ECOSYSTEM

 ECOSYSTEM

INTRODUCTION

Ecosystem is the smallest structural and functional unit of nature or environment. It is a self regulatory and self sustaining unit.

Ecosystem may be large or small. A single drop of water may be an ecosystem.

Ecosystem may be temporary or permanent.

TYPES OF ECOSYSTEM

An ecosystem may be natural or artificial.

Natural ecosystem is divided into two basic categories –

Terrestrial ecosystem : E.g., forest, grassland, tree, desert ecosystem.

Aquatic ecosystem : Aquatic ecosystem is again of two types:

Lentic ecosystem : E.g., Stagnant fresh water, lake, pond, swamp.

Lotic ecosystem : Running freshwater ecosystem. E.g., river.

Artificial ecosystem : These are man made ecosystem. E.g., cropland, gardens etc.

On the basis of size, types of ecosystem are :-

Mega ecosystem –Ocean/Sea

Macroecosystem –Forest

Microecosystem –Pond

Nanoecosystem –Drop of water

COMPONENTS OF ECOSYSTEM

An ecosystem is composed of two components –

Biotic component

Abiotic component

BIOTIC COMPONENTS

Biotic component is made up of many different inter 
dependent population, e.g., plants, animals, microbes, etc.

Types of biotic component are - producer, consumer& decomposer 

 

PRODUCERS

All the autotrophs of an ecosystem are called producers. The green plants are the main producers. Producers are generally chlorophyll bearing organisms which produce their own food by the process of photosynthesis, in which producers absorb solar energy and convert it into chemical energy. So producers are also called transducers or converters. E.g., yellow green algae, algal protist etc.

Energy enters into the ecosystem through the producers. 

The solar energy is the only ultimate source of energy in the ecosystem. This energy is available for the remaining living organisms.

Other examples of producers are –

Chemoautotrophs : Iron bacteria, sulphur bacteria, nitrifying bacteria.

Phytoplankton : In an aquatic ecosystem, rooting plants called phytoplankton are the major autotrophs.

Phytoplanktons may produce as much food as produced by the larger shrubs and trees in unit area.

CONSUMER  

All the heterotrophs of the ecosystem are known as consumers. It includes micro-organisms. These directly
(on herbivores) or indirectly (on carnivores) depend on the producers for food.

Types of consumer are : macroconsumers and micro-consumers.

Macroconsumers / Phagotrophs or holozoic digest their food inside the body of organism i.e. first ingestion then digestion.

Macro-consumers are of following type :

Primary consumer : Such living organisms which obtain food directly from producers or plants are known as primary consumers.

E.g., Herbivores of ecosystem, cow, grazing cattle, rabbit.

They are also known as secondary producers as they synthesize complex materials in the cells by the digestion of food which is obtained from the plant.

Secondary consumers or primary carnivores: 

Those animals which feed upon primary consumers and obtain food. Those carnivores which kill and eat the herbivores are called predators. E.g., dog, cat, snake. In aquatic system, whale is a secondary consumer. It is an example of a filter feeder because it feeds on plankton.

 

The organisms which completely depend on dead animals are not examples of predators but they all are scavengers or detritivores. E.g., Vulture, crow, fox.

Vulture is a scavenger not predator because it never kills any animal. Vulture is also a decomposer. In vulture, the break down of the food material takes place inside the body and then released into the soil in the form of waste material and minerals.

All predators are carnivores but all carnivores are not predators.

Plant parasites are known as primary consumers while animals parasites (E. coli bacteria, Entamoeba histolytica, liver fluke, tapeworm) are known as secondary consumers.

All the insectivorous plants play the double role i.e. producer as well secondary consumer because they synthesize their own food through photosynthesis and they eat insects simultaneously.

Man and peacock are omnivores.

Organisms which use milk or curd are known as secondary consumers.

Top (tertiary) consumers : Those animals which kill other animals and eat them, but are not killed & eaten by other animals in nature are called tertiary consumers. E.g., Lion, man, peacock.

Micro-consumers/Decomposers or Scavengers/Osmotrophs are those living organisms which decompose the dead body of producers and consumers. 

The main decomposers in ecosystem are bacteria and fungi.

Decomposers play a significant role in mineral cycle.

 

DECOMPOSITION

Decomposers are responsible for converting complex organic material of dead minerals or plants into simpler organic matter through the process of decomposition and release mineral substances into the soil where these are reused by the producers, so that soil is considered as the best resource of minerals.

The upper layer of the soil is the main site for decomposition process in the ecosystem.

The process of decomposition involves several processes. These processes can be categorised as:

1.     fragmentation of detritus

2.     leaching 

3.     catabolism

4.     humification

5.     mineralization 

Detritivores (e.g., earthworm) breakdown detritus into smaller particles (called fragmentation).

By the process of leaching, water soluble inorganic nutrients' go down into the soil horizon and get precipitated as unavailable salts.

In bacteria and fungi, process of decomposition completely takes place outside the body. They  carry out catabolism and release extracellular enzymes from their body on dead remains and decompose it into simpler organic substances and then absorb it. So these are called as osmotrophs (absorptive).

In the process of decomposition, some nutrients get tied up with the biomass of microbes and become temporarily unavailable to other organisms. Such incorporation of nutrient in living microbes (bacteria & fungi) is called nutrient immobilisation.

Humification and mineralization occur during decomposition in the soil. Humification leads to formation of humus which is highly resistant to microbial action & undergoes extremely slow decomposition. Humus serves as a reservoir of nutrients.

Mineralization results in the release of inorganic substances (e.g., CO₂, H₂O) and variable nutrients (NH₄⁺, Ca⁺⁺, Mg⁺⁺, K⁺ etc.) in the soil. 

Decomposition is largely an oxygen requiring process.

Factors affecting decomposition –

Temperature and soil moisture are important and regulate decomposition through their effects on the activates of soil microbes.

Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition.