Structure And Function Ecosystem ECOSYSTEM TERRESTRIAL FOREST DESEART

Structure And Function

Ecosystem ECOSYSTEM TERRESTRIAL FOREST, DESEART GRASSLAND AQUATIC FRESH WATER SALT WATER PONDS, LAKES STREAMS WETLANDS, MARINE ESTUARIES

ECOSYSTEM COMPONENTS PRODUCER BIOTIC ABIOTIC CONSUMER AIR, WATER, TEMPERATURE, SOLAR RADIATION DECOMPOSER HERBIVORES P. C CARNIVORES S. C TOP CARNIVORES T. C

STRUCTURE OF ECOSYSTEM • Species composition- all plants, animals and microbes in the ecosystem. • Stratification- vertical distribution of different species occupying different levels.

FUNCTIONS OF ECOSYSTEM • • PRODUCTIVITY DECOMPOSITION ENERGY FLOW NUTRIENT CYCLING

PRODUCTIVITY • Primary production- amount of biomass or organic matter produced per unit area over a time period by plants. • expressed in terms of weight or energy • Primary productivity-rate of biomass production • Productivity is of 2 types- GPP and NPP • GPP- rate of production of organic matter during photosynthesis. • NPP – available biomass for the consumption to heterotrophs. It is GPP-R =NPP • Primary productivity depends on environmental factors, nutrient availability and photosynthetic

DECOMPOSITION (steps) • • • Fragmentation Leaching Catabolism Humification Mineralisation

• Decomposition - break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition. • Dead plant remains such as leaves, bark, flowers and dead remains of animals, including fecal matter, constitute detritus, which is the raw material for decomposition. • The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation.

• Detritivores (e. g. , earthworm) break down detritus into smaller particles. This process is called fragmentation. • By the process of leaching, watersoluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. • Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism.

• Humification and mineralisation occur during decomposition in the soil. • Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients. • The humus is further degraded by some microbes and release of inorganic nutrients occur by the process known as mineralisation.

• The rate of decomposition is controlled by chemical composition of detritus and climatic factors. • In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and watersoluble substances like sugars. • Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. • Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.

Energy Flow • We know that plants and photosynthetic and chemosynthetic bacteria (autotrophs), fix suns’ radiant energy to make food from simple inorganic materials. Plants capture only 2 -10 per cent of the PAR and this small amount of energy sustains the entire living world. So, it is very important to know how the solar energy captured by plants flows through different organisms of an ecosystem. All organisms are

Functions of ecosystem

Trophic level

Trophic levels

ENERGY FLOW • Sun is the only source of energy for all ecosystems on Earth. • Producers fix sun’s radiant energy to make food from simple inorganic materials. • Solar energy captured by plants flows through different organism of an ecosystem. • There is an unidirectional flow of energy from the sun to producers and then to consumers.

• The green plants in the ecosystem terminology are called producers. • All animals depend on plants for their food needs are called consumers. • Animals that feed on the producers are called primary consumers. • Animals that eat other animals which in turn eat the plants are called secondary consumers. • Animals that eat other animals which in turn eat secondary consumers are called tertiary consumers.

DETRITUS FOOD CHAIN • The detritus food chain begins with dead organic matter. • DFC made up of decomposers which are heterotrophic organism, mainly fungi and bacteria. • They meet their energy and nutrient requirements by degrading dead organic matter or detritus.

v Producers belong to the first trophic level, herbivores (primary consumer) to the second and carnivores (secondary consumer) to the third. v The important point to note is that the amount of energy decreases at successive trophic levels. v When any organism dies it is converted to detritus or dead biomass that serves as an energy source for decomposers. v Organisms at each trophic level depend on those at the lower trophic level for their energy demands.

v. Each trophic level has a certain mass of living material at a particular time called as the standing crop. v The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area. v. The number of trophic levels in the grazing food chain is restricted as the transfer of energy follows 10 per cent law – only 10 per cent of the energy is transferred to each trophic level from the lower trophic level.

Ecological pyramids are graphical representations of the number of individuals in different nutritional levels. For example, the plant-insect-bird-hawk food chain can be represented as an ecological pyramid

Plants absorb energy from the sun, the insects eat the plants, the birds eat the insects, and the hawks eat the birds. Hence, the energy of the sun has been transferred from the sun to the tissues of the hawk. Since the number of individuals in each level usually decreases, the resulting diagram looks like a pyramid

PYRAMID OF NUMBERS Pyramids of number allow us to compare the number of organisms present in each trophic level at a particular time. Although pyramids of number are pyramid-shaped there are two important exceptions. Pyramids will be upside down or inverted if there a lot of small animals feeding on a large plant. They are also inverted where an animal has a large number of small parasites feeding on it. One human, for example, can have a large number of head lice. In the diagram, the butterfly larva is being fed on by a large number of parasitic wasps.

Pyramid of biomass Biomass is a measure of the total amount of living material present. Pyramids of biomass allow us to compare the mass of organisms present in each trophic level at a particular time. Most pyramids of biomass are pyramid-shaped, but there is one important exception which you should know about. This is when the producer is a small organism which multiplies very rapidly. In this case, the total biomass of the producers present at any one time may be less than the total biomass of the primary consumers. The pyramid will again be inverted

PYRAMIDS OF ENERGY Pyramids of energy allow us to compare the amount of energy passing through each trophic level over a period of time. They differ from the other two types of ecological pyramid which measure the number and biomass of organisms present in each trophic level at a particular time. Pyramids of energy are always pyramid-shaped. There are no exceptions to this rule.