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Environment and Ecology

news-details Image Source Feb 15, 2021 21:31 IST , Updated: Sep 04, 2021 04:31 IST · 7 min read

1) Environment

Environment means anything that surround us, it includes animals, plants, soil, water and other living (biotic) and non-living (abiotic) things, physical, chemical and other natural forces.

It comprises both "living (biotic): water, light, radiation, temperature, humidity, atmosphere, acidity, and soil", and "non-living (abiotic): man, decomposers, organisms, plants and animals" components.

2) Ecology

The word "ecology" was coined in 1866 by the German scientist Ernst Haeckel.

Ecology is the study of the relationships between living organisms, including humans, and their physical environment. It seeks to understand the vital connections between plants and animals and the world around them.

Ecology also provides information about the benefits of ecosystems and how we can use Earth's resources in ways that leave the environment healthy for future generations.

Ecology not only deals with the study of the relationship of individual organisms with their environment, but also with the study of populations, communities, ecosystems, biomes and biosphere as a whole.

There are six levels of organisation of ecology: Biosphere, Biome, Ecosystem, Community, Population and Individual.

2.1) Individual

An individual is one organism and is also one type of organism (e.g. human, cat, moose, palm tree, gray whale, tapeworm, or cow in our example). The type of organism is referred to as the species.

2.2) Population

Population is a group of organisms usually of the same species, occupying a defined area during a specific time.

2.3) Community

A community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis.

Animals require plants for food and trees for shelter. Plants require animals for pollination, seed dispersal, and soil micro organism to facilitate nutrient supply. Communities in most instances are named after the dominant plant form (species).

2.4) Ecosystem

The term "Ecosystem" was first coined by A.G.Tansley, an English botanist, in 1935.

An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life.

An ecosystem can be as small as an oasis in a desert, or as big as an ocean, spanning thousands of miles. An oasis is an small patch of vegetation surrounded by desert.

There are two types of ecosystem: 1) Terrestrial Ecosystem (Forest Ecosystems, Grassland Ecosystems, Tundra Ecosystems, Desert Ecosystem etc.) and 2) Aquatic Ecosystem (Freshwater, Marine).

Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts. Abiotic factors include - Energy, Rainfall, Temperature, Atmosphere, Substratum, Materials, Latitude and altitude and Humidity etc.

These biotic and abiotic components are linked together through nutrient cycles and energy flows.

Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system.

Biotic factors include Plants, Animals, and Microbes etc.They are classified according to their functional attributes into producers and consumers:

1) Primary producers (Autotrophs)

Primary producers, usually green plants and certain bacteria and algae synthesise carbohydrate from simple inorganic raw materials like carbon dioxide and water in the presence of sunlight by the process of photosynthesis.

In aquatic ecosystem producers are various species of microscopic algae.

Primary producers are consumed by primary consumers (generally herbivores), which are then consumed by secondary consumers and so on.

Plants make up the primary trophic level of the food chain.

2) Consumers (Heterotrophs or phagotrophs)

Consumers are unable to make their own energy, and instead rely on the consumption and digestion of producers or other consumers, or both, to survive.

Herbivores are animals whose primary food source is plant-based. Examples: deer, koalas, and some bird species, as well as rickets and caterpillars. Carnivores are animals that eat other animals. Examples: lion, tiger, snakes, sharks, sea stars, spiders, and ladybugs. Omnivores are animals that eat both plants and animal derived food. Example: Humans, bears, chickens, cockroaches and crayfis etc.


Primary consumers are herbivores, their food source is the first trophic level of organisms within the food web, or plants. Primary consumers feed exclusively on autotrophs. Example: a grasshopper, white-tailed deer and zooplankton that eat microscopic algae in the water.

Secondary consumers nearly always consume both producers and primary consumers and are therefore usually classed as omnivores. Secondary consumers make up the third trophic level of the food chain. Example: Spiders, snakes, seals, bears etc.

Tertiary Consumers feed on primary and secondary consumers, and may also eat producers (plants). For a food chain to have a tertiary consumer, there must be a secondary consumer available for it to eat. Example: birds of prey, big cats, and foxes.

Quaternary consumer is simply a consumer which preys upon a tertiary consumer. To be classed as a quaternary consumer within a food chain or food web, there must be a tertiary consumer available for the quaternary consumer to prey upon.

Quaternary consumers are found in the fifth trophic level and are not to be found in every food chain. The higher up the consumer ladder one goes, the more the energy required to support it. Example: white shark, polar bear and alligator etc

Quaternary consumers are not necessarily apex predators, an apex predator is at the top of the food chain in which it exists, and is not the living prey of any other organism.

3) Micro consumers - Saprotrophs (decomposers or osmotrophs)

Saprotroph are organism that feeds on nonliving organic matte known as detritus at a microscopic level. Saprotrophic organisms are considered critical to decomposition and nutrient cycling and include fungi, certain bacteria, and funguslike organisms known as water molds (phylum Oomycota).

The products of decomposition such asinorganic nutrients which are released in the ecosystem are reused by producers and thus recycled.


An ecotone is an area that acts as a boundary or a transition between two ecosystems or biomes. A common example could be an area of marshland between a river and its riverbank.

Examples of ecotones include marshlands (between dry and wet ecosystems), mangrove forests (between terrestrial and marine ecosystems), grasslands (between desert and forest), and estuaries (between saltwater and freshwater).

It could contain species that are entirely different from those found in the bordering systems. Generally, there is a greater number of species found in these regions (ecotones) and this is called the edge effect.

Ecological niche

Ecological niche is a term for the position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role in the ecosystem.

A niche is unique for a species, which means no two species have exact identical niches.

2.5) Biome

A biome is a large community of vegetation and wildlife adapted to a specific climate they exist in. The seven major types of biomes are Tundra, Taiga, Temperate deciduous forest, Tropical rain forest, Savannah, Grassland and Desert.

A biome, the largest geographic biotic unit includes various communities and is named for the dominant type of vegetation, such as grassland or coniferous forest.

A biota is a term used for all the living things at a certain time at a certain place, examples of biota include Cambrian biota and Madagascan biota.

Read More: Biomes of the World

2.6) Biosphere

The biosphere (ecosphere) is made up of the parts of Earth where life exists. The biosphere extends from the deepest root systems of trees to the dark environment of ocean trenches, to lush rain forests and high mountaintops.

Since life exists on the ground, in the air, and in the water, the biosphere overlaps all these spheres - atmosphere (air), hydrosphere (water) and lithosphere (land).

The biosphere measures about 20 kilometers from top to bottom, almost all life exists between about 500 meters below the ocean's surface to about 6 kilometers above sea level.

Biosphere is absent at extremes of the North and South poles, the highest mountains and the deepest oceans, since existing hostile conditions there do not support life.

Food Chain and Trophic Level

A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community.

The trophic level of an organism is the position it occupies in a food web.

A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves.

The trophic level of an organism is the number of steps it is from the start of the chain.

A food web starts at trophic level 1 with primary producers such as plants, can move to herbivores at level 2, carnivores at level 3 or higher, and typically finish with apex predators at level 4 or 5.

The path along the chain can form either a one-way flow or a food "web".

Ecological communities with higher biodiversity form more complex trophic paths.

The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.

Related Questions
  1. The amount fo energy during transfer from one trophic level to another in an ecosystem:

    A) Increases

    B) Decreases

    C) Remain Constrant

    D) May increase or decrease

    Show answer

    UPPSC 2019

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