Unit 3 Lecture 18 Flashcards
What is population ecology?
How population sizes change over time and space
- immigration move into populations and emigration move out of populations
What are two major goals of population growth?
- Use math to describe the dynamics of population change
- Use this to try to predict what will happen to populations
Recall, population growth rate is a proxy for _____ but also sets up pressure for ____
fitness; selection
One should assume that if a population is growing then that population is what?
More fit
Population growth also sets up pressure for selection because overtime what happens?
The fitness is going to start to level off because we are going to reach the carrying capacity of the population, there’s going to be more competition for resources
What does life tables represent?
Summary of survival and reproduction across lifetime
Explain how tables can be different across populations across time
Different populations will have different survivorship curves and different data in their table, even in the same species, sometimes depends on the months they were born
Name the 3 different types of survivorship curves
- Type I: lots of offspring live to old age, up until old age where then it decreases
- Type II: Constant death rate across age
- Type III: Lots of offspring die young (few individuals survive very early on, but then when you increase to a certain age, survivorship will increase for some individuals and will live to old one)
US human population has what type of survivorship curve?
Type I Survivorship
What kind of life history strategy would you expect to see in populations with type III survivorship curve?
Make lots of small offspring, forgo parental offspring
- Type I curve seen when there is little predation, most mortality due to old age
- Type III curve often seen when there is lots of predation
Give an example for each type of survivorship
curve
- Type I: Call mountain sheep survive to old age
- Type II: song thrushes have about the same chance of survival at any age
- Type III: Cleome droserifolia seeds, only 39 survive to produce 1 year old plants
How do you calculation population still living next year?
Starting population x survival rate
How do you calculate population of newborns next year for age 0? for rest of the ages?
(Number still living x Fecundity) + (Number living the following year x fecundity)
Same number as still living next year
How do you calculate total population
add up all of the total populations
What is the equation for population growth rate?
Nt+1 / Nt = λ (lambda)
- Nt+1 : number of individuals in time T+1 (starting population size)
- Nt: Number of individuals in time T (total population next year)
What can we use lambda for?
To estimate what population size at time T+1 (future) is equal to lambda x original population size
Nt+1 = λNt
True or False
If age specific survival rate and fecundity stays constant, the population will grow at the same rate no matter the age structure of the population
False
What is stable age distribution
If survival and fecundity stay the same, the population will reach a predictable age distribution
- Does not mean the overall population size isn’t growing, it means that the proportion of individuals in each age class will remain the same
Once population reach stable age distribution, growth rate becomes _____
Constant
- Growth rate >1 population is still growing
- Growth rate = 1 population is not changing
- Growth rate < 1 population is declining
