Question

''Energy flow in a food chain is unidirectional'' Justify...

Answer 1

1.Because the energy moves progressively through the various trophic levels and is no longer available to the previous trophic level. The energy captured by autotrophs does not revert back to the solar input.

2.Pesticides, used for crop rotection when washed down into the soil/water body, are absorbed by the plant/producer along with water and minerals.

3.Being non-biodegradable , these chemicals get accumulated progressively in the food chain and enter our body.

Hope this helps!!!

Answer 2

(i)The producers convert solar energy into
chemical energy in the form of organic
compounds.
(ii)The primary consumers (herbivores) derive
their nutrition from the producers. According to
the energy transfer law, only 10% of energy is
transferred from one trophic level to the other.
So, the energy that is captured by the producers
does not revert back to the Sun and the energy
transferred to the herbivores does not come
back to the producers. It just keeps on moving
to the next trophic level in a unidirectional way.
That is why the flow of energy in the food chain
is always unidirectional.
A large number of pesticides and chemicals are
used to protect our crops from pests and
diseases. Some of these chemicals are washed
down from the soil, while some enter the water
bodies. From the soil, they are absorbed by
plants along with water and minerals; and from
the water bodies, they are taken up by aquatic
plants and animals. As these chemicals cannot
decompose, they accumulate progressively at
each trophic level. This increase in the
concentration of harmful chemicals with each
step of the food chain is called biomagnification.
As human beings occupy the top level in food
chain, these chemicals get accumulated in our
bodies.