The image related to that question is attached below.
In the figure, we can see that on the left side, sea otters are very influential in the population of sea creatures, if the killer whales are not in the environment. That's because sea otters are strong predators of sea urchins. However, sea urchins are not as influential in the size of the seaweed population, providing little effect on that population. This is because sea otters control the population of sea urchins through predation. Thus, if more sea urchins are consumed by sea otters, the sea urchin population becomes small and consequently the consumption of algae (by sea urchins) is small.
On the right side of the figure, killer whales are great predators of sea otters and establish a strong predatorism, being very influential in the population of sea otters. This predatorism causes the otter population to decrease and stay in controlled and limited sizes. In this case, with few sea otters in the environment, their predatorism in relation to sea urchins is less, allowing the sea urchin population to grow and to consume more seaweed, providing a strong impact on the seaweed population.
