User:Lathapooja/Sandbox

=== Pyramids of Number, Biomass and Energy Definition: "An ecological pyramid is a graphical representation of an ecological parameters like number or biomass or accumulated energy at different trophic levels in a food chain in an ecosystem." Charles Elton (1927) developed the idea of ecological pyramids. Therefore, they are also termed as Eltonian pyramids. In a pyramid, the various steps of food chain are represented sequence wise with producers at the base, herbivores above them, followed by primary carnivores and so on with top carnivores at tip of the pyramid. A pyramid may be upright (broad at base, tapering towards tip), inverted (narrow base, becomes broader towards tip) or spindle shaped (broader in middle and narrow at both base and top). Types of ecological pyramids: There are three types of ecological pyramids – a) Pyramid of number: 1. It is the graphic representation of the arrangement of number of individuals of different trophic levels in a food chain in an ecosystem. 2. The pyramid of numbers deals with the relationship between the number of primary producers, herbivores and carnivores at successive trophic levels. 3. In most cases the pyramid of numbers is upright or straight in shpae (or may be inverted also). 4. The base of all such pyramids always represent the number of primary producers. 5. The successive structures on the base are represented by the number of consumers. 6. The maximum number of individuals occurs at the producer level. 7. The top of the pyramid represents the number of top carnivores. They are very few in nu8. In such ecological pyramids, the size of organisms increases with each trophic level i.e. from the producer level to the top carnivore level while their number decreases in food chain. Example: Grassland ecosystem, pond ecosystem. Grassland ecosystem: In grassland ecosystem, the pyramid of numbers is upright or straight. The producers are mainly grasses are always more in number. The primary consumers as grasshoppers, rabbits, mice etc. are lesser than the number of grasses. The primary consumers are eaten by relatively smaller number of secondary consumers as frog, lizzard, snake etc. These secondary consumers are consumed by only a few tertiary or top b) Pyramid of biomass: 1.Pyramid of biomass is a graphic representation of biomass present per unit area in different trophic levels. 2. The total amount of dry weight of living or organic matter in an ecosystem at given time is called biomass. 3. In most of the ecosystems, Pyramid of biomass is upright or straight eg. grassland or forest ecosystems or terrstial habitats (or it may be inverted also eg pond ecosystem.) 4. In terrestrial habitat, maximum biomass occurs at the level of producers.consumers as hawk, p5. There is gradual decrease in biomass of organisms at successive trophic levels from producers onward to top carnivores. 6. It is found that about 10-20% of the biomass is transferred from lower trophic level to higher trophic level. 7. But the pyramid of biomass is inverted in aquatic habitats or in pond ecosystem. 8. In pond ecosystem or in sea, the producers are the smallest organisms that are phytoplanktons. 9. The biomass of phytoplaktons is less than that of zooplanktons in which it is less than that of carnivores or secondary consumers. 10. In this ecosystem, the producers are the smallest organisms while carnivores are large in size. 11. Consequently, there is a gradual increase in biomass of organisms at successive trophic levels from producers onwards to top carnivores (fishes). 12. It results in formation of inverted pyramid in pond or sea ecosystec) Pyramid of energy: 1. Pyramid of enregy is a graphic representation of 'amount of energy per unit area in different trophic levels of a food chain. 2. The pyramids of energy are always upright or straight. 3. According to second law of thermodynamics, there is gradual decrease in energy at successive trophic levels. 4. The energy is highest at the producer level and it gradually decreases at subsequent trophic levels i.e. herbivores (primary consumer level) and different carnivores (secondary consumer level) 5. It is so because at each transfer, about 80-90 percent of energy available at lower trophic level is used to perform various metabolic activities and release of energy in the form of heat during respiration. 6. Only 10 % of the energy available. ===