Structural components

Ecosystems are complex systems comprised of various structural components that interact with each other and their environment. The primary structural components of an ecosystem is as follows: 

A. ABIOTIC COMPONENTS : These are non-living factors that influence the ecosystem. Examples include:

Climate: Temperature, precipitation, humidity, and sunlight.

Geology: Soil composition, terrain, and landforms.

Hydrology:  Water bodies such as rivers, lakes, and oceans, as well as the water cycle.

Atmosphere: Gases such as oxygen, carbon dioxide, and nitrogen.

B. BIOTIC COMPONENTS: These are living organisms within the ecosystem. They can be further categorized into:

Producers: Autotrophic organisms like plants and certain bacteria that produce organic matter through photosynthesis or chemosynthesis.

Consumers: Heterotrophic organisms that consume other organisms for energy. They include herbivores, carnivores, omnivores, and decomposers.

Decomposers: Organisms like bacteria and fungi that break down dead organic matter into simpler substances, facilitating nutrient cycling.

C.TROPHIC LEVELS: These represent the hierarchical levels of feeding relationships within an ecosystem. They include:

Primary Producers: Organisms that produce energy from sunlight or inorganic compounds.

Primary Consumers: Herbivores that consume primary producers.

Secondary Consumers: Carnivores that feed on primary consumers.

Tertiary Consumers: Carnivores that consume secondary consumers.

Detritivores: Organisms that feed on detritus, such as earthworms and some insects.

Decomposers: Microorganisms that break down dead organic matter.

D. HABITAT: The physical environment where an organism lives. Habitats can vary widely, including forests, grasslands, deserts, oceans, and freshwater bodies.

E. NICHE: The role or function of an organism within its habitat. It includes the organism's interactions with other species and its physical environment.

F. COMMUNITY: All the populations of different species that live and interact within a particular area.

G. POPULATION DYNAMICS: The study of how populations change over time, including factors such as birth rates, death rates, immigration, and emigration.

Understanding these structural components helps ecologists study and manage ecosystems, as well as comprehend the impacts of human activities on ecological systems.

Functions and Productivity of an Ecosystem

The functions and productivity of an ecosystem are closely intertwined with its structural components. The functions of an ecosystem encompass the processes and interactions that occur within it, ultimately sustaining life and maintaining environmental balance. Here are the key functions of ecosystems:

1. Primary Production: Ecosystems convert energy from the sun into organic matter through photosynthesis. Plants, algae, and some bacteria are primary producers that create energy-rich compounds, serving as the foundation of the food web.

2. Nutrient Cycling: Ecosystems facilitate the cycling of nutrients such as carbon, nitrogen, phosphorus, and others between living organisms and the environment. Decomposers break down dead organic matter, returning nutrients to the soil or water, where they can be taken up again by plants.

3. Habitat Provision: Ecosystems provide habitats for a wide variety of organisms. Different species have evolved to occupy specific niches within ecosystems, each adapted to particular environmental conditions and resources.

4. Biodiversity Maintenance: Ecosystems support a diverse array of species, each playing a role in the functioning of the ecosystem. Biodiversity ensures resilience against disturbances and enhances ecosystem productivity.

5. Climate Regulation: Ecosystems influence local and global climate patterns through processes like evapotranspiration, carbon sequestration, and the release of aerosols. Forests, for example, regulate temperature and humidity, while oceans absorb and store large amounts of heat.

6. Water Regulation: Ecosystems play a crucial role in regulating the water cycle by influencing precipitation, runoff, and groundwater recharge. Wetlands, for instance, act as natural sponges, reducing flooding by absorbing excess water during heavy rainfall.

7. Pollination and Seed Dispersal: Ecosystems provide essential services such as pollination and seed dispersal, facilitating the reproduction and spread of plant species. Pollinators like bees, butterflies, and birds are vital for the reproduction of many flowering plants.

8. Pest Control: Ecosystems maintain a balance between predator and prey populations, helping to control pests and regulate population sizes. Natural predators keep populations of herbivores in check, preventing overgrazing and ecosystem degradation.

9. Recreation and Cultural Services: Ecosystems offer recreational opportunities such as hiking, birdwatching, and ecotourism, contributing to human well-being and quality of life. They also hold cultural significance for many indigenous communities, providing spiritual and aesthetic value.

10. Carbon Sequestration and Storage: Ecosystems, particularly forests, grasslands, and wetlands, serve as carbon sinks, absorbing carbon dioxide from the atmosphere and storing it in vegetation and soil. This helps mitigate climate change by reducing the concentration of greenhouse gases in the atmosphere.

    
    

    These functions collectively contribute to the resilience, stability, and sustainability of ecosystems, supporting life on Earth and providing numerous benefits to humans and other species.

PRODUCTIVITY OF AN ECOSYSTEM

The productivity of an ecosystem refers to its ability to produce biomass or organic matter through photosynthesis per unit area during a specific period, typically a year. It is a measure of the energy flow and nutrient cycling within the ecosystem. Productivity can be classified into two main types:

1. Primary Productivity: This refers to the rate at which energy is converted by photosynthetic organisms, such as plants, algae, and some bacteria, into organic matter through the process of photosynthesis. Primary productivity is usually measured in terms of biomass produced per unit area per unit time, such as grams of carbon per square meter per year (gC/m²/year). It is influenced by factors such as solar radiation, temperature, water availability, and nutrient availability. Terrestrial ecosystems like forests, grasslands, and wetlands, as well as aquatic ecosystems like oceans, lakes, and rivers, exhibit varying levels of primary productivity.

2. Secondary Productivity: Secondary productivity refers to the rate at which consumers, such as herbivores, carnivores, and decomposers, convert organic matter into biomass through consumption and assimilation. It represents the energy flow through the ecosystem from producers to consumers. Secondary productivity is influenced by factors such as the availability of food resources, reproductive rates of organisms, and ecosystem structure. High primary productivity often supports higher levels of secondary productivity by providing more energy-rich resources for consumers.

The productivity of an ecosystem is crucial for supporting biodiversity, providing habitat and food resources for organisms, and sustaining ecological processes. It also has implications for ecosystem services such as carbon sequestration, nutrient cycling, and climate regulation. Understanding ecosystem productivity is essential for ecosystem management and conservation efforts, as changes in productivity can affect the stability and functioning of ecosystems and have implications for human well-being.

Food Chains

A food chain is a linear sequence of organisms in an ecosystem, where each organism serves as a source of food for the next organism in the chain. It represents the transfer of energy and nutrients from one trophic level to another within a community. Food chains typically consist of multiple trophic levels, including producers, consumers, and decomposers, and they illustrate the flow of energy and matter through ecosystems. Components of food chain are - 

PRODUCERS(AUTOTROPHS)

Producers are organisms that produce their own food through photosynthesis or chemosynthesis, converting solar energy into chemical energy stored in organic compounds. In terrestrial ecosystems, producers are primarily green plants, algae, and certain bacteria that capture sunlight and use it to synthesize organic molecules such as glucose. In aquatic ecosystems, phytoplankton, algae, and aquatic plants serve as primary producers, forming the base of the aquatic food chain.

CONSUMERS(HETEROTROPHS)

Consumers are organisms that obtain energy and nutrients by consuming other organisms. They are classified into different trophic levels based on their feeding habits and position in the food chain.

Primary consumers (herbivores) feed directly on producers, consuming plant material as their primary source of energy. Examples include grasshoppers, rabbits, and deer.

Secondary consumers (carnivores) feed on primary consumers, consuming herbivores as their primary food source. Examples include foxes, snakes, and small fish.

Tertiary consumers (top carnivores) feed on secondary consumers, consuming carnivores as their primary food source. Examples include wolves, eagles, and large predatory fish.

DECOMPOSERS

Decomposers are organisms that break down dead organic matter and recycle nutrients back into the environment. They play a crucial role in the decomposition and nutrient cycling processes within ecosystems.

Decomposers include bacteria, fungi, and detritivores (such as earthworms and scavengers) that feed on decaying organic material, breaking it down into simpler compounds that can be absorbed by plants and other organisms.

At the base of the food chain lie the primary producers. The primary producers are autotrophs and are most often photosynthetic organisms such as plants, algae, or cyanobacteria.

The organisms that eat the primary producers are called primary consumers. Primary consumers are usually herbivores, plant-eaters, though they may be algae eaters or bacteria eaters.

The organisms that eat the primary consumers are called secondary consumers. Secondary consumers are generally meat-eaters—carnivores.

The organisms that eat the secondary consumers are called tertiary consumers. These are carnivore-eating carnivores, like eagles or big fish.

Some food chains have additional levels, such as quaternary consumers—carnivores that eat tertiary consumers. Organisms at the very top of a food chain are called apex consumers.

Example of a simple food chain in a terrestrial ecosystem:

Grass serves as the primary producer in this food chain. It utilizes sunlight, water, and nutrients from the soil to photosynthesize and produce glucose, which serves as food for the next trophic level.

 The grasshopper is a primary consumer, feeding directly on the grass. It consumes plant material for energy and nutrients, such as carbohydrates and proteins, and serves as food for organisms at higher trophic levels.

 The frog is a secondary consumer in this food chain. It preys on grasshoppers as its primary food source, obtaining energy and nutrients from the herbivorous insects.

 The snake is a tertiary consumer, feeding on birds as its primary prey. It captures and consumes birds for energy and nutrients, completing this simple food chain.

In this example, energy and nutrients flow from the grass (producer) to the grasshopper (primary consumer), then to the bird (secondary consumer), and finally to the snake (tertiary consumer). Each trophic level transfers energy and biomass from lower to higher levels, with energy being lost as heat and metabolic processes at each transfer. This food chain illustrates the transfer of energy and nutrients through a linear sequence of organisms within a terrestrial ecosystem.

TYPES OF FOOD CHAINS

GRAZING FOOD CHAIN

Food webs

A food web is a complex network of interrelated food chains within an ecosystem, illustrating the flow of energy and nutrients through the biotic components (organisms) of the ecosystem. Unlike a simple linear food chain, which depicts a single pathway of energy transfer from producers to consumers, a food web represents the interconnectedness of multiple organisms and trophic levels.

1. Producers: At the base of the food web are the producers, typically green plants, algae, and some bacteria, which use sunlight to perform photosynthesis and convert inorganic substances into organic matter. These primary producers form the foundation of the food web by providing energy to the rest of the ecosystem.

2. Primary Consumers(Herbivores): Primary consumers are organisms that feed directly on producers. They include herbivores such as insects, rabbits, deer, and many species of fish that consume plants or algae as their primary food source.

3. Secondary Consumers(Carnivores): Secondary consumers are organisms that feed on primary consumers. They are carnivores that prey on herbivores. Examples include snakes, birds of prey, and carnivorous fish.

4. Tertiary Consumers(Predators): Tertiary consumers occupy the highest trophic level in the food web and feed on secondary consumers. They are often apex predators that have few or no natural predators themselves. Examples include large carnivores like lions, wolves, and sharks.

   
   

   5. Decomposers: Decomposers are organisms, mainly bacteria and fungi, that break down dead organic matter (detritus) and waste materials, returning nutrients to the soil or water for reuse by primary producers. They play a crucial role in nutrient cycling and ecosystem functioning.

In addition to these primary components, food webs can also include omnivores (organisms that consume both plants and animals), scavengers (organisms that feed on dead animals), and detritivores (organisms that consume detritus).

Key features of food webs include:

• Interconnectedness: Organisms in a food web are connected through multiple feeding relationships, illustrating the complex interactions within an ecosystem.
• Energy Flow: Energy flows through the food web from producers to consumers and ultimately to decomposers, with energy transferred and transformed at each trophic level.
• Trophic Levels: Organisms are grouped into trophic levels based on their position in the food chain, reflecting their role as producers, consumers, or decomposers.
• Food Chain Length: The number of trophic levels and the length of food chains vary depending on the complexity of the ecosystem and the diversity of species present.

Food webs provide a holistic view of ecosystem dynamics, highlighting the interconnectedness and interdependence of species within a given ecosystem. They are essential tools for studying ecological relationships, biodiversity, energy flow, and the impacts of disturbances or environmental changes on ecosystems.

Trophic levels

Trophic levels represent the hierarchical levels in a food chain or food web, indicating the position of organisms based on their feeding relationships and energy transfer within an ecosystem. Each trophic level represents a stage in the flow of energy from producers to consumers and decomposers. There are typically four main trophic levels:

1. Primary Producers(Autotrophs):

   
   

   Primary producers are organisms that produce their own food through photosynthesis or chemosynthesis, converting energy from sunlight or inorganic compounds into organic matter. They form the base of the food chain and are usually represented at the first trophic level. Examples include plants, algae, and certain bacteria.

2. Primary Consumers(Herbivores):

   
   

   Primary consumers are organisms that feed directly on primary producers, consuming plant material as their primary food source. They occupy the second trophic level in the food chain. Examples include herbivorous insects, small mammals, and some species of fish.

3. Secondary Consumers(Carnivores):

   
   

   Secondary consumers are organisms that feed on primary consumers, consuming herbivores as their primary food source. They occupy the third trophic level in the food chain. Examples include carnivorous insects, larger mammals, and predatory birds and fish.

4. Tertiary Consumers(Top Predators):

   
   

   Tertiary consumers are organisms that feed on secondary consumers, consuming carnivores as their primary food source. They occupy the fourth trophic level in the food chain. Tertiary consumers are often apex predators with few or no natural predators themselves. Examples include large carnivores like lions, wolves, and sharks.

In addition to these main trophic levels, ecosystems may also include additional trophic levels such as omnivores (organisms that consume both plants and animals), scavengers (organisms that feed on dead animals), and decomposers (organisms that break down organic matter).

Understanding trophic levels is crucial for studying energy flow, nutrient cycling, and ecological interactions within ecosystems. Trophic relationships help to illustrate the complex web of interactions among species and the importance of maintaining balance and stability in ecosystems. Human activities, such as habitat destruction, overexploitation of resources, and pollution, can disrupt trophic relationships and have significant impacts on ecosystem health and biodiversity.

Ecological pyramids

ECOLOGICAL PYRAMIDS

An ecological pyramid is a graphical representation of the relationship between different organisms in an ecosystem. Each of the bars that make up the pyramid represents a different trophic level, and their order, which is based on who eats whom, represents the flow of energy. Energy moves up the pyramid, starting with the primary producers, or autotrophs, such as plants and algae at the very bottom, followed by  the primary consumers, which fed on these plants, then secondary consumers, which fed on the  primary consumers, and so on.  Ecological pyramids are prepared on the basis of number of organisms, their biomass and energy in each trophic level.

Ecological pyramids are mainly of three types: .

1. Pyramid of number

2. Pyramid of biomass

3. Pyramid of energy

1.  PYRAMID OF NUMBER

a)  It is the graphic representation of the number of organisms present in unit area of various trophic levels of a food chain with producers at the base and top consumers at the apex.

b) The pyramid of number may be inverted or upright.

c) Grassland, Pond and Forest Ecosystem are upright.

d) Parasites and tree Ecosystem are inverted in shape.

2. PYRAMID OF BIOMASS

a)It is the graphic representation of biomass of organisms present in unit area of various trophic levels of a food chain with the biomass of producers at the base and that of top carnivores at the apex. 

b)The pyramid of biomass of terrestrial ecosystem is upright or erect as there is gradual decrease in the biomass of organisms from the second trophic level to the final trophic level.

c) However, the pyramid of biomass of aquatic ecosystems (pond, lake, river etc). is inverted i.e. broad apex and tapering base which is because of the progressive increase in the biomass of the organisms from the second trophic level to the final trophic level.

d) In an aquatic ecosystem, most number of producers (algae) is microscopic and unicellular. They are more in number but their biomass is less than that of primary consumers.

e) The biomass of secondary consumers is more than that of primary consumers and the biomass of the final trophic level is the largest of all the trophic levels. Therefore, the pyramid of biomass of an aquatic ecosystem is always inverted.

f) Grassland and Forest Ecosystem are upright.

g) Pond  and water bodies are inverted .

3. PYRAMID OF ENERGY

a) A pyramid of energy is a graphical representation of the amount of energy at each trophic level of a food chain. They are expressed in units of energy per area per time.

b) Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost upon transfer.

c) The amount of energy and matter transferred through food to successive higher levels become less and less. Greater amount of energy is available at the producer (autotrophs) level than at the primary consumer level (herbivores).

d) The energy production of primary consumer is greater than that of secondary consumers (primary carnivores) and the energy at the tertiary consumer level (top carnivores) is produced in minimum amount.

Biogeochemical cycles

Biogeochemical Cycles

Energy flows directionally through ecosystems, entering as sunlight and leaving as heat during energy transformation between trophic levels but the flow of nutrient is cyclic. The nutrients are vital for the growth of organisms and sustenance of life in the biosphere is derived by the interaction of matter and energy. The organic and inorganic matters move reversibly in the atmosphere, hydrosphere, biosphere and Lithosphere through various cycles known as a Biogeochemical cycle. This recycling of the nutrients is called biogeochemical or nutrient cycling. (Bio - living; geo - rock; chemical - element)

TYPES OF BIOGEOCHEMICAL CYCLES

Gaseous Cycle

In this type of cycle, the reservoir is either atmosphere or hydrosphere and it includes Water, Carbon, Nitrogen Cycle etc.

Sedimentary Cycle

 In this type of cycle, the reservoir is the earth crust and it includes Potassium, Calcium, Magnesium, Phosphorus, Sulphur Cycle etc.

CARBON CYCLE

Atmospheric carbon in the form of carbon dioxide is the critical source of carbon in an ecosystem. The Ecosystems gain most of the carbon from the atmosphere by the process of photosynthesis. In the process of photosynthesis carbon dioxide from the atmosphere, together with solar energy and water is converted into food and carbon gets trapped in the biomolecules. Carbon moves from one reservoir to another by these processes:

Combustion: Burning of wood and fossil fuels by factory and auto emissions transfers carbon to the atmosphere as carbon dioxide.

Photosynthesis: Carbon dioxide is taken up by plants during photosynthesis and is converted into energy rich organic molecules, such as glucose, which contains carbon.

Metabolism: Autotrophs convert carbon into organic molecules like fats, carbohydrates and proteins, which animals can eat.

Cellular respiration: Animals eat plants for food, taking up the organic carbon (carbohydrates). Plants and animals break down these organic molecules during the process of cellular respiration and release energy, water and carbon dioxide. Carbon dioxide is returned to the atmosphere during gaseous exchange.

Precipitate: Carbon dioxide in the atmosphere can also precipitate as carbonate in ocean sediments.

Decay: Carbon dioxide gas is also released into the atmosphere during the decay of all organisms.

WATER CYCLE 

Over two thirds of the Earth's surface is covered by water. It forms an important component of most life forms, with up to 70% of plants and animals being composed of water. Vast quantities of water cycle through Earth's atmosphere, oceans, land and biosphere. This cycling of water is called the water or hydrological cycle. The cycling of water is important in determining our weather and climate, supports plant growth and makes life possible.

Evaporation: Most water evaporates from the oceans, where water is found in highest abundance. However some evaporation also occurs from lakes, rivers, streams and following rain.

Transpiration: Is the water loss from the surface area (particularly the stomata) of plants.

Evapotranspiration: The processes of evaporation and transpiration are often collectively referred to as evapotranspiration.

Condensation: The process by which water vapour is converted back into liquid is called condensation. You may have observed a similar process occurring when dew drops form on a blade of grass or on cold glass. Water in the atmosphere condenses to form clouds.

Precipitation: Water returns to Earth through precipitation in the form of rain, sleet, snow or ice (hail). When rain occurs due to precipitation, most of it runs

off into lakes and rivers while a significant portion of it sinks into the ground.

Infiltration: The process through which water sinks into the ground is known as infiltration and is determined by the soil or rock type through which water

moves. During the process of sinking into the Earth's surface, water is filtered and purified.

Melting  and freezing: Some water freezes and is 'locked up' in ice, such as in glaciers and ice sheets. Similarly, water sometimes melts and is returned to oceans and seas.

NITROGEN CYCLE

Nitrogen cycle, the series of natural processes by which certain nitrogen-containing substances from air and soil are made useful to living things, are used by them and are returned to the air and soil. All  living things must have nitrogen to build proteins.  The nitrogen cycle is essential to plants in unfertilised soils because in such soils the nitrogen compounds are not available to the plants in any other way. Animals and other living things that do not make their food, depend on the nitrogen cycle indirectly. Most animals, for example, eat plants or eat plant-eating animals.

The nitrogen cycle consists of five natural processes: nitrogen fixation, nitrification, assimilation, denitrification, and decay(ammonification).

NITROGEN FIXATION

a)  Nitrogen is an essential constituent of protein and is a basic block of al living tissue. It constitutes nearly 16% by weight of al proteins but the elemental Nitrogen is useless for living organism.

b)  Only a few single-cell organisms, like bacteria can use nitrogen from the atmosphere directly. The elemental nitrogen is needed to be converted into

organic compounds(nitrates or ammonia) which can be absorbed by the living organisms. This process is known as nitrogen fixation. It is carried out by

nitrogen-fixing bacteria.

c) Nitrogen fixation on earth is accomplished in three different ways:

1.  By microorganisms- bacteria and blue-green algae.

2. By man using industrial processes- e.g., fertilizer factories.

3. To a limited extent by atmospheric phenomena such as thunder and lighting.

NITRIFICATION

Nitrifying bacteria change the ammonium ions into nitrites and nitrates. Nitrosomonas and Nitrobacter are examples. Some of the nitrates are used by plants. The process of converting ammonium ions to nitrites or nitrates is called nitrification.

 ASSIMILATION

In this process nitrogen fixed by plants (nitrate) is converted into organic molecules such as proteins, DNA, RNA etc. These molecules make the plant and animal tissue. Plants assimilate ammonium and nitrates into proteins which are transferred through the food chain.

AMMONIFICATION

a)  Assimilation produces large quantities of organic nitrogen, including proteins, amino acids, and nucleic acids. Ammonification is the conversion of organic nitrogen into ammonia.

b) The ammonia produced by this process is excreted into the environment and is then available for either nitrification or assimilation.

 DENITRIFICATION

 Denitrification is the reduction of NO3- to gaseous N2 by anaerobic bacteria. This process only occurs where there is little to no oxygen, such as deep in the soil near the water table.  Hence, areas such as wetlands provide a valuable place for reducing excess nitrogen levels via denitrification processes.

SULPHUR CYCLE

The SO2 emissions by the volcanoes, which occur naturally. They either go up in the air, or be decomposed to become H2S .In the air, the sulphates promote condensation, then when it  precipitates it goes to either land or water.

When it  precipitates to land, the plants receive them through the soil. When the plant dies and decomposes it becomes sulfate again. Then the microorganisms

in the soil reduce the sulfate to hydrogen sulfide.

The decaying of organisms may lead to the sedimentation of sulfates and sulfides and the organic sedimentation. In the organic sedimentations, it takes millions of years to turn them into fossil fuel. Fossil Fuels are then dug up by energy companies, which produces smoke in the process.

PHOSPHORUS CYCLE

Phosphorus is an important element for all forms of life. As phosphate (PO4), it  makes up an important part of the structural framework that holds DNA and RNA together. Like calcium, phosphorus is important to vertebrates; in the human body, 80% of phosphorus is found in teeth and bones.

The phosphorus cycle differs from the other major biogeochemical cycles in that it  does not include a gas phase; although small  amounts of phosphoric acid (H3P04) may make their way into the atmosphere, contributing—in some cases - to acid rain.

The water, carbon, nitrogen and sulfur cycles all include at least one phase in  which the element is in  its gaseous state. Very little phosphorus circulates in the atmosphere because at Earth's normal temperatures and pressures, phosphorus and its various compounds are not gases. The largest reservoir of phosphorus is in sedimentary rock.

When it rains, phosphates are removed from the rocks (via weathering) and are distributed throughout both soils and water. Plants take up the phosphate ions from the soil. Plants take up inorganic phosphate from the soil. The plants may then be consumed by animals. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA.

When the plant or animal dies, it decays, and the organic phosphate is returned to the soil. Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus. This process is known as mineralisation.

 Since most of our phosphorus is locked up in sediments and rocks, it's not available for plants to use. A lot of the phosphorus in soils is also not available to plants.

These cycles are interconnected, as elements such as carbon, nitrogen, and phosphorus are essential for the growth and survival of organisms, and they influence each other's availability and cycling in ecosystems. Human activities, such as burning fossil fuels, deforestation, and industrial agriculture, can disrupt these cycles, leading to environmental problems such as climate change, eutrophication, and habitat degradation. Therefore, understanding and managing biogeochemical cycles are crucial for maintaining the health and sustainability of ecosystems.

Types and characteristics of ecosystem

An ecosystem is a self - regulating group of biotic communities of species interacting with one another and with their nonliving environment exchanging energy and matter. A pond, Lake, desert, grassland, forest etc . are common example of ecosystem. In simple term, ecology is defined as the study of ecosystem. The term 'Ecosystem' was coined by  A.G. Tansley in  1935.

TYPES OF ECOSYSTEM

1. Terrestrial Ecosystem  2. Aquatic Ecosystem

Terrestrial ecosystems are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:

A. Forest Ecosystems

B. Grassland Ecosystems

C. Tundra Ecosystems

D. Desert Ecosystem

A. Forest Ecosystem

A forest ecosystem consists of several plants, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests

help in maintaining the temperature of the earth and are the major carbon sink. Depending upon the climatic conditions forests can be of different types :

1.  Tropical Rain Forest

2. Tropical Deciduous forests

3. Tropical Scrub Forests

4. Temperate Rain Forests

5. Temperate Deciduous Forests

6. Evergreen Coniferous Forests

B. GRASSLAND ECOSYSTEMS

Grasslands are open areas of land where grasses or grass like plants are the dominant species. Other forms of vegetation such as trees are rare in grasslands because they are not suited to thrive in the grassland dry environment.

Three types of grasslands are found to occur in different climatic regions:

1. TROPICAL GRASSLANDS

2. TEMPERATE GRASSLANDS

3. POLAR GRASSLANDS

C. TUNDRA ECOSYSTEM

These are covered with snow for most of the year all the biomes. Tundra is the coldest of all the biomes.

*Low biotic diversity

*Simple vegetation structure

*Energy and nutrients in the form of dead organic material.

Tundra is separated into two types:

1 . Arctic Tundra

2.  Alpine Tundra

D. DESERT ECOSYSTEM

Deserts are found throughout the world. These are regions with very little rainfall. The days are hot and the nights are cold. About 1⁄3 of our world's land area is covered by deserts. Deserts are of three types based on climatic conditions.

TROPICAL DESERTS: Like Sahara and Namibia in Africa and Thar desert in Rajasthan.

TEMPERATE DESERTS : Like Mojave in Southern California.

COLD DESERTS: Like the Gobi desert in China.

2. AQUATIC ECOSYSTEM

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely

                                                                                           :

1.  Freshwater Ecosystem

2. Marine Ecosystem

1. Freshwater Ecosystem

 The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams, and wetlands. These have no salt content in contrast with the marine ecosystem.

2. Marine Ecosystem

The marine ecosystem includes seas and oceans. These have a larger salt content and greater biodiversity in comparison to the freshwater ecosystem.

Characteristics of ecosystems include biodiversity, productivity, resilience, and stability. Biodiversity refers to the variety of species and genetic diversity within an ecosystem. Productivity is the rate of biomass production through photosynthesis and primary production. Resilience is the ability of an ecosystem to withstand and recover from disturbances, while stability refers to the ability to maintain structure and function over time.

Ecosystems also provide various ecosystem services such as air and water purification, climate regulation, nutrient cycling, and provision of food and raw materials.