How does strong armlike bones help aquatic species survive on land?​

Parasitism could be considered a form of which of these types of relationships? -mutualism -commensalism -predator-prey -mimicry

Plz ! ive been stuck on this forever

The concept of keystone species is controversial among ecologists because most organisms are highly interdependent. if each of the trophic levels is dependant on all others how can we say one is most important