Community ecology Flashcards
How do mutualisms evolve?
From relationships that are initially antagonistic.
State the process in which pollen feeding could have formed a mutualism from an antagonistic relationship.
Pollen feeding may have led to increased rates of pollen transfer. Plants may have formed mechanisms to entice pollen feeders and ensure pollen transfer had increased success. They may have enticed the pollen feeders with nectar, and the pollinator would become specialised to transfer pollen and obtain resources from the host - increasing their success.
How was the idea of antagonistic relationships forming mutualisms tested?
A strain of amoeba proteus was inoculated with a bacterium. Initially, the bacteria caused the hosts to be smaller, grow slowly and often killed the hosts. 5 years later the bacterium had evolved to be harmless to the amoeba - the amoeba had evolved to be dependent on the bacterium for metabolic functions. Tests showed that the species could no longer exist alone.
What is an obligate symbiotic relationship?
The idea that both species live in a permanent close relationship e.g. lychen is made up of algae and cyanobacteria.
What is a community?
An association of interacting populations, usually defined by the nature of their interaction and/or the place in which they live.
What is a closed community?
The idea that species are bound to each other by their interactions.
What is the individualistic view of communities?
The idea that communities are associations of species assembled by chance, independent of other species presence or absence - this is also referred to as an open community.
Why might interconnected closed communities exist?
Common environmental needs that then leads to an interdependence among the species.
What is the succession?
The idea that communities change overtime.
What is primary succession?
The idea that communities develop from new never before occupied space.
What is secondary succession?
Where communities are affected by the occurrence of disturbances such as fires or hurricanes, and species then recolonise.
What can recolonisation of small gaps in a community provide information on?
Whether a community assembly is deterministic or random.
What is founder controlled colonisation?
Communities where any species has an equal chance to colonise the gap and the future composition is determined by chance. It maintains diversity.
What is dominance controlled colonisation?
The species differ in competitive ability and the outcome can be predicted by competitiveness, although they undergo succession often. It maintains less diversity.
What is species richness?
The number of species in a fixed area.
What is species evenness?
How many of each species is present in an area.
What is the Shannon index?
A diversity index that incorporates species richness and evenness.
What is trophic structure?
It is determined by the feeding relationships between organisms.
What is a food chain/web?
The transfer of food energy from its source in photosynthetic organisms through herbivores and carnivores.
What do food webs show?
Who eats whom in a community.
What is bottom up regulation?
The imperfect transmission of energy controlled by primary production. It means higher levels are smaller.
What is a keystone species?
A species that has a disproportionate effect on the community.
Give some examples of keystone species.
Pisaster, coral, African elephants.
What is top down regulation?
The idea that a top predator controls the population dynamics.
