Final answer:
Predators obtain food through active hunting or ambush strategies, with sessile animals such as barnacles and carnivorous plants using the latter. Keystone species predators are integral in maintaining ecological community structure by controlling prey populations.
Step-by-step explanation:
Predators obtain food through two main strategies: active hunting or ambush and trap techniques. Active hunters move through their environment searching for prey. In contrast, ambush predators, such as sessile animals like barnacles and many carnivorous plants, rely on their prey coming to them.
Sessile animals are typically filter feeders or have developed specialized structures to capture prey. For instance, barnacles use feathery appendages to filter plankton from the water, whereas carnivorous plants have evolved various traps to capture insects and small animals.
Predators often concentrate their efforts in regions where their prey is most abundant. This can lead to a high degree of specialization, including the development of specific hunting skills, physical adaptations, and an acute sense of their prey's habits and habitats.
Keystone species, such as some predators, play a critical role in maintaining the structure of an ecological community by controlling population sizes and thereby affecting the biodiversity of the community.