3 - Communities and Food Webs

List 3 examples of community organisation

• species composition

• temporal organisation

• trophic organisation

Define species composition

each community has a characteristic set of species in terms of relative abundance

Define temporal organisation

cycles of activity (daily/seasonal)

Define trophic organisation

patterns of energy transfer

Define species richness

the total number of species within a community

Define a keystone species

those on which others depend on, with their loss leading to the loss of other species

Define a dominant species

a species that sets the state of the community (oak trees in an oak forest)

Define an indicator species (2 points)

those which provide information about a community

• can be used as a marker of overall condition of the community

Give an example of an indicator species

trout require the high oxygen content of clear water and so their presence gives a clear indication of the environment

Define dinural

active during the day

Define nocturnal

active during the night

Define crepuscular

active during twilight hours, such as dawn and dusk

Define three types of interaction

• predation

• parasitism

• mutualism

Define predation (2 points)

the complete consumption of one organism by another

• one is harmed, one benefits

Define parasitism

consumption of part or all of an organism by another

• one is harmed, one benefits (usally lives on in the host)

Define mutualism

an interaction where both organisms benefit

Give two examples of mutualism

• pollination

• cleaner fish

Define the rule of tens

on average, only 10% of the energy makes it from one trophic level to the next

Chain shortening

energy loss and reduced populations means that population chains will be under selection pressures to shorten

How does chain shortening occur?

if super predators take out all the prey in the trophic level below it, it will have to move on to the next level below

Guilds

aggregations of species in food webs in terms of similar functional types for simplicity

Compartmentalisation

food webs can be compartmentalised into groups where interactions are strong but between which interactions are weak