Pop Ecology Flashcards
Population ecology focus
Factors affect pop size
Unique features of pops
7
- Distribution
- Structure ( age structure, sex ratio)
- size (N)
- Density (N/ area)
- Growth rate (r)
- Pattern of growth ( logistical/ exponential)
- Life history traits
Pop size
- numbers individuals in pop
Pop density
- number individuals in area ( volume )
Estimating pop size
Moving?
Yes: mark recapture
No: quadrant sampling
Range of tolerance
Range abiotic where organisms can survive
Limits of tolerance
- upper/ lower limits particular (usually abiotic) factor where organisms survive
Geographic range
Where species live
How to do mark recapturing
1 visit: mark individuals
2 visit: capture and count how many are marked
(#marked 1 (M)/ estimated pop size (Ñ) ) =
( # marked 2 (m) / total captured 2 ( n))
N= M*n/m
Assumptions for mark recapturing ?
4
1) pop closed so N constant ( no birth/ death, move in/ out pop)
2) all same change be caught
3) marking don’t affect later catchability
4) don’t loss mark
Pop size (N) changes with time (4 factors and formula)
1) #births (increase N)
2) #deaths ( decrease N)
3) # immigrations (increase )
4) leaving ( emigrating) ( decrease)
N(t) = N (original) + B - D + I - E
How calculate pop parameters
2
Per capita ( per person ) basis
- let compare did pop sizes
Birth / death rates
3
b = B/N
d = D/N
Abs number births / deaths = B/D
range 0 to 1
What is r ( intrinsic growth )
1 and formula and 3
- per capita growth rate
r= b-d
b>d , r>0, pop increase
b< d , r< 0 , pop decrease
b=d, r=0 , pop doesn’t change
Patterns of growth
Logistical and exponential
Exponential growth
6
- J- shape
- resources not (yet) limited
- typically found: few individuals found new pop / bottleneck and start recovery with lots resources
- r density independent
- # individuals added pop is function (N)
- # individuals added depends on r
Logistics growth
6
- realistic, eventually runout resources
- growth rate level ~ 0
- max pop size specific environment can support (K)
- initial growth exponential
- r decreases as pop increases / resources limited
- r density dependent
Carrying capacity
- max pop size specific environment can support (K)
- not constant, depends variables
- can change with time/location
What pop density is r highest?
3
Low pop density
Small N (K-N)/K = K/K = exponential
- r smaller, eventually fluctuates around 0
2 factors prevent exponential pop growth
2 with 3 and 1
Density dependent: - often biotic ( composition)
- less E reproduction, less reproductive success, less survival
- less births, more deaths
Density independent: - often abiotic ( natural disasters, cold snaps )
Hint: more likely happen if pop increases
Life history traits
1+ 8 eg
Life stages ( birth —> growth —> reproduction—> death)
- age specific survivorship
- age first reproduction
- sex ratio offspring
- reproductive lifespan
- # offspring
- size offspring
- amount parent care
- growth rate
Survivorship curves and 3 types
- # individuals surviving as function age1) increase survivorship till old ( large mammals)
2) steady survivorship ( some birds , lizards , rodents )
3) decreases survivorship when young ( sea turtles, fish , plants )
Life history traits and natural selection
- LHT linked fitness
- can’t max all LHT same time ( lots babies and care)
- NS max total lifetime fitness
K- selected
7
K: little offspring and high survivorship
- stable environment
- high competition
- long lifespan
- type 1 survivorship
- reproduce more/ equal 1
- few big offspring
r - selected
8
r: lot offspring and low survivorship
- unstable/ unpredictable envious
- short lifespan
- type 2 survivorship curve
- sex maturity fast
- max r
- usually reproduce once
- lots small babies
