic factors in an ecosystem is always changing as biotic factors use or excrete abiotic factors. Every biotic factor affects abiotic factors as well as other biotic factors around it. Every living organism in an ecosystem plays a particular role while living, moving in that ecosystem.

The position of any living organism in context to other living organisms and the role it is playing is called 'Niche'. Eg. A sunflower plant in a garden evolves oxygen in the air and provides food and shelter for insects like ants, honey-bees etc.

Can You Tell?

1. What is the role of microbes in above interaction?

2. How do producers obtain abiotic factors?

3. From where do the consumers get their food?

Teacher's Note

Niche is like your role in your family. You study, play, and help at home. Each plant and animal has a special job in nature too. The sunflower gives oxygen and food to insects, just like you help your family.

Exam Trick

Remember: Niche = your special job. Think of your favorite cricket player. They have a special position and job in the team. Every animal in nature also has a special job!

Points To Remember

Plants produce food using sunlight through photosynthesis.
Animals eat plants or other animals for food.
Decomposers break down dead things and return nutrients to soil.
Heat is released at every step in the ecosystem.
Everything in an ecosystem is connected to everything else.

Most of the ecosystems are complex and there is tremendous quantitative and qualitative variety of species in them. In ecosystems of tropical country like India, few species of living organisms are found every where in a large number. Remaining species of plants and animals are found in a small number. Some species are very few in number. Variety of ecosystems is found on earth. Each place has a different ecosystem. eg. Forest, pond, ocean, river etc. Types of ecosystems are formed according to size, place, climate, types of plants and animals.

Teacher's Note

India has many different ecosystems because it has forests, deserts, mountains, and rivers. Each one has different plants and animals. This is why India is rich in nature.

Exam Trick

Remember: Tropical = hot and wet (India is tropical). That is why we have so many types of plants and animals here. It is very different from cold countries!

Points To Remember

Ecosystems can be forests, ponds, rivers, oceans, or grasslands.
Each ecosystem has its own type of plants and animals.
Climate affects what can live in an ecosystem.
Some species are common, some are very rare.
Earth has many different ecosystems in different places.

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