BSC3052 CONSERVATION BIOLOGY FSU EXAM 2 WITH
ANSWERS GRADED A+
1. Stochastic Mod- - Give a range of outcomes from the same initial conditions
els - Most important when studying small populations and
making short to medium term predictions
- Most population viability analyses will include some form
of stochasticity
2. Sources of Varia- - Environmental stochasticity
tion - Demographic stochasticity
- Catastrophes
3. Environmental - Temporal variation in vital rates driven by changes in the
Stochasticity biotic or abiotic environment
- Local and small populations are often most at risk from
environmental stochasticity
- Increases extinction risk
- Bad years are bad for the average growth rate
- Strings of bad years can lead to extinction
4. Incorporating - *refer to slides 12-20 lecture 10 for math*
Stochasticity - Models with no stochasticity predict population size
into a - If you add variability, you predict a lower size
Count-Based - Models with stochasticity predict a distribution of popula-
Model tion sizes; added stochasticity, predicts lower populations
5. Catastrophes - Hard to predict or model but ultimately may be a common
contributor to extinction
- Multiple viable populations are necessary to be resilient
to a catastrophe
- Spatial variation in the environment can help avoid ex-
tinction
- Not predicable from historical data
6. Demographic - Extinction may occur due to order of births and deaths
Stochasticity - Increases extinction risk and is strongest at small popu-
lation sizes
- Probabilistic births and deaths matter
+ Example 1:
- 50% probability of 1 female offspring
- 30% probability of dying every year
1/2
ANSWERS GRADED A+
1. Stochastic Mod- - Give a range of outcomes from the same initial conditions
els - Most important when studying small populations and
making short to medium term predictions
- Most population viability analyses will include some form
of stochasticity
2. Sources of Varia- - Environmental stochasticity
tion - Demographic stochasticity
- Catastrophes
3. Environmental - Temporal variation in vital rates driven by changes in the
Stochasticity biotic or abiotic environment
- Local and small populations are often most at risk from
environmental stochasticity
- Increases extinction risk
- Bad years are bad for the average growth rate
- Strings of bad years can lead to extinction
4. Incorporating - *refer to slides 12-20 lecture 10 for math*
Stochasticity - Models with no stochasticity predict population size
into a - If you add variability, you predict a lower size
Count-Based - Models with stochasticity predict a distribution of popula-
Model tion sizes; added stochasticity, predicts lower populations
5. Catastrophes - Hard to predict or model but ultimately may be a common
contributor to extinction
- Multiple viable populations are necessary to be resilient
to a catastrophe
- Spatial variation in the environment can help avoid ex-
tinction
- Not predicable from historical data
6. Demographic - Extinction may occur due to order of births and deaths
Stochasticity - Increases extinction risk and is strongest at small popu-
lation sizes
- Probabilistic births and deaths matter
+ Example 1:
- 50% probability of 1 female offspring
- 30% probability of dying every year
1/2
