BIO 322 Exam 2 ASU
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) - answerA. 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 - answerConservation 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 - answer1) demographic stochasticity
2)Environmental stochasticity
3) Allee Effect
4) Inbreeding
5) Genetic drift
all lead to greater risk of extinction
What is demographic stochasticity? - answervariation in birth rates and death rates due
to random differences among individuals
What is the Allee effect? - answer- 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 - answerbreed from closely related people or animals, especially over many
generations and therefore loss of diversity over time
What is genetic drift? - answerThe 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? - answerUnpredictable changes in the
environment that can cause extinction of small populations
What is the most critical attribute defining degree of endangerment for the ICUN? -
answerPopulation size
What is the extinction vortex? - answer- 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 - answerAn 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) - answerthe smaller the population, the more heterozygosity lost over time
Why is demographic stochasticity an important cause of extinction for small populations
ONLY? - answerevery 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? - answer1)
Discrete generations
2) Completely random mating
3) Nm = Nf (even sex ratio)
4) Random family sizes
5) Constant population size
If a population is not ideal, convert N to Ne and then calculate the rate of loss of H. It is
almost always the case that Ne < N
Which of the following risks is the result of random variation in the survival and
production of offspring and is especially of concern for a small population? -
answerdemographic stochasticity: random variation among individuals in birth rate,
death rate, and sex of offspring. (declines quickly with population size)
Why do conservation scientists care about genetic diversity within species? - answer1)
Long-term: evolutionary potential
-populations may diverge into new subspecies or even full species
2) Long-term: evolutionary flexibility
-ability to respond to epidemics, climate change
3) Short-term: individual and population health
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) - answerA. 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 - answerConservation 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 - answer1) demographic stochasticity
2)Environmental stochasticity
3) Allee Effect
4) Inbreeding
5) Genetic drift
all lead to greater risk of extinction
What is demographic stochasticity? - answervariation in birth rates and death rates due
to random differences among individuals
What is the Allee effect? - answer- 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 - answerbreed from closely related people or animals, especially over many
generations and therefore loss of diversity over time
What is genetic drift? - answerThe 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? - answerUnpredictable changes in the
environment that can cause extinction of small populations
What is the most critical attribute defining degree of endangerment for the ICUN? -
answerPopulation size
What is the extinction vortex? - answer- 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 - answerAn 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) - answerthe smaller the population, the more heterozygosity lost over time
Why is demographic stochasticity an important cause of extinction for small populations
ONLY? - answerevery 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? - answer1)
Discrete generations
2) Completely random mating
3) Nm = Nf (even sex ratio)
4) Random family sizes
5) Constant population size
If a population is not ideal, convert N to Ne and then calculate the rate of loss of H. It is
almost always the case that Ne < N
Which of the following risks is the result of random variation in the survival and
production of offspring and is especially of concern for a small population? -
answerdemographic stochasticity: random variation among individuals in birth rate,
death rate, and sex of offspring. (declines quickly with population size)
Why do conservation scientists care about genetic diversity within species? - answer1)
Long-term: evolutionary potential
-populations may diverge into new subspecies or even full species
2) Long-term: evolutionary flexibility
-ability to respond to epidemics, climate change
3) Short-term: individual and population health
