Functions of an Ecosystem

2020-04-29 11:07:14

Functions of an Ecosystem
- Energy Flow
- Ecological Succession

Energy Flow

Flow of energy from producer to top consumers aka Energy Flow always unidirectional and from lower to higher.
There is loss of energy as heat in each trophic level, it decreases while going upwards.
Trophic level interaction deals with how the mem of ecosys are connected.
Food chain : sequence of organisms that feed on one another. Types are Grazing food chain and Detritus food chain : starts from dead organic matter which is initial source.
Food web : all possible transfers of energy and nutrients among the organisms in an ecosystem.

Ecological Pyramids

each levels of trophic shown, length of horizontal bar is number of Individuals divided into
Pyramid of numbers : horizontal bars represent the number of individuals.
- It can be partially upright ex in forest ecosystem where herbivores are more in number than the producers.
- Ex of inverted pyramid is found in parasitic food chains where thousands of parasites feed on one body.
Pyramid of Biomass : individuals are weighted instead of being counted i.e their dry weight measured in g/m2.
- Most eco pyramids on lands are upward and aquatic pyramids are inverted.
Pyramid of Energy : It shows the conversion of energy and heat energy at each trophic level.
- It is always upwards with a large energy base.
- This concept helps to explain the biological magnification phenomena.

Pollutants and Trophic Levels

Bioaccumulation : Refers to the accumulation of a toxic chemical in the tissue of a particular organism.
- how pollutants enter a food chain, inc in conc of pollutant from env to first organism in a food chain.
- DDT is not a biologically active ie not toxic to humans but it accumulates in the tissue of animals causing Bioaccumulation.
Biomagnification : refers to the increased concentration of a toxic chemical the higher an animal is on the food chain.
- ie tendency of pollutant to inc its conc from one trophic level to the next.
- The pollutant must be long-lived, mobile, soluble in fats, biologically active
- They are generally present in fatty tissues of animals.
- But when DDT accumulated organism is consumed by another organism of higher trophic level the concentration of DDT in the body increases.

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Types of Biotic Interaction

Neutralism is 0,0

Image unavailable in web version: Biotic Interaction S.No. 3. 4. 5. Ty pe Mutualism Commensalism Amens alism Competition Predation Parasitism Spices 1 Species 2 (+) Benefited (-) Harmed (O) Neither Benefited nor harmed.

Bio-geo Chemical Cycle

Bio Geo chemical cycle : cyclic movement of mineral nutrients from non-living to living and back
Nutrient cycle type of BGC Cycle shows how nutrients move from physical env to living organsims and then back. Eg Carbon and Nitrogen cycles. They are of 2 types :
- Perfect cycle where they are replaced as soon as consumed eg gaseous cycles
- Imperfect cycle : some nutrients are lost from cycle eg sedimentary cycle.

Gaseouse Cycles

in this the reservoirs are atmosphere and hydrosphere

Water Cycle Image unavailable in web version: The water cycle Condensation Transpiration Precipitation Evaporation Percolation|400x400

Carbon Cycle Image unavailable in web version: apÅD u09 , 2’ue6JO

Nitrogen Cycle

The various ways of Nitrogen fixation are :
- By microorganisms : free living bacteria eg azotobacter and anaerobic clostridium and symbiotic bacteria eg Rhizobium, Anabeaena Spirulina.
- by man using industrial processes far exceeds natural fixation
- Atmospheric phenomena like thunder and lightning.

Sedimentary Cycle

reservoir is the Earth’s crust.

Phosphorus cycle ![[Pasted image 20210601190644.png]]

Calcium cycle ![[Calcium-cycle-in-the-transformation-of-carbon-into-acetylene-Carbon-sources-include.png|500]] ![[370px-The_carbonate_cycle_in_the_water_environment.jpg]]

Magnesium cycle ![[Pasted image 20210601190855.png]]

Ecological Succession

It is a process of through which an ecosystem develops and stabilises. It changes the species structure of an ecolocial over a time from a pioneer community to climax community.
one community replaces other until stabilisation.
leads to establishment of stable climax community ie last stage of succession.
the intermediate community is called seral communities.
first plant to colonise an area called pioneer community
stage leading to the climax community are called successional stages or seres.

Various stages of Ecological succession

Nudation : dev of bare area without any form of life caused due to factors such as volcanic eruption, floods, erosion, earthquake, forest fire.
Invasion : is the successful establishment of species in a barren area this could be brought about by air, water etc. The adjustment of these species is called as ecesis. Their reproduction and inc in numbers is called aggregation.
Competition and Coaction : Compete with other organism for food, space and other resource.
Reaction : Modification of environment through influence of living organism is called reaction.
Stabilisation : last stage where climax or final community becomes stable.

Characterstics of climax community

Increased productivity. Productivity means the rate of generation of biomass in an ecosystem and expressed in gm/sq mtr. Productivity of autotrophs is called primary productivity and for heterotrophs it is called secondary productivity.
shift of nutrients from the reservoirs.
increased diversity of organisms - niche development.
inc in complexity of food web.

Primary Succession

Takes place in a barren areas never having any vegetation no organism ever existed. Ex Volcanic eruptions, Retreat of glaciers, landslides etc.
in a new site takes place when few hardy pioneers species example mosses, lichens, fungi etc grow.
They die and their organic matter is buried in crevices, gaps etc and on soil where seeds etc grow leading to the development of vegetation.
At end pioneer species disappear due to condition change and invasion.

Secondary Succession

occurs when mature or intermediate species in a region is destroyed due to events like forest fire, flood, harvesting, epidemic, pest attack.
They are taken over by hardy harbaceous species like grasses, mosses etc. Leading to the development of a forest community over the years.
It starts on an already well developed soil and are faster vis a vis Primary succession.

Allogenic and Autogenic Succession

Succession that are brought about by biotic components living in the ecosystem is called Autogenic Succession
Where as succession brought by outside force or abiotic components is called allogenic succession. Ex by volcanoes, flooding, forest fires etc.

Autotrophic and Heterotrophic

Succession where initially green plants are more are called autotrophic succession and where animals are more is called heterotrophic.

Succession occurs faster in middle of large continents.
Net Primary Productivity = Gross primary productivity - Respiration losses
Detritus is the raw material for decomposition.
Leaching is the process by which soil soluble inorganic nutrients go down the soil horizon and precipitate as salts.
When humus is further degraded by microbes and release of inorganic nutrients occur this process known as mineralisation.
- This process is faster when detritus is rich in Nitrogen and water soluble substances and slower when it is rich in lignin and chitin.
Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). Plants capture only 2-10% of it.
Organisms that meet their nutrient requirement by degrading dead organic matter or detritus are called saprotrophs. Ex Fungi, mushrooms and bateria.
Each trophic level has a certain mass of living material at a particular time called as the standing crop.
- It is measured as the mass of living organism/ Biomass or number of unit in an area.
Pyramid of numbers and Biomass can be both inverted and upright. Pyramid of energy is always upright can never be inverted.
The entire sequence of communities that successively change in a given area are called sere(s).
The amount of nutrients, such as carbon, nitrogen, phosphorus, calcium, etc., present in the soil at any given time, is referred to as the standing state.