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TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > Photosynthesis, Respiration and Energy Relationships

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State that light is the initial energy source for almost all communities

State that the carbon dioxide fixed by photosynthesis is released by respiration

State that the energy released during breakdown/respiration of complex compounds in an organism is used to do work or is lost as heat

Define biomass

The total mass of organic matter in organisms or ecosystems. Water is not organic matter and so is not included.

Explain biomass and energy transfer in a food chain in terms of growth, respiration, cell activities, and waste

State that when energy transformations take place, including those in living organisms, the process is never 100% efficient, commonly being 10-20%

Explain what is meant by a pyramid of energy and reasons for its shape=

Energy is lost in several ways as it flows along these pathways of consumption. Most plant tissue is uneaten by herbivores, and this stored energy is therefore lost to the plant-herbivore-carnivore food chain. In terrestrial communities less than 10 percent of plant tissue is actually consumed by herbivores. The rest falls into the detritus pathway, although the detritivores consume only some of this decaying tissue. Oil and coal deposits are major repositories of this unused plant energy and have accumulated over long periods of geologic time.

Design a pyramid of energy given appropriate information

| Foxes

||||||| Rabbits

|||||||||||||||| Grasses

Explain that energy enters and leaves an ecosystem, but nutrients must be recycled

Heat energy is lost and dissipated into the environment. Because of this, it flows in one direction only. Like energy, minerals such as carbon, nitrogen and phosphorus exist in different forms. Unlike energy, these forms can be continuously recycled and so used repeatedly by organisms. Most have a geological and a biological component. The former is the long-term reservoir, while the latter is the short term recycling method.

Draw the carbon cycle to show the processes including photosynthesis, respiration, combustion, and fossilisation

Explain the role of Saprotrophs (decomposers) in returning elements to the environment in inorganic form

The final link in all food chains is made up of decomposers, those heterotrophs that break down dead organisms and organic wastes. A food chain in which the primary consumer feeds on living plants is called a grazing pathway; that in which the primary consumer feeds on dead plant matter is known as a detritus pathway. Both pathways are important in accounting for the energy budget of the ecosystem.

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