Explain trophic interactions between organisms in an ecosystem using food chains, food webs and pyramids of biomass and energy A food chain shows the relationship in which energy and nutrients are transferred from plants to first order consumers (herbivores), to second order consumers (carnivores), to higher order consumers. The arrow means ‘is eaten by’. Thus grass ? rabbit ? fox means that the grass is ‘eaten by’ the rabbit and the rabbit is ‘eaten by’ they fox. All food chains must begin with a producer, an autotroph which can convert raw materials into organic compounds that can be used by the other organisms in its ecosystem.
In most cases the autotroph is a plant using photosynthesis to capture cunlight in order to convert carbon dioxide into glucose and oxygen. Some bacteria, e. g. deep-sea bacteria found near volcanic vents, can use chemosynthesis to obtain their energy and these bacteria begin the food chain in their ecosystem. If you drew all the food chains that exist in a natural ecosystem, you would form a food web. Food webs show all the interacting and interconnecting food relationships. Each step along a food chain is a trophic level.
Producers are the first trophic level, first order consumers occupy the second trophic level, second order consumers occupy the third trophic level etc. In a food web, an organism may occupy several trophic levels, depending upon which food source you are investigating, e. g. a bear is a first order consumer when it eats berries but a second order consumer when it eats a fish that ate algae and a third order consumer when it eats a fish that are a fish that ate algae. Energy Pyramids: Unlike materials, which flow through natural cycles, energy passes in a one-way flow.
This flow of energy can be shown as a food chain, beginning with the Sun being the original source of energy for nearly every food chain. The flow of energy begins when radiant energy is captured by autotrophs in photosynthesis and the producer converts the radiant energy into chemical energy in the bonds of its organic complex molecules, e. g. in sugars, starch, lipids, proteins and nucleic acids. Animals obtain energy when they eat an autotroph or eat other organisms which have eaten autotrophs.
Organisms use energy for all body functioning such as movement, growth, maintaining body temperature, repair and maintenance of old and damaged cells and cellular metabolism. The chemical energy in the complex organic molecules is released by cellular respiration. At each stage, or trophic level, only about 10% of the energy is passed onto the next trophic level. For example, imagine a plant captures 100 units of energy. When a herbivore eats that plant, it gains 10 units of energy (10%). The carnivore that eats the herbivore only gains one unit of the original 100 units (10% of 10 units).