Feeding relationships: food chains and food webs

The most obvious interaction between different organisms in an ecosystem is feeding. During the feeding, one organism is obtaining food-energy and raw materials- from another one. One organism eats another but then may itself be food for a third species. This process is called food chain

Since so little energy is transferred from the base to the top of a food chain, a top carnivores must eat many herbivores. In turn each herbivore is likely to feed on many different plant species. All these feeding relationships can be shown in a food web.The more complicated the food web, the more stable the community is. The amount of energy that is passed on in a food chain is reduced at every step. Since energy can be neither created nor destroyed, it is not lost but is converted into some other form. During respiration, some energy is transferred to the environment as heat.

Sun provides the energy to drive the food chainProducers- plants can convert light energy to chemical energy in food compoundsConsumers are organisms that obtain food energy from other organismsPrimary consumers- herbivores. They obtain their energy in food compoundObtained from producers.Secondary consumers-carnivores. They obtain energy in food compounds Obtained by eating primary consumersCarnivores are eaten by tertiary consumers

Less than 1% of the energy released from the sun falls onto leaves

Energy transfer to primary consumer 5-10%•Much of plant body e.g. lignin and cellulose is indigestible consumer rarely eats whole plant- roots or stems may be left behind

Respiration losses occur from each trophic level. Each organism uses some of the food compounds it has synthesized or obtained as food to release energy to drive metabolic reactions. Respiration is not 100% efficient and eventually all of this energy is lost as heat

Energy transfer to secondary consumer is between 10-20%•Animal material has a higher energy value•Animal material is more digestible

Energy transfer to decomposers is very variable but eventually the entire energy content of the animal and plant remains will be released as heat from inefficient respiration

Energy’ fixed’ by producers is only 5-8%of the energy that falls onto their leaves:•Some is transmitted•Some is not the correct wavelength