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ECOSYSTEM

The interaction between the living organism and the non-living environment is called ecosystem.

Interaction of biotic and abiotic components is the characteristic of the ecosystem.
Identification and description of plant and animal species of an ecosystem gives its species composition.
Vertical distribution of different species occupying different levels is called stratification.
The components of the ecosystem are seen to function as a unit:
- Productivity
- Decomposition
- Energy flow and
- Nutrient cycle
Description of pond as an ecosystem:
- The abiotic components include all dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond.
- The solar input, cycle of temperature, day length, regulates the rate of function of the entire pond.
- The producer (autotrophic) includes phytoplankton, some algae and the floating, submerged and marginal plants found in edge of pond.
- The consumers are represented by zooplankton, free swimming and bottom dwelling animals.
- The decomposers are fungi, bacteria especially abundant at the bottom of the pond.
Basic events (in terms of function) in an ecosystem:
- Conversion of inorganic into organic material (photosynthesis) by producers.
- Consumption of the autotrophs by heterotrophs.
- Decomposition and mineralization of the dead organic matter
- Unidirectional flow of energy and its loss as heat to the environment.

PRODUCTIVITY:

Primary productivity:
Gross primary productivity: (GPP) is the rate of production of organic matter during photosynthesis.
Net primary productivity (NPP):
- A considerable amount of energy is utilized by plants in respiration.
- Gross primary productivity minus respiration losses (R) is the net primary productivity.
- GPP R = NPP.
Net primary productivity is the available biomass for the consumption to heterotrophs (herbivore and decomposers).
Secondary productivity: is the rate of formation of new organic matter by the consumer.

DECOMPOSITION:

Earthworm is said to be friends of farmer as they help in Breakdown the complex organic matter as well as in loosening of soil thus, helps in aeration and entry of root.
break down complex organic matter into inorganic substances like CO₂, water and nutrients.
Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute the detritus.
The process of decomposition completed in following steps:
- Fragmentation: Breakdown of detritus into smaller particles by detritivore
- Leaching: Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
- Catabolism: Bacterial and fungal enzymes degrade detritus into simple inorganic substances.
- Humification: Accumulation of dark coloured amorphous substances called humus.
- Highly resistance to microbial action.
- Undergo decomposition at an extremely slow rate.
- Being colloidal in nature, it serves as reservoir for nutrients.
- Mineralization: The humus is further degraded by some microbes and release of inorganic nutrients occur.

(earthworm).

Importance of humus:

Factor affects rate of decomposition:

Decomposition is largely an oxygen-requiring process.
Detritus rich in chitin and lignin has slow rate of decomposition.
Detritus rich in nitrogen and water-soluble substance like sugar has faster decomposition.
Temperature and soil moisture regulate decomposition.
Warm and moist environment favor decomposition.
Low temperature, dryness and anaerobiosis inhibit decomposition.

ENERGY FLOW IN ECOSYSTEM:

Sun is the only source of energy for all ecosystems on earth (Except deep sea hydrothermal ecosystem)
Less than 50% of incident solar radiation is Photosynthetically Active Radiations (PAR).
Plants capture 2-10 % of PAR and used in photosynthesis.
All organisms depend on the producers, either directly or indirectly.
Energy flow in the ecosystem is unidirectional i.e. energy transferred from producer to consumers.
Energy transfer is not absolute and spontaneous, unless energy is degraded it cannot be transferred. When energy transferred from one trophic level to another, lot of energy lost in the form of heat to the environment.
Only 10% of energy transferred from one trophic level to other.

Food chain:

Grazing food chain (GFC): It extends from producers through herbivore to carnivore.
Detritus food chain (DFC): Begins with dead organic matter (detritus) and pass through detritus feeding organism in soil to organisms feeding on detritus-feeders.
In aquatic ecosystem GFC is the major channel for energy flow.
In terrestrial ecosystems, a much larger fraction of energy flows through the detritus food chain than through GFC.
Different food chains are naturally interconnected e.g. a specific herbivore of one food chain may serve as food of carnivores of other food chains. Such interconnected matrix of food chains is called food web.
Trophic level: A group of organism irrespective of their size having same source of energy or similar food habit constitute a trophic level.
Standing crop: each trophic level has a certain mass of living material at a particular time called as the standing crop.
The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.
The number of trophic levels in a food chain is restricted by 10 % flow of energy, less amount of energy available to the last trophic level.

ECOLOGICAL PYRAMID:

The base of the pyramid is broad and it narrows down at the apex.
The relationship between organisms can be expressed in terms of number, energy or biomass.
The base of the pyramid is represented by producer and apex is the top consumer; other trophic levels are in between.
In most ecosystems, all the pyramids, of number, of energy and biomass are upright.
The pyramid of number in a tree ecosystem is inverted.
The pyramid of biomass in sea also inverted because the biomass of fishes is far exceeds that of phytoplankton.
Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next, some energy is always lost as heat at each step.

Limitations of ecological pyramids:

It does not take into account the same species belonging to two or more trophic levels.
It assumes a simple food chain, it never exits in nature.
It does not accommodate food web.
Saprophytes are not given place in ecological pyramids. ECOSYSTEM
- The interaction between the living organism and the non-living environment is called ecosystem.
- Interaction of biotic and abiotic components is the characteristic of the ecosystem.
- Identification and description of plant and animal species of an ecosystem gives its species composition.
- Vertical distribution of different species occupying different levels is called stratification.
- The components of the ecosystem are seen to function as a unit:
  - Productivity
  - Decomposition
  - Energy flow and
  - Nutrient cycle
- Description of pond as an ecosystem:
  - The abiotic components include all dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond.
  - The solar input, cycle of temperature, day length, regulates the rate of function of the entire pond.
  - The producer (autotrophic) includes phytoplankton, some algae and the floating, submerged and marginal plants found in edge of pond.
  - The consumers are represented by zooplankton, free swimming and bottom dwelling animals.
  - The decomposers are fungi, bacteria especially abundant at the bottom of the pond.
- Basic events (in terms of function) in an ecosystem:
  - Conversion of inorganic into organic material (photosynthesis) by producers.
  - Consumption of the autotrophs by heterotrophs.
  - Decomposition and mineralization of the dead organic matter
  - Unidirectional flow of energy and its loss as heat to the environment.
PRODUCTIVITY:
- Primary productivity:
- Gross primary productivity: (GPP) is the rate of production of organic matter during photosynthesis.
- Net primary productivity (NPP):
  - A considerable amount of energy is utilized by plants in respiration.
  - Gross primary productivity minus respiration losses (R) is the net primary productivity.
  - GPP R = NPP.
- Net primary productivity is the available biomass for the consumption to heterotrophs (herbivore and decomposers).
- Secondary productivity: is the rate of formation of new organic matter by the consumer.
DECOMPOSITION:
- Earthworm is said to be friends of farmer as they help in Breakdown the complex organic matter as well as in loosening of soil thus, helps in aeration and entry of root.
- break down complex organic matter into inorganic substances like CO₂, water and nutrients.
- Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute the detritus.
- The process of decomposition completed in following steps:
  - Fragmentation: Breakdown of detritus into smaller particles by detritivore
  - Leaching: Water soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
  - Catabolism: Bacterial and fungal enzymes degrade detritus into simple inorganic substances.
  - Humification: Accumulation of dark coloured amorphous substances called humus.
  - Highly resistance to microbial action.
  - Undergo decomposition at an extremely slow rate.
  - Being colloidal in nature, it serves as reservoir for nutrients.
  - Mineralization: The humus is further degraded by some microbes and release of inorganic nutrients occur.
(earthworm). Importance of humus: Factor affects rate of decomposition:
- Decomposition is largely an oxygen-requiring process.
- Detritus rich in chitin and lignin has slow rate of decomposition.
- Detritus rich in nitrogen and water-soluble substance like sugar has faster decomposition.
- Temperature and soil moisture regulate decomposition.
- Warm and moist environment favor decomposition.
- Low temperature, dryness and anaerobiosis inhibit decomposition.
ENERGY FLOW IN ECOSYSTEM:
- Sun is the only source of energy for all ecosystems on earth (Except deep sea hydrothermal ecosystem)
- Less than 50% of incident solar radiation is Photosynthetically Active Radiations (PAR).
- Plants capture 2-10 % of PAR and used in photosynthesis.
- All organisms depend on the producers, either directly or indirectly.
- Energy flow in the ecosystem is unidirectional i.e. energy transferred from producer to consumers.
- Energy transfer is not absolute and spontaneous, unless energy is degraded it cannot be transferred. When energy transferred from one trophic level to another, lot of energy lost in the form of heat to the environment.
- Only 10% of energy transferred from one trophic level to other.
Food chain:
- Grazing food chain (GFC): It extends from producers through herbivore to carnivore.
- Detritus food chain (DFC): Begins with dead organic matter (detritus) and pass through detritus feeding organism in soil to organisms feeding on detritus-feeders.
- In aquatic ecosystem GFC is the major channel for energy flow.
- In terrestrial ecosystems, a much larger fraction of energy flows through the detritus food chain than through GFC.
- Different food chains are naturally interconnected e.g. a specific herbivore of one food chain may serve as food of carnivores of other food chains. Such interconnected matrix of food chains is called food web.
- Trophic level: A group of organism irrespective of their size having same source of energy or similar food habit constitute a trophic level.
- Standing crop: each trophic level has a certain mass of living material at a particular time called as the standing crop.
- The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.
- The number of trophic levels in a food chain is restricted by 10 % flow of energy, less amount of energy available to the last trophic level.
ECOLOGICAL PYRAMID:
- The base of the pyramid is broad and it narrows down at the apex.
- The relationship between organisms can be expressed in terms of number, energy or biomass.
- The base of the pyramid is represented by producer and apex is the top consumer; other trophic levels are in between.
- In most ecosystems, all the pyramids, of number, of energy and biomass are upright.
- The pyramid of number in a tree ecosystem is inverted.
- The pyramid of biomass in sea also inverted because the biomass of fishes is far exceeds that of phytoplankton.
- Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next, some energy is always lost as heat at each step.
Limitations of ecological pyramids:
- It does not take into account the same species belonging to two or more trophic levels.
- It assumes a simple food chain, it never exits in nature.
- It does not accommodate food web.
- Saprophytes are not given place in ecological pyramids.

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