Energy flow in ecosystem
INTRODUCTION:All organisms must obtain a supply of energy and nutrients from their environment in order to survive. The transformations of energy in an ecosystem begin first with the input of energy from the sun.
- Because, it is the first step in the production of energy for living things, it is called “Primary production”.
- Photosynthesis -- Chemical reaction where green plants use water & carbon dioxide to store the sun’s energy in glucose.
- ENERGY is stored in glucose.
- Glucose is stored as starch in plants
- The majority of autotrophs are photoautotrophs that harness the energy of the sun and pass some of this energy onto consumers through feeding pathways.
- The energy contained within producers and consumers is ultimately passed to the decomposers that are responsible for the constant recycling of nutrients.
- Thus, there is a one-way flow of energy through the biotic community and a cycling of nutrients between the biotic and abiotic components of the ecosystem
- Energy flow cannot occur in reverse direction.
- Starts from autotrophs (the producer level, i.e., first trophic level) to Heterotrophs including plant eaters or Herbivores (second trophic level) and so on.
- The amount of energy decreases with successive trophic levels.
- Only About 1% of energy from the sun is used by green plants & rest remains unutilized.
- Similarly, there is loss of energy in each trophic level.
- The transfer of food energy between the organisms in an ecosystem can be tracked by constructing food chains, food webs, pyramids of numbers, biomass and energy and energy flow diagrams.
Attributes of Ecosystems:
- Metabolism (energy flow)
- Material cycles
- Response to the environment
- Porous boundaries
- Emphasis on function, not species
How are energy flow and feeding relationships in ecosystems modelled? Ecologists use three models to illustrate energy flow and feeding relationships in an ecosystem:
Food chains: Food chains show the flow of energy from plant to animal and from animal to animal. Plants are called producers because they “produce” food in the form of carbohydrates during photosynthesis. Consumers eat plants and other organisms. Each step in a food chain is called a trophic level.
Food webs: Many animals are part of more than one food chain in an ecosystem because they eat or are eaten by several organisms. Interconnected food chains are illustrated in a model called a food web. Animals that eat plants and other animals are called omnivores.
Food pyramids: A food pyramid (or ecological pyramid) is a model that shows the loss of energy from one trophic level to another. When one organism consumes another, the energy stored in the food organism is transferred to the consumer. However, not all of this energy is incorporated into the consumer’s tissues. Between 80 and 90 percent of it is used for chemical reactions and is lost as heat. This means ecosystems can support fewer organisms at higher trophic levels, as less energy reaches these levels.
How do dead organisms contribute to energy flow?
Decomposition describes the breakdown of organic wastes and dead organisms. Energy is released in decomposition. When living organisms carry out decomposition, it is called biodegradation.
Detrivores, such as small insects, earthworms, bacteria,and fungi, obtain energy and nutrients by eating dead plants and animals, as well as animal waste.
Decomposers, such as bacteria and fungi, change wastes and dead organisms into nutrients that can once again be used by plants and animals.