Each species has made adaptions to survive.
Each species has different genes that characterize it. Each species does
something that affects our ecosystem. Taking one of those species out
(the tiger or the lion for example) could change the entire food chain
and ecosystem in that particular area.
Bats eat thousands of bugs. Bats are becoming extinct. If we kill the
bats, than who will eat the bugs? If no one is there to eat the bugs,
than farmers create new pesticides to kill these bugs that can be
hazardous to the environment or even to us.
We need to care about the remaining animal species because each one
provides us with something, whether it be knowledge, or it be less bugs,
we need each animal to maintain the fragile balance of our world.