patterns in space and time Flashcards
what is community ecology
the study of patterens in the structure and behaviour of multispecies assembalages
what is meant by the term synergistic emergent properties
when the interactions of an
individual components produce new functi9nos which make the community more than the sum of its parts
what determines the species which assemble to make a community
1) the habitat species pool- species which are able to survive the environmental constraints
2) the geographic species pool - species which can overcome dispersal constraints e.g. mountains etc
if a species can overcome environmental and dispersal constraints what do they form
an ecological species pool which makes up the community
how can a community be defined
any scale within a hierarchy of habitats
what is species richness
the total number of species
what are some of the challenges faced when describing species richness
1) needs skilled taxonoists
2) only a small sample is counted- therefore number of species depends on number of samples counted
3) more common species are represented first
4) when do you stop sampling
how do you know when an appropriate number of samples has been taken when calculating species richness
once a plateu of species richness has been reaches then the right number of samples has been taken to represent to community
why may species counts be misleading
disparities in size mean counts are misleading
- larger individuals will take up more room per square metre therefore they will be less abundnat
what is a better technique to indentify diversity
biomass per speices per unit area
what does the simpsons index show
the probability that 2 randomly selected individuals belong to the same species
what is the difference between simpsons index, simpsons index of diversity
1) probability 2 randomly selected individuals belong to same species
2) probability 2 randomly selected individuals belong to different species
what is shannon weiner diversity index
uses species richness and abundance to measure the uncertainty in predicting the species identiy of an individual taken at random
what do rank abundance diagrams show
provide a more complete picture of species abundance and distribution in a community
what does classification of species allow
assumes communities consist of discrete entities and groups communtites which are similar
what does ordination of species allow
allows communities to be organised on a graph so most similar in species composition and abundance appear closer together
how can boundires cause issues in the study of community ecology
- there are often blurred transition zones e.g. aquatic vs terrestrial which frogs move between
what did clements mean when they said a community was a superorganism
that members tightly bound together now and in evolutinary history
outline Gleasons individualistic concept
that relationships of coexisting species are simply a result of similarities in requirements and tolerances and chance
when will a species only occur
1) if the individual is able to reach the location
2) if there are approproiate conditions
3) competiton and predation dont preclude it
how can disturbances disrupt a community
- influence availability of space or food
- change physical enviro
what is the founder controlled responce to distrubance
species are equallt able to colonise an opening made by disturbance
what is dominance controlled responce to disturbance
when some species are competitvley superiror so an initial coloniser cant maintain its presence
what is ecological succession
the non-seasonal directional and continuous pattern of colonisation and extinction on site by species populations
what is clements monoclimax theory
in any given climatic region a single climax will dominate
what is Tansley polyclimax theory
that local climax is governed by a combinatino of factors
what is Whittakers climax pattern hypothesis
a continuity of climaxes along environemental gradients
