Population Distribution and Abundance Flashcards
population
a group of individuals of a single species inhabiting an area determined by natural or human made boundaries
distribution
the size, shape and location as well as density
abundance
total number of individuals, or biomass, of a species in an area (limited by space)
what limits distribution
environmental limits - water, temp, soils and biological factors such as food, competition and predators
fundamental niche
physical conditions under which a species might live in the absence of interaction with other species
realised niche
actual niche limited by biotic interactions such as competition, predation, disease and parisitism
distribution patterns on small scales
individuals in populations have random, regular or clumped distribution patterns
- social interactions and physical environments cause patterns
- social organisms (clumped)
- territorial (regularly spaced)
- patchy resources (clumped)
- aggressive (regularly spaced)
- non-aggressive (random)
patterns of distribution on large scale
individuals in a population are clumped and live in restricted areas
organism size and population density
population density declines with increasing organism size
- Allee effect: populations shrink when too small to maintain a viable population size
- extinction debt: can no longer recover
- seedlings survive at high densities
- when trees at low densities
what causes extinction
habitat loss, climate change, competition, hybridisation, loss of mutualists
- being rare
rarity
restricted geographic range, narrow habitat tolerance, small population size
abundant species
extensive range, broad habitat tolerance and large population size
co-extinction
extinction of one species triggers loss of its mutualists. often happens with specialists
