ANMOLSHARMALIVE.
An ecosystem is a functional unit of nature, where living organisms interact each other and with the physical environment.
ECOSYSTEM – STRUCTURE & FUNCTION
Types of ecosystems • Climatic conditions: Solar input, cycle of temperature,
• Terrestrial ecosystem: Forest, grassland, desert etc. day-length etc.
• Aquatic ecosystem: Pond, lake, wetland, river & estuary. • Autotrophic components: Phytoplankton, some algae
• Man-made ecosystem: Crop fields and aquarium. and the floating, submerged and marginal plants.
• Consumers (heterotrophs): Zooplankton, free swimming
- Entire biosphere is regarded as global ecosystem.
and bottom dwelling forms.
- In an ecosystem, biotic and abiotic components interact
• Decomposers: Fungi, bacteria and flagellates.
and function as a unit.
- Vertical distribution of different species occupying Pond performs all the functions of an ecosystem. E.g.
different levels is called stratification. E.g. in a forest, o Autotrophs convert inorganic into organic material using
trees occupy top strata (layer), shrubs the second and herbs solar radiant energy.
& grasses the bottom layers. o Heterotrophs consume the autotrophs.
o Decomposition and mineralization of the dead matter to
Pond (Aquatic ecosystem) release them back for reuse by the autotrophs.
A pond is a shallow, simple, self-sustainable water body that 4 basic components of functioning of an ecosystem:
exhibits all basic components of an ecosystem. 1) Productivity 2) Decomposition
• Abiotic components: Water and soil deposit. 3) Energy flow 4) Nutrient cycling
1. PRODUCTIVITY
- Solar energy is the basic requirement for an ecosystem to decomposers). i.e., NPP is the Gross primary productivity
function and sustain. minus respiration losses (R).
- Amount of biomass (organic matter) produced per unit area NPP = GPP – R
over a time period by plants during photosynthesis is called - Secondary productivity: It is the rate of formation of new
primary production. It is expressed in weight (g–2) or organic matter by consumers.
energy (kcal m–2). - Primary productivity varies in different ecosystems
- The rate of biomass production is called productivity. It is because it depends on
expressed in g–2 yr–1 or (kcal m–2) yr–1. o The plant species inhabiting an area.
- It is divided into gross primary productivity (GPP) and net o Environmental factors.
primary productivity (NPP). o Availability of nutrients.
- Gross primary productivity (GPP): It is the rate of o Photosynthetic capacity of plants.
production of organic matter during photosynthesis. A - Annual net primary productivity of whole biosphere is
considerable amount of GPP is used by plants in respiration. about 170 billion tons (dry weight) of organic matter. Of
- Net primary productivity (NPP): It is the available this, despite occupying about 70 % of the surface, the
biomass for the consumption to heterotrophs (herbivores & productivity of the oceans is only 55 billion tons.
2. DECOMPOSITION
- It is the breakdown of complex organic matter by d. Humification: Accumulation of humus (dark amorphous
decomposers into inorganic substances like CO2, water and substance) in soil. Humus is resistant to microbial action
nutrients. It is largely an oxygen-requiring process. and so decomposes very slowly. Being colloidal, it serves
- Raw material for decomposition is called Detritus. E.g. as a reservoir of nutrients.
dead plant remains (leaves, bark, flowers etc.), dead e. Mineralization: It is the release of inorganic nutrients
remains of animals, fecal matter etc. due to the degradation of humus by some microbes.
Steps of decomposition Factors influencing decomposition
a. Fragmentation: It is the breakdown of detritus into • Chemical composition of detritus:
smaller particles by detritivores (e.g. earthworm). o Decomposition is slow in detritus rich in lignin & chitin.
b. Leaching: Water soluble inorganic nutrients go down o It is quicker in detritus rich in nitrogen and water-soluble
into soil horizon and precipitate as unavailable salts. substances like sugars.
c. Catabolism: Degradation of detritus into simpler • Climatic factors (temperature & soil moisture):
inorganic substances by bacterial and fungal enzymes. o Warm and moist environment favour decomposition.
o Low temperature & anaerobiosis inhibit decomposition
The above three processes occur simultaneously.
resulting in buildup of organic materials.
1
, ANMOLSHARMALIVE.
3. ENERGY FLOW
- Sun is the only source of energy for all ecosystems (except - Detritus is made up of decomposers (saprotrophs) such
deep sea hydro-thermal ecosystem). as fungi & bacteria. They secrete digestive enzymes that
- Of the incident solar radiation, less than 50% is breakdown detritus into simple, inorganic materials, which
photosynthetically active radiation (PAR). are absorbed by them. Thus, they get energy & nutrients.
- Plants and photosynthetic bacteria (autotrophs), fix solar - In an aquatic ecosystem, GFC is the major conduit for
radiant energy to make food. energy flow.
- Plants capture only 2-10% of the PAR. This energy - In a terrestrial ecosystem, a much amount of energy flows
sustains the entire living world. through the DFC than through the GFC.
- Ecosystems obey 2nd Law of thermodynamics. They need - DFC may be connected with GFC at some levels. Some
a constant supply of energy to synthesize the molecules. It organisms of DFC are prey to the GFC animals. Some
helps to counteract the entropy. animals (cockroaches, crows, human etc.) are omnivores.
Producers (Autotrophs): Such interconnections of food chains are called food web.
- These are organisms that synthesize food. - A specific place of organisms in the food chain is known
- In a terrestrial ecosystem, major producers are herbaceous as their trophic level.
and woody plants. Primary producers in an aquatic
ecosystem are phytoplankton, algae and higher plants.
- The energy trapped by the producer is passed on to a
consumer or the organism dies.
Consumers (heterotrophs):
- These are animals that directly or indirectly depend on
plants for food. They include:
o Primary consumers (herbivores): Feed on plants. E.g.
insects, birds, mammals, molluscs etc. - The amount of energy decreases at successive trophic
o Secondary consumers (primary carnivores): Feed on levels. When an organism dies it becomes dead biomass
herbivores. E.g. frog, fox, man etc. (detritus). It is an energy source for decomposers.
o Tertiary consumers (secondary carnivores): Feed on - Organisms at each trophic level depend on those at the
primary carnivores. E.g. tiger, lion etc. lower trophic level for their energy.
- The chain of feeding relationship between different - The amount of living material in a trophic level at a given
organisms is called a food chain. It is 2 types: time is called standing crop. It is measured as the biomass
• Grazing Food Chain (GFC): Here, primary consumer (mass of living organisms) or the number in a unit area.
feeds on living plants (producer). E.g. - Biomass of a species is measured in terms of fresh or dry
weight. Dry weight is more accurate because it is the exact
mass of body which remains constant.
• Detritus Food Chain (DFC): Here, primary consumer - Number of trophic levels in GFC is restricted as it follows
feeds on dead organic matter (detritus). Death of 10% law (only 10% of energy is transferred to each trophic
organism is the beginning of the DFC. level from the lower trophic level).
ECOLOGICAL PYRAMIDS
- The representation of a food chain in the form of a pyramid
is called ecological pyramid.
- The base of a pyramid represents producers (first trophic
level). The apex represents tertiary or top-level consumer.
- Ecological pyramids are 3 types: Pyramid of number,
Pyramid of biomass and Pyramid of energy.
a) Pyramid of number: E.g. grassland ecosystem.
c) Pyramid of energy: Primary producers convert only 1%
of the energy in the sunlight available to them into NPP.
b) Pyramid of biomass: It shows a sharp decrease in
biomass at higher trophic levels.
2
An ecosystem is a functional unit of nature, where living organisms interact each other and with the physical environment.
ECOSYSTEM – STRUCTURE & FUNCTION
Types of ecosystems • Climatic conditions: Solar input, cycle of temperature,
• Terrestrial ecosystem: Forest, grassland, desert etc. day-length etc.
• Aquatic ecosystem: Pond, lake, wetland, river & estuary. • Autotrophic components: Phytoplankton, some algae
• Man-made ecosystem: Crop fields and aquarium. and the floating, submerged and marginal plants.
• Consumers (heterotrophs): Zooplankton, free swimming
- Entire biosphere is regarded as global ecosystem.
and bottom dwelling forms.
- In an ecosystem, biotic and abiotic components interact
• Decomposers: Fungi, bacteria and flagellates.
and function as a unit.
- Vertical distribution of different species occupying Pond performs all the functions of an ecosystem. E.g.
different levels is called stratification. E.g. in a forest, o Autotrophs convert inorganic into organic material using
trees occupy top strata (layer), shrubs the second and herbs solar radiant energy.
& grasses the bottom layers. o Heterotrophs consume the autotrophs.
o Decomposition and mineralization of the dead matter to
Pond (Aquatic ecosystem) release them back for reuse by the autotrophs.
A pond is a shallow, simple, self-sustainable water body that 4 basic components of functioning of an ecosystem:
exhibits all basic components of an ecosystem. 1) Productivity 2) Decomposition
• Abiotic components: Water and soil deposit. 3) Energy flow 4) Nutrient cycling
1. PRODUCTIVITY
- Solar energy is the basic requirement for an ecosystem to decomposers). i.e., NPP is the Gross primary productivity
function and sustain. minus respiration losses (R).
- Amount of biomass (organic matter) produced per unit area NPP = GPP – R
over a time period by plants during photosynthesis is called - Secondary productivity: It is the rate of formation of new
primary production. It is expressed in weight (g–2) or organic matter by consumers.
energy (kcal m–2). - Primary productivity varies in different ecosystems
- The rate of biomass production is called productivity. It is because it depends on
expressed in g–2 yr–1 or (kcal m–2) yr–1. o The plant species inhabiting an area.
- It is divided into gross primary productivity (GPP) and net o Environmental factors.
primary productivity (NPP). o Availability of nutrients.
- Gross primary productivity (GPP): It is the rate of o Photosynthetic capacity of plants.
production of organic matter during photosynthesis. A - Annual net primary productivity of whole biosphere is
considerable amount of GPP is used by plants in respiration. about 170 billion tons (dry weight) of organic matter. Of
- Net primary productivity (NPP): It is the available this, despite occupying about 70 % of the surface, the
biomass for the consumption to heterotrophs (herbivores & productivity of the oceans is only 55 billion tons.
2. DECOMPOSITION
- It is the breakdown of complex organic matter by d. Humification: Accumulation of humus (dark amorphous
decomposers into inorganic substances like CO2, water and substance) in soil. Humus is resistant to microbial action
nutrients. It is largely an oxygen-requiring process. and so decomposes very slowly. Being colloidal, it serves
- Raw material for decomposition is called Detritus. E.g. as a reservoir of nutrients.
dead plant remains (leaves, bark, flowers etc.), dead e. Mineralization: It is the release of inorganic nutrients
remains of animals, fecal matter etc. due to the degradation of humus by some microbes.
Steps of decomposition Factors influencing decomposition
a. Fragmentation: It is the breakdown of detritus into • Chemical composition of detritus:
smaller particles by detritivores (e.g. earthworm). o Decomposition is slow in detritus rich in lignin & chitin.
b. Leaching: Water soluble inorganic nutrients go down o It is quicker in detritus rich in nitrogen and water-soluble
into soil horizon and precipitate as unavailable salts. substances like sugars.
c. Catabolism: Degradation of detritus into simpler • Climatic factors (temperature & soil moisture):
inorganic substances by bacterial and fungal enzymes. o Warm and moist environment favour decomposition.
o Low temperature & anaerobiosis inhibit decomposition
The above three processes occur simultaneously.
resulting in buildup of organic materials.
1
, ANMOLSHARMALIVE.
3. ENERGY FLOW
- Sun is the only source of energy for all ecosystems (except - Detritus is made up of decomposers (saprotrophs) such
deep sea hydro-thermal ecosystem). as fungi & bacteria. They secrete digestive enzymes that
- Of the incident solar radiation, less than 50% is breakdown detritus into simple, inorganic materials, which
photosynthetically active radiation (PAR). are absorbed by them. Thus, they get energy & nutrients.
- Plants and photosynthetic bacteria (autotrophs), fix solar - In an aquatic ecosystem, GFC is the major conduit for
radiant energy to make food. energy flow.
- Plants capture only 2-10% of the PAR. This energy - In a terrestrial ecosystem, a much amount of energy flows
sustains the entire living world. through the DFC than through the GFC.
- Ecosystems obey 2nd Law of thermodynamics. They need - DFC may be connected with GFC at some levels. Some
a constant supply of energy to synthesize the molecules. It organisms of DFC are prey to the GFC animals. Some
helps to counteract the entropy. animals (cockroaches, crows, human etc.) are omnivores.
Producers (Autotrophs): Such interconnections of food chains are called food web.
- These are organisms that synthesize food. - A specific place of organisms in the food chain is known
- In a terrestrial ecosystem, major producers are herbaceous as their trophic level.
and woody plants. Primary producers in an aquatic
ecosystem are phytoplankton, algae and higher plants.
- The energy trapped by the producer is passed on to a
consumer or the organism dies.
Consumers (heterotrophs):
- These are animals that directly or indirectly depend on
plants for food. They include:
o Primary consumers (herbivores): Feed on plants. E.g.
insects, birds, mammals, molluscs etc. - The amount of energy decreases at successive trophic
o Secondary consumers (primary carnivores): Feed on levels. When an organism dies it becomes dead biomass
herbivores. E.g. frog, fox, man etc. (detritus). It is an energy source for decomposers.
o Tertiary consumers (secondary carnivores): Feed on - Organisms at each trophic level depend on those at the
primary carnivores. E.g. tiger, lion etc. lower trophic level for their energy.
- The chain of feeding relationship between different - The amount of living material in a trophic level at a given
organisms is called a food chain. It is 2 types: time is called standing crop. It is measured as the biomass
• Grazing Food Chain (GFC): Here, primary consumer (mass of living organisms) or the number in a unit area.
feeds on living plants (producer). E.g. - Biomass of a species is measured in terms of fresh or dry
weight. Dry weight is more accurate because it is the exact
mass of body which remains constant.
• Detritus Food Chain (DFC): Here, primary consumer - Number of trophic levels in GFC is restricted as it follows
feeds on dead organic matter (detritus). Death of 10% law (only 10% of energy is transferred to each trophic
organism is the beginning of the DFC. level from the lower trophic level).
ECOLOGICAL PYRAMIDS
- The representation of a food chain in the form of a pyramid
is called ecological pyramid.
- The base of a pyramid represents producers (first trophic
level). The apex represents tertiary or top-level consumer.
- Ecological pyramids are 3 types: Pyramid of number,
Pyramid of biomass and Pyramid of energy.
a) Pyramid of number: E.g. grassland ecosystem.
c) Pyramid of energy: Primary producers convert only 1%
of the energy in the sunlight available to them into NPP.
b) Pyramid of biomass: It shows a sharp decrease in
biomass at higher trophic levels.
2
