Ecosystems Science Notes

Ecosystems Science Notes

Important Points:


→ Living beings means biotic factors and non-living things are abiotic factors. The interactions between the two form an ecosystem. The structure which is formed due to these reciprocal relationships is called an ecosystem, Biotic and abiotic factors and their interactions form an ecosystem.

→ Decomposers: The carbohydrates, proteins and lipids which are organic substances are converted back into inorganic substances such as hydrogen, oxygen, calcium, iron, sodium, potassium, etc. by decomposers.
→ Decomposers are microorganisms that act on the dead bodies of animals and plants and bring about this natural degradation.

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Structure of an ecosystem

→ Every living organism needs some abiotic factors for survival. Each one thus adapts to the surrounding abiotic factors in their own way.
→ The abiotic factors are: Air, water, soil, sunlight, temperature, humidity, etc.
→ The abiotic factors have an impact on the biotic components in an ecosystem. The abiotic factors thus determine the survival and numbers of living organisms.
→ Due to interactions between biotic and abiotic components, the amounts of abiotic factors fluctuate. Every living organism may increase or decrease the proportion of abiotic components affecting other living organisms.


  • Niche is the role played by the living organism in its own ecosystem.
  • The position of the organism and role played by it in response to other organisms together form the niche.
  • E.g. A sunflower plant produces oxygen during the process of photosynthesis and also provides food and shelter for insects.

→ Types of ecosystem

  • Earth is a vast boundless ecosystem. On the Earth there are various types of ecosystems.
  • Complex interactions take place in each ecosystem. E.g. Forest, lake, oceans, rivers.
  • Ecosystems are based on size, place, climate, types of resident plants and animals.
  • Ecosystems are also subdivided according to specific functions that are carried and according to scientific viewpoints about a particular functioning of the ecosystem.
  • In tropical belt on the earth, there is great diversity of life.
  • Different ecosystems are linked directly or indirectly with each other. They cannot be separated totally as different units.

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  • Biome is a general term given to an aggregation of many small ecosystems. The living organisms in any biome have similarities with each other. The abiotic factors and climate is specific for each biome.
  • There are two main types of biomes: 1. Land biomes. 2. Aquatic biomes.

Land biomes

The biomes that are present only on the land are called land biomes. Land biomes are subdivided into subtypes according to the distribution of abiotic factors therein. E.g.

  • Grasslands
  • Evergreen forests
  • Desert
  • Tundra/Polar ecosystems
  • Ecosystems in Taiga
  • Tropical rainforests

→ The word Iceland ecosystem as given in the textbook is wrong. Iceland is a country. Ecologists use the word Tundra ecosystem or Polar ecosystems for snow covered regions.

→ Grassland ecosystem and Forest ecosystem:

Grassland ecosystem Forest ecosystem
Climate Rainfall is not enough, longer summer and limited rainfall. Excessive rain
Characteristics Grasslands Natural ecosystems. Different types of organic and inorganic factors, variety of climate, rainfall and temperature.
Animals Goat, sheep, giraffe, zebra, elephant, deer, chital, tiger, lion, birds, insects, microbes, etc. Variety of different animals.
Plants Vast growth of grass, shrubs and dwarf plants. Huge trees, creepers and variety of plants.

→ In Dudhwa forest around 150 years ago the one-horned* Rhino were in good number. But due to uncontrolled poaching and hunting, the one-horned Rhino became extinct in twentieth century. However, on 1st April 1984 the rhinos were restored here with special efforts. Now Dudhwa has become sanctuary for single-horned Rhino.

→ It is always said one-horned rhino and not single-horned rhino. Since it is more scientific and internationally accepted, we have used the term, one-horned rhino and not single-horned rhino.

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In India there are about 520 wildlife sanctuaries and National Parks in which ecosystem conservation is taken care of.

Sanctuary/ National Parks Animals
The Great Himalayan National Park White panther
Kaziranga National Park (Assam) Elephants, wild boars, wild buffaloes, deer, tigers, panthers, Rhinos
Bharatpur (Rajasthan) Variety of birds and mainly aquatic birds.
Ranthambore (Rajasthan) Tigers
Gir (Gujarat) The only habitat for Asiatic lion

Aquatic Ecosystems

71% of the earth’s surface is covered over with water. Only 29% of the earth has land. According to area, aquatic ecosystems are largest on the earth. Aquatic ecosystems are subdivided into:

  • Fresh water ecosystems
  • Marine ecosystems
  • Brackish water/Creek ecosystem.
Fresh water ecosystem Marine Ecosystem Brackish water/Creek ecosystem
Ecosystems like ponds, lakes and rivers. Ecosystems containing more saline /salty water. Ecosystems having less saline water where fresh water and salty water mix with each other.

→ Loss of ecosystem due to human interference:

→ There is destruction of every ecosystem due to man-made activities. The natural functioning of the ecosystems is disturbed due to many actions such as mining, deforestation, pollution. Some of such actions can even cause complete destruction of the ecosystem. Some animals too are exterminated.

→ The word ‘Diminishment’ as given in the textbook is not grammatically correct, Thus you can use the word, loss or destruction.

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Human activities responsible for destruction of the ecosystems:

→ Population explosion and overuse of resources:

Human beings occupy the top consumer’s position in any ecosystem. Human population explosion has caused tremendous pressure on the natural resources. The increased needs of the human beings result into more and more depletion of the natural resources. The changing lifestyle and the consumerism resulted into excessive consumption of natural resources. All these together causes stress on the ecosystems resulting into more pollution, more creation of solid waste materials, etc.


→ Due to increased population, there is need of more housing. This results into increased urbanization. Construction of houses, and creation of other infrastructure caused excessive utilization of agricultural fields, wetlands, grasslands, forests, etc.
→ The increased demand results into loss of natural habitats of many plants and animals. In this way, urbanization leads to loss of ecosystems.

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Industrialization and transport

→ The increasing industrialization causes more and more utilization of the raw materials. In order to obtain these resources, natural forests are cut down. This causes destruction of natural habitats. The construction of roads, railways, bridges all contribute to the loss of natural habitats.


→ When large number of people visit a particular place, there is pressure on the resources therein. The amenities provided to the tourists, cause destruction of the local ecosystems.

Large Dams (Mega-projects)

→ Huge mega projects like dams can cause vast land surface to be submerged. The surrounding vegetation and grasslands can go under water. The forests nearby are completely destroyed.
→ The water currents in the lower area are lessened. Moreover, many human settlements are destroyed. The people are displaced.

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→ When due to any cause, the two countries declare war against each other, it results into massive destruction of natural ecosystems. There is bombardment, mine explosions and other hazardous actions that destroy human life and property. Wars can change or completely destroy natural ecosystems.
→ Due to natural disasters such as earthquakes, volcanic eruptions, floods or droughts and also due to man-made changes, some natural ecosystems are either changed or completely destroyed.
→ It is very essential to protect and conserve natural ecosystems because they help to maintain the balance in the biosphere.

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