ANT 15 UC Davis

Life History

1. choices made toward survival+reproduction

2. Two factors: Timing, allocation

3. Quality vs quantity when it comes to offspring

Timing+allocation

1. Timing: when events in your life cycle occur(marriage, birth of offspring

2. Allocation: how resources are split between demands

Life history Theory

1. How evolutionary forces shape timing of events

2. Ex: how fast organism grows, what age it matures, how long it lives

3. Two life cycles: biological+cultural

Evolution

1. it is change in transmitted info through time

2. change in allele or gene frequencies from generations

Mutation

1. changing structure of a gene

2. for evolution to work, the mutation must be passed down generations

gene flow

1. one population of organisms moves with another population and then changes representation

genetic drift

1. variation in relative frequency of different genotypes in small population; making some genes easy to disappear as individuals die or do not reproduce

Natural selection

genes/traits are represented at higher frequencies in the next generation because the individuals carrying them were more successful at surviving & reproducing than others in that particular environment

Reproductive Success

1. ability to pass on genes

2. offspring production and survival

fitness

how good particular variant (gene,phenotype) is in a particular habitat

Lamarcks two key insights

1. Environment brings changes to animals

2. Life was ordered complicated and strove to become better over time

3. Ex: giraffes stretching necks over generations for leaves

Darwin's insight from Thomas Malthus's work

1. struggle for existence among plants and animals—and that the ones that were best suited to compete would survive and spread their variations to their descendants, whereas those that weren't suited would be destroyed

Three necessary and sufficient conditions for Evolution by Natural Selection

1. Populations are limited--more offspring are born than can survive.

2. This variation is heritable: offspring resemble their parents.

3. There is variation in the fitness of organisms.

Mendel's three insights into genes from his pea experiments

1. inheritance of each trait is determined by "units" or "factors" (gene)

2. individual one such unit from each parent

3. Trait may not be visible but can still be passed down

Genes vs alleles

1. Genes code for a trait

2. alleles are variants of the trait

Homozygous vs Heterozygous combinations

Homozygous: BB, bb

heterozygous: Bb

Genotype and phenotype

1. Genotype: Complete set of genes that an organism possesses

Phenotype: Observable traits of an organism

Survival of the fittest?

NO. Survival of the most adequate.

Adaptation

1. trait that has been shaped by natural selection

2. has a function, might not be obvious

3. traits can change function or make it nonfunctional

Ways of identifying adaptations

1. Traits that are complex, costly, or highly unique

2. If the same trait appears independently in different species

Phenotypic plasticity

Some genes code for traits that are invariant (e.g., eye color), others respond flexibly to the environment.

Heritability

the ability of a trait to be passed down from one generation to the next

Individual selection vs Group selection

1. Individual selection: selection acts at the individual level to favor/disfavor traits

2. Group selection: proposes that some traits are favored at the group level even if they should be disfavored at the individual level

Tinbergen's 4 Levels of Causation

1. Proximate: Immediate.

2. Ultimate: happening at the end of the process. 3.Contemporary: happening now.

4. Chronicle: a sequence of events

Phylogeny

Evolutionary history of a species

Altruism

when an organism behaves in ways that benefit other organisms at a fitness cost to itself

Mechanisms that explain most altruism

1. kin selection

2. reciprocity

Kin selection

1.selection that favors traits that increase the reproductive success of other individuals that share much of the same genetic material.

2. i.e. Close Relatives

Hamiltons rule

Selection favors altruism when the following occurs

Reciprocity

When an organism temporarily reduces its fitness for another with the expectation of the other organism acting or returning such behavior in the future

What are vampire bats doing

1. Need to eat 50-100% of their body weight in blood every night; Will starve after 60 hrs without eatingLose up to 25% of body weight and unable to maintain their body temperature

2. healthy will share with weak

Tolerated theft

give because cost of defending the resource is less than the benefit

Asexual reproduction

reproducing without sex

cost of meiosis

You only get to pass half your genes on to your offspring

cost of recombination

Must combine male and female genomes without making major mistakes. Recombination also may lead to loss of beneficial traits.

cost of mating

1. Energy spent on finding and competing for mates

2. Vulnerability to predators while mating

3. Exposure to sexually transmitted diseases

4. Injury during sex

why has sex evolved

1. Gets rid of harmful mutations

2. Produces beneficial genetic variation

Lottery Hypothesis

You don't play the same number on every ticket.

tangled bank hypothesis

Variety of offspring also helps to eliminate competition for resources

Red queen hypothesis

stay one step ahead of parasites that might adapt to a stable genotype

Disruptive selection

process by which extreme values for a trait are selected over intermediate values

This process selected against mid-sized gametes, leaving small (sperm) and large (egg) gametes

Intitial Inequity of Sex: Egg vs Sperm

1. difference in size

2. female= larger gamete

3. male= smaller gamete

batemans principle

The idea that, since eggs require greater energy to produce than sperm, females should be choosier sex and this should result in greater variance in the reproductive success of males.

coolidge effect

Males show continually high sexual performance or motivation given the introduction of new receptive females

Darwin's observations that led to the idea of Sexual Selection

1. Males are usually larger, generally have larger horns, antlers, and teeth

2. Male-male aggression more frequent than female-female aggression

3. Males aggressively pursue females more often than females aggressively pursue males

4. Males have more adornments, brighter colors, sing, and display more in mating rituals

what is sexual selection

sexual selection: male & female

Three types of sexual selection

1. Intersexual choice

2. intrasexual competition

3. intersexual coercion

intersexual choice

1. members of one sex, usually females, chooses which members of the other sex can copulate

2. Female Choice

intrasexual competition

1. members of one sex, usually males, compete to gain mating access to the other

2. Male-male competition

intersexual coercion

members of one sex, usually males, use force to obtain mating access from the other

handicap principle

the greater the handicap an individual carries, the greater its ability must be to offset that trait

"sexy son" hypothesis

If males develop a trait that leads to female mating interest, it will increase in the population even if it has no direct fitness value

male competition

Greater in polygynous species where males have higher variance in reproductive success...and more competition for mates. Remember that if one male has many mates, other males may have none

sexual dimorphism

distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves.

sperm competition

males in some species develop equipment to maximize their sperm's chances of fertilization-large testicle size

sexual coercion

1. Differing pressures on the sexes can lead to conflicts of interest

2. Males may not be satisfied with not being chosen, and other males are not always available to protect females

3. Males may wish to protect their investment-Exacerbated when males have already been selected to be large and aggressive

4. Can result in coercive mating tactics: forced copulations, sequestration, and aggressive mate guarding

exception proving the rule

1. shorebirds

2. females are larger than males

3. females defend one male and compete to defend large territories

principle of allocation

the principle that if an organism allocates energy to one function, it reduces the amount of energy available to other functions

life history trade offs

1. Offspring quality versus quantity

2. Current versus future reproduction

3. Mating effort versus parenting effort

Principle of allocation

not possible to invest in growth and reproduction at the same time

allometry

correlation of traits to body size

Primates are "Slow" Species

Compared to another mammal of the same body size, primates mature even slower and live even longer; however, compared to another mammal of the same body size, primates have even slower rates of reproduction.

Closest Living Relatives

Orangutan, Gorilla, Chimpanzee, Bonobo

individual variation

1. a considerable variation within species: Within species

2. individuals differ in their energy budgets

3. i.e., one individual chooses to buy a house or a car; another can afford to buy both!