Our Environment | Class 10 CBSE | Web Notes | Part 1: Ecosystem- What are its Components?

• The biotic and abiotic factors which surround any living organism are called its environment.

ECOSYSTEM – WHAT ARE ITS COMPONENTS?

• Organisms and physical surroundings interact with each other and maintain a balance in nature.
• All the interacting organisms in an area together with the non-living constituents form an ecosystem.
• Biotic components: Include all living organisms.
• Abiotic components: Include physical factors like temperature, rainfall, wind, soil, and minerals.
• Natural ecosystems: Forests, ponds, lakes, etc.
• Human-made (artificial) ecosystems: Gardens, crop fields, aquariums, etc.
• An aquarium is a self-sustaining system because it includes biotic factors (fishes, aquatic plants, animals, etc.) and abiotic factors (free space, water, oxygen, and food).
• Organisms can be grouped as producers, consumers, and decomposers.

Producers:

• They make food from inorganic compounds, e.g., green plants and some bacteria.
• Green plants make organic compounds (sugar and starch) from inorganic substances using solar radiant energy in the presence of chlorophyll. This is called photosynthesis.

Consumers:

• Organisms that directly or indirectly depend on producers for food. They consume food from producers or by feeding on other consumers.
  • Herbivores: E.g., grasshopper, rabbits, deer, etc.
  • Carnivores: E.g., frog, tiger, lion, etc.
  • Omnivores: E.g., humans, bears, birds, dogs, etc.
  • Parasites: E.g., roundworms, tapeworms, leech, etc.

Decomposers:

• They break down dead remains and waste products of organisms (complex organic substances) into simple inorganic substances. Inorganic substances go into the soil and are used by plants.
• If an aquarium is not cleaned, fishes and plants will die. Microorganisms (bacteria and fungi) break down the dead remains and waste products of organisms.
• If decomposers are absent, garbage, dead animals, and plants will not decompose, leading to accumulation of organic materials and causing pollution.

Food Chains and Webs

• A food chain is the series of organisms feeding on one another or organisms taking part at various biotic levels.
• Each step or level of the food chain forms a trophic level.
• Autotrophs (producers): First trophic level.
• Herbivores (primary consumers): 2^nd trophic level.
• Small carnivores (secondary consumers): Third trophic level.
• Larger carnivores (tertiary consumers): Fourth trophic level.



Food Chain: (a) In forest (b) In grassland (c) In a pond



Trophic levels

• Food is a fuel to provide energy. Thus, the interactions among various components involve the flow of energy.
• Autotrophs capture solar energy and convert it into chemical energy.
• From autotrophs, energy goes to heterotrophs and decomposers.
• The study of the flow of energy reveals that:
  • Green plants in a terrestrial ecosystem capture about 1% of the solar energy that falls on their leaves and convert it into food energy.
  • When primary consumers eat green plants, a lot of energy is lost as heat, some is used for metabolism, growth, and reproduction. About 10% of the food is turned into body. This is the average amount of organic matter present at each step and reaches the next level of consumers.
  • Food chains generally consist of only 3 or 4 steps since so little energy is available for the next trophic level.
  • There are generally many individuals at the lower trophic levels. Producers are in the greatest number.
  • Each organism is generally eaten by two or more kinds of organisms, which in turn are eaten by several other organisms. This series of branching relationships of food chains is called a food web.



A food web



Diagram showing flow of energy in an ecosystem

• Energy flow diagram shows the following features:
  • Energy flow is unidirectional. It does not revert back from autotrophs to the Sun or from consumers to autotrophs.
  • Energy available at each trophic level gets diminished progressively due to loss of energy at each level.
• Some harmful chemicals may enter bodies through the food chain, e.g., pesticides and other chemicals are washed into the soil or water. From the soil, plants absorb them. From water bodies, aquatic plants and animals take them up, thus entering the food chain.
• Non-degradable chemicals get accumulated at each trophic level. This is called biological magnification. Thus, cereals, vegetables, fruits, and meat contain pesticide residues. Their concentration is maximum in the human body because humans occupy the top level in any food chain.
• Methods to reduce intake of pesticides:
  • Minimize the use of chemical pesticides.
  • Wash fruits and vegetables thoroughly before use.
  • Use organic fruits and vegetables.

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1. Ecosystem – What Are Its Components? 2. How Do Our Activities Affect the Environment?

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