It is very common to see two species competing for the same habitat and/or food. This can sometimes lead to the extinction of the weaker animal. Other times, one of the species learns to adapt to the situation by eating other foods or learning how to live in a different place. For example, if a coyote pack and a cougar are in the same area and they are both after deer, it isn't going to work. The deer population will drop very quickly and either the cougar or coyotes will have to move somewhere else or learn to eat other animals. Animals are surprisingly good at adapting to sudden problems like new arrivals. If take a invasive species (non-native) and put it in an environment where no other species can compete or learn to kill, what is going to happen? What will happen is that the new species will overrun everything else that gets in its way and either kill it or force it to adapt. There are many examples where two species live together in the same habitat where they both are benefiting from their relationship. One example is birds and hippos. The birds will sit on the hippos backs for hours and eat the bugs that have been living on them. The hippos don't mind this because the birds are helping them out. Another example is of honey bees and flowers. This is probably the most common mutualistic relationship around. The bees take the nectar from the flowers and pollinate them at the same time. The flowers don't need the nectar but they do need to be pollinated so that they can grow. Both species are benefited with this relationship. When humans interact with species in an ecosystem, it can be mutualistic, competitive, or exploiting. An example of mutualistic would be scientists out studying plants and animals to get a better idea of how they live. The scientist are pretty good about not harming anything while at the same time, they are receiving lots of information that could be later used to help these plants and animals that aren't surviving well. Humans can be competitive while hunting for deer or elk. Hunters don't like the coyotes, cougars, bobcats, and wolves hunting where they are because they are hunting for the same thing. Exploiting can be pretty much anything that humans want to kill. Seeing as how humans have the complete advantage over all other species, they can take an unfair advantage at any time. For example, hunters hunting deer, or little kids playing in the woods or building forts on trees, or kids going out and shooting little animals, ect.