Question

What do the arrows in a food web represent? Where are the concentrations of energy in a food web? How is energy lost in a food web? Can a population in a food web be affected if another population that is not directly connected to it changes? How?

Answer 1

(1)The transfer of food energy from autotrophs to heterotrphs through a series of organisms is termed as food chain and interconnection of more than one food chain is known as food web.The arrow in food web represents the energy transfer from one organism to other or it may also represent the organism eaten by them .Eg.

Plants--->grasshopper--->frog--->Snake--->vulture

So the arrow from plants shows energy transfer from plants to grasshopper or plants are eaten by grasshoppers and so on.

(2)The concentration of energy in food web is mainly present in producer or autotrophs.Autotrophs have ability to absorb the sunlight and change its solar energy into chemical energy.Heterotrophs are not able to concentrate the energy directly from the Sun.The high amount of energy is converted by plants through photosynthesis ,then it transfer to the heterotrophs.In food chain from each level the amount of energy will be decreased by 10%. So the last organism in the food chain have least energy as comparison to the producer.Producer will be the First in energy trophic level and carnivores will be the last in energy trophic level.

(3) Energy is lost in food web by 10% to each trophic level.This energy will be lost in the form of metabolic process,respiration,feacal matter and death also.Organism uses energy for their survival and reproduction, which includes ingestion,assimilation,respiration , production of biomass and waste.The main loss of energy in respiration.

(4)Yes,in a food web if organism is not directly connected then also affects the another population.There is a keystone species (predators) present in food web which is present in the higher trophic level and found in less number but it directly or indirectly effects the food web.

The indirect effects of species shown by organism present in aquatic and terrestrial ecosystem.for example a fish populations affects the production of seed plants.

In a pond having fish and less larva of dragon fly, the increase or decrease number of dragonfly is directly or indirectly affected by fish..if less fish then more dragonfly or if more fish then less dragonfly and dragonfly also controlled by pollinators, if it is less in number,less eaten by pollinators then it will not helps in the plants production due to less pollination.So,fish is not directly connected to plants but affects it's production.