Unit 4 - Lesson 4: Energy Transfer & Food Webs

Question 1

When an organism eats, what does it gain?

Answer 1

Energy.

Question 2

What is the energy an organism gains when it eats used for?

Answer 2

This energy is used as fuel for metabolism (all the chemical processes occurring in the body, for example, respiration).

Question 3

What percentage of the energy received by an organism from food is passed on to the organism that eats it? What does this mean?

Answer 3

10%. This means energy is lost further up the food chain. Therefore, there are less tertiary consumers than secondary and less primary consumers than producers.

Question 4

Why is energy lost between trophic levels?

Answer 4

1. Energy is wasted (excretion - urine, egestion - faeces and heat loss from respiration).
2. Energy is used keeping the organism alive (respiration, movement, etc.)
3. The higher trophic level does not eat the whole body of the lower trophic level.
4. Some of the food ate is not digested. For example, dietary fibre is not digested so we don’t obtain energy from it.

Question 5

What do the arrows in a food web represent?

Answer 5

‘Eaten by’ & ‘direction of energy flow’.

Question 6

What are food webs?

Answer 6

Food webs are lots of food chains linked. This makes them a much more detailed analysis of the organisms in the habitat or ecosystem.

Question 7

What can we track in food webs due to it’s increased complexity, given the extra organisms?

Answer 7

We can track energy transfer.

Question 8

What type of dependency are all the species in a food web? What does this mean?

Answer 8

All species in a food web are interdependent. This means if something happens to one species, all the others are affected also.

Question 9

Where does all our energy ultimately come from?

Answer 9

All our energy ultimately comes from the sun.

Question 10

What process do plants and other producers use to turn light energy into glucose?

Answer 10

Photosynthesis.

Question 11

How are we wasting vast amounts of the sun’s original energy input?

Answer 11

All our energy ultimately comes from the sun. Plants and other producers turn light energy into glucose via the process of photosynthesis. We then eat the plant or eat an animal that has ate the plant. With all this heat loss, we’re wasting vast amounts of the sun’s original energy input.

Question 12

What is heat the by-product of?

Answer 12

Metabolism. Just like a lamp gives off heat as waste, so do you.