4.6 Community Ecology II

Question 1: Barnacles of the Rhizocephalan group were thought to be hermaphroditic, but it was later discovered (by Charles Darwin!) that the tiny males insert themselves into the bodies of the much larger females – there to live on the female’s body nutrients and internally fertilize the eggs of the females. This relationship could be described as which?

A. Interspecific parasitism

B. Intraspecific parasitism

C. Intraspecific mutualism

D. Interspecific competition

C. Intraspecific mutualism

what is a keystone species?

an organism that plays a disproportionately large role in maintaining the structure, function, and stability of an ecosystem, and its removal can lead to significant ecosystem changes or collapse

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what is a Trophic cascade

A trophic cascade is a powerful indirect interaction where a predator's impact "trickles down" to affect the density and/or behavior of the prey's prey, often resulting in dramatic changes in ecosystem structure and nutrient cycling

what are some examples of a trophic cascades resulting from the loss of top predators?

• Robert Paine’s barnacle experiment

• Kelp forests in coastal California, Washington, and Oregon – ‘flipping’ to ‘Urchin barrens’ after loss of Sea otters and Sunflower Sea star

• Changes in Yellowstone National Park after the loss of wolves and their subsequent reintroduction

• Robert Paine’s barnacle experiment

• Kelp forests in coastal California, Washington, and Oregon – ‘flipping’ to ‘Urchin barrens’ after loss of Sea otters and Sunflower Sea star

• Changes in Yellowstone National Park after the loss of wolves and their subsequent reintroduction

Are all ‘keystone species’ top predators?

No, in some cases species including prairie dogs, beavers, elephants, and others are considered keystone species. Sometimes you also hear the term, ‘ecosystem engineer’ used in this context.

Question 2: Why would Keystone ‘builders’ have such an outsize effect on their community?

A. They can physically alter the environment.

B. They can be food for many important predators.

C. They can create ‘micro-habitats’ and ecological niches for other species.

D. All of the above

D. All of the above

what are keystone predators

• sea otter/sea star

• wolves

• orcas

what are keystone builders

• elephants

• beavers

• prarie dogs