CONCEPT OF ECOLOGY AND ECOSYSTEM���SANTANU GUPTA�ASSISTANT PROFESSOR�DEPARTMENT OF BOTANY�MALDA COLLEGE
Ecology
All living organism, whether plant or animal or human being is surrounded by the environment, on which it derive its needs for its survival.
Each living component interacts with non –living components for their basic requirements form different ecosystem.
Definition
Ecology is the study of interactions among
organism or group of organisms with their
environment. The environment consists of both biotic
components (living organisms) and abiotic components
(non – living organisms).
or
Ecology is the study of ecosystems.
Ecosystem is the basic functional unit of ecology.
The term ecosystem is coined form a Greek word meaning study of home.
Definition
A group of organisms interacting among themselves and with environment is known as ecosystem. Thus an ecosystem is a community of different species interacting with one another and with their non living environment and one another and with their
non- living environment exchanging energy and matter.
Example
Animals cannot synthesis their food directly
but depend on the plants either directly or indirectly.
Types of ecosystem
Terrestial ------Aquatic
Marine ------Fresh water
Lotic----lentic
Examples
Pond, lake
(ii) Marine ecosystem
Example :
Seas and sea shores
Man – made (or) Artificial ecosystems
Artificial ecosystem is operated (or) maintained by man himself.
Example
Croplands, gardens
STRUCTURE (or) COMPONENTS OF AN ECOSYSTEM
The term structure refers to the various components.
So the structure of an ecosystem explains the relationship
between the abiotic (non –living) and the biotic (living) components.
An ecosystem has two major components
Biotic components
The living organisms (or) living members in an ecosystem collectively form its community
called biotic components (or) biotic community.
Examples
Plants (producers), animals (consumers), and microorganisms (decomposers).
Members of components of an ecosystem (or)
Classification biotic components
The members of biotic components of an ecosystem are grouped in to three based on how they get food
I. Procedures (Autotrophs)
Procedures synthesize their food themselves
through photosynthesis
Example :
All green plants, trees.
Photosynthesis
The green pigments called chlorophyll, present in
the leaves of plants,
converts CO2 and H2O in the presence of sunlight into
carbohydrates.
6CO2 + 12H2O ----------------------> C6H12O6 + 6O2+6H2O
This process is called photosynthesis
2. Consumers (heterotrophs)
Examples
Plant eating species
Insects, rabbit, goat, deer, cow, etc.,
Classification of consumers
Consumers are further classified as
(i) Primary consumers (Herbivores) (Plant eaters)
Primary consumers are also called herbivores,
they directly depend
on the plants for their food. So they are called plant eaters.
Examples :
Insects, rat, goat, deer, cow, horse, etc.,
FOOD CHAIN, FOOD WEB �AND
ECOLOGICAL PYRAMID
Concept of trophic level in an ecosystem
(Greek word ‘trophic’ = to food or feeding)
A trophic level refers to the position of an organism in the food chain. The number of trophic levels is equal to the number of steps in the food chain. The green plants (producers) occupying the first trophic level (T1) are called producers. The energy produced by the producers is utilized by the plant eaters (herbivores) they are called primary consumers and occupy the second trophic level (T2).
Herbivores are eaten by carnivores, which occupy the third trophic level (T3). They are also called secondary consumers or primary carnivores. Carnivores are eaten by the other carnivores, which occupy the fourth trophic level (T4). They are called the tertiary consumers or secondary carnivores. Some organisms which eat both plants and animals are called as omnivores (Crow). Such organisms may occupy more than one trophic level in the food chain.
FOOD CHAIN
The sequence of eating and being eaten in an ecosystem is known as food chain.
e.g. in grassland ecosystem,
in forest ecosystem,
Two types of food cains –
It starts with green plants, its primary producers and terminates in carnivores. The grazing food chain derive its energy basically from green plants. They are found only in natural ecosystem.
e.g. In pond ecosystem,
Phytoplankton Zoo plankton Small fish
Carnivorous fish
b) Detritus food chain:
It starts with death organic matters which are consumed by the detrivores and decomposers. Partially decompose death organic matters and even the decomposers are consumed by detrivores and their predators. Detritus food chains obtain energy, primarily from plant biomass and secondarily from microbial biomass and tertiarilly from carnivores.
b) Detritus food chain:
It starts with death organic matters which are consumed by the detrivores and decomposers. Partially decompose death organic matters and even the decomposers are consumed by detrivores and their predators. Detritus food chains obtain energy, primarily from plant biomass and secondarily from microbial biomass and tertiarilly from carnivores.
e.g. In mangrove or esturine ecosystem,
Leaf litters Saprotrophs
+ Small carnivorous fish Large carnivorous fish
Small algae Detrivores
( crabs, insect larva, nematode, small fishes)
FOOD WEB
Food web is a network of food chains, where different types of organisms are connected at different trophic levels so that there are number of options of eating and being eaten at each trophic level.
d) Food web is constructed to describe species interaction called direct interaction.
e) Food web can be used to illustrate indirect interactions among different species.
f) Food can be used to study bottom-up or top down control of community structure.
g) Food web can be used to reveal different patterns of energy transfer in terrestrial and aquatic ecosystems.
ECOLOGICAL PYRAMID
The graphical representation of trophic structure and function of an ecosystem starting with producers at the base and successive trophic levels forming the apex is known as ecological pyramids. There are 3 types of ecological pyramids:
a) Pyramid of Number:
It represents the number of individual organisms at each trophic level. Depending upon the types of ecosystem and food chains pyramids of number are of two types –
Grassland ecosystem and pond ecosystem show upright pyramid of number.
Upright pyramid of number in grassland ecosystem
Upright pyramid of number in pond ecosystem
The pyramid of number in forest ecosystem looks spindle shaped.
The pyramid of number in a parasite ecosystem is always inverted .
b) Pyramid of Biomass:
A graphical representation of the amount of organic material (biomass) present at each successive trophic level in an ecosystem is called pyramid of biomass. It is based upon the total biomass each trophic level in a food chain. It can be upright or inverted.
Grassland and forest ecosystems show upright pyramids of biomass.
The pyramid of biomass for pond ecosystem is always inverted in shape.
c) Pyramid of Energy:
A graphical representation of energy flow at each successive trophic level in an ecosystem is called pyramid of energy. The bottom of the pyramid of energy is occupied by the producers. There is a gradual decrease in energy transfer at successive tropic levels from producers to the upper levels. Therefore, the pyramid of energy is always upright.
Pyramid of energy
Biogeochemical Cycles
Biogeochemical Cycles
describe the flow of elements from the environment through living things and back to the environment.
Biogeochemical Cycles
Reservoirs
places (called reservoirs) where the elements are accumulated or held
Assimilation
Transfer of elements from the abiotic into the biotic
Release
Transfer of elements from the biotic back into the abiotic
Hydrological Cycle�(water cycle)
Reservoirs
Open water - oceans, lakes, rivers……
Water vapor -clouds, fog
Groundwater
Glaciers, snow and ice
Hydrological Cycle�(water cycle)
Assimilation
plants
animals
Hydrological Cycle�(water cycle)
Release
plants
animals
Hydrological Cycle
Carbon Cycle�(carbon is required for building organic compounds)
Reservoir
The atmosphere (as CO2)
Fossil fuels (oil, coal,…)
Organic materials (tissues of plants and animals).
Carbon Cycle�(carbon is required for building organic compounds)
Assimilation
plants
use CO2 in photosynthesis
animals
consume plants or other animals made up
of carbon compounds
Carbon Cycle�(carbon is required for building organic compounds)
Release
plants release CO2 during breathing and decomposition
animals release CO2 during breathing and decomposition
CO2 is released during combustion of fossil fuels and other materials
Carbon Cycle
Nitrogen Cycle�(Nitrogen is required for the manufacture of �amino acids and nucleic acids)
Reservoirs
In the atmosphere (as N2)
In the soil as
NH4+ or ammonium
NH3 or ammonia
N02- or nitrite
N03- or nitrate
Nitrogen Cycle�(Nitrogen is required for the manufacture of �amino acids and nucleic acids)
Assimilation
plants can absorb either NH4+ or N03-
animals obtain nitrogen by eating plants and other animals
Nitrogen Cycle�(Nitrogen is required for the manufacture of �amino acids and nucleic acids)
The stages in the assimilation of nitrogen:
Nitrogen Fixation:
Some bacteria turn N2 to NH4+
Lightning and radiation turn N2 to N03-
Nitrification:
Some bacteria turn NH4+ to N02- then to N03-
Release
Denitrifying bacteria change N03- back to N2
Animals excrete NH4+ or NH3 in their urine
Nitrogen Cycle�(Nitrogen is required for the manufacture of �amino acids and nucleic acids)
Nitrogen Cycle
Phosphorus Cycle�(Phosphorus is required for the manufacture�of ATP and all nucleic acids)
Reservoir
sediment and rocks contain phosphorus. When they erode, they transfer phosphorus into the water and soil
Phosphorus Cycle�(Phosphorus is required for the manufacture�of ATP and all nucleic acids)
Assimilation
plants absorb inorganic phosphate from the soil
animals obtain organic phosphorus when they eat plants or other animals
Phosphorus Cycle�(Phosphorus is required for the manufacture�of ATP and all nucleic acids)
Release
plants release phosphorus when they decompose
animals release phosphorus when they decompose
animals excrete phosphorus in their waste products
Phosphorus Cycle