Ecosystem

What is an Ecosystem?

An ecosystem is a complex community of living organisms interacting with one another and their nonliving environment in some area. These interactions give rise to a complex web of relationships that sustains the ecosystem through the flow of energy and cycling of nutrients. The balance of nature helps us understand how different species live together and affect their environment.

Characteristics of Ecosystem

An ecosystem has the following characteristics:

• An ecosystem consists of biotic (living) and abiotic (non-living) components.

• Energy flows in one direction through different trophic levels.

• Necessary nutrients are continuously recycled through nutrient cycling.

• Organisms are connected through food chains and food webs.

• Ecosystems are dynamic and maintain ecological balance through natural interactions.

Units of an Ecosystem

An ecosystem is made of several interrelated units:

Habitat

• A habitat is the natural environment in which an organism lives and thrives.

• It comprises both the biotic and abiotic elements that an organism needs to survive, like food, water, or shelter.

• For example, forests are habitats for a uniquely large diversity of species, from birds and mammals to insects and plants, while deserts provide habitat for organisms like cacti, lizards, and scorpions.

Niche

• A niche means the function and status a species occupies in its environment, encompassing all interactions between the species, biotic and abiotic variables.

• What the species eats and how it procures food, how it interacts with other organisms—these make a niche.

• For instance, pollination, the collection of nectar, and the collection of pollen are the niche activities of the bee.

Community

• A community consists of different species that live together in a common habitat, but the interactions among its members define the structure and dynamics.

Population

• A population may be defined as a group of interbreeding individuals of the same species that either is or has the potential to be isolated in some particular locale.

• Population dynamics investigates changes in these populations over time and space, due to events such as birth, death, immigration, and emigration.

• For example, some models describe the growth of a population, like exponential growth models that describe very fast-growing populations with no limiting factors, or logistic growth models that stabilise the carrying capacity of the environment due to limiting factors such as food and space.

Types of Ecosystem

In ecology, an ecosystem is divided into different types based on region or on the basis of nature, such as land or water. Ecosystems are mainly classified into terrestrial and aquatic ecosystems based on their physical environment. They may also be classified as natural and artificial ecosystems.

• Terrestrial Ecosystem

• Aquatic Ecosystem

Terrestrial Ecosystem (Forest, Desert, Mountain, Grassland)

The terrestrial ecosystem contains land-based ecosystems where species interact among themselves as well as abiotic factors like climate, temperature, energy flow, food chain, and other factors. The types of terrestrial ecosystems on Earth are:

Aquatic Ecosystem (Marine, Freshwater)

The aquatic ecosystem is largely made up of animals and aquatic life, such as lakes, oceans, and seas. Aquatic animals, fish, and sea creatures all fall under this biological system. As water is plentiful, living things survive using oxygen dissolved in water. This ecosystem is much larger than the Earth's ecosystem, as it covers most of the Earth. The two types of aquatic ecosystems are:

Components of an Ecosystem

An ecosystem consists of two major components: biotic and abiotic components. These components interact with one another to maintain ecological balance and support ecosystem functioning. These interactions support the energy flow and nutrient cycling, making the ecosystem dynamic and self-sustaining.

Abiotic Components (Physical and Chemical factors)

Abiotic factors are the nonliving parts of an ecosystem that have a huge effect on living organisms within it. The factors create an environment in which biotic ones operate and play a very important role in shaping the structure and functionality of the ecosystem. Abiotic factors can be broadly classified into two major groups: physical and chemical factors.

Physical Factors

• Sunlight: It is the fundamental source of energy in almost every ecosystem. It triggers photosynthesis—such is the process whereby producers like plants and algae turn light energy into chemical energy for storage in glucose.

• Temperature: It appears to be one of the major controlling factors for metabolic rates, enzyme activity, and other physiological functions of living organisms.

• Water: It is indispensable for all living organisms because it is the primary constituent of cells and a medium for the majority of biochemical reactions. The types of vegetation and the different species of animals are a function of the water availability.

• Soil: It is a very complex mixture of mineral particles, organic matter, water, air, and living organisms. Its composition varies widely and influences the types of plants that may be grown in it.

Chemical Factors

• pH: It is the measure of the acidity or alkalinity of substances. It ranges on a scale from 0 to 14, where 7 is considered neutral, below 7 is acidic, and above 7 is alkaline.

• Minerals: These are inorganic elements essential for various physiological functions, both in plants and animals. Common minerals include calcium, magnesium, potassium, and iron.

• Gases: The type of organisms that are found in either water or soil can, at times, be determined by the availability of oxygen. In aquatic ecosystems, this could result in hypoxia. It can affect the rate of photosynthesis and thus the productivity of an ecosystem. CO2 concentration within the atmosphere controls the greenhouse effect and global climate patterns.

Biotic Components (Producers, Consumers, Decomposers)

All living organisms that coexist, interrelate, and interact with one another, as well as the abiotic factors of the ecosystem, are termed the biotic components. Those can be producers, consumers, and decomposers. These biotic factors contribute to balancing the ecosystem.

Producers (Autotrophs)

Producers are organisms able to obtain their food from photosynthesis or chemosynthesis and form the first trophic level in an ecosystem. They are therefore the energy sources for all other organisms.

Photosynthetic Producers: These are plants, algae, and certain bacteria—for example, cyanobacteria. They use sunlight, carbon dioxide, and water to synthesise glucose and oxygen.

• For example, primary producers are green plants, grass, trees, and phytoplankton in aquatic ecosystems.

• Photosynthetic producers convert sunlight into chemical energy through photosynthesis.

• The total energy they capture is called Gross Primary Productivity (GPP).

• After subtracting the energy they use for their own life processes (respiration), the remaining energy—Net Primary Productivity—is what becomes available to herbivores and other organisms in the food chain.

Chemosynthetic Producers: They are present mostly in extreme environments, for example, deep-sea vents. These include some bacteria that produce food through chemical reactions between inorganic molecules.

Consumers (Heterotrophs)

Consumers are organisms that cannot prepare their food and obtain energy by consuming other organisms. Consumers are categorised based on their diets as follows:

• Primary Consumers (Herbivores): These are organisms that get energy directly from producers. Examples of these are cows, deer, and caterpillars that eat plants.

• Secondary Consumers (Carnivores): These are the organisms that consume the primary consumers. Examples are lions, snakes, and frogs that eat herbivores.

• Tertiary Consumers (Top Predators): These are carnivores that feed on other carnivores. Examples are eagles, sharks, and orcas, which feed on the secondary consumers.

• Omnivores: These are consumers who developed the trait of consuming both plants and animals. Examples are humans, bears, and pigs.

Decomposers

Decomposers form a core constituent of an ecosystem and serve to break down dead organic material to return the nutrients to the environment. In this way, the process is important in maintaining self-sustaining and healthy ecosystems by guaranteeing a constant supply of basic elements required by producers.

Bacteria: These microorganisms are very effective decomposers that are found almost everywhere on the planet. They are crucial in degrading complex organic compounds, namely proteins, carbohydrates, and lipids, into simpler molecules. In the case of cellulose, for example, which is a polymeric compound, one of the chief constituents of plant cell walls, and indigestible to most animals, there are some specialised bacteria involved in breaking it down.

• Aerobic bacteria: These are organisms that require oxygen to live and multiply in, for instance, soil and water conditions with adequate availability of oxygen. They decompose the organic matter quickly and produce carbon dioxide, water, and minerals.

• Anaerobic bacteria: do not use oxygen for their survival and are found in places such as deep sediments, waterlogged soils, or in the digestive tracts of animals. They decompose organic material more slowly, with byproducts that are methane and other gases.

Fungi: They release enzymes that break down complex organic materials like lignin and cellulose into simpler compounds, known as decomposition. Fungi can degrade some of the most resistant plant materials and are extremely important in forest ecosystems, which break down fallen logs and leaf litter.

• Saprophytic Fungi: These fungi derive nutrients from dead or decaying organic matter. A wide network of thread-like hyphae penetrates the organic material, releasing enzymes outside that hydrolyse it before finally getting absorbed.

• Mycorrhizal Fungi: These are symbionts with plant roots. Although they don't themselves act as decomposers, they assist in nutrient cycling by breaking down organic matter into the soil, where they become more readily available to plants.

Detritivores: Earthworms are Detritivores by nature. They ingest high amounts of soil along with organic litter, break it down in the digestive systems, and excrete it in the form of castings rich in nutrients. This aerates the soil, improves its structure, and enhances nutrient availability to plants.

Functions of an Ecosystem

The primary function of any ecosystem is the exchange of energy from one kind of life to another, which keeps running in a circle and preserves the entire life of the planet. Without a highly balanced biological system, there would be no life on Earth at all.

Energy Flow

• The energy flow in an ecosystem begins with the ability of producers to capture solar energy by photosynthesis.

• Plants convert solar energy into chemical energy, and the latter is passed on to the consumers.

• The transfer of energy from the producers to primary consumers is to the secondary consumers, carnivores, and finally to the tertiary consumers, the top predators.

• According to Lindeman's 10% Law, only about 10% of the energy available at one trophic level is transferred to the next trophic level, while the remaining energy is lost as heat during metabolic activities.

Nutrient Cycling

• Nutrient cycles refer to those processes that work towards the balancing of major elements within an ecosystem.

• The carbon cycle reports on the movements of carbon between the atmosphere, hydrosphere, lithosphere, and biosphere.

• The nitrogen cycle shows how nitrogen is converted into various chemical forms as it moves through the atmosphere, terrestrial, and marine ecosystems.

• The water cycle describes the continuous movement of water on, above, and below the surface of the Earth.

• The phosphorus cycle describes the pathway phosphorus takes through rocks, water, soil, and living organisms.

• These nutrient cycles maintain soil fertility and ensure the continuous availability of essential nutrients required by living organisms.

Important Ecological Concepts

Ecological concepts help in understanding the connection of organisms with their environment and the balance maintenance that keeps an ecosystem thriving. The key concepts include the food chain, energy flow, nutrient cycling, population dynamics, and ecological succession.

Food Chain

A food chain is a linear sequence that shows the flow of energy and nutrients from one organism to the next in an ecosystem.

• Producers: The very bottom of the food chain; usually plants or algae, photosynthesising for energy.

• Primary Consumers: Herbivores that consume producers.

• Secondary Consumers: Carnivores consume primary consumers.

• Tertiary Consumers: Higher-level carnivores that consume the secondary consumers

• Decomposers: Organisms, mostly bacteria and fungi, involved in the breaking down of dead organisms to return nutrients to the ecosystem.

There are two major types of food chains:

• The grazing food chain, which starts with producers.

• The detritus food chain begins with dead organic matter.

Ecological Pyramids (Numbers, Biomass, Energy)

An ecological pyramid is a graphic representation that details or highlights the different trophic levels of an ecosystem in a specific locality.

• Pyramid of Numbers: The number of individual organisms in each trophic level is described. Often shows vast numbers of producers and progressively fewer consumers.

• Pyramid of Biomass: It describes the total mass of living tissue associated with each trophic level. There is a decrease in the biomass from producers via intermediate consumers to final consumers.

• Pyramid of Energy: It describes energy at each trophic level. It shows that energy is lost at each level (approximately 90%) because it is utilised for respiration and metabolic processes.

The pyramid of energy is always upright because energy decreases at each successive trophic level and cannot be recycled.

Food Web

A food web is the complete network of interconnected food chains within an ecosystem, illustrating the various routes energy and nutrients can take.

• Connected Chains: Multiple food chains overlap and intersect with one another.

• Biodiversity: Identifies the feeding diversity of relationships and dependencies among different organisms.

• Stability: The stability of the ecosystem is shown by giving alternative feeding options to organisms.

Ecological Succession

Ecological succession is the natural and gradual process by which ecosystems change and develop over time. Here are some important points:

• There are two types: Primary succession (on bare land with no life, like after a volcanic eruption) and secondary succession (in areas where life existed before, like after a forest fire).

• Pioneer species like lichens and mosses are the first to colonise barren areas and start soil formation.

• Climax community is the final, stable stage of succession where the ecosystem becomes balanced and mature.

• Succession increases biodiversity and improves nutrient cycling, making the ecosystem more complex over time.

• It can take hundreds to thousands of years for an area to fully go from bare land to a climax forest or ecosystem.

Human Impact on Ecosystems

Pollution, whether it be in the air, water, or soil, pertains to the inclusion of deleterious elements into an ecosystem, hence changing the natural self-proceeding and therefore affecting biodiversity. Air pollution through emissions gives rise to acid rain, while water pollution contaminates aquatic environments, and soil pollution causes the degradation of land quality. These pollutants harm organisms and disrupt the food chains and functions of ecosystems.

Deforestation from logging and agriculture is followed by habitat loss and changes in diversity. It also causes soil erosion as a result. Climate change, on the other hand, results in an increase in the level of CO2 in the atmosphere. Rising temperatures, resulting from climate change, alter species distribution and disrupt ecosystem health. The mitigation approaches are by reducing the emission of greenhouse gases through renewable energy sources.

Conservation Efforts

Conservation may involve the creation of protected areas, such as national parks, and the maintenance of biodiversity through sustainable agriculture, forestry, and sea fishing. On the other hand, restoration ecology targets rehabilitating degraded ecosystems to almost their natural state to ensure that there is enrichment of biodiversity and improvement in ecosystems that provide services. This helps to reduce the impact of humans and ensures the health of the ecosystem.

Ecosystem Services

Ecosystems provide various services important for life. This includes:

• Provisioning services - food and timber, fuel

• Regulating services - climate regulation and pollination, flood control

• Supporting services - soil formation and nutrient cycling

• Cultural services - recreation, and ecotourism)

Ecosystem NEET MCQs (With Answers & Explanations)

Important topics from the Ecosystem that are important for the NEET exam:

• What is an Ecosystem?

• Structure of Ecosystem

• Types of Ecosystem

• Ecosystem Functions

• Important Concepts - Food Chain, Food Web, Ecological Pyramid

Practice Questions for NEET

Q1. The term ecosystem was coined by:

1. E.P. Odum

2. A.G. Tansley

3. E. Haeckel

4. E. Warming

Correct answer: 2) A.G. Tansley

Explanation:

Ecosystem - Ecology is concerned with four levels of biological organisation – organisms, populations, communities, and biomes. The term "ecosystem" was coined by A.G. Tansley in 1935, while the term "ecology" was coined earlier by Ernst Haeckel. Therefore, the correct answer is A.G. Tansley.

Hence, the correct answer is option 2) A.G. Tansley

Q2. Which one of the following is not a functional unit of an ecosystem

1. Energy flow

2. Decomposition

3. Productivity

4. Stratification

Correct answer: 4) Stratification

Explanation:

An ecosystem can be visualized as a functional unit of nature, where living organisms interact among themselves
and also with the surrounding physical environment.

Stratification -

The vertical distribution of different species occupying different levels is called stratification. For example, trees occupy the top vertical strata or layer of a forest, shrubs the second, and herbs and grasses occupy the bottom layers.

Hence, the correct answer is option 4) Stratification.

Q3. Pyramid of numbers is:

1. Always upright

2. Always inverted

3. Either upright or inverted

4. Neither upright nor inverted

Correct answer: 3) Either upright or inverted

Explanation:

The number of predators can be more than the number of producers, as in the case of insects taking food from a tree. This will present an inverted number pyramid. A small number of herbivores feeding on a large number of plants will give an upright number pyramid.

Hence, the correct answer is option 3) Either upright or inverted.

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