From omnivorous birds eating plants and insects, there is a food chain of green plants → omnivorous birds → eagles.
(2) Evolution of animals: invertebrates evolved into vertebrates, and the evolution of vertebrates was primitive fish → primitive amphibians → primitive reptiles → primitive birds and mammals. Insects are invertebrates, birds, chickens and eagles are birds, while foxes and mice are mammals. So the tallest animals in this food web are foxes and mice.
(3) Because the toxic substances of pesticides are not easy to decompose and excrete in organisms, pesticides accumulate step by step along the food chain, so the higher the nutritional level, the more toxic substances, while the eagle has the highest nutritional level in the food chain, so the toxic substances in its body accumulate the most, which is called biological enrichment.
(4) If for some reason, there are a large number of rodents in this ecosystem, then in a short time, the number of foxes and hawks will increase with the increase of rodents, because the relationship among hawks, foxes and mice is eating and being eaten.
(5) Ecosystem consists of abiotic parts and biological parts. Abiotic parts include sunlight, air, water, temperature, soil (sediment) and so on. The biological part includes producers (green plants), consumers (animals) and decomposers (bacteria and fungi). In the picture, green plants are producers and animals are consumers. Therefore, in addition to the above-mentioned organisms and abiotic components such as sunlight, air and water, there must be decomposers.
So the answer is:
(1) (Draw arrows from green plants to omnivorous birds)?
(2) The fox and the mouse
(3) eagle
(4) The fox and the eagle
(5) decomposer