Trophic Interactions In Communities

Question 1

Why are predator prey cycles important

Answer 1

Predators may influence the distribution and abundance of their prey and vice versa

Question 2

What is the Lotka-Volterra predator prey cycle

Answer 2

Predator and prey abundance fluctuate in response to each other.
When prêt abundance high, predator abundance increases.
When predators exhaust food supply, prey and predator numbers decline.
When predator population is low, prey population can increase again.

Question 3

Why is the Lotka-Volterra model unrealistic

Answer 3

Many predators take on more than one prey and generalist predators are not tightly tied to the dynamics of any one prey species

Question 4

What’s a multi species system

Answer 4

Bothe predator and prey are influenced by other ecological interactions (predation of predators, competition between prey)

Question 5

What are the properties of food chains

Answer 5

Organism size increases with trophic level
A species can occupy more than one trophic level (sprat way fish larvae and zooplankton)
Tend to be limited to 4 or 5 trophic levels
There’s an approximately constant ratio of 2-3 prey for every predator in all food webs

Question 6

What are guilds

Answer 6

A group of species exploiting a common resource in a similar fashion (filter feeders)
Guilds simplify the study of food webs and community organization by reducing the No. of components.

Question 7

What’s a keystone species

Answer 7

Sometimes a role is occupied by a single species and it’s removal changes the community structure.
Their affect is much greater than would be predicted from their abundance.
Influence of keystone may be too down or bottom up

Question 8

Example of keystone species

Answer 8

Enhhdra lutris Sea Otter
Sea otters control sea urchin numbers which in turn control kelp forests

Question 9

What are dominant species

Answer 9

Unlike keystone species dominant species in a community are numerically dominant.
May be more tolerant to environmental extremes
Human removal can cause changes in community structure

Question 10

What’s too down cascade

Answer 10

Food chain or web is disrupted by the removal of a top predator or third or fourth lvl consumer.

Question 11

What’s bottom up cascade

Answer 11

A primary producers or primary consumer is removed

Question 12

What can lead to trophic cascade

Answer 12

Removal of important species

Question 13

What does an ecosystem approach to fisheries management consider

Answer 13

Trophic impacts of fisheries removal