Life History/Trait Variation (exam 2)

Define Senescence

Biological aging and gradual decline in fucntion

Why are longer lived organisms often larger than shorter lived organisms?

Longer lived organisms have less predation, so they are able to focus their energy on growing larger and reproduce later in life. Short lived organisms are smaller because they focus the majority of their energy on survival due to more predation and as a result also produce sooner

Why do Bats live longer than Mice even though they are both small species?

Bats liver longer because flight allows them to escape predators

Why do mice frequently develop cancer?

Their lifespans are really short so there is little evolutionary benefit from investing in cancer prevention mechanisms

Which animals rarely develop cancer despite having large number of cells and long lifespans?

Elephants, whales, and tortoises

Why do elephants, whales, and tortioses rarely develop cancer?

Long-lived species gained a strong fitness advantage from preventing cancer that allows them to live a long lifespan and reproduce more successfully. Natural selection favored genes that improve DNA repair and cancer suppression.

When would delayed senescence be favored?

Favored when survival rates are high

Why does aging occur?

Aging occurs partly because repair mechanisms decline over time, not because repair mechanisms are absent

What are advantages to semelparity?

-Can reproduce many offspring at once

-If environmental conditions are ideal, many offspring may survive

What are disadvantages of semelparity?

-high energy investment in a single reproductive event

-no future reproductive opportunities

-high risk if environmental conditions are poor

What is the equation for phenotypic variation?

Vp = Vg + Ve

How does height exhibit additive genetic variation?

Many genes contribute small effects that combine additively to determine an individual’s height

Define Additive Genetic Variation

It is when the effects of multiple alleles simply add together to influence a trait

-Ex: 0 tall alleles —> shortest, 2 tall alleles —> slightly taller, together

Define polygenic trait?

Polygenic traits are traits influenced by multiple genes whose effects combine to produce a range of phenotypes

Is the color of hydrangeas determined by genetics or environment?

Environment because it is based on the acidity of the soil

How can the phenotype change without the DNA sequence changing?

The expression of the gene differs, that is the gene is either turned on or off. DNA needed for the gene expression is there, just not active/expressed

Define epigenetics

Changes in gene expression that occur without changing the DNA sequence; often caused by chemical tags attached to DNA

-methyl tags; can turn genes off and later be removed to restore gene activity

What can influence epigenetic marks?

-Environmental factors such as diet, stress, toxins can change how genes are expressed without changing the DNA sequence itself

Describe the Agouti gene in mice?

-Agouti gene on increases risks of obesity, type 2 diabetes, and cancer; yellow mouse

-Agouti gene off through methylation results in a healthier phenotype; brown mouse

-this is an example of epigenetics

What are environmental effects on trait for flamingos and beetles?

-Flamingos are naturally white, however due to their diet, they eat a lot of carotenoids that makes them appear pink

-Beetles that live in areas of high nutrition develop horns and areas of low nutrients, horns are absent or really small

In heritable variation what does h² represent?

represents the proportion of the variation in a trait within a population that is due to genetic differences among individuals.

What can be used to determine the heritable of a trait?

Offspring-parent regressions

H² ≈ 1.0 → represents?

trait was passed to offspring from parents; trait was strongly genetic

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• H² ≈ 0.0 → represents?

trait was strongly determined by environmental factors

How do you interpret heritability via H² = 0.72

-72% of variation is due to genetic differences

-28% of variation is due to environmental differences

Define evolution

change in allele frequencies in a population over time; the smallest unit is the population

Define gene pool

All the alleles present in population

Define polymorphic and fixed locus

-multiple alleles present

-only one allele present

Genotype Frequency Formula is?

Genotype Frequency = Number with phenotype / total number of the population

What are the formulas for the dominant and recessive allele frequencies?

Dominant: p = f(A) = 2n_AA + n_Aa / 2N

Recessive q = f(a) = 2n_aa + n_Aa / 2N

p + q = 1

Random mating will produce genotypes of the next generation in these proportions

f(A) = p

f(a) = q

f(AA) = p²

f(aa) = q²

f(Aa) = 2pq

What metrics can we use to describe a populations gene pool?

allele frequencies

genotype frequencies

genetic variation; amount of genetic differences

heterozygosity

heritability