Video Transcript
The diagram shows the transfer of energy, in kilojoules, between three organisms of a
food chain: A, a producer such as a banana tree; B, an omnivore such as a monkey;
and C, a carnivore such as a jaguar. How much energy does A receive in total at the start of the chain?
When energy first enters a food chain like this one, it is usually captured as light
from the Sun by producers like plants. The plants, such as producer A, can convert light energy into chemical energy in the
form of organic compounds through photosynthesis. These organic compounds can transfer energy to organisms in higher trophic levels,
like consumer B and C, when they eat and digest organisms in the trophic level
below.
However, not all of the light energy that was initially available can be absorbed by
the plant. For instance, some energy is lost as it reflects off the leaves. As energy moves through a food chain, around 90 percent is lost at each trophic
level, as shown by the curvy arrows on the left of this diagram. This may be due to various metabolic processes like cellular respiration, which
releases some energy as heat, or various substances that cannot be digested by
consumers, like tree bark, bones, or hair. As a result of these losses, only approximately 10 percent of the energy from the
trophic level before is transferred to the trophic level above. This is represented by these values within the boxes on the right.
Now, we need to work out how much energy producer A, the banana tree, received in
total at the start of the food chain. 500 kilojoules of energy is transferred from the banana tree to the monkey, and 4500
kilojoules of energy is lost by the banana tree. This means that the banana tree initially received 4500 kilojoules plus 500
kilojoules of energy, which equals 5000 kilojoules. So, the correct answer to this question is 5000 kilojoules.
