Community Interactions in the Rocky Shore

Question 1

Ecological niche

Answer 1

Sum total of an organism’s use of the biotic and abiotic aspects of its environment

Question 2

Rocky shore communities traits (5)

Answer 2

Diverse phyla 
Epifauna, many sessile communities
Distinct zonation pattern
High density and patchiness
Space is a limiting factor

Question 3

Connell’s Barnacle Experiment
3 Observations
3 Hypotheses
Summary and Experiment

Answer 3

Observations:
Chthamalus found in upper intertidal, lots of emersions
Balanus found in lower intertidal, lots of submersions
Barnacle larvae found all over intertidal
A very narrow band of overlap, stark transition

Hypotheses:
Space competition by Balanus limits Chthamalus in the lower intertidal
Environmental toleration differences lead to the distributions
Other - predators, intraspecific competition

Summary and Experiment
Transplanted both species into a mix of different environments.
The combination of environmental tolerance and competition creates this pattern
Chthamalus is excluded from lower portions of the intertidal zone by Balanus
Balanus is excluded from the top of the intertidal by sensitivity to desiccation

Question 4

Inducible defences

Answer 4

Plastic phenotypic response to predators

Must be able to sense predators when they are growing

Question 5

Two types of trophic cascades in rocky shores

Answer 5

Density mediated trophic cascades: Trophic cascades caused by the consumptive, lethal effects of the predator on the prey

Trait mediated trophic cascades: Trophic cascades caused by the non-consumptive, non-lethal effects of the predator on the prey

Question 6

Intermediate Disturbance Hypothesis

Answer 6

At very high levels of disturbances, very few species are able to survive so species richness and evenness are low.

At very low levels of disturbances, a single dominant species tend to dominate the habitat so species richness and evenness are low.

At an intermediate amount of disturbance, the highest species richness and evenness is seen

Question 7

Keystone Species

Answer 7

They have a disproportionate effect on their environment for their small density

Question 8

Dominant Species

Answer 8

Have a large effect on the environment that is proportionate to their density

Question 9

Bioengineers

Answer 9

These are habitat formers

Play a large role in habitat structure

Question 10

Foundation species

Answer 10

These are species that provide habitat for other species. Habitat forming species

Question 11

How do foundation species facilitate ecological interaction (5)

Answer 11

Provide habitat
Provide relief from physically stressful conditions
Provide shelter from predators
Alter chemical composition of the habitat
Harbor prey items