3-population ecology Flashcards
population
group of individuals of the same species that live in the same area at the same time
population size
total number of individuals in a popuation
population density
number of individuals per unit area (or volume)
how to choose which sampling technique
organism DOESN’t move? –> QUADRAT SAMPLING
organism DOES move? –> Mark-recapture techniques
Mark-recapture
visit 1
- capture indivduals
- count and mark them (M)
- release them
give marked individuals time to spread out…
visit 2
- capture individuals (n)
- some will be marked (m)
- some will be unmarked
- count them!!!
Lincoln-Peterson method of mark-recapture estimation VARIABLE MEANINGS
M = number of individuals marks on the first visit
n = number of individuals captured on 2nd visit
m = number of individuals captured during second visit that were marked
assumptions of the Lincoln-Peterson method
-
the population is closed
- N does not change between sampling periods
- no births, deaths, or movement of individuals in/out of the population
-
individuals do not differ in their probability of being caught
- marking does not affect probability of being caught
- individuals do not lose marks between sampling periods
Calculating population size at different time points VARIABLE MEANINGS
Nt = population size (N) at time t
Nt+1 = population size (N) at time t+1
D = number of individuals that die between t and t+1
B = number of individuals that born between t and t+1
per capita
per person/individual
Per capita birth rate (range from 0 to infinity)
b = B/N
Per capita death rate (range from 0 to 1)
d = D/N
r variable meaning
per capita growth rate or intrinsic growth rate of the population
r = b - d
CALCULATING POPULATION GROWTH RATE (r) USING b & d
- if b = d the r = 0 → population size is not changing
- if b > d, then r > 0 → population size is increasing
- if b > d, then r < 0 → population size is decreasing
EXPONENTIAL GROWTH
unrestricted growth of a population that increases at a constant growth rate (r)
looks like a j
- r is density-independent under exponential growth
- r won’t change, no matter how big or small the population gets
- the larger the per capita growth rate (r), the steeper the curve
- the larger a population get the more individuals get added to the population with time
LOGISTIC GROWTH
- A pattern of growth that starts fast, but then slows due to limiting factors
- eventually, the population will stop growing (r=0) once it has reached the environment’s carrying capacity
S-SHAPED CURVE
- r is density-dependent under logistic growth
- r will decrease as the population gets bigger and uses more resources
- formula now incorporates the concept of a carrying capacity into the equation