CBSE Class 10 Answered

The given food chain can be depicted as follows-

Plants → Goat → Man

Each member of family of 5 persons derived their average energy need of 2700 kcal by consuming the goat meat. 

1 kcal = 1000 calories, 2700 kcal = 2700000 calories

1 cal = 4.2 J, 2700000 = 11340000 J

According to the 10% law of energy transfer, only 10% of energy is transferred from one trophic level to another. So, if man receives 11340000 J of energy, it is 10% of the energy available in goat meat.

So, the goat receives 113400000 J of energy from the plants.

Now, plants capture only 1% of energy from the Sun. So, plants have received 113400000000 J of energy from the Sun.

So, 113400000000 J or 27,000,000,000 cal or 27,000,000 kcal of energy.