Unit 2: Population Ecology Flashcards
What is Population?
a group of individuals of the same species that live in the same area at the same time, also may potentially interact with each other
Can defining a population border be difficult?
Yes
Species exist as Metapopulation. What is Metapopulation?
a population of populations, connected by migration or gene flow
What is Population Size?
(N) the number of population members in a habitat at the same time
What are methods for determining Population Size (N)?
- count all individuals in the populations
- sub-sample and extrapolate
- mark-recapture
Is the method: “count all individuals in the population” for determining (N) possible?
It is usually not possible, except for those endangered species
What are the different types in the method: “sub-sample and extrapolate”?
Quadrat & Transect
What is a Quadrat sample?
square made of various materials used to determine population size and density in slow moving or stationary organisms
What is a Transect sample?
a path along which one counts and records occurrences of the objects of study
What are the potential difficulties if the “sub-sample and extrapolate” method?
- over what area do you extrapolate
- Heterogenous habitat
- movement of individuals
What is Mark-Recapture?
technique used to determine populations size in mobile organisms
What is the mark step in Mark-Recapture?
catch some individuals and mark them
What is the recapture step in Mark-Recapture?
return later, catch some individuals, tally number marked and unmarked
How do you estimate population size based on Mark-Recapture?
N = Mn/m
(N = estimate population size
M = number marked sample 1
m = number marked in recapture sample 2
n = total in recapture sample 2)
What assumptions are made about Mark-Recapture?
- individuals not moving in/out of study area
- individuals mix between captures
- no catch bias
- individuals do no learn to avoid/seek traps
- no change in survival rate for marked individuals
What is Population Density?
number of population members divided by the area or volume being measured
What is Population Dispersion?
how individuals are distributed relative to one another
How many types of population dispersion is there?
3
What is Uniform dispersion?
relatively equal spacing among individuals
What is Random dispersion?
individuals has equal probability of occurring anywhere in the area
What is Clumped dispersion?
individuals are closer than expected by chance
What is Demography?
statistical study of changes in populations over time, which depend on the traits of focal organisms (birth/immigration = positive & death/emigration = -)
What is Life Table?
table showing the life expectancy (and/or other traits) of a population member based on its age
What do life table statistics estimate for?
cohort
