Lecture 4: Community Ecology

Be able to interpret differences in the relative magnitude of the Shannon-Wiener diversity index (H’).

higher H’ means greater diversity, more species, and even more abundance)

Identify trophic positions for each species in a given food web/chain, and identify which links are direct and indirect

Producers —> Primary consumers —> Secondary consumers —> Tertiary consumers —> Decomposers

Direct links is a one-step feeding relationship while indirect links are more of a cause-and-effect.

Describe how a keystone species can maintain species diversity in a community.

Keystone species keep the population of dominant species in check, making sure their population doesn’t grow out of control and eliminate their food source.

Describe ecological succession and the characteristics of pioneer and climax species.

The sequence of changes in an ecosystem over time

Pioneer species are resilient and grow quickly

Climax species need a stable environment and grow slowly

Contrast the nature and time-frame of primary versus secondary succession.

Primary succession starts on lifeless ground with no soil. Takes centuries

Secondary succession starts after a disaster kills all life, but leaves the soil. Takes decades

Compare pioneer and climax communities.

Pioneer communities have low biodiversity, fast growth, and simple food webs.

Climax communities have high biodiversity, slow growth, and complex food webs.

Using the island theory of biogeography, predict differences in species richness (and competition) on islands in relation to their size and distance from the mainland.

Species richness is highest on large islands close to the mainland and decreases as islands get smaller or further away because oh higher immigration to closer islands and lower extinction on large islands.

Describe how island size and distance from the mainland is thought to impact rates of immigration and emigration of species on islands.

Larger islands have more resources, and thus low extinction and high immigration rates. Closer islands have higher immigration rates as well.