BY
BANGAMOTI HANSDA ASSISTANT PROFESSOR DEPARTMENT OF BOTANY
NARAJOLE RAJ COLLEGE
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. 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. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.
Structure of Ecosystem
Each organism has two main components
Abiotic
The non living factor or the physical environment prevailing in an ecosystem forms abiotic components.
Climatic factors- It includes rain, temparature, light, wind, humidity etc.
Edaphic factors- It includes soil, pH, topography, minerals.
Biotic
The living organisms include plants, animals and micro-organisms in an ecosystem forms biotic components.
Biotic components are further classified into 3 main groups.
Producers- Producers are organisms that make their own food; they are also known as autotrophs. They get energy from chemicals or the sun, and with the help of water, convert that energy into useable energy in the form of sugar, or food. The most common example of a producer are plants.
Consumer- The animal lack chlorophyll and are unable to synthesis their own food therefore they feeds on plants or other animals for energy.
There are four types of consumers
Primary Consumer:Animal feeding on plants, e.g. rabbit, deer, goat etc.
Secondary Consumer: The animal feeding on Herbivores are called as secondary consumer or primary carnivores, e.g. cats, foxes, snakes etc.
Tertiary Consumer: These are large carnivores which feed on secondary consumers, e.g. wolves.
Quarternary Consumer: They are also called omnivores these are largest carnivores which feed on tertiary consumers and are not eaten up by any other animals, e.g. lion and tiger.
Decmposers- Decomposers are organisms that break down dead or decaying organisms and wastes. Their role is ecologically essential as they recycle the nutrients through a natural biological process (decomposition). Examples of decomposers are fungi and bacteria that obtain their nutrients from dead plant or animal material.
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. If a grassland ecosystem has 10,000 kilocalories (kcal) of energy concentrated in vegetation, only about 1,000 kcal will be transferred to primary consumers, and very little (only 10 kcal) will make it to the tertiary level. Energy pyramids such as this help to explain the trophic structure of an ecosystem: the number of consumer trophic levels that can be supported is dependent on the size and energy richness of the producer level.
A food chain describes the feeding relationships of different organisms in a linear fashion. This is the simplest way of showing feeding relationships.
In scientific terms, a food chain is a chronological pathway or an order that shows the flow of energy from one organism to the other. In a community which has producers, consumers, and decomposers, the energy flows in a specific pathway. Energy is not created or destroyed. But it flows from one level to the other, through different organisms.
Food web is an important ecological concept. Basically, food web represents feeding relationships within a community (Smith and Smith 2009). It also implies the transfer of food energy from its source in plants through herbivores to carnivores (Krebs 2009). Normally, food webs consist of a number of food chains meshed together. Each food chain is a descriptive diagram including a series of arrows, each pointing from one species to another, representing the flow of food energy from one feeding group of organisms to another.
What is Ecological Pyramid?
An ecological pyramid is a graphical representation of the relationship between the different living organisms at different trophic levels. It was given by G.Evylen Hutchinson and Raymond Lindeman.
It can be observed that these pyramids are in the shape of actual pyramids with the base being the broadest, which is covered by the lowest trophic level, i.e., producers.
The next level is occupied by the next trophic level, i.e., the primary consumers and so on.
They show the feeding of different organisms in different ecosystems.
It shows the efficiency of energy transfer.
The condition of the ecosystem can be monitored, and any further damage can be prevented.
Limitations of the Ecological Pyramid
More than one species may occupy multiple trophic levels as in case of the food web. Thus, this system does not take into account food webs.
The saprophytes are not considered in any of the pyramids even though they form an important part of the various ecosystem.
These pyramids are applicable only to simple food chains, which usually do not occur naturally.
These pyramids do not deliver any concept in relation to variations in season and climate.
They do not consider the possibility of the existence of the same species at different levels.
Three types of ecological pyramid exist. They are as follows:
Pyramid of Numbers
In this type of ecological pyramid, the number of organisms in each trophic level is considered as a level in the pyramid. The pyramid of numbers is usually upright except for some situations like that of the detritus food chain, where many organisms feed on one dead plant or animal.
Pyramid of Biomass
In this particular type of ecological pyramid, each level takes into account the amount of biomass produced by each trophic level. The pyramid of biomass is also upright except for that observed in oceans where large numbers of zooplanktons depend on a relatively smaller number of phytoplanktons.
Pyramid of Energy
Pyramid of energy is the only type of ecological pyramid, which is always upright as the energy flow in a food chain is always unidirectional. Also, with every increasing trophic level, some energy is lost into the environment.
Pyramid of number Pyramid of biomass
Pyramid of energy
A pyramid of energy or pyramid of productivity shows the production or turnover (the rate at which energy or mass is transferred from one trophic level to the next) of biomass at each trophic level. When an ecosystem is healthy, this graph produces a standard ecological pyramid.
Production:
Gross Primary Production (GPP)= chemical energy produced over a given period of time.
R= energy that is used by the producers within their lifetime
Net Primary Productivity (NPP)= amount of energy available to consumers
NPP=GPP-R
Productivity:
Rate at which chemical energy is produced in an ecosystem.
Expressed in units such as “grams of organic matter per square meter per year
In general, those ecosystems with the highest net productivity are those with the greatest producer biomass
