Components: Producers & Consumers | Biology for SSS 3 PDF Download

Components of Ecosystem

Every ecosystem is composed of two components

1. Biotic Component 
2. Abiotic Component

Biotic Component

Formed by living things. e.g., plants, animals, microbes.

Types of Biotic Components

1. Producer

All the autotrophs of ecosystem are called producers. They prepare their own food. The green plants are the main producers. In the process of photosynthesis, producers absorb solar energy and convert it into chemical energy so producers are also called transducers or converters.

Energy enters into the ecosystem through the producers. The solar energy is the only ultimate source of energy in ecosystem. This energy is available for the remaining living organisms.

Other e.g. of producers are -

• Chemotoautotrophs : (iron bacteria, sulphur bacteria, nitrifying bacteria)
• In aquatic ecosystem : Floating plants called phytoplanktons are the major autotrophs.

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

2. Consumer

All the heterotrophs of the ecosystem are known as consumers. They directly (herbivores) or indirectly (Carnivores) depend on the producers for food.

Types of Consumers

(i) Macroconsumers
(ii) Microconsumers

(i) Macro Consumers (Phagotrophs or Holozoic)

They digest their food inside the body of organism i.e. first ingestion then digestion.

Macro consumers are of following types:

(a) 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.

(b) Secondary Consumers or Primary Carnivores – Animals which feed upon primary consumers and obtain food. The carnivores which kill and eat the herbivores, are called predators. e.g. Dog, cat, snake Note :

•  The organism which completely depends on dead animals are not example of predators but they all are the scavangers or detrivores. e.g. Vulture, crow, fox.
•  All predators are carnivores but all carnivores are not predators.

(c) Top Consumers – Those animals which kill other animals and eat them, but they are not killed & eaten by other animals in the nature. e.g. Lion, man, hawk, peacock.

(ii) Micro Consumers/Decomposers /Saprotrophs/Osmotrophs 

Those living organisms which decompose the dead body of producers and consumers are known as decomposers or reducers or transformers or osmotrophs.

Note 

• The main decomposers in ecosystem are bacteria and fungi.
• Decomposers play a significant role in mineral cycle. Decomposers are responsible for converting complex organic material of dead animals 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.
• In Bacteria and fungi, process of decomposition completely takes place outside the body. They release 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).  

Special Point of Biotic Factor

• Nutrient Immobilisation- 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.
• In aquatic system, whale is secondary consumer. It is an example of filter feeder because it feeds on plankton.
• 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.
• Plant parasites are known as primary consumers while animals parasites (E.coli bacteria, Entamoeba histolitica, liver fluke, tapeworm) are known as secondary consumers.
• All the insectivorous plants play the double role i.e. producer as well as secondary consumer because they synthesise 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 consumer.
  Note :
  Inorganic materials (CO₂ ,H₂O, Light), autotrophs (Producers) and decomposers are essential in ecosystem but, macro consumers are non-essential.

Abiotic Component

• Abiotic components include inorganic substances or minerals; organic substance and atmospheric factor.
• Inorganic substances are P, S, N, H, Mg, K, CO2, NO2 etc. These are raw materials for plants.
• Organic substances are proteins, carbohydrates, lipids in dead organic substances.
• Atmospheric factors are light, temperature, humidity, rain, water, gas etc.

Function of Ecosystem 

There are two basic functions of ecosystem.

(i) Biogeochemical Cycle (Mineral Cycle)
(ii) Energy Flow – The storage, expenditure, transformation of energy is based on two basic law of thermodynamics –

• Energy is neither created nor destroyed but only transformed from one state to another state.
• The law of entropy – The transfer of food energy from one to another organism leads to loss of energy as heat due to metabolic activity.

Food Chain

In ecosystem every organism depends on other organism for food material and all organism are (herbivores to carnivores) arranged in a series in which food energy is transferred through repeated eating and being eaten. It is called food chain. In food chain, energy flow is in the form of food.
In a food chain, food material or food energy transfer is from one tropic level to next tropic level.

Four tropic levels are present in the ecosystem, because level of energy decreases during the flow of energy from one tropic to the another tropic level.

First tropic level    [T₁] = Producers

Second tropic level   [T₂] = Primary consumers

Third tropic Level   [T₃] = Secondary consumers

Fourth tropic level [T₄] = Top consumers

Note:

1. There are five tropic levels found in highly complex ecosystem in which tertiary consumer is present in between the secondary consumers and top consumer. Then the fifth tropic level(T5) is formed by the top consumer.

2. In food chain energy flow is unidirectional (producers to herbivores)

3. Shorter food chains will provide greater energy.

4. Generally the decomposers (Bacteria and Fungi) are not included in the food chain but when included then included as the last tropic level.

Types of Food Chain

In nature three types of food chains are present.

1. Grazing Food Chains or Predatory Food Chain 

Most of food chain in nature are of this type. This food chain begins with producers (plants) and in successive order it goes from small organisms to big organisms.

Aquatic Ecosystem 

Producer Pri.           consumer Sec.     consumer     Top consumer

Grassland Ecosystem 

2. Parasitic Food Chain 

This food chain also starts from producers but in successive order it goes from big organism to the smaller organism. e.g.
 Tree Ecosystem

Note : Both above food chains are directly dependent on solar radiation (as a primary source of energy) and have rapid energy flow.

 3. Detritus Food Chain or Saprophytic Food Chain 

This food chain begins with decomposition of dead organic matter by decomposers so it is also known as saprophytic food chain. In this food chain primary consumers are bacteria and fungi.
Dead organic matter →  bacteria fungi

Note :

• In mangrove vegetation this food chain goes up to big organism.
• Dead mangroves leaves →  Bacteria & fungi → Amphipds, molluscs, crabs, nematodes →  small fishes → fish eating birds.
• In detritus food chain, energy flow is rather very slow yet magnitude of energy is great because vast no. of decomposers are involved.
• It indirectly depends on light.

Ecosystem/Food Chain – In an aquatic ecosystem, GFC (Grazing Food Chain) is the major conduit (source) of energy flow. As against this, in a terrestrial ecosystem, a much larger energy flows through the detritus food chain than through the grazing food chain.
In Sunderbans, Tigers feed on the fishes and crab in the absence of their natural prey.