Efficiency formula?
Reveal answer
(Energy at higher level ÷ energy at lower level) × 100.
Key words: × 100
5(b) FEEDING RELATIONSHIPS · RECALL
5.9 Energy transfer between trophic levels
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Is energy recycled in an ecosystem?
Reveal answer
No — lost as heat.
Key words: heat
Why is plant-to-herbivore efficiency low?
Reveal answer
Cellulose indigestible → lost in faeces.
Key words: cellulose
What is meant by the term energy transfer efficiency?
Reveal answer
The percentage of energy at one trophic level that is transferred to the next.
Key words: energy transfer efficiency
What is meant by the term respiration?
Reveal answer
Chemical reactions in cells that release energy from glucose.
Key words: respiration
Energy losses between trophic levels, Not eaten. Cause? Example?
Reveal answer
Cause: Parts of the organism are not consumed. Example: Roots, bones, wood.
Key words: Not eaten
Energy losses between trophic levels, Not digested. Cause? Example?
Reveal answer
Cause: Some food is egested in faeces. Example: Cellulose in herbivore faeces.
Key words: Not digested
Energy losses between trophic levels, Excretion. Cause? Example?
Reveal answer
Cause: Waste products contain energy. Example: Urea in urine.
Key words: Excretion
Energy losses between trophic levels, Respiration. Cause? Example?
Reveal answer
Cause: Energy transferred to surroundings as heat. Example: Movement, maintaining body temperature.
Key words: Respiration
True or false, and why? “Exactly 10% is transferred every time.”
Reveal answer
False. About 10% is an average; real efficiencies vary widely.
True or false, and why? “The lost energy is destroyed.”
Reveal answer
False. It is transferred to the surroundings, mainly as heat, or to decomposers.
True or false, and why? “Long food chains are inefficient because predators are lazy.”
Reveal answer
False. Energy is lost at every transfer, so less is available at each higher level.
Producers hold 10 000 kJ and primary consumers 1 000 kJ. Calculate the efficiency of energy transfer.
Reveal answer
1 000 ÷ 10 000 × 100 = 10%.
Key words: 10%
Why are there rarely more than five trophic levels?
Reveal answer
Too little energy is left at the top to support another level.
Key words: energy
Why is energy transfer to birds and mammals especially low?
Reveal answer
They respire a lot to keep body temperature constant → much energy transferred to the surroundings as heat.
Key words: body temperature