Question

why do some plants feed on insect.? how does a pitcher plant catch insect

Answer 1

because some plants lack chlorophyll and cant make their own food, so they feed on insects to gain their food...
a pitcher plant have chlorophyll although catch insects because it is grown at places having nitrogen deficency and to complete that deficency it feed on insects as it can get nitrogen from the insects.....,,

Answer 2

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Insectivorous Plants are plants which feed on insects

Insectivorous Plants grow in soil which do not contain sufficient nitrogen mineral.

But These plants are green and need to carry out photosynthesis to obtain a part of the food required.

So, insectivorous plants feed on insects to obtain the nitrogen needed for their growth.

Eg. → Pitcher Plant