Ecology energy flow pathway in an ecosystem

Energy flow pathway in ecosystem, food chain, food web, ecological pyramid,

1. TOPIC : ENERGY FLOW PATHWAY IN Ecosystem -ANURAG pandey

2. INTRODUCTION An ecosystem consists of all the organisms living in a community as well as all the abiotic factors with which they interact. The dynamics of an ecosystem involve two processes: energy flow and chemical cycling. Energy is the capacity to do work. Energy exists in two forms potential and kinetic. Potential energy is the energy at rest {i.e., stored energy). Kinetic energy is the energy of motion (free energy). The source of energy required by all living organisms is the chemical energy of their food. The chemical energy is obtained by the conversion of the radiant energy of sun. In any ecosystem there should be unidirectional flow of energy.

3. Primary source of energy in all ecosystem is the sun. Approximately 57% of sun energy is absorbed in the atmosphere and scattered in the space. Some 35% is spent to heat water and land areas and to evaporate water. Approximately 8% of light energy striking plant surface, 10% to 15% is reflected, 5% is transmitted and 80 to 85% is absorbed. An average of only 2% (0.5 to 3.5%) of the total light energy striking on a leaf is used in photosynthesis and rest is transformed into heat energy. The movement of energy through the trophic levels of a food chain is called as energy flow. This energy flow is based on two important Laws of Thermodynamics

4. The first law of Thermodynamics: It states that the amount of energy in the universe is constant. It can neither be created nor destroyed, but it may change from one form to another. The solar energy of the sun is converted in to chemical energy of carbohydrate. The second law of thermodynamics: The Second Law of Thermodynamics is about the  quality  of energy . It states that as energy is transferred or transformed, more and more of it is wasted It occurs at each trophic level, 90% energy is lost ( as heat and in metabolic processes) and only 10% is transfer from one trophic level to another.

5. ENERGY FLOW IN AN ECOSYSTEM: Living organisms can use energy in two forms radiant and fixed energy. Radiant energy is in the form of electromagnetic waves, such as light. Fixed energy is potential chemical energy bound in various organic substances which can be broken down in order to release their energy content. Producers: Organisms that use the solar energy to produce their own food. E.g. plants, algae and some bacteria.   Consumers: All animals depend on plants (directly or indirectly) for their food needs. Hence, they are called consumers and also heterotrophs. Decomposers: The heterotrophic organisms, mainly fungi and bacteria, which obtain their energy and nutrient requirements by degrading dead organic matter or detritus are called decomposers

6. SUN PRODUCERS CONSUMERS DECOMPOSERS CHEMICAL ENERGY CHEMICAL ENERGY RADIENT ENERGY HEAT ENERGY HEAT ENERGY ENERGY FLOW IN AN ECOSYSTEM HEAT ENERGY

7. Productivity It is the rate at which organic matter is produced by producers. It is usually expressed in units of mass per unit area (or volume) per unit time (mass/unit area/unit time). Primary productivity: It is the rate at which biomass produced per unit area by the primary producers (both photoautotrophs and chemoautotrophs). Gross primary productivity (GPP): The total rate of photosynthesis, including the biomass used up in the respiration during the period of measurement. Net primary production (NPP): The rate of the storage of biomass in the plants that exceeds the respiratory used up in the respiration during the period of measurement. NPP = GPP - R

8. Trophic level The producers and consumers in ecosystem can be arranged into several feeding groups, each known as trophic level (feeding level). In any ecosystem, producers represent the first trophic level, herbivores present the second trophic level, primary carnivores represent the third trophic level and top carnivores represent the last level.

9. Food chain-:- It is the relation between one trophic level to adjacent trophic level. The transfer of energy and nutrients through a succession of organisms through repeated process of eating and being eaten. In food chain initial link is a green plant or producer which produces chemical energy available to consumers. Food chain in any ecosystem runs directly in which green plants are eaten by herbivores, herbivores are eaten by carnivores and carnivores are eaten by top carnivores. Food chains are of three types: Grazing food chain Parasitic food chain Saprophytic or detritus food chain

10. Food web Many food chains exist in an ecosystem, but these food chains are not independent. A complex of interrelated food chains makes up a food web. Food web maintains the stability of the ecosystem. The greater the number of alternative pathways the more stable is the community of living things.

11. Energy Flow models Single Channel Energy Flow Models: The flow of energy takes place in a unidirectional manner through a single channel of green plants to herbivores and carnivores. The energy which is passed to the next trophic level is never reverted back to the lower level. Y-shaped Model of Energy Flow : It is also called double channel model. In nature, both grazing and detritus food chains operate in the same ecosystem. It explain the connection between a grazing and a detritus food chain. Y-shaped model of energy flow

12. THE TEN PERCENT LAW This law was introduced in context to energy flow in ecosystems by Raymond Lindeman. According to this law, during the transfer of energy from organic food from one tropic level to the next, only ten percent of the energy from organic matter is stored as flesh. The remaining is lost during transfer, broken down in respiration, or lost to incomplete digestion by higher trophic level. The ten percent law gives us a basic understanding on the cycling of food chains. This law shows the inefficiency of energy capture at each successive tropic level

13. Ecological pyramid The concept was first introduced by Charles Elton. It is a graphic representation of the relationship between organisms at various trophic levels in a  food chain . The basis of an ecological pyramid is biomass,  energy , and number. Types of ecological pyramid : Pyramid of number: It represent the total no. of individuals of different species belonging to each trophic level in an ecosystem. Pyramid of mass : It represent the total dry weight of the living beings of different species at each trophic level at a particular time. Pyramid of energy : It shows the flow of energy from one trophic level of a community to the next.

14. Pyramid of biomass Pyramid of numbers Pyramid of energy

15. CONCLUSION Sun is the ultimate source of energy. Energy flow in an ecosystem is always unidirectional. Energy in an ecosystem is never destroyed but it is converted from one form to another. Plants play a vital role in converting the solar energy to the chemical energy, making the sun’s energy available to the organisms at higher tropic levels. Only 10 % of energy is passed to the successive tropic level. If any of the link in a food chain or food web (interconnected food chains) is removed efficient energy flow will not occur.