What is an Ecosystem? – Types, Importance and Functions of Ecosystem

Environmental biology is one of the critical Biology Topics that involves understanding how humans impact the environment and how to address environmental issues.

The Concept of the Ecosystem – Biotic and Abiotic Factors

An ecosystem is a community of living organisms (plants, animals, and microbes) in conjunction with the non-living components of their environment (like air, water, and mineral soil), interacting as a system. These biotic and abiotic components are linked together through the nutrient cycles and energy flows. Ecosystems are controlled both by the external and internal factors. External factors such as climate, the parent material that forms the soil, and topography control the overall structure of an ecosystem and the way things work within it but are not themselves influenced by the ecosystem. Actually, the ecosystem is a structural and functional unit of the biosphere or segment of nature consisting of the community of living beings and the physical environment, both interacting and exchanging materials between them.

Definition of Ecosystem

Ecosystem is the functional unit of ecology that deals with the interrelationship between the living and the non-living objects of the environment.

• Ecosystem is the scientific study of the relationship of living organisms with each other and with their environment (Haeckel, 1870).
• An ecosystem is a system formed in a given area in which the living organisms function together by interacting among themselves and with the surrounding non-living factors.

Important Characteristics of an Ecosystem

• It is normally an open system with a continuous, but variable influx and loss of materials and energy.
• An ecosystem is an overall integration of the whole mosaic of interacting organisms and their environment.
• It is a basic, functional unit with no limits or boundaries.
• It consists of biotic and abiotic components interacting with each other.
• Its functional unit is capable of energy transformation, circulation, and accumulation.
• An ecosystem is the smallest unit of the biosphere.
• Different types of ecosystems are present in different areas.

Scope and Importance of Study Ecosystem
Taylor (1936), in an attempt to define ecology, has very rightly pointed out the scope of ecology by stating that ecology is the science of all the relations of ecosystems, all organisms to all their environments. Ecology plays an important role in agriculture, crop rotation, weed control, management of grasslands, range management forestry, biological surveys, pest control, fishery biology, and in the conservation of soil, wildlife, forests, water supplies, water bodies like rivers, lakes, and ponds.

The ecosystem is defined as a dynamic entity composed of a biological community and its associated abiotic environment. Often the dynamic interactions that occur within an ecosystem are numerous and complex. Ecosystems are also always undergoing alterations to their biotic and abiotic components. Some of these alternations begin first with a change in the state of one component of the ecosystem, which then cascades and sometimes amplifies into other components because of relationships.

Some Important Terms Related to Ecosystem

• Atmosphere: The multilayered gaseous covering over the earth’s surface, is known as the atmosphere, e.g., O2, CO2, and other gases. It filters sunlight reaching the earth, affects climate and it is a reservoir of several gaseous elements, which are essential for life.
• Hydrosphere: All sources of water taken as a whole, namely oceans, rivers, streams, lakes, ponds, pools, polar ice caps, prater vapour, etc., form the hydrosphere. About \(\frac{3}{4}\)th of the earth’s surface (75%) is covered with hydrosphere.
• Lithosphere: The solid component of the earth, is called the lithosphere. It is multi-layered and its layers are the crust, mantle, and outer and inner core.
• Biosphere: The life-supporting environment of planet Earth, is called the Biosphere, which is composed of air, water, and soil, which are the components of three major sub-divisions of the biosphere-atmosphere, hydrosphere, and lithosphere respectively. It is expanded 7 km vertically below the sea level and 6 km vertically above the sea level, i.e., the sum of 13 km region of the earth.
• Flora: Species content of plants in an area.
• Fauna: Species content of animals in an area.
• Ecological Niche: The specific physical space is occupied by an organism and where organisms play their functional role in an ecosystem. In another way, ecological niche means the ultimate distributional unit within which each species is held by its structural and instinctive limitations.
• Biomass (or standing crop): The sum total of organisms (both plants and animals) of a specific region in place on earth, is called biomass of that place.
• Autecology: The study of an organism in relation to its surrounding living and non-living factors (habitat), is termed, autecology.
• Synecology: The study of associations of a group of organisms in relation to their environment in a particular area, is termed synecology.
• Benthos: Organisms living on or at the bottom of the water bodies, are called benthos, e.g., snail, sponge, coral, sea-anemone, etc. The animal benthos are classified as filter feeders (e.g., clam) and deposit feeders (e.g., snails).
• Necton: Organisms that can swim in water freely are called nectons, e.g., fishes, whales, prawns, etc.
• Phytoplankton: Free floating or freely suspended minute plants mostly unicellular or multicellular, are called phytoplanktons, e.g., unicellular algae (Chlamydomonas) or colonial algae (viz. Volvox, etc.). They are mostly autophytes.
• Zooplankton: Free floating microscopic animals, are called zooplanktons, e.g., Cyclops, Daphnia, and other small arthropods.
• Habitat: The place where an organism lives in nature.
• Autotrophs: Chlorophyll-containing green plants, are called autotrophs. They act as producers in an ecosystem.
• Homeostasis: The process during which the biological system tends to resist change and to remain in a state of equilibrium.
• Cybernetics: The science of control of an ecosystem.
• Biome: When the plant formation is controlled by biotic factors [activities of living organisms like plants, animals, and solid microorganisms], then the final steady stage in the succession, is generally called a biome, e.g., Tropical rainforest ecosystem, etc.
• Plankton: The term plankton indicates any dead or living organisms [plants or animals] that float passively in water and are more or less dependent on water currents or wind action for their movements.
• Population and community: The term population is used to include groups of individuals of any one kind of organism occupying a given area. Community includes all the populations of an ecosystem.
• Microenvironment: The intimately local and immediate surroundings of an organism.
• Macroenvironment: The sum total of the physical and biotic conditions existing external to the organism and its microenvironment.

Patterns or Types of Ecosystems

There are different types of ecosystems:
1. Natural Ecosystem
The natural ecosystem is one that develops under natural conditions without any human support, e.g., Sea, river, grassland, desert, forest, etc. It is also divided into the Terrestrial ecosystem and the Aquatic ecosystem.

(a) Terrestrial Ecosystem:
This ecosystem occurs over land. This type of ecosystem consists of-

• Forest ecosystem
• Grassland ecosystem
• Desert ecosystem

(b) Aquatic Ecosystem: This ecosystem occurs in water bodies. This type of ecosystem consists of-

• Freshwater ecosystem, e.g., ponds, lakes streams, swamps. It is also divided into lotic ecosystem and lentic ecosystem.
• Marine ecosystem: This type of ecosystem includes saltwater bodies, e.g., sea and estuary.

2. Artificial Ecosystem
The artificial ecosystem is one that has been created and is being maintained by human beings, e.g., village, city, garden, poultry, piggery, darns, apiary, aquarium, etc. There are a few characteristics of artificial ecosystems-

• Lesser diversity compared to natural ecosystems.
• Artificial ecosystems have well-defined goals. But it is more fragile and more vulnerable, due to lack of diversity.
• Have more productive value from anthropocentric perspectives.
• Artificial ecosystem can enhance the sustenance capacity of the population, by improving their design pattern.
• The artificial ecosystem depends upon natural cosmic laws.

According to the Permanency of Ecosystem

• Permanent ecosystem: A permanent ecosystem is one that persists for a long duration, e.g., a forest.
• Temporary ecosystem: A temporary ecosystem in one that persists for a short period, e.g., a rainwater pond or ditch.

According to the Components of the Ecosystem

• Complete ecosystem: An ecosystem that has all the components, is called a complete ecosystem, e.g., a forest.
• Incomplete ecosystem: An ecosystem that is deficient in one or more components, is known as an incomplete ecosystem, e.g., rainwater pond (without consumer), or sea bottom (without producer).

According to the size of the Ecosystem

The whole biosphere functions as a global ecosystem.

• Macro ecosystem: A large ecosystem is known as a macro ecosystem, e.g., a sea or marine ecosystem.
• Meso ecosystem: The ecosystem that is not so large is known as a meso ecosystem, e.g., a forest ecosystem.
• Micro ecosystem: A small ecosystem is known as a micro-ecosystem, e.g., a pond ecosystem.
• Nano ecosystem: An ecosystem that is very small is known as a nano ecosystem, e.g., an aquarium.

Ecosystem functional type is a modern ecological concept to characterize ecosystem functioning. This is a group of ecosystems that share similar dynamics of matter and energy exchanges between biotic and physical environments. The ecosystem is very complex, and the wonderful interaction of living and non-living things with their environment has been the foundation of energy flow.

Kinds of Ecosystem:

Components of Ecosystem

An ecosystem comprises several factors that may be dealt with under two categories Abiotic components and biotic components. Abiotic factors comprise elements like light, air, temperature, etc. and biotic components consist of consumers like eagle, lizard, shark, etc.

A. Abiotic Components

Except for living components, all non-living components in the ecosystem are abiotic components. Abiotic components are divided into three categories – Physical, Inorganic, and Organic components, and Physiographic or Topographic components.

1. Physical Components
Light, air, temperature, solar energy, water humidity, and atmospheric pressure are the primary physical components of the ecosystem that help to maintain the vitality of the living world.
(a) Solar Energy: Green plants are able to convert solar energy into chemical energy that is stored as potential energy in food substances. Consumers take this food and thus a relationship between producers and consumers is maintained in the ecosystem.

(b) Light:
It is the primary source of energy of the living world. Various life processes are influenced directly or indirectly by this factor. It also affects the distribution, colour and certain structures in terrestrial animals. It influences their pigmentation (skin colour) in several ways. In birds, light affects reproductive activities. The light factor also affects the orientation behaviour and normal daily activities of terrestrial animals. For example, cockroaches, moths, bats, etc., are active during the night. Light is also one of the major factors controlling the distribution, movement, coloration, and development of certain structures in aquatic organisms. The occurrence of bioluminescence in the sea is the result of low intensities of light.

(c) Temperature:
It may be divided into three types – optimum, maximum, and minimum. An optimum temperature is necessary for the processes of growth and development to proceed at a normal rate. In this temperature range, all life processes function smoothly and efficiently. The chemical constituents of the protoplasm suffer considerable range at around 38°C. The proteins, one of the chief constituents of the protoplasm, become denatured and coagulated at considerably high temperatures. However, the average maximum temperature for living organisms lies between 40°C-45°C.

(d) Water:
It is one of the most important physical factors that affects the vital processes of all living beings. It sets in motion the nutrients of the solid for the availability of plants. It forces the habit for a number of organisms. Along with the other factors, it regulated the structure and distribution of plants and animals. Water actions also influence the distribution of organism. Thus the differences between a lotic and a lentic community are mainly due to a substantial difference in the current factors.

(e) Humidity:
Humidity together with light and temperature plays a vital role in regulating the activities and distribution of organisms. The atmospheric humidity influences the form and structure of plants. It directly affects the transpiration rate in plants. Animals in rainforests live only when the air is almost saturated with moisture. On the other hand, desert animals live where the air is extremely dry.

(f) Wind:
Wind exerts in influence on both the Configuration and distribution of plants. It also affects other factors like water content and temperature in a’ given area, through its effect on evaporation. The direct effect of strong winds is mechanical leading to uprooting of trees and permanent curvatures in plants. Indirectly, it affects the transpiration rate by making the air surrounding the plants the most. The wind is also involved in the dispersal of pollen, seeds, and fruits.

(g) Atmospheric Pressure:
It exerts its own impression on the living world. It varies inversely with altitude. Low atmospheric pressure results in low oxygen pressure – a harmful condition due to less oxygenation of tissues.

2. Inorganic Components
The inorganic components of the ecosystem are water, soil, mineral elements, etc., which are involved in the material cycle. Potassium, calcium, sulfur, magnesium, phosphorous, iron, etc., mineral salts, and oxygen, nitrogen, carbon, hydrogen, etc., are the primary inorganic components of the ecosystem. Living organisms construct their bodies with the help of these elements. The nature of the solid, its water holding capacity; percolation of water through the solid; amount of water under the solid; solid air; soil temperature; and acidic, basic, or neutral nature of soil (soil pH) – all contribute towards the development of plants and vegetation.

3. Organic Components
The organic components of the ecosystem are proteins, carbohydrates, lipids, amino acids, dead and decomposed body, humus, urea, etc., all of which are synthesized in the biotic phase. These organic components produce a connecting link between living and non-living as biochemical substances.

4. Physiographic or Topographic Components
The altitude, undulating landscapes, amount of light falling on a place or wind blowing through the region, steep slopes, etc. constitute the topographic factors of an ecosystem.

B. Biotic Components

Plants, animals, and microbes constitute the biotic components. On the basis of a functional point of view, the living organisms of the ecosystem are divided into two components by Odum (1966), e.g., Producer and consumer.

1. Producer
Producers are autotrophic organisms, i.e., green plants which are able to manufacture food from simple inorganic substances in the presence of light energy and chlorophyll by photosynthesis yielding carbohydrates, proteins, fats, and other complex materials. In general, all green plants are known as producers. However, in a true sense, green plants only convert solar energy into chemical energy of food. So, in terms of energy, green plants are actually converters of energy or transducers.

There are certain bacteria that can prepare their own food by the chemosynthesis process. So, these bacteria are also producer-organisms. A part of synthesized food is used by the producers themselves and the remaining portion is used by the consumers and decomposers. In this process, a part of the solar energy is stored within the producer’s body as potential energy and again consumers release this energy by the respiration process as heat and kinetic energy.

2. Consumer
Consumers are heterotrophic organisms that ingest other organisms or particulate organic matter. Animals mainly depend directly or indirectly on the producer for their food, therefore, they are entitled as consumers. Consumers are of two types – Macroconsumers or phagotrophic, and Microconsumers or decomposers.

(i) Macroconsumers:
These include relatively big heterotrophic organisms, largely animals that ingest other organisms or food synthesized by the producers. Macro-consumers are of three kinds – Primary consumers, Secondary consumers, Tertiary consumers, and Quaternary consumers.

• Primary Consumers (Consumers of first order): The plant-eaters are called primary consumers. They include minute zooplankton like Cyclops, Daphnia, Stenocypris, Protozoa, etc. Some phytoplankton like Brachionus, Asplanchna, etc., and some benthic or bottom-form animals like insect larvae, fish, and mollusks act as primary consumers. Primary consumers of land are herbivorous animals, e.g., grasshoppers, pigeons, rabbits, monkeys, goats, cows, etc.
• Secondary Consumers (Consumers of second order): The carnivorous animals feeding on the primary consumers, are called secondary consumers, e.g., toads, lizards, and spiders are insect eaters, and dogs, cats, fox are small carnivores.
• Tertiary Consumers (Consumers or third order): These are flesh-eaters and eat the dead flesh from leftovers of the secondary consumers or carnivores, e.g., tigers, lions, whales, sharks, hawks, eagles, vultures, etc.
• Quaternary Consumers: The carnivores that are not killed or rarely killed and eaten by other animals, are called quaternary consumers. Quaternary consumers are present in some food chains. These organisms prey on tertiary consumers for energy. They are usually present at the top of a food chain. Lions, tigers, vultures, etc., are regarded as quaternary consumers.

(ii) Microconsumers or Decomposers:
These are heterotrophic usually microscopic organisms like bacteria and fungi which break down and decompose the complex substances of dead organisms (producers and macroconsumers), absorb the decomposed products, and release inorganic nutrients for reuse by the producers. Thus the decomposer organisms play a very important role within an ecosystem by helping to recycle the materials in the biosphere so that the process of life may go on like an unending chain. The producers, phagotrophs, and saprotrophs, thus, make up the biomass of the ecosystem – the living weight.

Difference between Biotic components and Abiotic components:

Biotic Components	Abiotic Components
1. These components represent the living organisms that are present in an ecosystem.	1. This type of component represents the non-living structure of the ecosystem.
2. It includes producers, consumers, and decomposers.	2. It includes all inorganic nutrients, organic matter, and other physical factors.
3. The biotic components utilize the chemical energy for their functions.	3. The abiotic components are influenced by the light and heat.

Differences between Producers and Consumers:

Producers	Consumers
1. Producers are autophytes. They prepare their own food by photosynthetic process.	1. Consumers are heterotrophs. They cannot produce their own food. So, they are compelled to depend for food on the producer.
2. Products contain green pigment (chlorophyll) in their body.	2. They are devoid of green pigment (chlorophyll) in their body.
3. They can convert the absorbed solar energy into chemical energy and store it within the food.	3. They cannot absorb the solar energy.
4. Producers release the oxygen during photosynthesis.	4. They cannot produce oxygen.
5. Producers present in the trophic level of the ecosystem much more in number than consumers.	5. Comparatively these are present in low numbers.
6. Producers are mainly green plants and some chemosynthetic bacteria.	6. Consumers are mainly animals (herbivores and carnivores).

Differences between Producers and Decomposers:

Producers	Decomposers
1. Producers are autotrophic. They can produce their own food by the photosynthetic process.	1. Decomposers are heterotrophic. They are able to take their food from dead and decaying substances of producer’s and consumer’s body.
2. They are competent for the synthesis of food due to the presence of green pigment chlorophyll.	2. Due to the absence of chlorophyll within the body, they are unable to prepare the food.
3. They are capable of oxygen synthesis.	3. They are not capable of oxygen synthesis.
4. They produce complex carbohydrate food substances with the help of inorganic components and solar energy.	4. The complex organic compounds from the dead body of producers and consumers are converted into simple substances.
5. Producers are mainly green plants and some chemosynthetic bacteria.	5. Decomposers are generally saprophytic-like bacteria and fungi groups of organisms.

Differences between Consumer and Decomposer:

Consumer	Decomposers
1. In the ecosystem they take the producers as their food.	1. In the ecosystem they take their food from the dead and decaying substances, from producers and consumers.
2. On the basis of their food taking, consumers are of three types – Primary, Secondary, and Tertiary.	2. Food-taking habits of all are the same.
3. Consumers are of mainly two types – herbivorous, and carnivorous.	3. Decomposers are all saprophytic in nature.
4. Consumers take the complex food substances, e.g., Animals.	4. Decomposers take the simple food substances, e.g., Bacteria and fungi.

Serial Modus Operandum of Ecosystem

• Use of solar energy by producers.
• Synthesis of organic substances by the producer in the presence of abiotic components.
• The food made by the producer is distributed among the different consumer levels serially.
• Decomposition of the complex substance of dead organisms (producers and macro consumers) by micro consumers and conversion into inorganic nutrients for reuse by the producer.