Peter - mån 4

Question 1

Omnivory

Answer 1

Predator feeds on two trophic levels, prey and resource.

Question 2

Fascilitation

Answer 2

Eg mycorhizas. Each partner provides a resource that the other can benfit from.

Question 3

Food chains

Answer 3

Onlt vertical arrows. Used to be the common picture. Length is usually restricted to 3-4 levels in terrestrial chains, as energy is lost at each transfer. herbivores lose a lot eating from plants. This is not the case in the sea, as planctons don’t have these restrictions, efficiancy is high, possibility of 6-7 levels.

Question 4

Estimate number of trophic levels in food webs

Answer 4

Length of food chains is the number of transfers. Each link is counted and the number of transfers is summed. Divided by the number of chains.

Question 5

Food chain length

Answer 5

Depends on productivity and size of the ecosystem. Increases with the size of the system (area x productivity). Food webs consists of many food chains. A predator only eats a fraction of the production of lower trophic levels. Productivity per area is not so important, but total production can support more trophic levels.

Question 6

Top predator design

Answer 6

Given a certain production at the lower levels, there may not be enough energy left for a large top predator.
The design of the top predator also puts a limit to how many levels can be created. It is imporrible to create a predator bug and fast enough to take large prey.
It may be impossible to imagine a predator that is fast anough to catch