A biotic community intreacts with enviornment in which it lives. for example a human being intreacts with animals, plants for foods and also intreacts with neighbours. He also intreacts with enviornment which supplies him materials and energy. This constitute the ecosystem. Thus ecosystem may be defined as

“ The entire intreacting system of organism together with environmental factors with which they intreacts. In other words , it is self sustained community of organisms”

It includes all the communities of an area functioning with their physical enviornment. For example ,a pond lakes river, garden crop field are common examples of enviornment

Abiotic substances These includes air, water, soil, basic elements and compounds of the environment.The abiotic environment of ecosystem are divide into three parts:

(a) The physical factors such as temperature, relative humidity precipitation etc.

(b) Inorganic substances such as water, carbon, nitrogen etc.

(c) Organic substances such as protien, carbohydrates lipids etc.

These are buildings blocks of living body and link between biotic and abiotic components

The term ecosytem was first purposed by A>G Tansely (1935) who defined it as ecosystem is self sustained community

The term ecosystem is made up of two words : (eco and system). Eco means ecological sphere or region of space where living things can exists while system means intreacting organism living in a particular habitat. Thus the system resulting from the integration of all living and non living factors of organisms is called ecosystem.

An ecosystem is dynamic entity composed of a biological community and its associated abiotic environment.

The materials continually cycle fron the environment into living organisms and from organisms by death into the environment. The cycle called bio-geological cycle. Solar energy continuosally trapped from the sun, which is the ultimate sources of energy

And energy is lost via respiration and heat losses and escapes to environment.

It includes all living organisms and its environment. The biotic component can be divided into two major groups:

(a) Autotrophs (b) Hetrotrophs(a) Autotrophs (auto=self, troph=

nourshing): self food producing organisms are known as autotrophs. They depend on the environment for their food materials utilize sunlight for their food, hence called producers………………………………….

Hetrotrophs(Hetro-other; trophs nourshing)

The hetrotrophs are the organisms mostly animals that cannot utilizes sunlight directly for their food prepration , because they do not have chlorophyll. Hence they consumes plants and their products produced by autotrophs. In this complex organic substances produced by plants are broken down into smaller forms.

Living organisms which consumes food, synthesied by producers are called consumers. Based on dependency, they are classified into three major groups.

Primary totally dependent on plants Secondary dependent on primary Tertiary They depend on both primary

and secondary. The placements of individuals

organisms depend upon the type of food they eat and occupation of organism in food chain.

(1) Herbivores : plant eating organism (2) Carnivores : organisms eating herbivores (3) Omnivores : Organisms eating herbivores

and carnivores This classification is easy to

understand because the terms directly indicate (e) type of food they eat.

1st order consumer, 2nd order consumer,3rd order consumer, 4th order consumer

GRASSGRASSHOPPERFROGSNAKEHAWK Hence grass is producer, grasshoper is 1st

order frog is 2nd snake is 3rd , hawk is 4th order

The main function of ecosystem are as: (1) Flow of energy (a) from sun to

producers (b) producers to consumers (c)

consumer to decomposers (2) Cyclic use of materials The chemical

elements composing the abiotic components are circulated in an ecosystem starting from nutrients pool (soil) to produces , producers to consumer

Consumers to decomposers and then back to pool.

Flow of energy takes place in an ecosystem takes place through food chain . In an ecosystem , unidirectional flow of energy is normally observed . Unlike the nutrients like (C,N etc) which moves In cyclic manner and care reused by producers after flowing through food chain, energy is not reused in ecosystem. This energy flow is based on two laws of thermodynamics .

(1) First law of thermodynamics (2) Second law of

thermodynamics………………………………….

Energy can neither be created nor be destroyed but can be transformed from one form to another is first law of thermodynamics. The solar energy trapped is converted into biochemical energy.

According to second law “energy cannot flow from a cold body to hot body by itself” one of the example is such a photosynthesis ,where conversion of light energy into potential chemical energy is invariably accompanied with dispersion of some energy as heat energy .

“An ecological pyramid is graphical representation of ecological parameters like number or biomass or accumulated energy at different tropic levels in food chain of an ecosystem.

The idea of ecological pyramid was developed by Charles Eltro , an English man . So ecological pyramid is also called Eltronian pyramids.

In these pyramid the first tropic level i.e. producer forms the base and the successive level i.e. herbivores at middle and next carnivores in simple form, if we arrange the organism in a food chain according levels ,they often form pyramid.

Type of pyramid they are of 3 types(1) Pyramid number (2) Pyramid biomass(3) Pyramid of energy

9

It shows the relationship between the producers,herbivores and carnivores at successive tropic level in terms of their number. Different shapes in ecosystem.

(1) Grassland ecosystem: producer are grass ,these numbers gradually shows decrease towards apex. The primary consumer are rabbit, cow, goat and are lesser in number than grass. The secondary consumers snakes, wolves and lizzards and are less than herbivores

In this the number of producers per unit of space may be little for example a single tree might support a greater number of herbivores e.g. Fruit eating birds. The herbivores in turn support still greater number of carnivores

The amount of living material present in an organism are called biomass. It is measured as fresh and dry.

(1) Grassland ecosystem: here biomass present in grass is more than present in herbivores and that of herbivores more dependent than carnivores

Out of these three types of ecological pyramids , the energy pyramid gives the best picture of overall nature of ecosystem. It is picture of rates of passage of food mass through food chain. There is always a gradual decrease in energy content of successive tropic levels from producer to consumers. Because there is also a loss of energy. By respiration and other process

An ecosystem is not static in nature. It is dynamic in nature and changes its structure as well as function.

Ecological succession is defined as orderly process of changes in the community structure and function with time mediated through modifications in physical environment cumulating in an ecosystem.

Ecological succession are different types.(1) Hydrach starting in watering area lihe

ponds lakes. The pioneer community which are phytoplanktoms, are replaced by roots submerged plants.

Growths of these plants keep on adding organic matter and after death thus layer of soil builds up and shallowing of water takes place. Then stage is come where plants are slightly on water slightly on lands.

Xerosere this type of succession originates on bare rocks which is deficient I n water and organic matter. The pioneer community here consist of foliose lichens. These lichens produce some weak acid and help in disintegration of rocks

there growth helps in building up gradually organic matter, humus, soil. Then followed by herbs, shrubs and finally the forest trees.

Thus, succession tends to move towards mesic conditions whether starts from moist or dry conditions and finally result into trees……….

For the sake of study ecosystem are divided in two main categories:

(1) Natural ecosystem(2) man made ecosystem Natural ecosystem are of three typesA Terrestrial B fresh water ecosystemC Marine ecosystem A large geographical area with its

specific and complex flora and fauna called biome. The type of climax vegetation of a biome depends upon the physical factors like nature of soil, amount of rainfall etc.

Forest cover about 1/12th of earth surfaces but half of the worlds flora and fauna. Forest are the natural community with dominance of tress they cover about 40 percent of the land. There are of three types:

(1) Tropical rain forest (2) Temperate deciduous forest (3) confereous forest.

Tropical forest contain high humidity Deciduous forest experience :

temperature, rain cold etc. Confereous forest have short summers,

long and cold winters.

There are mainly two component (1) Biotic (2) Abiotic component Abiotic component = this component consist

of organic and inorganic substances in soil and atmosphere. The climate are vary from forest to forest.

Biotic component= it contain s as : Producers : this component consist of living

organisms such as producers consumers and decomposers. In the forest there are lot of tress like Dipterocrapus ( rose wood), tectona grandis(Teak) etc.

consumers: these feed on producers include primary, secondary, tertiary.

The grass land ecosystem occupies 19% of earth surfaces. The grass land biome occur in regions , where the climate is cool to cold during winters and in summers. It has also two ecosystem:

(1) Abiotic ecosystem these include nutrients present in soil and atmosphere. Thus elements like C,H,O,N etc. are supplied by carbon dioxide , water present in air and soil of the area.

(2) Biotic component it has following parts Producers the grass land are characterized by

treeless plant dominated by variety of grass species main species are cynodon, cenchrus etc.

(1) Consumers the various types of consumers are as :

Primary consumers the herbivores feeding on grass such as animals like cows, goat etc. Besides them there are also some insects species like leptocorisa dysderus etc.

Secondary consumers snakes lizards etc.Tertiary consumers hawks which feed

secondary. (2) Decomposers several fungi and

bacteria decay the dead organic matter of different forms .

These are characterized by (1) Desert around 1/5th of earth surfaces

(2) due to deficiency of water and high temperature of desert , desert having scanty flora and fauna

(3) days are extremely hot and nights are cold

(4) some animals like ants spiders lizards snakes insect eating birds are present in this ecosystem

There are many kinds of aquatic ecosystem mainly fresh water ecosystem and marine ecosystem. They differ widely with regards to abiotic factors and living organisms. The important ecosystem are as follows as

Ponds ecosystem pond ecosystem is an example of lentic ecosystem , this ecosystem rich in vegetation , micro organisms plants and animals these are having following zones as

Litorial zones this is a shallow water zones and includes variety of floating organisms & plants here penetration of light is very high. And rich in nutrient area

Limentic zones this is open water zones here penetration of light is small than litorial zones and contain phytoplanktoms

Profoundal zones this is deep zones. Here biological activity is intense and are adapted to cold water.

It includes two components(1) Abiotic component(2) Biotic componentAbiotic component it contains inorganic and

organic components. Only small amount is form in soluble form and large amount is present in bottom sediments and in organisms.

Biotic component it includes producers and consumers. E.g. volvox anabaena are the primary and mysids lycops are secondary.