environmental science and ecosystem

Environmental Science

LIVE & LET LIVE

What is Environmental Science?

The study of how humans interact with their environment

Our environment is everything that surrounds us, both natural and man-made.

Environment: the total of our surroundings

• All the things around us with which we interact:• Living things

• Animals, plants, forests, fungi, etc.

• Nonliving things• Oceans, clouds, soil, rocks

• Our built environment• Buildings, human-created living centers

• Social relationships and institutions

SEGMENTS OF ENVIRONMENT

• Atmosphere – it is composed of several distinct layers such as troposphere, stratosphere, mesosphere and ionosphere.

• Hydrosphere – Water – Ocean

• Lithosphere – Solid part of the Earth crust.– The crust includes minerals, soil and rock.– Largest volume of Earth’s interior – Mantle.

• Biosphere – It is the part of the earth which includes Air, Land, Water, Rock within which life occurs.

ENVIRONMENTAL ETHICS

• It is our moral obligation to future generations to provide them clean environment, full of natural resources in good conditions.

• All organisms are valuable but human are really matter becoz they are capable to improve the earths environ. And make it better and sustainable place, both for themselves and for other organisms.

• The Env. Ethics evaluate the relationships, rules, principles b/w the humans and their env. to lead a better life at present and to provide best env. to future generations.

ENVIRONMENTAL VALUES

• In terms of utility, the env. has a great value to individual as well as to a community. The natural resources provide individuals life supporting amenities, economic benefits, etc.,

• Millions of beautiful and intriguing species populate the earth and help sustain a habitable env.

• The earth has a rich diversity of flora and fauna which altogether make the earth’s env. more valuable.

ENVIRONMENTAL KNOWLEDGE• It is essentil

To identify the env. problems To know the root cause of the problems To know the intensity and effect of the env. problems

To attain a knowledge and understand the diff. processes of ecological systems which in turn helps to solve the problems.

To develop an appropriate technology which will advocate safe, creative, environmentally sound and suitable solutions to the env. problems.

Objectives of Environmental Education

• Participation - working towards stainable development• Knowledge• Values - to develop an ethic of respect and

responsibility for the environment.• Skills - acquire skill to identify the env. Problems – work

with others to resolve, minimize and prevent them.• Awareness - create awareness and promoting env.

Friendly life style• R&D Activities - • Environmental related Laws.• To adopt technology without affecting the environment.

Living things+

Nonliving things

= ECOSYSTEM

• Environmental Studies – Impact on the society and involvement of the society in combating the causes of env. Degradation.

• Environmental Science – Systematic study of biotic and abiotic inter relationship.

• Env. Engg. - causes and effects of pollutants• Env. Chemistry - study of various chemical

phenomena taking place in diff. segment of env.• Env. And Ecology – interdisciplinary in nature and

biology, chemistry, geography, agri, etc.,

FORMAL EDUCATION

• Awareness programme through children and youth - - they create new idea

• Inter disciplinary approach adopted – To achieve sustain

• Hands on experience– Education must be imparted not only through books but

also through first hand experience in field activities.

NON FORMAL EDUCATION

• It organises extracurricular activities like

eco development camp,

posters,

competition,

exhibition,

seminar,

club activities, mobile exhibition

• Other activities like tree plantation, fencing, cleaning water bodies

• Education through arts, crafts, street plays, Advertisement, etc.,

• Considering the env. In its total ability including nature, artificial, ecological, etc.,

• Considering the people at various level and their involvement.

• Considering education with multi disciplinary approach• Examine major env. Issues.• Develop problem solving skills • Promote active participation at various levels.• Discover symptoms and root causes of env. degradation.

Awareness through seminar/conf/Posters/short film/Advt.

Env. Edu. Through children/coll.students

Env. Info. System (EIS)

World Env. Day 5th June

Training Programmes & R&D

• Ecosystem - living things in a given area, non-living chemical and physical factors of their environment, linked together through nutrient cycle and energy flow

Types of Ecosystem

Natural Artificial/Man-made

Terrestrial (Forest, Grass land, Desert)

Aquatic

Fresh water Marine

Lotic -river, stream or spring. Lentic -lake, pond or swamp.

Population

Population

+ Population

COMMUNITY

Name the three members in every community.

Producers

Consumers

Decomposers

All energy in a food web comes from the…

What makes ecosystems different?

Amount of water

Amount of sunlight

Type of soil

1

2

3

Ecology:

Study of the distribution and abundance of organisms, the flows of energy

and materials between abiotic and biotic components of ecosystems.

Ecosystem Structure: The living components of an ecosystem /

The roles of organisms in an ecosystem:

• Producer (autotrophy): make food; plants, algae

• Consumer (heterotrophy): eat other organisms

• Decomposer: eat dead organic matter; bacteria and fungi

Classes of Consumers

Herbivore – primary consumer – eats plants

Carnivores – secondary – meat eaters; eat herbivores

Omnivores – eat plants/animals.

What causes ecosystems to change?

Natural causes:

Drought

Disease

Fire

Overpopulation

3

2

1

4

What causes ecosystems to change?

Changes caused by humans:

Water pollution

Air pollution

Land pollution

Construction

1

2

3

4

How can humans help to prevent changes in ecosystems?

Use resources wisely

Laws that control pollution

Clean up litter

Keep rivers and lakes clean

1

2

3

4

ABIOTIC components

Ecosystems:Fundamental Characteristics

• Solar energy provides practically all the energy for ecosystems.

• Inorganic substances, e.g., sulfur, boron, tend to cycle through ecosystems.

• Organic compounds, such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

BIOTIC components

• The biotic components of an ecosystem can be classified according to their mode of energy acquisition.

• In this type of classification, there are:

• Autotrophs and Heterotrophs

• Organisms that produce their own food from an energy source, such as the sun, and inorganic compounds.

• Organisms that consume other organisms as a food source.

Ecosystems:Fundamental Characteristics

Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy

Trophic Levels• A trophic level is the position occupied by an

organism in a food chain.• Trophic levels can be analyzed on an energy

pyramid.• Producers are found at the base of the pyramid and

compromise the first trophic level. • Primary consumers make up the second trophic

level.• Secondary consumers make up the third trophic

level.• Finally tertiary consumers make up the top trophic

level.

Trophic Levels Found on an Energy Pyramid

• The greatest amount of energy is found at the base of the pyramid.

• The least amount of energy is found at top of the pyramid.

Source: corpuschristiisd.org/user_files/91702/Ecosystem.ppt

FOREST ECOSYSTEM (TERRESTRIAL ECOSYSTEM)

A forest is an area with a high density of trees. World’s total land area is 13,076 million

hectares Of which total forests account for about 31% of the

world’s land area.

In India, the forest cover is roughly 19% of the total land area.

The forest ecosystems are of great concern from the environmental point of view.

FOREST ECOSYSTEM (TERRESTRIAL ECOSYSTEM)

It provides numerous environmental services like;

• Nutrient cycling,• Maintaining biodiversity• Providing wildlife habitat• Regulating stream flow• Storing water• Reducing flooding• Preventing soil erosion• Reclaiming degraded land & many more….

Structure and Function of FOREST ECOSYSTEM

Biotic components

I. Producer Organisms In a forest, the producers are mainly trees.

Trees are of different kinds depending upon the type of forest developed in that climate.

Apart from trees, climbers, epiphytes, shrubs and ground vegetation.

Dominant species of trees in major types of forest ecosystems are:

Tectona grandis, Acer, Betula, Picea, Pine, Cedrus.

Structure and Function of FOREST ECOSYSTEM

Biotic components - ConsumersIn a forest, consumers are of three main types;

a) Primary Consumers

These are Herbivores which feed directly on producers. Eg:

Ants, Beetles, Bugs, spiders etc. feeding on tree leaves.

Larger animals such as Elephants, Deer, giraffe etc. grazing on shoots and/or fruits of trees.

b) Secondary Consumers

These are carnivores and feed on primary consumers.

• Eg: Birds, Lizards, Frogs, Snakes and Foxes.

c) Tertiary Consumers

These are secondary carnivores and feed on secondary consumers

These include top carnivores like Lion, Tiger.

Biotic components – Decomposers

These include wide variety of saprotrophic micro- organism like;

Bacteria Fungi Actinomycetes (Streptomyces).

They attract the dead or decayed bodies of organisms & thus decomposition takes place.

Therefore, nutrients are released for reuse.

II. Abiotic components

• These include basic inorganic & organic compounds present in the soil & atmosphere.

• In addition dead organic debris is also found littered in forests.

Structure and functions of Grassland Ecosystems

I. Biotic components

• Producer Organisms

• In grassland, producers are mainly grasses; though, a few herbs & shrubs also contribute to primary production of biomass.

• Some of the most common species of grasses are:– Brachiaria sp., Cynodon sp., Desmodium sp.,


I. Biotic components - Consumersa) Primary Consumers • The primary consumers are herbivores feeding directly on

grasses. These are grazing animals such as • Cows, Buffaloes, Sheep, Goats, Deer, Rabbits etc.• Besides them, numerous species of insects, termites, etc

are also present.

b) Secondary Consumers• These are carnivores that feed on primary consumers

(Herbivores)• These include;-Frogs, Snakes, Lizards, Birds, Foxes,

Jackals etc.

c) Tertiary Consumers• These include hawks etc. which feed on secondary

consumers.


I. Biotic components – Decomposers

These include wide variety of saprotrophic micro- organism like: Bacteria; Fungi; Actinomycetes

They attract the dead or decayed bodies of organisms & thus decomposition takes place.

Therefore, nutrients are released for reuse by producers.



These include basic inorganic & organic compounds present in the soil & aerial environment.

The essential elements like C, H, N, O, P, S etc. are supplied by water, nitrogen, nitrates, sulphates, phosphates present in soil & atmosphere.

DESERT ECOSYSTEM• A desert is a landscape or region that receives almost

no precipitation.• Deserts are defined as areas with an average annual

precipitation of less than 250 millimeters per year.• It occupies about 17% of the earth’s surface.• Deserts are characterized by hot days & cold nights.• The deserts of the world are mainly located in the

South- western United States, Mexico, North

America, Asia (Thar, Gobi, Tibet) & west Asia.• Deserts are characterized by scanty flora & fauna.• Soils of deserts often have abundant nutrients but little or

no organic matter.

I. Biotic components1) Producer Organisms• In a desert, producers are mainly shrubs/bushes; some grasses & a

few trees.• Dominant plant species include: Succulents (water -

retaining plants adapted to arid climate or soil conditions) & hardy grasses.

2) Consumer Organisms• These include animals such as insects, reptiles which are capable of

living in xeric conditions• Besides some birds & mammalians like camel etc are also found.

3) Decomposers• Due to poor vegetation with very low amount of dead organic matter,

decomposers are poor in desert ecosystem.• The common decomposers are some bacteria & fungi, most of which

are thermophillic.


• Due to high temperature & very low rainfall, the organic substances are poorly present in the soil.

Freshwater Ecosystems

I. Biotic components1) Producer Organisms

• It includes submerged, free floating and amphibious macrophytes (like; Hydrilla, Wolfia, Azolla, Typha etc.) and minute floating and suspended lower phytoplanktons (like; Ulothrix, Spirogyra, Oedogonium etc.)

2) Consumer Organisms

• a) Primary consumers: These are zooplanktons (ciliates, flagellates, other protozoan, small crustaceans) and benthos.

• b) Secondary consumers: These are carnivores like insects and fishes feeding on herbivores

• c) Tertiary consumers: These are the large fishes feeding on small fishes.

3) Decomposers Micro – organisms like bacteria, fungi and actinomyctes.

Freshwater EcosystemsII. Abiotic component

• These are the inorganic as well as organic substances present in the bottom soil or dissolved in water. In addition, to the minerals, some dead organic matter is also present.

Marine or Ocean Ecosystem

• Marine ecosystems are among the Earth's aquatic ecosystems. They include: Oceans, Estuaries and Lagoons, Mangroves and Coral reefs, the Deep sea and the Sea floor.

• These are the gigantic reservoirs of water covering approximately 71% of the Earth's surface (an area of some 361 million square kilometers).

• These ecosystems are different from freshwater ecosystem mainly because of its salty water.

I. Biotic components1) Producers It includes phytoplanktons (diatoms,

dinoflagillates), large seaweeds (mainly algae like chlorophyceae, phaeophyceae & rhodophyceae; angiosperms like Ruppia, Zostera, posidonia ), and mangrove vegetation (like Rhizophora, Carapa etc.)

2) Consumers

• a) Primary consumers: These are herbivores and feed directly on producers (Crustaceans, Mollusks, fish etc.)

• b) Secondary consumers: These are carnivorous fishes (Herring, Mackerel)

• c) Tertiary consumers: These are top carnivorous fishes (Cod, Haddock, etc.)

3) Decomposers These are micro – organisms like bacteria, fungi



• High Na, Ca, Mg and K salt concentration, variable dissolved oxygen content, light & temperature make a unique physiochemical conditions in marine water.

•


Biological Productivity

• The rate of biomass production

/ unit area / unit time is called Productivity.

• The total amount of org.matter on any particular ecosystem is called Biomass.

• The change in Biomass over a given period of time is called Net Production.

• There are 2 kinds of production– Primary Production– Secondary Production


Primary Productionrate of biomass production of a community The process is carried out by autotrophs by forming sugar

from sunlight, CO2 & H2O through photosynthesis. The energy left after respiration is net primary production.

hv6CO2 + 6H2O C6H12O6 + 6O2 (Photosythesis)

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

(Respiration)


Secondary Production

– The production by heterotrophs from the primary production is called SP.

– Defined as the rate of energy transferred and stored at consumer level over a period of time.

– Heterotrophs which cannot make their own food but must feed on other living organisms.

Food Chains

Transfer of energy and nutrients from one feeding group of organism to another

• The producers, consumers, and decomposers of each ecosystem make up a food chain.

• There are many food chains in an ecosystem.• Food chains show where energy is

transferred and not who eats who.

Example of a Food Chain

Types of Food Chains• Grazing food chain

Plants

Herbivores

(cattle, elephant, etc.)

Prim.Carnivores

(tigers, lions, snakes, etc.)

Second.Carnivores (hawk, owl, fox, etc.)

Types of Food Chains

• Detritus Food Chain - The org. waste and dead matter derived from grazing food chains are called detritus.

Dead Organic Materials (Decomposing org.matter)

Detrivores (Algae, Fungi, Bacteria, earthworms, etc.,)

Chemical Energy -- Simpler Org. Compds

CO2 + H2O

• Detritus food chain

Biomagnification

• Biological Magnification– Ecological Balance :

• Maintaining and Regulating the population size

- In addition, at each trophic level, the concn. of food chains keep on increasing,

Food Webs In ecosystems, some consumers feed on a

single species, but most consumers have multiple food sources.

Hawk eats both mouse and snake.

In this way, individual food chain becomes inter-connected to form a food web.

Food Webs• All the food chains in an area make up the food web of the area.• Maintaining the stability of an eco system

ENERGY FLOW IN ECOSYSTEM


• All organisms must obtain a supply of energy and nutrients from their environment in order to survive.

• The transformations of energy in an ecosystem begin first with the input of energy from the sun.

• Because, it is the first step in the production of energy for living things, it is called “Primary production”.

• Photosynthesis -- Chemical reaction where green plants use water & carbon dioxide to store the sun’s energy in glucose.

• ENERGY is stored in glucose. Glucose is stored as starch in plants

• The energy contained within producers and consumers is ultimately passed to the decomposers that are responsible for the constant recycling of nutrients.

• Thus, there is a one-way flow of energy through the biotic community and a cycling of nutrients between the biotic and abiotic components of the ecosystem

• Energy flow cannot occur in reverse direction.• The amount of energy decreases with successive trophic

levels.• Only About 1% of energy from the sun is used by green

plants & rest remains unutilized.• Similarly, there is loss of energy in each trophic level.• The transfer of food energy between the organisms in an

ecosystem can be tracked by constructing food chains, food webs, pyramids of numbers, biomass, etc.,


NUTRIENT CYCLES

• Nutrient cycles involve storage and transfer of nutrients through different components of the ecosystem, so that the nutrients are repeatedly used.

• The cyclic movements of chemical elements of the biosphere between the organisms and environment are referred as “BIOGEOCHEMICAL CYCLES”

BIOGEOCHEMICAL CYCLES

• It involves biological, geological and chemical systems and all are interlinked through a cyclic chain.

• It is the complete pathway that a chemical element flows from the atmosphere, water, rock or soil to the living organisms and again back to the atmosphere, water, rock or soil.

• The return of chemical elements from living organisms to abiotic component is called Mineralization.

PLANTS

ANIMALS

MICRO-ORGANISMS

NUTRIENTS

CYCLE OF NUTRIENTS

• There are 4 different biochemical cycles

– Hydrological cycle (water)– Carbon cycle– Nitrogen cycle– Phosphorous cycle

HYDROLOGIC CYCLE

• In this cycle, fresh water evaporates and condenses on the earth. Oceans are the main source of evaporated water, which leaves behind salts.

• Water also evaporates from fresh water bodies, from land and plants.

HYDROLOGIC CYCLE

The steps involved in hydrologic cycles are– evaporation – condensation– infiltration – runoff– precipitation

CARBON CYCLE• Carbon enters plants as CO2

– Bacteria process carbon in a fashion that allows it to be recycled.

– Obtain energy from the molecules, and convert carbohydrates to carbon dioxide as a result of respiration.

• Photosynthesis removes carbon from the abiotic environment (fixes carbon into organic molecules)

• Carbon moves through food chain through consumption of one organisms by another

• Cellular respiration, combustion, and erosion of limestone return carbon to the atmosphere, water and abiotic environment.

DEATH FOOD

BURNING

COMBUSTION

RESPIRATION

AIR CO2 PLANTS

ANIMAL RESPIRATION

WOOD FOSSIL FUEL

The source of atmospheric carbon dioxide is variable but only plants can utilize atmospheric carbon directly

Fig.2.11.2 Carbon Cycle

NITROGEN CYCLE

• Nitrogen is crucial for all organisms– Nucleic acids– Proteins– Chlorophyll

• Nitrogen- 78% in Atmosphere

• N2 is very stable and must be broken apart by organisms, combined with other atoms into a usable form.

• The process of entering atm. Nitrogen into the organism and again back to the environment completes the Nitrogen cycle.

1) Nitrogen Fixation NF can be carried out by symbiotic N fixer and non-symbiotic N fixer and other natural as well as industrial process.

– Conversion of N2 → NH3

• Symbiotic bacteria, associated with roots of legumes and flowering plants. eg. Rhizobium which convert N into the organic nitrogen for their own cells. when these organisms die or leave wastes certain other bacteria and fungi return the N to the soils and atm.

• Non-symbiotic N fixers are both aerobic and anaerobic bacteria as well as cyano bacteria. These occur in soil, marine and fresh water.

• Lightening storms convert atm.N into nitrates and reaches the soil through rain water. They can also be converted to ammonia by denitrifying bacteria.

2) Nitrification

• Conversion of NH3 → NO3

• Nitrosomonas convert ammonia to nitrite. Nitrobactor converts nitrite to nitrate. This nitrate is taken up by higher plants and convert it into protein and nucleic acids.

3) Eutrophication

• Discharge of excess qty of nitrogeneous compds into rivers and lakes can result excessive growth of algae and macrophytic plants.

4) Ammonification

• Amino acids and nucleotides are broken down into

NH3 or NH4

5) Denitrification

• The reduction of NO3 to N2 .

• Denitrifying bacteria release gaseous nitrogen back in to the atmosphere

Consumers

Detritus

Atmospheric Nitrogen

Plants

Soil nitrite Soil nitrate Nitrobacter Nitrosomonas

Ammonification Heterotrophs

Litter fall

Uptake

Denitrification Pseudomonas

Wet & dry deposition

Fig.2.11.1 Nitrogen Cycle

Nitrogen fixation by free living & symbiotic

microbes.

Nitrification

Soil ammonia

PHOSPHOROUS CYCLE• The only cycle that does not have a gaseous state

• Inorganic phosphate PO43- is released from rocks and

sediments through the action of erosion.

• Soil PO43- is absorbed by plants and incorporated into nucleic

acids, phospholipids and ATP (adenosine triphosphate).

• Animals obtain most of their PO43- by consumption of other

animals and from water.

• PO43- is released to the soil again by decomposers.

• Dissolved PO43- gets absorbed by algae and aquatic plants

• Decomposers break down waste and returns PO43- to

sediments on the seabed.

Parental Rock

Soluble PO43- in soil.

(orthophosphates)

Bacteria Insoluble phosphate

Plants (Roots)

Animals Death

Bone/ Teeth

Decomposition

Bacterial Decomposition

Fig.2.11.3 Phosphorus Cycle

Oxygen Cycle

Oxygen is the most import. element in our life.

About 21% of Oxygen is present in the atm. As free O2.

Plants and animals can take the free O2 from the atm. through a process called respiration, and it release CO2 and water into the atm.

Oxygen Cycle

ATMOSPHEREPLANTS & ANIMALS

O2

O2

CO2

CO2

ECOLOGICAL PYRAMIDS

• An”Ecological pyramid” is a graphical representation that shows the relative amounts of energy or matter contained within each tropic level in a food chain or food web.

• An ecological pyramid shows the relationship between producers and consumers at different tropic levels in an ecosystem

• There are three ecological pyramids– Pyramid of Numbers– Pyramid of Biomass– Pyramid of Energy

Pyramid of Number

• It is the graphical representation of the no. of individuals in various trophic levels of food chain / unit area at any given time.

• In Gross land, Pond eco systems

Producers > Herbivores > Carnivores– Hence the pyramid is upright

• When the ecosystems contain lesser no. of producers than those of consumers, the apex of the pyramid is directed downwards. This types of pyramids are called Inverted Pyramids.

Examples of Inverted Pyramid

• Tree Ecosystem– A single tree harbors many fruit eating birds

(Prim.consumer) and these birds in their turn, host numerous parasites. (sec.consumer)

Pyramid of Biomass• It represents the total dry mass (in grams per square

meter of area) of all the organisms in each tropic level at a particular time.

Inverted Pyramid

Pyramid of Energy• It represents the rate of energy flow and/or productivity

at successive tropic levels. The pyramids of energy are always upright.

Energy

Amount of Energy decreases from

Producers

PC

SC

TC

Since the flow of energy is unidirectional, the pyramid energy is UPRIGHT

Ecological Succession

• Natural, gradual changes in the biotic community towards a stable or climax condition;

• The changes are progressive and predictable.

• The occurrence of sequence of communities over a period of time in the same area is termed as ES.

• Based on the nature of habitat: primary or secondary.

– Primary – begins in a place without soil

– Secondary – where soil already exists

• Based on the types of organisms.

– Autotrophic Succession

– Heterotrophic Succession

Primary Succession

Pioneer species• A group of organisms, such as lichens, found in

the primary stage of succession.

Climax community

• A community that has reached a stable stage of ecological succession

Based on Nature of habitat: Primary Succession

• PS is defined as the initial establishment and development of an ecosystem which occurs on a site previously unoccupied by living organism.

• The organisms that establish their first are called “Pioneer organisms” / Primary colonizers.

• Simple plants first.

• Gradual arrival of more complicated and larger plants as the habitat changes

• Unfavorable for life at first.

• Ends with a “climax community” – ecosystem stays constant, provided there are no changes in abiotic influences.

Secondary Succession

Secondary Succession

• Community development in the previously occupied areas is replaced by other community.

• If successions starts on an area, previously colonized, and the soil is organically enriched, it is known as SS.

• SS is defined as the reestablishment of a new ecosystem at a site where community was existing earlier but disrupted by natural or artificial means like storm, fire, flood or human activities.

• E.g., loss of trees after disease, Fire or wind, deforestation etc.

• More rapid than primary succession.

Primary Vs Secondary

• No soil.• Pioneer species.

• Weathering & decomposition

• End = Climax community.

• Soil already exists.• Seeds have suitable

soil conditions.• Occurs much faster.• Climax community.

Based on types of Organisms

• Autotrophic Succession: It begins in a predominantly org. env. characterized by early and continued dominance of Autotrophic Organisms like green plants.

• Heterotrophic Succession: It begins in a predominantly org. env. characterized by early dominance of Heterotrophs like bacteria, fungi and animals.

Process of Succession

1. Nudation

2. Invasion

3. Migration

4. Colonisation

5. Ecesis

6. Aggregation

7. Competition and reaction

8. Climax or stabilization


1. Nudation: The process of formation of a bare area is known as Nudation

• Caution– Industrial / Agricultural – Manmade– Climatic Change– Biotic disturbances – Natural

• Landslides• Floods


2. Invasion: The process of successful establishment of new species in the bare area is known as Invasion

3. Migration: The process of movement of organisms in to the bare area is known as Migration.

The seeds, spores of the species invade (enter by force) to the bare area by the agents such as Air and Water.


4. Colonisation: Occupation of the bare area by first or pioneer community is called colonisation

5. Ecesis: After reaching the bare area, the new species starts to establish themselves in it. Establishment of pioneer community is called Ecesis. Such pioneer reacts with the medium like soil or water and establishes themselves.

Process of Succession6. Aggregation: The final stage of Invasion by a Pioneer group is called Aggregation. The species which has successfully settled in the new area, reproduce and aggregate into large population in the new area.

7. Competition and Reaction: After establishment, various species compete among themselves for space, light and nutrients. Communities which cannot withstand during competition, are replaced by other communities till a climax community is established.


8. Stabilization: This is the final stage in the process of ecological succession. The climax community becomes more or less stabilized for a long period of time. It can maintain itself in equilibrium with the climate of that area.