Lecture 8: Modeling Population Size (Exam 2) Flashcards
1
Q
The two principles of ecology
A
- all populations grow exponentially under ideal conditions
- no population can grow exponentially forever
2
Q
How we count populations
A
in a closed population: births - deaths
in open population: add immigrants + births, subtract emigrants + deaths
3
Q
why we count populations
A
- taxes, elections, business plans, constraints on social services, and other factors are affected by population size
4
Q
What Thomas Malthus argued
A
while populations increase exponentially, food supply increase linearly
5
Q
Why we model exponential growth and how we do it
A
- to make predictions about how populations might grow or change over time
- predict how quickly populations will grow under ideal conditions
- equation: dN/dt = rN
6
Q
why we model logistic growth
A
- no population can grow exponentially forever;
7
Q
What carrying capacity is and how its quantified mathematically
A
- maximum number of individuals the environment can support
- known as “K”;
- K - N = # of individuals environment can still support
- (K-N)/K is fraction available for growth
8
Q
logistic growth equation and how to use
A
dN/dt = rN [ (K-N)/ K ]
9
Q
the types of curves generated by both equations (and when to use which equation!
A
logistic growth: S shaped curve
exponential growth: J shaped curve
10
Q
models versus biological reality
A
- populations are messier than models
- populations rarely grow into J or S curves
- models are useful tools for thinking about population growth
