Speciation.
you will never see them again
There won't be any more animals.
what would happen is that the animal species would become an invasive species and they would eat all of the plants and food sources, which would starve out animal and human resources, which then would die out animal and human species, and without them, the plants soon will die out, which then they're would be nothing to take care of the earth.
If an animal becomes extinct, there will be no more of that species left like the Dodo. No more are left as they are extinct.
The animal that preys upon that species would grow fatter, and produce more young.
A human gamete cannot fertilize an animal egg. Members of any animal species can only reproduce with other members of its own species, or in some cases with members of a very closely related species, and there is no species that is close enough to the human species to allow for cross breeding. Possibly when the Neanderthal species existed, it could have cross bred with H. sapiens, and maybe it did.
To make a long answer short, when a variation helps an animal survive in its habitat, that animal will become more successful than it used to be, and enough variation can lead to a new species.
the animals that can adapte to the environment changes will live
By the theory of evolution, new species form through the process of natural selection. This process most often starts with a random mutation in the genome (a random gene suddenly changes or becomes a "mutation"). This mutation either helps, or hinders the new animal (or mutant if you will hehe). If it helps them survive better than the older species, then this new mutant species will become more abundant. If not, than the new species will die off. This process does not happen all at once though, it usually takes a generous amount of mutations and thousands of years for this to happen.
Allot of the affects will depend on the animal that becomes extinct, and the ecosystem they inhabit. In an extreme case, if plankton was wiped out of the oceans, most whales would die out from lack of food. All the species that depend on plankton, such as Sea Turtles, coral beds, and the young creatures that rely on both to thrive would starve without this broad group to feed from. As the food chain collapsed, species further down the chain would suffer as prey became scarce, populations, and births would drop, increasing the decline. Species like the seal and shark would have to hunt further for prey, if it could be found at all causing strain and eventual die off. The cycle would go on and on. Most of the time, if an entire species becomes extinct, then all the animals depending on that animal will suffer the same fate. Now, if things happen the other way around, and the predator species becomes extinct first. For example, say Sharks die out, seals would overpopulate their habitat and consume all their prey causing the same type of collapse, but starting smaller, then snowballing as the affects multiplied through out the environment.
It depends on the experiment and the animal. Sometimes the animal becomes incapable to lead a Normal life so scientists perform mercy killing. especially lab rats.
An animal becomes extinct, but protests do not. The ability to protest is part of the Bill of Rights and is listed as freedom of speech.