Environment and Ecology

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

Silent Spring is an environmental science book by Rachel Carson, published in 1962, the book documented the environmental harm caused by the indiscriminate use of pesticides.

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.

The carrying capacity of an environment is the maximum population size of a biological species that can be sustained by that specific environment, given the food, habitat, water, and other resources available.

The specific place where an organism lives is called its habitat.

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.

The cycling of elements in an ecosystem is called the biogeochemical cycle.

There are two types of ecosystem:

1) Terrestrial Ecosystem (Forest Ecosystems, Grassland Ecosystems, Tundra Ecosystems, Desert Ecosystem etc.) and

2) Aquatic Ecosystem (Freshwater, Marine).

The World Ocean (Marine Ecosystem) is the largest existing and most stable ecosystem on our planet.

Oceans is stable ecosystems since it stays unchanged over the long term.

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.

Trophic level

Trophic level is defined as the position of an organism in the food chain and ranges from a value of 1 for primary producers to 5 for marine mammals and humans.

The method to determine the trophic level of a consumer is to add one level to the mean trophic level of its prey.

Trophic levels can be represented by numbers, starting at level 1 with plants.

Further trophic levels are numbered subsequently according to how far the organism is along the food chain.

Level 1: Plants and algae make their own food and are called producers.
Level 2: Herbivores eat plants and are called primary consumers.
Level 3: Carnivores that eat herbivores are called secondary consumers.
Level 4: Omnivores that eat eat both plants and animal (carnivores or herbivores) derived food.

The pyramid of energy is always upright because when the energy flows from one trophic level to another, some energy is always lost as heat in each step. The pyramid of energy can never be inverted.

The pyramid of biomass is inverted in a pond or lake ecosystem. The biomass of phytoplankton is less as compared with that of the small herbivorous fish, that feed on these producers.

In a food chain only around 10 per cent of the energy is passed on to the next trophic level.

Apex predators by definition have no predators and are at the top of their food web.

For a food chain to have a tertiary consumer, there must be a secondary consumer available for it to eat and so on.

The higher up the consumer ladder one goes, the more the energy required to support it.

1) Producers (Autotrophs)
Primary producers, usually green plants and certain bacteria, phytoplankton, 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 (Primary consumers) are animals whose primary food source is plant-based. Examples: deer, koalas, and some bird species, as well as rickets and caterpillars.

Carnivores (Secondary consumers) are animals that eat other animals. Examples: lion, tiger, snakes, sharks, sea stars, spiders, and ladybugs.

Omnivores (Tertiary Consumer) are animals that eat both plants and animal derived food. Example: Humans, bears, chickens, cockroaches and crayfis etc.


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 as inorganic 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.

The term was coined by Joseph Grinnell to use it in a research program in 1917, in his paper "The niche relationships of the California Thrasher".

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.

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