LE 7: Intro to Population Ecology Flashcards
What is a population?
a group of organisms of the same species that live in a particular geographic area at the same time, with the capability of interbreeding
What are the characteristics of a population?
They can vary in density because some can be concentrated in areas more so than others.
Live within a certain geographic range because they need certain resources that can only be found in certain habitats.
Abiotic and biotic factors affect how concentrated a population. A destroyed habitat can lead to pushing species into a smaller habitat that reduces a population size. Competitor species can push other species into a niche that has less resources, leading to a decline in population.
What is the Transect Method?
Transect method: travel along a line and count everything from a certain distance from the line
- limited to species that are stationary; ≠ work well for moving species
- ideal for evenly spaced/ random species (clustered = variation that occurs)
What is the Mark Recapture Method?
Mark Recapture Method: Capture and mark species, let them go, and recapture species on the second visit
Assumptions:
- no births/deaths and immigration/emigration
- marked and non-marked are equally likely to be caught (random mixing)
- population is well mixed
- survivability of individuals ≠ affected by their marks
- ≠ lose their marks
Ideal:
- moving species
- ≠ want open population that can result in a larger estimated population size
- want tagging methods that ≠ affect survivability of the species
What is the formula for the Mark Recapture Method to determine a total population size?
N = MC/R where…
N = estimate of population size
M = total # of animals captured + marked on first visit
C = total # of animals captured on the second visit
R = # of animals captured on the first visit and then recaptured on the second visit
How is population growth measured?
Change in pop size = (Births - Deaths) + (Immigration - Emigration)
Cohort life tables
- Cohort: group of individuals born at the same time
- peak fecundity = greatest # in average offspring/ individual
