Why is the external appearance of living organisms so diverse?

All living organisms on our planet occupy different habitats. Depending on where the habitual environment for the organism is located – in the air, on the ground, in the soil – various adaptations of these organisms differ. Also, the difference in the external appearance of organisms is explained by the way of life of this or that organism. In addition, organisms have different types of food: vegetable, animal. Each organism occupies some place in the food chain. The diversity of organisms makes the ecosystem sustainable.