BIO 322 Exam ASU- Questions with Complete
Solutions
Population trend: How do we know if population size is stable, increasing, or declining
through time? (look at lecture slides for each because it is too long, equations are easier to
look over on them)
A. Estimate trend in N from historical records; or reconstruct past N from modern-day allelic
diversity (or use both methods)
lambda > 1 population grows
lambda = 1 population stable
lambda < 1 population shrinks
B. Estimate population trends using time-series data
C. Estimate population trends using a statistical method such as simple linear regression
D. Estimate population trends using a demographic matrix model
biology of rarity
Conservation Science is concerned with the distinctive problems faced by small populations
because population size (N) is inversely related to risk in terms of amount of genetic variation
and numbers of individuals. We will call this the biology of rarity.
Perils of small populations
1) demographic stochasticity
2)Environmental stochasticity
3) Allee Effect
4) Inbreeding
,5) Genetic drift
all lead to greater risk of extinction
What is demographic stochasticity?
variation in birth rates and death rates due to random differences among individuals
What is the Allee effect?
- A form of positive density-dependent feedback in which as N declines, per capita population
growth rate declines
- Happens due to:
1) Mate finding or pollination problems
2) Cooperative hunting suffers
3) Protection from predators declines
4) Disrupts social interactions (courtship displays, communal rearing of young)
Inbreeding
breed from closely related people or animals, especially over many generations and therefore
loss of diversity over time
What is genetic drift?
The frequency of alleles with the same fitness may change at random through time in a process
called genetic drift. If there are two alleles at a locus, and they have the same fitness, random
sampling can cause their relative frequencies in a population to change. Genetic drift has
important consequences for the random substitution of genes and the Hardy-Weinberg
equilibrium.
, What is environmental stochasticity?
Unpredictable changes in the environment that can cause extinction of small populations
What is the most critical attribute defining degree of endangerment for the ICUN?
Population size
What is the extinction vortex?
- a small population declines and becomes more vulnerable to processes that lead to extinction
like habitat destruction, pollution, over-harvesting, or invasive species
- often multiple, simultaneous, or repeated impacts to most or all populations that cause
extinction
effective population size
An estimate of the size of a population based on the numbers of females and males that
successfully breed; generally smaller than the total population.
relationship between effective pop. size and time (genetic heterozygosity in a population)
the smaller the population, the more heterozygosity lost over time
Why is demographic stochasticity an important cause of extinction for small populations
ONLY?
every individual contributes a lot to the population's chance of survival when populations are
small
What five assumptions are required for creating an ideal population?
Solutions
Population trend: How do we know if population size is stable, increasing, or declining
through time? (look at lecture slides for each because it is too long, equations are easier to
look over on them)
A. Estimate trend in N from historical records; or reconstruct past N from modern-day allelic
diversity (or use both methods)
lambda > 1 population grows
lambda = 1 population stable
lambda < 1 population shrinks
B. Estimate population trends using time-series data
C. Estimate population trends using a statistical method such as simple linear regression
D. Estimate population trends using a demographic matrix model
biology of rarity
Conservation Science is concerned with the distinctive problems faced by small populations
because population size (N) is inversely related to risk in terms of amount of genetic variation
and numbers of individuals. We will call this the biology of rarity.
Perils of small populations
1) demographic stochasticity
2)Environmental stochasticity
3) Allee Effect
4) Inbreeding
,5) Genetic drift
all lead to greater risk of extinction
What is demographic stochasticity?
variation in birth rates and death rates due to random differences among individuals
What is the Allee effect?
- A form of positive density-dependent feedback in which as N declines, per capita population
growth rate declines
- Happens due to:
1) Mate finding or pollination problems
2) Cooperative hunting suffers
3) Protection from predators declines
4) Disrupts social interactions (courtship displays, communal rearing of young)
Inbreeding
breed from closely related people or animals, especially over many generations and therefore
loss of diversity over time
What is genetic drift?
The frequency of alleles with the same fitness may change at random through time in a process
called genetic drift. If there are two alleles at a locus, and they have the same fitness, random
sampling can cause their relative frequencies in a population to change. Genetic drift has
important consequences for the random substitution of genes and the Hardy-Weinberg
equilibrium.
, What is environmental stochasticity?
Unpredictable changes in the environment that can cause extinction of small populations
What is the most critical attribute defining degree of endangerment for the ICUN?
Population size
What is the extinction vortex?
- a small population declines and becomes more vulnerable to processes that lead to extinction
like habitat destruction, pollution, over-harvesting, or invasive species
- often multiple, simultaneous, or repeated impacts to most or all populations that cause
extinction
effective population size
An estimate of the size of a population based on the numbers of females and males that
successfully breed; generally smaller than the total population.
relationship between effective pop. size and time (genetic heterozygosity in a population)
the smaller the population, the more heterozygosity lost over time
Why is demographic stochasticity an important cause of extinction for small populations
ONLY?
every individual contributes a lot to the population's chance of survival when populations are
small
What five assumptions are required for creating an ideal population?
