What is Environment?

The word Environment means ‘surroundings’ (environs). Therefore, the environment of an individual, object, or system includes all of the other entities – both living (biotic) and non-living (abiotic)-with which it is surrounded. In an environment.

What are the different types of environment?

Primarily, the environment can be categorised into two:

Natural Environment: It includes all living and non-living things that occur naturally. For example, the environment in a forest surrounding an animal.

Human-made/ Artificial Environment: It is the environment made by humans i.e. they don’t occur naturally. For example, ForumIAS classroom.

What are the different components of an Environment?

The environment has two types of components: Biotic and Abiotic

What is an Ecosystem?

“Ecosystem” term was first coined by A.G. Tansely, in the year 1935. In simple terms, it is a community of living and non-living things that work together. The living and non-living things continuously exchange materials and energy between them. It forms the structural and functional unit of the biosphere (sphere of life). Ecosystem varies greatly in size. It can be as small as a pond or as large as a forest or sea.

Generalised Classification of Ecosystem:

Ecosystem is divided into two basic categories: Terrestrial and the Aquatic.

Terrestrial: Forest, grassland and desert are some examples of terrestrial ecosystems.

Aquatic: Pond, lake, wetland, river and estuary are some examples of aquatic ecosystems.

Ecosystems can be man-made too. Examples include an aquarium, crop field

Structure of an Ecosystem

The ecosystem consists of living (biotic) and non-living (abiotic) components. These components are linked with each other through nutrient cycling and energy flow. We will learn these processes in detail in the next discussion.

Autotrophs: They are the “Primary Producers”. They make their own food and do not “eat” others. Autotrophs can be of two types:

Phototrophs: They derive their energy from the Sun – the primary source of energy on the planet. These are the green plants that make their own food by the process of photosynthesis.

Chemotrophs: They obtain their energy from chemicals through a process called chemosynthesis and can make their own food. Example: Cyanobacteria

Heterotrophs: They are called “Consumers.” They take nourishment from others. They are not capable of making their own food. They can’t do photosynthesis. Hetero means “others”. They can again be classified into:

Micro Consumers / Saprotrophs / Osmotrophs: These are organisms that feed on dead organic matter generated from plants and animals (‘sapro’=rotten or decaying). They are again of two types:

Decomposers: These are those microorganisms such as bacteria and fungi that feed on and decompose other dead organic material.

Detritus feeders: These are small animals which feed on partially decomposed organic material. They contribute to the break down of detritus (remains of dead organisms). Examples: earthworms, mites etc.

Macro-consumers (Phagotrophs): These are consumers which feed on other living organisms for their source of energy. Phagotroph means nourishment by eating (phago=eating). They are of the following types:

Primary consumers (Herbivores): They feed directly on plants. Example: Cow, goat, grasshopper etc.

Secondary consumer (carnivore): They feed on primary consumers. They are the flesh-eating organisms. Example: fox, snakes, etc.

Tertiary consumer (Top carnivore): They are the ones feeding on secondary consumers. Example: hawk, tiger, lion etc.

Omnivores are those that eat both plants and animals. Some of us, (who are not vegetarians) are omnivores!!! Other examples include crow, rats etc.

Abiotic Components

Climatic and physical factors -air, water, soil and sunlight; rainfall, temperature, humidity, soil texture and geomorphic conditions.

Inorganic materials– Examples: carbon, nitrogen, sulfur, phosphorous, carbon-di-oxide, water, etc. These are involved in the cycling of materials in the ecosystems.

Organic materials– These are proteins, carbohydrates, lipids, humic substances, etc. They largely form the living body and link the abiotic compounds with the biotic factors.

What are the services provided by Ecosystem?

Regulatory      Maintaining the quality of air and soil, moderation of Earth’s climate, decomposition of waste

Habitat            provide refuge to wild plants and animals- contribute to the biological and genetic diversity

Production      Provision of food, shelter, clothing, fuel, medicines etc.

Aesthetic         Cultural, recreation and aesthetic benefits

Important Associated Concepts:

Habitat: The environment in which a particular organism lives is called its habitat.

All the populations living in the same place at the same time interact, forming a community. Such community also interacts with the non-living world around it, thus forming an ecosystem. Therefore, habitat is a part of the ecosystem.

Ecological Niche: The role and functional position of an organism within an ecosystem is called Ecological niche. Ecological Niche is species specific- No two species can have exact same niche.

A niche includes: the role the species plays (e.g. A pollinator, a decomposer), the food it eats, where it lives, where it reproduces and its interactions with other species.

Ecotone: Ecotone is a junction or boundary between two or more diverse ecosystems. For example, where the land (terrestrial system) meets sea (aquatic system), and there is a wetland having mangroves. They are ecotones.


1 Which of the following terms describe not only the physical space occupied by an organism, but also its functional role in the community of organisms?

a) Ecotone

b)Ecological niche

c) Habitat

d) Home range


2.) Which one of the following is the best description of the term “ecosystem”?

a) A community of organisms interacting with one another

b) That part of the Earth that is inhabited by living organisms

c) A community of organisms together with the environment they live in

d) The flora and fauna of a geographical area.


3.) Which of the following is not a feature of the Eutrophic lakes?

a.) They are generally occupied by blooms

b.) They have high plant nutrient flux

c.) They have low primary productivity

d.) They are dominated by blue green algae


Its high primary productivity which makes occupied by blooms.

4.) Which of the following is true about Species Diversity?

a.) It refers to the species richness only

b.) It refers to the species evenness only

c.) It is a combination of both species richness and evenness

d.) None of the above


Species Diversity refers to the number of different species present in a region and the abundance of the particular species.

5.) Which of the following is true about speciation?

  1. It refers to the formation of new species
  2. Genetic variations effect it
  3. Variation in ecosystem effects the speciation

Select the correct answer from the codes given below-

a.) 1,2,3

b.) 1 and 2 only

c.) 2 and 3 only

d.) 1 and 3 only


Speciation is the the formation of new species. It is effected by genetic and ecological variations.

Leave a Reply

Your email address will not be published. Required fields are marked *