Communities of living things and their physical surroundings interact as an ecological unit within an ecosystem, which is a structural and functional unit of the biosphere. As a result, an ecosystem also contains non-living elements.
The three areas of study for ecosystem function are:1. Energy flow: Food Chain, Trophic Level, Ecological Pyramid.
2. Nutrient Cycle: (Bio-Geo chemical Cycle).
3. Ecological Succession
1. Energy Flow through Food Chain :
Food Chain:
The food chain refers to the series of feeding groups of organisms that transfer nutrients and energy to one another. The food chain is a diagram that shows how energy moves linearly from an organism at one trophic level to another at a higher level.
Kind of Food Chain :
Grazing Food chain:
It starts from autotrophs & energy usually comes from the sun.
- In an aquatic ecosystem, the grazing food chain is the major conduit for energy flow.
- In Terrestrial Ecosystem the food chain cycle follow as – Plant → Caterpillar → Lizard → Snake and so on.
- Aquatic Ecosystem follows – Phytoplankton → Zooplankton → Fish → Pelican.
Detritus Food chain:
- It begins with dead organic matter (fallen leaves) that is consumed by saprotrophic (detritivorous) organisms such as bacteria, fungus, and protozoans. Detritus Food Chain is a significant energy conduit in the terrestrial ecosystem.
- Example: Litter → Earthworms → Chicken → Hawk.
Trophic levels :
- 80 to 90 percent of an organism’s energy or biomass is lost during each trophic level (10 percent energy transmitted) as heat energy. As a result, the length of the food chain is restricted to 4-6 trophic levels.
- A single organism may occupy more than one trophic level at once because the term “species” is not used in the trophic level definition. As an illustration, a sparrow is a primary consumer when it consumes seeds and fruits but a secondary consumer when it consumes insects.
- Bioaccumulation & Biomagnification are two processes used to transport non-degradable contaminants (chlorinated hydrocarbons) through the trophic level.
Bioaccumulation :
It is the process through which pollutants enter the food chain, from the environment to the first organism at a given trophic level. It symbolizes the movement of harmful material up the food chain from one organism to another. Nonylphenol is an example.
Bioconcentration :
It means, the intake and retention of material in an organism solely through breathing air or water in a terrestrial or aquatic setting. Similar to bioaccumulation, but with a different cause.
Biomagnification :
It is a rise in toxin concentration in a food chain at multiple trophic levels rather than in an organism. Over time, heavy metals or harmful substances slowly accumulate inside organisms. This means that the most amount of poison is present at the top level. Pollutants must be mobile, soluble in fats, physiologically active, and long-lived for bio-magnification to occur. Examples include mercury through fish, Radioactive isotopes from soil contamination, PCB, and cyanides. DDT caused eagle eggs to have incredibly thin shells and eggs shattered before they could hatch.
Food Web :
A web or network of food chains is what the term “food web” refers to when describing the feeding relationships within a community. The more intricate the food web, the more stable it will be because if one species disappears, another could fill its place and preserve balance (simple & smaller prone to extinction).
Ecological Pyramids :
It is a diagrammatic representation of trophic levels. It helps us to recognize keystone species; Identify bio-accumulation and bio-magnification.
There are 3 categories of Ecological Pyramids-
1. Pyramid of Number – upright [grassland ecosystem] & inverted.
2. Pyramid of Biomass – upright as well as inverted.
3. Pyramid of Energy – always upright.
Pyramid of Number :
It represents the no. of an organism at each trophic level. Since it is very difficult to count all organisms, therefore this pyramid does not completely define trophic structure. The energy flow in it is Upright and inverted.
- Upright: In grassland, no. of grass > no. of herbivores> no. of carnivores.
- Inverted: Herbivores > primary production. For example – caterpillars and insects feed on a single tree.
Pyramid of Biomass :
A visual representation of the biomass present in a unit area at different trophic levels is called a Pyramid of biomass. By quantifying the biomass available in each trophic level of an energy community at a certain time, it illustrates the link between biomass and trophic level. The upright biomass pyramid and the inverted biomass pyramid are the two main varieties of this pyramid.
It is used to get around the Pyramid of Number’s restrictions. Instead of counting individuals, each trophic level was weighed. It is the amount of living matter at a particular period and represents the total standing crop biomass at each trophic level. The amount of living things (biomass) in a given region is measured. gm/unit area or kcal/unit area are the units of measurement. It is upright and Inverted.
Because fish have a far higher biological mass than phytoplankton, the marine biomass pyramid is typically inverted.
- Upright: In most terrestrial ecosystems i.e. biomass of autotrophs is maximum.
- Inverted: In an aquatic ecosystem, for instance, the primary producers in a pond are phytoplankton because of their short life periods and high turnover rates (rapidly replaced by new plants). As a result, at any given time, their overall biomass is lower than the biomass of herbivores they support.
Pyramid of Energy :
- At each trophic level, it shows the entire amount of energy. Because of the 10% Rule, it is always upright. Thermodynamics law is represented by it. After the sixth trophic level, there is either little or no energy left.
2. Bio-Geo Chemical Cycle :
- Processes including biology, geology, and chemistry are all included in biogeochemical cycles. The carbon cycle, nitrogen cycle, and hydrological cycle are three major biogeochemical cycles.
- A perfect nutrient cycle, with the exception of water, would be one in which nutrients are restored as quickly as they are used. Sedimentary cycles, on the other hand, are somewhat imperfect because some nutrients are lost from the cycle and end up trapped in sediments.
Gaseous Cycle :
It is also known as the perfect cycle as nutrients are replaced as fast as utilized like Nitrogen, Carbon.
Carbon cycle:
1. Global Carbon Cycle
It consists of the following steps
- Photosynthesis: Plants use sunlight to utilize CO2 & convert inorganic carbon into organic matter (food) & release oxygen.
- Respiration: food is oxidized to liberate energy (exothermic), CO2, and water. CO2 is released into the atmosphere through this process.
- Decomposition: Organic matter decomposed by micro-organism & release CO2 into the atmosphere.
- Combustion: Burning of biomass releases CO2 into the atmosphere.
2. Geological Carbon Cycle
It takes millions of years because carbon is slowly released from long-term storage in the atmosphere, oceans, soil, rocks, and fossil fuels. Carbonic acid is formed when anhydride CO2 dissolves in water. Due to its instability, carbonic acid breaks down into carbonate ions, nitrogen which combine with calcium ions to produce calcium carbonate. Shells of marine organisms are made of calcium carbonate.
Nitrogen cycle :
Nitrogen fixation is the process of capturing or converting nitrogen gas into ammonia, nitrite, and nitrate, which are then easily assimilated by plants and microorganisms. There are three ways to recycle it:
- Atmospheric fixation: Volcanic activity, combustion, and lightning all aid in the fixation of N2.
- Industrial fixation: Molecular nitrogen is broken into atomic nitrogen at high temperatures and pressure, which mixes with hydrogen to generate ammonia. Because the amount of nitrogen fixed by industrial processes was far more than the amount fixed by natural cycles.
- Bacterial Fixation: When an animal or plant dies, other bacteria in the soil break down the various nitrogen molecules into nitrates and then another type of bacterium breaks down the nitrates and nitrites into elemental nitrogen. This whole process is called bacterial fixation.
- Found in other biologically significant chemicals as well, including urea and alkaloids. In particular, formations known as root nodules, the nitrogen-fixation bacteria are located in the roots of legumes (often the plants that produce our pulses).
Symbiotic nitrifying bacteria:
- Leguminous plant: Live in root nodule – Rhizobium.
-
Non-leguminous: Frankia Azospirillum, Blue green algae (Anabaena,
Spirulina).
Free-living nitrifying bacteria
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Aerobic: Azotobacter, Beijerinckia, Klebsiella (some), Cyanobacteria
(some). - Anaerobic: Nostoc, Clostridium, Desulfovibrio.
- Diazotrophs bacteria – fix atmospheric nitrogen gas into ammonia.
It has symbiotic nitrifying bacteria like-
- Leguminous plant: Similar to Rhizobium, they reside in root nodules.
- Non-leguminous plants: such as Spirulina, Frankia Azospirillum, and blue-green algae.
Free-living nitrifying bacteria
- Aerobic: Cyanobacteria, Azotobacter, Beijerinckia, Klebsiella.
- Anaerobic: Desulfovibrio, Nostoc, and Clostridium.
- Diazotrophs microorganisms fix nitrogen gas in the atmosphere into ammonia.
Water Cycle :
- The hydrological cycle is the periodic movement of water. It starts with water evaporating from the ocean’s surface. Clouds form as wet air cools and water vapours condense as it is elevated. Around the world, moisture is moved until it eventually returns to the surface as precipitation. Solar radiation is one of two driving forces and the other is Gravitation.
- The sun’s heat energy causes the water in lakes, rivers, and oceans to evaporate. Large volumes of water are also transpired by plants. Water vapour in the air condenses into clouds, which then release precipitation that falls owing to gravity.
Sedimentary Cycle :
It is also known as imperfect as nutrients are lost & lock into sediments, hence unavailable for cycling.
Phosphorous:
Phosphorous aids in cell growth and is a crucial component of energy-storing molecules including ATP, DNA, and lipids (fats & oils). Crop yields may be impacted by insufficient phosphorus in the soil. It is found in phosphate rocks and is the cause of the microscopic plants that float freely.
Phosphorous Cycle :
Rocks release phosphate ions as a result of weathering and rain. Then, the inorganic phosphate is dispersed in the soil and water. Organic phosphate is made available to plants in soil by microorganisms that convert organic materials to inorganic phosphorus. It is known as Mineralization. Animals eat plants, and plants absorb inorganic phosphate from the soil. Phosphate is integrated into organic molecules, including DNA, in both plants and animals. When an animal or plant dies, its corpse decomposes, returning organic phosphate to the soil. Waterways and oceans are also affected by phosphorus in soil.
3. Ecological Succession :
Ecological succession means when numerous communities are displaced due to extensive natural or artificially caused destruction, succession ensues. This process keeps going until a mature and stable society emerges. It includes species like-
- Species that colonize new territory first are known as pioneer species. It includes mosses, lichens, bacteria, and fungi. They exhibit rapid growth but have brief lifespans.
- Sequential or persistent Seralian stages or seral communities are the several communities or stages (mosses, herbs, shrubs, and trees) that replace one another throughout succession. These species are slow-growing and long-lived. The successional sequence is represented by the communities that succeed one another.
- The climax Community/Species are the community that is formed during the terminal (last) stage of succession and is referred to as the climax community. They last a long time, are stable, mature, and more sophisticated.
Types of Succession :
Autogenic & Allogenic
- Autogenic = It means succession by living inhabitants.
- Allogenic = It means succession bought by outside forces.
Autotrophic & Heterotrophic
- Autotrophic = In this succession, green plants are greater in quantity.
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Heterotrophic = In this succession, heterotrophs are greater in quantity.