ecological networks

Question 1

Give three examples of mutualistic webs

Answer 1

1) Pollination networks
2) Frugivore networks (plants and their animal seed dispersers)
3) Ant-plant networks (plants that provide food and/or domatia for ants, which in turn provide protection for the plants

Question 2

What is a trophic cascade?

Answer 2

It occurs when predators in a food web suppress the abundance or alter the behaviour of their prey, thereby releasing the next lower trophic level from predation

Question 3

List traits that increase further up the food chain

Answer 3

1) Body size
2) Longetivity
3) Home range area
4) Vulnerability to habitat fragmentation

Question 4

Lists traits that decrease further down the food web

Answer 4

1) Vulnerability to stress
2) Ability to adapt (evolve)
3) Species richness (insurance)

Question 5

Why are food chains generally short? Give three reasons.

Answer 5

1) Dynamical constraints –> species abundance declines with trophic status
2) Energetic constraints –> energy is lost moving upwards in the web (only 10% is available to the next trophic level)
3) Morphological constraints –> structural limites to the maximum size a predator can attain

Question 6

Give three examples of strong interactors (keystone species) in ecological networks

Answer 6

1) Predatory starfish
2) African elephants - destruction of woody vegetation maintains savanna
3) Ground predators in Polynesia drive ground nesting birds to extinction