Lecture 5-6: Population Ecology Flashcards
Why do we care about population numbers?
- Conservation (to see what species are vulnerable for extinction)
- to see available resources
- (health) to measure danger of potential viruses
When are differential equations suited for population
when the population growth is continuous
Difference equations
discrete model
best used for episodic reproduction
Continuous time model
N= (No) . e^rt
Discrete time model
N= (No) . theta^t
what is the relationship between theta and r?
theta = e^r
r= ln (theta)
What keeps populations from exploding or going extinct?
- density dependent regulation
- how the population numbers affect population growth
- the population grows faster when the population Is smaller because of the abundance of resources
Model of density dependent equation
Dn/Dt= rN (1-R/k)
Describe variables in Nt= (KNo)e^rt/ K+No (e^rt-1)
What is this equation?
K= carrying capacity
No= initial population
r= instantaneous rate of increase
t= time over timestamp
this is the sigmoid growth curve with an s shape
What does the inflection point represent in the sigmoid growth curve
- when population starts to grow slower
allee effect
- when, in small populations, there are negative effects on population growth due to difficulty to reproduce
example” meerkats
Fecundity
how many daughters a mother will produce in her lifespan
Survivorship
Chances of survival to the next timestamp
Components of a life history strategy
- reproduction timing (episodic or continuous)
- number of offspring
-parental investment - lifespan
Life tables
Data summarizing life events of individual and when they typically occur
Survivorship schedule
Lx denotes likelihood of being alive at next Time stamp
Fecundity schedule
Mx denotes expected daughters mother will produce
Cost of reproduction
(Fecundity)- (Survivorship)
Net Reproduction Rate
Ro= ∑Mx . Lx
Mx denotes number of offspring produced if she isn’t expected to die early
Lx accounts for if she does die early
Generation Time
Average age female gives birth
T=∑LxMx/Ro
Semalparity
When species undergo reproduction at once right before they die
examples: salmon
