8. Community Organisation Flashcards
What are the 4 main biological processes that shape abundance of species?
Competition, predation, herbivory and mutualism
If the 4 groups do structure the ecosystem, what should happen?
We should see competing regulation of the ecosystem
Where there might be a place where the system isn’t regulated
The environment is not stable enough, too much turnover and change
How could predation and herbivory shape a community?
In terms of who eats who
How can complexity be reduced?
By measuring, biodiversity, trophic levels, feeding groups and importance
What is species richness?
How many species in a place, don sent really tell us much else
What structure can capture the complexity of nature?
Food webs
What are the benefits of food webs?
Allows us to see the whole diversity of life
What can we see in a food web?
Complexity, see how many predators there are in the system, few at top many at bottom?
If a web as few chains what is the problem for the ecosystem?
Big loss in the food chain, other animals effected
What can food webs be structured by?
Body size
What can damage to a food web be problematic?
Takes a long time for the food web to recover, another perturbation could happen while the system is recovering
What limits food chain height?
Species at the top are highly dependable on the species below
What is web lumping?
Putting many animals of one groups together in a food web
What do species do in times of low resource?
Canabalism
What is inteagil predation?
Predators eat other predators
What is omnivoury?
Species that feed on more than one level on a food chain
What is a sub webs?
Describe parts of the main webs
What feeds on fish larvae?
Sea nettle and bass
Why did sea nettle focus more on fish larvae?
Oxygen depletion in the sea caused the sea nettle to move away from fish eggs
How can we allocate species to trophic levels?
Normally body size, but also green plants herbivory ect
How can we subdivide each trophic level?
Using wood webs
How would animals form a guild?
Feeding in the sam way, bound to compete more than other birds
How can feeders be split into groups?
How they feed, eg on a cabbage, pit strip and sap feeders
What could guild grouping suggest?
That species are redundant, functional redundancy
What is a keystone species?
If a high percentage of species are lost when one is removed from a community, that species is said to be important
What are cassowarys so important?
Seeds germinate by passing through a cassowary
How are sea otters key stone?
Keep the concentration of urchins down with protects the kelp
How can fish control a river ecosytem?
Can control invertebrates, eg increase river growth in plants
What is a top predator?
Nothing eats it?
What is a nasal species?
Is only eaten
What is connectness?
Number of possible interactions divided by possible interactions
What is linkage density?
Average number of links per-species
Why do links in a food web say pretty much the same?
In a larger food web each species is feeding on more animals
What is the average length of a food chain from top to bottom?
5
What is the energetic hypothesis
energy transfer along the chain is inefficient and ulimately limiting
What is dynamic stability hypothesis
long chains are not sustainable, fluctuations at basal level ramify up the chain
What evidence is there for energetic hypothesis
less food means less structures in the food chain
What is the average prey to predator ratio
3:1
