yes endangerd animals would all be killed if it wasent for zoos
A species that "belongs" in a particular area, as you put it, is called a native species. I am sure that animals who find themselves in a non-natural habitat are called a non-native species, an invasive species, or introduced species. The introduction of some species into new environments can have devastating results - this is because the invasive species can eradicate necessary native species that are necessary to support a healthy ecosystem.
Plants give animals protection by providing some form of shelter in addition food and oxygen
Protection from grazing animals.
Some species do, some don't.
Yes some species of cacti are food for animals.
Some
lion
the blue whale
Some species of crayfish, such as the spiny lobster, are saltwater animals, while other species, such as the kabby or koura, are freshwater animals. It all depends on which species of crayfish you are referring to.
Yeah some species of sharks do it.
There are may research topics about animals. Some of them could be about endangered species, animals of the rain forest, or habitats of animals.
Some Arctic Animals can swim, as it's necessary for them to survive.