Food Chain and Food web

Food Chain and Food web

The formation and transfer of food energy in the ecosystem takes place from one level to the next in a hierarchical manner. The levels through which food energy passes from one group of organisms to the other group are called tropic levels.

The chain of transformation and transfer, of food energy in the ecosystem from one group of organism to the other group through a series of steps or levels (trophic levels) is called food chain.

In other words, the chain of transfer of food energy form one group of organisms to the other group in the biosphere (ecosystem) is called food chain and the point where food energy is transferred from one group of organisms to the other group is called trophic level.

On an average there are four trophic levels but they can vary from 2,3 to even 5, 6 etc depending on the length of food chain or size and scale of ecosystem we take into account.

Trophic Level- 1: This is the base of food chain where autotrophic primary producers like green plants produce food from nutrients, CO₂ and water by the process of photosynthesis. Sunlight is the primary source of energy entering the ecosystem.

Functioning of an Ecosystem

Functioning of an Ecosystem

An ecosystem is driven by the flow of energy and circulation of matter by biogeochemical cycle between the biosphere, lithosphere, hydrosphere and atmosphere. The solar radiation is the basic input of energy entering the ecosystem. In the living organisms or biosphere, the energy (chemical energy) and matter (food), collectively called as food energy, are transferred via food chain and food web through various trophic levels. Thus all the elements of an ecosystem are interdependent and integrated. An ecosystem itself is integrated with other ecosystems and thus they all become interdependent. In fact every ecosystem is part of the larger ecosystem, until the larger ecosystem of the earth-the biosphere – is formed. That is why we see climatic changes happening in one ecosystem affecting the other ecosystems.

Productivity of Ecosystem

Only a small fraction of sunlight striking the earth is concerted to chemical energy by primary producers. The rate of conversion of solar energy into chemical energy (organic matter) by autotrophs is called productivity of ecosystem. The productivity of ecosystem depends to two things:-

(i)                  The availability of solar radiation to autotrophic primary producers. The productivity of ecosystems goes in decreasing from equator to poles as the amount of solar energy received goes on decreasing from equator to poles. Therefore, plants in tropical areas will have higher productivity than plants in temperate or tundra region.

(ii)                The efficiency of plants to concert solar energy into food or chemical energy which is also called as primary production. It is measured in two ways:

(a)    Gross primary productivity which is total amount of chemical energy assimilated by the autotrophs from solar energy.

(b)   Net Primary Productivity is equal to Gross Primary Productivity minus the energy lost through respiration.

Ecosystem Ecology

Ecosystem Ecology emphasizes the movement of energy and nutrients among the biotic and abiotic components of ecosystems. It examines physical and biological structures and how these characteristics interact with each other. A major focus of ecosystem ecology is on functional processes, ecological mechanisms that maintain the structure and services produced by ecosystems. These include production of biomass, decomposition and tropic interactions. In short ecosystem ecology studies the interdependent functional processes behind food chain and food web and how all the applied to cases such as increased effects of atmospheric co₂ on coral reefs and fishes or to understand the effects of increased pesticides application on the pests and birds preying on them.

Ecosystems

Having done with basic concepts we will return to the ecosystems. As said earlier, ecosystem is a fundamental functional unit characterized by total assemblage of biotic community and abiotic components and their mutual interactions in a given space time unit.

Ecosystems can be classified as following:

(i)                 On the basis of habitats:

(a)   Terrestrial – Upland or mountain; Lowland; Warm Desert and Cold Desert.

(b)   Aquatic – Fresh Water; Marine.

(ii)               On the basis of human intervention:

(a)   Natural ecosystems e.g. tall grass or Amazon rainforest ecosystem.

(b)   Artificial or cultivated ecosystems e.g. rice field ecosystem.

Components of the Ecosystem

Biosphere

Biosphere

Having defend ecology and ecosystem, the next thing is biosphere. In simple words, biosphere is the largest i.e. earth. Alternatively it is the global sum of all ecosystems on the earth. Biosphere is that part of the earth which contains living organisms- the biologically inhabited soil, air and water. So, biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of lithosphere, hydrosphere and atmosphere. Biosphere becomes the largest ecosystem because it (the biospheric ecosystem) consists of biotic component (plants, animals, man, and micro-organisms), abiotic component (land, air and water) and energy component (solar and geothermal energy) and these are on the scale of earth.

The components are inter-related through a series of large cyclic mechanisms, collectively called as biogeochemical cycle. In biospheric ecosystem there is a continuous exchange of energy and matter. While the circulation of energy is unidirectional, the materials are circulated cyclically called as biogeochemical cycle.

Ecology

Ecology

Ecology is the science which studies the inter-relationships between biotic and a biotic components of a natural ecosystem on one hand among biotic components on the other. Thus ecology is the study of interrelationships and various processes between all organisms and their environment as well as among the organisms themselves.   

Ernst Haeckel coined the term ‘Oekology’ (Greek: oikos – house or dwelling as habitat, logos—study of). The concept of ecology evolved from Darwin’s concept of evolution of species through natural selection involving interaction between biological species and habitat.

Ecology is studied into two branches. First, autecology is the study of ecological relationship of single species in a given ecosystem. Second, synecology is the study of group of species living together as communities in relation to their habitats of a given ecosystem. It can be mentioned here that a group of individual organisms of the same species in a given area is called a population. While a group of population of different species in a given area is called a community. Based on this we have population ecology and community ecology.

The basic concepts and the focus areas of ecology are as follows:

(1)   Ecosystem as the fundamental unit of ecological study.

Ecosystem

ECOSYSTEM & ECOLOGY

Ecosystem

An ecosystem is a fundamental functional unit of ecological study. An ecosystem is a system – ecological system – in which organisms interact with each other and with their environment in a given and unit-time. In other words an ecosystem is a biotic community together with its physical environment considered as an integrated unit. Implied within this definition is the concept of a structural and functional unit, unified through life processes.

An ecosystem is broadly composed of two components:

(1)   Biome – All the plants, animal and microorganisms, in fact all the living beings in a given spatial unit. These are biotic elements.

(2)   Habitat – The Physical environment i.e. a biotic elements such as air, water and land.

Both these components are integrated by the continuous flow of energy and matter between them. We can call Energy as the third component of the ecosystem.

In other words each organism (including humans) is affected by and interacts with its environment. That environment is formed from a combination of interactive nonliving and living elements. When we consider both forms of elements and their interactions as a single entity we have an ecosystem at same level of organization.

Oxygen Cycle

Oxygen Cycle

Oxygen Cycle

Similarly in the oxygen cycle the imbalances are likely to emerge due to industrial combustion since 1860’s industrial revolution and decreasing vegetation cover.

Hydrogen or Hydrological Cycle

It is also called hydrological cycle or water cycle as most of the hydrogen circulates in the biosphere in the form of H₂O- moisture or water. Hydrological cycle at global scale involves following sequential processes as Evaporation →Condensation → Precipitation (rainfall, snowfall) → Percolation into the ground and surface runoff, both eventually transferring to water bodies and oceans →Evaporation again.

Water is an important substance in the biosphere because

(i)                 It is able to dissolve almost all substances;