ECOSYSTEM

UNIVERSITY OF PETROLEM & ENERGY STUDIES

DEHRADUN

Dr. KANCHAN DEOLI BAHUKHANDI

ECOLOGY:The term ecology was first coined by “Earnest Haeckel”

It was derived from two greek words.Okios : HouseLogo : Study Thus Ecology may be defined as study of organism in their natural house.

It is the branch of botany which deals with study of orgasnism in their natural habitat.

ECOSYSTEM:The term ecosystem was first coined by A.G Tansely.It consist of two Words.

Eco : Environment System : Interaction

Thus ecosystem may be defined interaction of all biotic and abiotic component in environment.

Ecosystem is the major ecological unit. It has both structure and function .

The structure is related to species diversity. The more complex is the structure the greater is the diversity of the species in the ecosystem.

An organism is always in the state of perfect balance with the environment. The environment literally means the surrounding.

Definition by Odum

According to odum “ Thus any system that include all the living organism i.e community in a given area interact with environment so that flow of energy clearly defined trophic level, biodiversity & material cycle ( i.e exchange of material between living and non living component within the system is known as Ecosystem.

Characteristics of Ecosystem

• Ecosystem is structural and functional unit of Ecology.

• Structure of ecosystem related to species diversity. Complex ecosystem has more species diversity.

• Function of ecosystem related to flow of energy and material balance.

• The relative amount of energy is needed to maintain the ecosystem.

• Complex ecosystem need less energy to maintain the ecosystem.

• Young ecosystem developed and change from less complex ecosystem to more complex ecosystem. This process is known as succession .

• Adaptation to local environment is one of the most important feature of biotic component of Ecosystem.

Principal step of Ecosystem:

1. Reception of energy by producer.

2. Manufacture of organic food by producer.

3. Consumption of organic matter by consumer.

4. Decmposition of organic compound.

5. Transformation of decomposed organic compound into suitable compound for the nutrition of producer.

Solar Energy ---- Autotrophs------Hetrotrophs (Chemical Energy)

TYPES OF ECOSYSTEM

1. Natural Ecosystem, 2. Artificial Ecosystem

Natural Ecosystem:

1. Terrestrial Ecosystem, 2. Aquatic Ecosystem

Terrestrial Ecosystem:

a. Forest Ecosystemb. Grass land Ecosystemc. Desert ecosystem

AQATIC ECOSYSTEM1. Fresh Water Ecosystem

A) Lotic Ecosystem – Running Water Eg. River, Spring

B) Lentic Ecosystem : Standing Water Eg. Pond, Lake, Swamp

2. Marine Ecosystem

Forest Ecosystem:

Forest are the natural Plant communities with dominance of flowering plants

Tree, shrubs, flower are present in plenty

In India forest occupy about 18 to 20 % of the total land area.

Forest can be divided into:

1. Tropical Evergreen Forest:

These forest contain a deep and dense vegetation of tall tree.

2. Tropical deciduous forest

These forest have broad leaved trees growing with shrubs, bushes andcreepers in between them.

3. Temperate deciduous forest

These occur in the area where well defined winters alternative with well defined

summer with sufficient rainfall.

Eg. Maple, elms, oak, peaches etc.

4. Coniferous Forest

These forest found in colder regions The dominant species are fir, pine, poplar.

A biotic component

1. Inorganic component

Minerals, metals, gases like co2, NO2 , SO2 etc.

2. Organic component

Eg. Fats, glucose, amino acid

Atmospheric component

Climatic component:

1. Temperature, 2. Humidity , 3. Rainfall

2. Wind Velocity 3. Pressure

3. Biotic Component:

P-

Biotic component consist of living organism represented by producer,

consumer and decomposers

1. Producers:

Producers are trees of different kind. Besides trees, shrubs & herbs are

also present.

Producers are called autographs which made their food by themselves

in the presence of sunlight , chlorophyll.

Consumer / Hetrotrophs:

Consumer are represented by herbivores, carnivores and omnivores which are directly or indirectly dependent on producers for their nutrition.

Consumers are further divided into herbivores and carnivores.

Herbivores:

Like ants, flies, beetles, leafhopper feed trees, leaves while larger herbivores are

elephant, deer, ziraaf etc.

Carnivores

Small Carnivores like snake, birds, fox feed on herbivores.

Large Carnivores : Lion & Tiger feed on small carnivores and herbivores.

Decomposers: A variety of micro organism like bacteria , fungi , protozoa which decompose the dead body

of plant and animal and convert into simpler form.

During decomposition process nutrient , nitrozen and carbon di-oxide gas is

released.

Pond Ecosystem

A pond is a self sufficient and self regulating system

1. Abiotic Component:

Light, heat, pH, water, organic and inorganic compound such as water itself , CO 2 ,

Ca, Mg, K, Fe, P,Na, amino acid, fats, glocose etc.

Biotic componenta) Producers:Producer forms complex organic substance such as carbohydrates, protein etc

.

Pond Ecosystem

Macrophytes:

Include mainly rooted larger plant which partially submerged or completely submerged or floating plants.

Species are trapa, typa, uticularia, chara, hydrilla.

• Floating Plant

Azolla, lemna, wolffia spirrodilla

Phytoplankton

Minute floating or suspended lower plants.

Eg. Volvex, diatoms, oscillateria

Consumer

They are hetrotrophs which depend for their nutrition on the organic foodmanufactured by producer. Most of the consumers are herbivores – a few insects some large fishes are carnivores feeding on herbivores.

1. Primary consumer:Feeding on living plants.

a) BenthosFish, insects, larvae, beetles & mollucs

b) ZooplanktonThese are chiefly rotifers Protozons, Euglena, feed directly on Phytoplankton

Secondary Consumer

Carnivores feed on herbivores . Eg. Fish, Water beetles

Tertiary Consumer : Large fish feed on small fish.

Decomposers: Known as micro- consumer. Fraction of decomposed dead organic matter of plant and animal (both producer as well as macro consumer ) into simpler form They are chiefly bacteria, fungi, actinomycetes

All the ecosystems of earth are connected to one another e.g. river ecosystem with ecosystem of ocean.

STRUCTURE OF ECOSYSTEM:

The structure of an ecosystem is basically a description of the organism and physical features of the environment including the amount and distribution of nutrients in a particular habitat.

It also provides information regarding the range of climatic conditions prevailing in the area.

From the structural point of view , all ecosystem consist of the following basic components:

• Abiotic component

• Biotic component

1. ABIOTIC COMPONENTS:

Ecological relationships are manifested in physiochemical environment.

Abiotic component of the ecosystem includes basic inorganic elements

and compounds such as soil, water, oxygen, calcium carbonates, phosphates and a variety of organic activities or death.

It also includes physical factors and ingredients as moisture, wind currents and solar radiation.

2. BIOTIC COMPONENTS:

The biotic components include all living organisms present in the

environmental system.

From nutrition point of view , the biotic components can be grouped into

two basic components.

• Autotrophic components

• Heterotrophic components

1. AUTOTROPHIC COMPONENTS :

It includes all the green plants which fix the radiant energy of sun and manufacture food from inorganic substances.

2. HETEREROTROPHIC COMPONENTS:

It includes non-green plants and all animals which take food from

autotrops . So, biotic components of an ecosystem can be described

under the following three heads.

• Producers

• Consumers

• Decomposers or reducers

a. PRODUCERS:

They use radiant energy of sun in photosynthetic process . algae and other hydrophytes of a pond, grasses of a field, trees of the forests are example of producers.

b. CONSUMERS:

Those living members of the ecosystems which consume the food

synthesized by producers are called consumers. under this category are included all different kinds of animals

that found in an ecosystem.

There are different classes of consumers, such as

• Consumers of the first order or primary consumers

• Consumers of second order or secondary consumers

• Consumers of third order or tertiary consumers

• Parasites, scavengers

I.CONSUMERS OF THE FIRST ORDER OR PRIMARY CONSUMERS:

These are purely herbivorous animals that are purely dependent on the producers or green plants for their food.

Eg. Insects, rodents, rabbits, deer, cows are some of the herbivores in the terrestrial ecosystem and small crustaceans and molluscs in the aquatic habitat.

II.CONSUMERS OF SECOND ORDER OR SECONDARY CONSUMERS:

These are carnivores and omnivores. Carnivores are flesh eating animals that are adopted to consume herbivores as well as plants as food.

Examples of secondary consumers are sparrow, crow, fox, wolves , dogs, cat and snakes etc.

III.CONSUMERS OF THIRD ORDER OR TERTIARY CONSUMERS:

These are top carnivores which prey upon other carnivores, omnivores and herbivores. Lions, Tigers, Hawk, vultures etc. are considered as tertiary or top consumers.

IV.PARASITES, SCAVENGERS: The parasitic plants and animals utilize the living tissues of different

plants and animals.

The scavengers utilize dead remain of animals and plants as their food.

FUNCTIONS OF ECOSYSTEMS:

An ecosystem is a discrete structural, functional and life sustaining environmental system.

The environmental system consists of biotic and abiotic components in a

habitat. Biotic components of the ecosystem include the living organisms,

plants , animals and microbes.

Whereas the abiotic components includes inorganic matter and energy.

FUNCTIONS OF ECOSYSTEMS:

Function of ecosystem involve energy flow and this energy comes from

the sun in the form of light or solar energy.

Thus, in any ecosystem we have the following functional components.

Inorganic constituents ( air, water and mineral salts)

Organisms ( plants, animals and microbes)

Energy input , which enters from outside (the sun)

Thus the principal steps in the operation of ecosystem are follows:

• Reception of the radiant energy of the sun

• Manufacture of organic materials from inorganic ones by producers

• Consumptions of producers by consumers and further elaboration of consumed materials and

• After the death of living producers and consumers, complex organic

compounds are degraded and finally converted by decomposers and converts into such forms that are suitable for the utilization by producers.

It is clear that there is transfer of both energy and nutrients from producers to consumers and finally to decomposers and transformers level.

In this transfer there is progressive decrease of energy.

FOOD CHAIN:

The simple chain of eating and being eaten in an ecosystem is known as food chain.

The transfer of food energy from the source in plants through a series of Organisms (herbivores to carnivores, carnivores to decomposers) that consume and are being consumed is called the food chain.

In each transfer some energy is lost Therefore the shorter the food chain the greater the energy available to that population.

IN any food chain the energy flow from primary producer to primary consumers to secondary consumers (Carnivores), from secondary consumers to tertiary consumers (carnivores/omnivores).

Food chains are of two basic types:

1. THE GRAZING FOOD CHAIN:

This type of food chain starts from the green plant base goes to grazing herbivores and on carnivores.

This types of food chain are diretly dependent on influx of solar radiation.

Example : Phytoplankton--------- Zooplankton------Fish----------ManGrass ----Grasshopper-----------------Frog---------------Sanke--------HawkGrass-----Rabbit --------Fox ----------------Tiger

2. THE DETRITUS FOOD CHAIN :IT start from dead organic matter and goes to detritus feeding organism (detrivores) and on to their predator. Detrivores are the consumers of dead organic matter. For Ex. Bacteria, Soil Mites, worms and fungi of decay.

Leaf litter → algae → Crab → Small carnivores Fish → Large Carnivores Fish (Mangroves ecosystem)

Dead organic matter → Fungi → Bacteria . .> protozoa > Rotifers ( Forest Ecosystem)

• This types of food chain chiefly depend on the influx organic matter produced in another system. Such ecosystem are mangroves, estuaries which are less dependent on direct solar radiation.

• A large quantity of leaf material falls in the form of litter into the water. The fllen leaves are colonized by small algae, which are also consumed by the saprotrophs or detritivores consisting of carbs, mollusks, shrimp , insect larvae, nematodes and fishes, which in turn are eaten by large carnivores fishes.

• Thus the grazing food chain derives its energy basically from plant energy while in the detritus food chain it is obtained primarily from plant biomass, secondarily from microbial biomass and tertiary from carnivores.

• In a food chain ,there is repeated eating in which each group eats the smaller one and is eaten by the larger one

In a food chain there is unidirectional flow of energy from sun to producer and then series of consumers .

• Usually 80-90% of potential energy is lost as a heat at each transfer.

• Usually there are 4-5 trophic levels in the food chain ,shorter food chain will provided greater energy.• a food chain is always straight .• Omnivores generally occupy more than 1 trophic level in a food chain .

Example of a Food Chain

Food Web• In ecosystem some consumers feed on a single species

, but most consumers have multiple food sources. As a result individual food chains become interconnected to form a Food Web

• A food web is a complicated system of relationships between plants, animals, and energy. 

• All food chains are interconnected with each other forming some interlocking pattern known as food web.

• Food web is the network of food chains where different types of organisms are connected at different trophic levels ,so that option of eating and being eaten at each trophic level.

Food Webs• All the food chains in an area make up the food web of the area.

ECOLOGICAL PYRAMID:The use of ecological pyramids was advanced by C.E. Elton ( 1927). There are different types of ecological pyramids . In each ecological pyramid, producer levels forms the base and successive level makes up the apex.

The trophic structure and function of an ecosystem can be indicated by means of ecological pyramid where producer constitute the base of pyramid and top carnivores making apex.

At each step in the food chain , a considerable portion of the potential energy is lost as heat.

As a result , organism in each trophic level pass on lesser energy to the next trophic level than they actually receive.

Three types of pyramidal relations may be found among the organisms at different levels in the ecosystem. These are as follows:

Pyramid of numbers

Pyramid of biomass

Pyramid of energy

1. PYRAMID OF NUMBERS:

It depicts the numbers of individuals in producers and in different

orders of consumers in an ecosystem.

The base of pyramid is represented by producers which are the most

abundant and in the successive levels of consumers , the number of

organisms goes on decreasing rapidly until there are few carnivores.

2. Pyramid of biomass : It depict the relationship between producers and consumers in term of their total dry weight. The pyramid of biomass can also be upright and inverted.

3. Pyramid of Energy :

It depict the relationship between producers and consumers in term of energy flow in an ecosystem. It is based on 10% law of energy . Therefore the pyramid of energy is always upright.

The amount of energy present at each trophic level is known as pyramid of energy.

Energy Flow and Nutrient Cycling

1. Nearly all ecosystems are dependent upon solar energy flow and finite pools of nutrients.        

2. Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur make up nearly all life.        

3. Energy flow in an ecosystem is a consequence of two fundamental laws of thermodynamics:

a. First law of thermodynamics states energy can neither be created nor destroyed; it can only be changed                 from one form of energy to another

b. Second law of thermodynamics: when energy is transformed from one form to another, there is always some loss of energy from the system, usually as low grade heat.

10 % Law of Energy

• About 10% of energy at a particular trophic levels incorporated into the next trophic level.

• According to 10% Law , only 10% energy is avaiable for the transfer to the next trophic level, rest of 90% lost in form of heat in an environment.

• The energy lost in excretion, respiration .•

 a. Thus, 1,000 kg (or kcal in an energy pyramid) of plant material converts to 100 kg

of herbivore tissue, which converts to 10 kg of first carnivores, which can support 1 kg of second level carnivores.

a. This rapid loss of energy is the reason food chains have from three to four links, rarely five.

a. This rapid loss of energy is also the reason there are few large carnivores.

Global Biogeochemical Cycles 1. Biogeochemical cycles are the circulation pathways of elements (e.g.,

carbon, oxygen, hydrogen, nitrogen or mineral elements) through the biotic and a biotic components of an ecosystem.

1. A reservoir is that portion of the earth that acts as a storehouse for the element.

3. An exchange pool is the portion of the environment from which producers take chemicals, such as the             atmosphere or soil.

4. The biotic community is the pathway (i.e., food chains) through which chemicals move.

5. Some cycles are primarily gaseous cycles (carbon and nitrogen); others are sedimentary cycles, (phosphorus

The Hydrologic (Water) Cycle 1. In the hydrologic cycle, freshwater evaporates and condenses on the

earth.

2. Evaporation of water from the oceans leaves behind salts.

3. Rainfall that permeates the earth forms a water table at the surface of the ground water.

4. An aquifer is an underground storage of fresh water in porous rock trapped by impervious rock

5. Freshwater makes up about 3 percent of the world's supply of water and is a renewable resource. 6. Freshwater becomes unavailable when consumption exceeds supply or is

polluted so it is not usable.

. The Carbon Cycle The carbon cycle is the set of biogeochemical processes by which carbon undergoes chemical reactions, changes form, and moves through different reservoirs on earth, including living organisms.

The geological component of the carbon cycle is driven by plate tectonics and includes processes like volcanic eruptions and burial of carbon-rich sediments on the ocean floor.

The biological component of the carbon cycle is driven by respiration and photosynthesis by living organisms.

Humans influence the global carbon cycle in several ways, but primarily through burning fossil fuels.

Terrestrial and aquatic organisms exchange carbon dioxide with the atmosphere.

Photosynthesis removes CO2 from atmosphere; respiration and combustion add CO2 to atmosphere.

CO2 from the air combines with water to produce bicarbonate (HCO3), which is a source of carbon for aquatic producers, primarily algae.

Similarly, when aquatic organisms respire, the CO2 they release combines with water to form HCO3.

4.

The reservoir for the carbon cycle is largely composed of organic matter, calcium carbonate in shells, and limestone, as well as fossil fuels.

The Nitrogen Cycle ()• The nitrogen cycle is the process by which nitrogen is converted between its various

chemical forms. Nitrogen gas (N2) is 78% of the atmosphere,.

• This transformation can be carried out via both• 1. Non biological : fixation occurs in lightning strikes,

• 2. biological processes : fixation is done by free-living or symbiotic bacteria.

some symbiotic bacteria (most often associated with leguminous plants) and some free-living bacteria are able to fix nitrogen as organic nitrogen. An example of mutualistic nitrogen fixing bacteria are the Rhizobium bacteria, which live in legume root nodules

Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (NH4

+), nitrite (NO2-), nitrate (NO3

-), and nitrogen gas (N2).

2. In the nitrogen cycle, plants cannot incorporate N2 into organic compounds and therefore depend on various types of bacteria to make nitrogen available to them.

          

c. Other nitrogen-fixing bacteria, living in nodules on the roots of legumes, make reduced nitrogen and organic compounds available to the host plant.

Nitrification

The conversion of ammonium to nitrate is performed primarily by soil-

living bacteria and other nitrifying bacteria.

Denitrification• Denitrification is the reduction of nitrates back into the largely inert nitrogen gas

(N2), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas           

Ammonification

When a plant or animal dies, or an animal expels waste, the initial form of

nitrogen is organic. Bacteria, or fungi in some cases, convert the organic

nitrogen within the remains back into ammonium (NH4+), a process called

ammonification or mineralization.

b. Nitrogen gas is converted to NO3- in the atmosphere when cosmic radiation, meteor trails, and lightning provide the high energy for nitrogen to react with oxygen.            

c. Nitrifying bacteria convert NH4+ to NO3-.

d. Ammonium in the soil is converted to NO3- by nitrifying bacteria in the soil in a two-step process:

1) First, nitrite-producing bacteria convert NH4+ to nitrite (NO3-).

2) 2) Then, nitrate-producing bacteria convert NO2 - to NO3-.

e. Denitrification is conversion of NO3- to nitrous oxide (N2O) and N2.            

f. There are denitrifying bacteria in both aquatic and terrestrial ecosystems.

g. Denitrification counterbalances nitrogen fixation, but not completely; more nitrogen fixation occurs.  

h. Humans contribute much to the nitrogen cycle when they convert N2 to ammonium and urea in fertilizers.

i. Eutrophication (over enrichment) results from fertilizer runoff; when rampant algae dies off, decomposers use up available oxygen during cellular respiration, and this results in a massive fish kill.

Nitrogen and Air Pollution

a. Production of fertilizers and burning of fossil fuels adds three times the nitrogen oxides to the                 atmosphere as normal

b. Acid deposition occurs when nitrogen oxides and sulfur oxides combine with water vapor.            

c. Photochemical smog results when nitrogen oxides and hydrocarbons react in presence of sunlight; smog contains ozone and peroxyacetylnitrate (PAN) and causes respiratory problems.            

d. Air pollutants are trapped near the ground by thermal inversions where cold air is trapped near the ground by warm air above.

The Phosphorus Cycle

1. In phosphorus cycle, weathering makes phosphate ions (PO4 and HPO4 2-) available to plants from the soil.        

2. 2. Some phosphate runs off into aquatic ecosystems where algae incorporate it into organic molecules.

3. Phosphate that is not taken up by algae is incorporated into sediments  in the oceans.

 4. Sediment phosphate only becomes available when geological upheaval exposes sedimentary rocks.

5. Phosphate taken up by producers is incorporated into a variety of organic compounds.        

6. Animals eat producers and incorporate some of phosphate into long-lasting teeth, bones, and shells.

7. Decay of organisms and decomposition of animal wastes makes phosphate ions available again.        

8. Available phosphate is generally taken up quickly; it is usually a limiting nutrient in most ecosystems.

       

. Phosphorus and Water Pollution

1. Humans boost the supply of phosphate by mining phosphate ores for fertilizers, detergents, etc.

2. Run-off of animal wastes from livestock feedlots and commercial fertilizers from cropland as well discharge of untreated and treated municipal sewage can all add excess phosphate to nearby waters.

3. Eutrophication is the name of this over-enrichment and can lead to algal blooms; when the

algae die off, decomposers use up the oxygen.

4. Biological magnification is the concentration of chemicals as they move up the food chain.

5. Oil spills add over 5 million metric tons of oil a year to oceans.       

6. Human activities including fishing have exploited ocean resources to the brink of extinction.

       

Consumers are further divided into herbivores and carnivores.

Herbivores:

Like ants, flies, beetles, leafhopper feed trees, leaves while larger herbivores are elephant, deer etc.

Carnivores

Small Carnivores like snake, birds, fox feed on herbivores.

Large Carnivores : Lion & Tiger feed on small carnivores and herbivores Consumers are further divided into herbivores and carnivores.s

Ecological succession

• Is defined as an orderly process of changes in community structure and function with time mediated through modifications in the physical environment and ultimately culminating in a stabilized ecosystem known as climax

Process

• Nudation

• Invasion

• Competition and coaction

• Reaction

• Stabilization

Hydrosere

• Free floating stage ( pioneer )

• Rooted floating stage

• reed swamp stage

• Sedge meadow stage

• Woodland stage

• Forest ( climax)

Xerosere

• Lichen ( pioneer)

• Mosses

• Herbs

• Shrubs

• Forest ( climax)