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CONCEPT OF AN

ECO SYSTEM

Dr.R.Priscilla, HoD of Physics,

ADM. College for Women,

Nagapattinam.

Eco System

The various communities of living organisms interact among themselves

As well as with their physical environment like soil, air and water. This functional unit or ‘system’ made up of living and non-living components is called an ‘ecosystem’. This term ‘ecosystem’ was coined by Tansley in 1935.

The interaction is through energy flow and

cycling of materials.

*This makes the ecosystem to sustain life

continuously.

*An eco system may be of any size. i.e, the whole

world may be considered as an ecosystem called

biosphere.

*They are natural but some man made and none

of the eco system is independent but all of them

are interdependent.

Structure and function of an

ecosystem

Two major components

1. The abiotic component which

includes the physical environment.

2. The biotic component comprising

of all the living organisms.

ABIOTIC COMPONENTS BIOTIC COMPONENTS

Sunlight Primary producers

Temperature Herbivores

Precipitation Carnivores

Water or moisture Omnivores

Soil or water chemistry (e.g., P, NH4+) Detritivores

etc. etc.

Abiotic component consists of

1. the solid mineral matter of the

earth(lithosphere)

2. the water in the oceans, lakes,

rivers and ice caps etc.(hydrosphere).

3.the gaseous mixture in the

air(atmosphere) and

4. the radiant solar energy.

The environment created and

maintained by the interactions of

the common environmental

factors, function as a whole unit.

Any of these factors cannot be

removed or altered without

affecting the other factors.

Therefore, the environment is

called HOLISTIC.

Producers, consumers and

decomposers

Biotic Component – the organisms of

ecosystems are divided into two

classes.

1. The producers:

autotrophs (green plants & certain

bacteria)

– produce their own food.

Since these organisms produce food for all

the other organisms they are also known

as producers.

2. consumers:

Heterotrops – depends on the producers for

the food.

Depends directly or indirectly upon the

autotrophs for their food.

Consumers Decomposers.

Consumers are of three kinds.

They are

1. Primary consumers

2. Secondary consumers

3. tertiary consumers.

Primary consumers

- a herbivore is a primary consumer.

- it derives its nutrition directly from plants

Secondary consumers

- a carnivore is a secondary consumer.

- it derives its energy from the producers

(plants)

Tertiary consumers

- they are Carnivores that feed on other

carnivores.

Omnivores are consumers that derive their

energy from both producers and herbivores.

Decomposers

- consists of bacteria and fungi.

- produce enzyme within their bodies.

- act on dead plant & animal material and

some of the degraded and digested

products and then absorbed.

- perform an invaluable service to the

ecosystem by the mineralization of organic

matter and made available for reuse.

The process of eating and being eaten forms

a chain.

Producer herbivore carnivore carnivore – back to producers.

The position of the organism in the food chain is

indicated by tropic levels.

Tropic level may be defined as the no. of links by

which it is separated from the producer.

Grass -» Grasshopper -» Lizard -» Snakes -»

Hawks.

Grass -» Mice -» Snakes -» Hawks

Grass -» Rabbits -» Dogs -» Tigers/Lions.

Trees -» Deer/Goats -» Foxes -» Tigers/Lions.

Trees -» Birds -» Snakes -» Hawks.

Phytoplankton -» Larvae -» Fishes -» Whales.

First Tropic Level – producers

2nd Tropic Level – herbivores

3rd Tropic Level – carnivores The same organism may operate in the ecosystem at

more than one tropic level,i.e, deriving food from more than one source.

An organism may be eaten by several organisms of a higher tropic level or an organism at a lower tropic level may feed upon several different organisms.

Thus we obtain several food chains linked together and intersecting each other to form a network known as FOOD WEB

Energy flow in a Eco system

Energy flow : In any eco system, for their structural

development and functioning obtain energy from a group

of organisms that are already present in a particular

system.

1.Energy travels only through single way

2.There is reduction of energy in each tropic level

* Energy level is const. for every ecosystem

* One cannot increase or decrease the energy level

* Can be converted into one state to another state

* A portion of energy remains unused during the

conversion of energy

* After conversion its reaction capacity gets reduced.

* Because of this, there is flow of energy from higher tropic

level to the lower tropic level.

* A part of the radiant energy of the sunlight is converted

into chemical energy by the producers and is stored in the

organic compounds

* The rest of the radiant energy is converted into heat

energy.

Food Chains, Food Webs and Ecological Pyramids.

Food Chains : The transfer of food energy from producers (plants) through a series of organisms,

i.e, Herbivores Carnivores Top carnivores

Decomposers

with repeated eating and being eaten is known as a food chain. It is also called as trophic level.

Example : In grassland ecosystem, the food chain starts from grasses and goes through the grasshopper, calotes, snake and the eagle or hawk in an orderly sequence.

Food webs

Though many food chains can be traced in

an ecosystem they never operate as isolated

sequences. But they are interconnected

with each other forming some interlocking

pattern. This is known as food web.

Ecological PyramidsThe interrelation between numbers, biomass and

energy contents of consumersof the first order,

second order and upto the top carnivores in any

ecosystem is represented in diagrammtic ways. They

are called as ecological pyramids. They are of three

types, viz.,Ecological

Pyramids

Pyramid of

numbers

Pyramid of

biomass

Pyramid of

energy

1. Pyramid of numbers :

The relationship between the

number of producers and the

primary, secondary and tertiary

consumers constitutes the pyramid

of numbers.

Tiger or lion(Top carnivores)

Fox (Sec.carnivores)

Rabbit(Pri.consumer)

Grasses(Pri. Producer)

Grassland ecosystem shows upright pyramid

In the grassland ecosystem the wide base of the pyramid represents the large number of primary

producers.

The primary consumers like the rabbit and the grasshopper form the second large number.

The top carnivores like the tiger is present in the least number and occupy the peak of the pyramid.

So in this way the numbers are represented in a diagramatic way and an upright pyramid is formed.

Pyramid of Biomass

Biomass is the amount of living organisms and

living matter present in a particular ecosystem

In grassland ecosysytem, the

Biomass of the producers is the

highest of all the trophic levels.

Tiger

Fox

GrassesPyramid of Biomass in Grassland Ecosystem

Here, not only the number decreases but the biomass also continue to

decrease from primary producers

to the top carnivores.

The relationship between the biomass of producers and the consumers of the

ecosystem can again be represented in the

form of upright pyramids.

Pyramid of energy_______Carnivores(Tertiary

consumers)

_________Carnivores(Sec.consumers)

________Herbivores (Pri.consumers)

________Producers

In an ecosystem the primary producers trap the sunlight energy and convert into chemical energy

through Photosynthesis.

The energy traped in the food materials flow in the food chain from the producers to the herbivores

and then to carnivores and finally to top carnivores.

Here the energy flow is always unidirectional and at successive trophic levels it decreases.

Therefore the pyramid of energy is always vertical.

The components of a forest

ecosystem are

Abiotic components – organic and inorganic matter present in the land and atmosphere.

Biotic components – living flora and fauna are the living cpts. of a forest. They are recognized as

Producers

consumers

Decomposers

Producers:

* trees are the primary producers.

* Vines and epiphytes are the two

characteristics of evergreen forest.

* In India tropical evergreen forest

are found along the West Ghats and

the NEFA

Consumers:

*The macro consumers (animals)

in different forests are well adapted for the

conditions prevailing there.

*Foliage arthropods such as ants, flies,

beetles, leaf hoppers, bugs and spiders are

found.

*Moles, squirrels, fruit bats, mongooses are

also present.

Decomposers:

The soil organisms found in the

forest are protozoan, flat worms,

nematodes, annelids, snails,

millipedes, centipedes, spiders,

spring tails, termites, trips and ants.

Some of the soil organisms and soil

bacteria play the role of

decomposers.

Productivity:

*Different types of forest vary in gross productivity

*The plants and other autotrophic organisms store

some dry matter by their photosynthetic activity. The

rate at which this dry matter is stored in the ecosystem

is called the primary productivity.

*The productivity is the highest due to the stable

environment, large availability of water and high

constant temperature.

Pond Ecosystem :

Ponds are small bodies of shallow standing

water.

They are characterized by relatively quite

waters and abundant vegetation.

A pond serves as a good example for a fresh

water ecosystem.

It consists of both abiotic and biotic

components.

The chief components of abiotic

components are heat, light, pH value,

organic and inorganic compounds

namely carbon di oxide, oxygen, calcium,

nitrogen, phosphates, amino acids, humic

acids, etc. The amount of these

components are estimated for biomass

determination.

The various organisms of the biotic

components are producers,

consumers and decomposers.

Producers – larger hydrophytes

and phytoplanktons which are

minute floating plants.

Consumers – primary consumers (insect

larvae, fish, mollies, zooplanktons),

secondary consumers ( insects and fish )

and tertiary consumers (large fish).

Decomposers – microbes such as

bacteria, actinomycetes and fungi. They

bring about the decomposition of

complex dead organic matter to simple

forms.

The term BIODIVERSITY was first coined by

the entomologist E.O. Wilson in 1986.

A neologism from biology and diversity, it refers

to the variety of life on the planet.

There is no single standard definition for

biodiversity.

1. Biodiversity may be defined as the totality

of different organisms, the genes they contain,

and the ecosystems they form.

2. The Convention on Biological Diversity defines

biodiversity as the variability among living organisms

from all sources including, among other things,

terrestrial, marine, and other aquatic ecosystems and the

ecological complexes of which they are a part; this

includes diversity within species, between species and of

ecosystems.

Biodiversity may be considered at three levels: genetic

diversity, species diversity, and ecosystem diversity

Genetic diversity

refers to the differences in genetic make-up between distinct species, as well as the genetic variations within a single species. This is the least visible and, arguably, least studied level of biological diversity.

Genetic diversity is the variety present at the level of genes. Genes, made of DNA, are the building blocks that determine how an organism will develop and what its traits and abilities will be.

This level of diversity can differ by alleles (different variants of the same gene, such as blue or brown eyes), by entire genes (which determine traits,

such as the ability to metabolize a particular substance), or by units larger than genes such as chromosomal structure.

More genetic diversity in a species or population means a greater

ability for some of the individuals in it to adapt to changes in the

environment.

Less diversity leads to uniformity, which is a problem in the long

term, as it is unlikely that any individual in the population would

be able to adapt to changing conditions.

As an example, modern agricultural practices use monocultures,

which are large cultures of genetically identical plants.

This is an advantage when is comes to growing and harvesting

crops , but can be a problem when a disease or parasite attacks

the field, as every plant in the field will be susceptible.

Monocultures are also unable to deal well with changing

conditions.

Within species, genetic diversity often increases with environmental variability, which can be expected.

If the environment often changes, different genes will have an advantage at different times or places.

In this situation genetic diversity remains high because many genes are in the population at any given time.

If the environment didn't change, then the small number of genes that had an advantage in that unchanging environment would spread at the cost of the others, causing a drop in genetic diversity.

Since the gene is the fundamental unit of natural selection, and thus of evolution, some scientists argue that the real unit of biodiversity is genetic diversity.

Species diversity

Species richness - the number of species within a particular sample area. in combination with)

Species evenness - this refers to the evenness in number of individuals of each species in the area

E.g. for two sample areas X and Y, there are two species, a, and b. In X, there are 92 individuals of species a, and only 8 of species b, while in Y, there are 50 individuals of each species.

If species richness only was used to account for species diversity in X, the diversity might seem lower than Y (although both have the same number of species), because almost all the individuals encountered would be from only one species.

Species evenness in conjunction with species richness is thus a more useful indicator of species diversity, because it takes into account rarer species.

The number of species currently described on earth is

between 1.4 and 1.7 million but the Global Diversity

Assessment suggests a conservative estimate of 1.75

million.

On land there are more species known than in the sea.

This is largely due to the extraordinary diversity of

beetles (Coleoptera);400,000 species are described.

An important aspect of species diversity is endemism,

that is, the species occurring in a restricted locality).

The Antarctic has a higher degree of endemism than the

Arctic.

When biodiversity is measured quantitatively, usually as the number of species or the value of a diversity index for a given community or area of habitat, it is known as ecosystem diversity.

Ecosystem is defined as a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit.

Habitat diversity is a more useful term than the of ecosystem diversity since habitats are easy to envisage(e.g forest, a coral reef, an estuary).

All species are presumed to interact with each other and to be

competing for similar limiting resources.

Ecologists have called this within habitat (or alpha) diversity.

At slightly larger scales habitat and / or community boundaries

are crossed and sampling covers more than one habitat and

community.

This scale has been called between habitat (or beta) diversity.

At an even larger scale (regional scale) where evolutionary rather

than ecological processes operate the pattern has been called

gamma diversity or more recently landscape diversity.

Landscape diversity can be defined as the mosaic of habitat over

larger scales often hundreds of km.

Biodiversity assessment need to be made at the

community habits and landscape levels if we are

to predict changes over time.

It is primarily the loss of habitats that leads to

both genetic and species diversity.

Therefore, species diversity can be

assessed in terms of the number of species

or the range of different types of species

an area contains.

Current estimates for the total number of

species in existence vary from 5 million to

nearly 100 million.

About 1.7 million of these species have

been identified to date. A complete and

current inventory of species is impossible

because many invertebrates, microorganisms

and lower plants (the three most diverse

life-forms) have not yet been identified

and named.

There has been a definite bias towards describing large organisms, those that are considered attractive or appealing (such as flowering plants and butterflies), those most closely resembling humans (vertebrates, especially mammals), and those that have a direct impact on human activities

Organisms that can be studied without complex procedures or expensive equipment have also taken precedence, as have those which are relatively easy to locate.

This, however, underestimates the importance of microorganisms including algae, bacteria, fungi, protozoa and viruses, which are vital to life on Earth.

So far, less than 3-5 percent of microorganisms have been described.

Values of biodiversity

Consumptive use

Productive use

Social value

Ethical value

Aesthetic value

Option value

India – A Mega Diversity Zone

Genetic diversity

Ecological diversity

Forest of India

Plant diversity

Animal diversity

Thank You