Question

it is said that the decrease in number of bees may affect the life on earth. how?

Answer 1

it is because bees carry pollen grains which helps in germination of plants thus playing a very vital role in plant reproduction.

Answer 2

Bees are a great source of pollination in Unisexual plants . If Bees will be not there then many problems may arrise in unisexual flower pollination . And since we the animals eat the products of flowers (commonly known as fruit) , it will affect us also.