What are the impacts when an animal species becomes endangered or extinct?

Answer 1

It depends on the animal and it's habitat

For an animal which doesn't really have any natural predators or have any prey, then not much to the ecology (such as Giant Pandas or the Dodo), but for animals which keep an eco-system in balance by keeping certain smaller animal population in check, it can be devastating to the environment if they're removed

Think about if bees were removed from an environment which had herbivores and carnivores, the bees pollinate flowers, which means that plants grow more freely and more wide-spread, the herbivores eat these plants, and the carnivores eat the herbivores - without the bees the natural food of the herbivores would die out, and thus their population would get smaller, and thus the food supply of the carnivores would get smaller - thus thinning the populations of the herbivores and carnivores, if unchecked the carnivores would kill off the herbivores before their population reduced, and so the entire food chain would be removed

Taking that example from the opposite end, if man hunted the carnivores to extinction or endangered list, then the herbivores would increase in population, eating more of the plants, meaning that the bees would have less plants to pollinate, so the bees population would be reduced in size as they die out from lack of food (nectar from the flowers), the herbivores would begin to die out because of lack of food, eventually the entire eco-system would collapse

Basically, most natural eco-systems are finely balanced, and removal of one of the elements sets the entire system off kilter, and eventually destroys it