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.

Generalized Classification of Ecosystem:

The 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.

Now let us check the different components:

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 through 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:

1. 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 that feed on partially decomposed organic material. They contribute to the break down of detritus (remains of dead organisms). Examples: earthworms, mites, etc.

2. Macro-consumers (Phagotrophs): These are consumers that 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 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

1. Climatic and physical factors -air, water, soil, and sunlight; rainfall, temperature, humidity, soil texture, and geomorphic conditions.
2. Inorganic materials– Examples: carbon, nitrogen, sulfur, phosphorous, carbon-di-oxide, water, etc. These are involved in the cycling of materials in the ecosystems.
3. 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 the Ecosystem?

UPSC has a favourite topic with respect to the Ecosystem. But more than UPSC, Test Series Coachings have ecosystem functions as a favourite topic. Here the functions of an ecosystem are to provide certain Goods & Services. (GST is applied by government, not on the ecosystem, but on people who pass on these services from ecosystems to us ?)

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.