Heterozygote Disadvantage

• depends on allele frequencies
• allele with higher frequency will survive
• unstable type of selection
• allele arises in short amount of time
• hard to notice in natural environment
• less common allele found in heterozygote (which is why it diminishes so rapidly)

• advantage because of a rare phenotype
• predators recognize the more common phenotype and form a search image
• maintains variation
• frequency of rare phenotype increases until it outnumbers the common phenotype (in that case the selection would reverse)
• 'balancing selection'

• Prey learns to recognize warnings (colours)
• stay away from the certain phenotype
• Ex. If all frogs are poisonous, the predator will avoid the most common, even though all are poisonous
• Gets rid of variation
• Less common forms die off

• Can only be caused by selection
• However, it is not the only force that causes a population to evolve

• no selection
• no mutation
• no gene flow
• random mating
• very large population size

• random sampling error due to finite population size
• a random change in allele frequencies
• The large a population is, the less effective genetic drift is
• Always operating, but stronger or weaker depending on the population size
• can oppose selection, but it depends on the selection, and the population size
• the larger the population, the less likely genetic drift will have any effect on it
• increases genetic variation between populations
• if the selection is small its more likely genetic drift will get rid of it

• Eventually, one allele drifts to fixation, while other alleles are completely lost

• isolated and closed to gene flow
• high frequencies in certain alleles
• founded by a small number of individuals that left a large number of source populations
• by chance, the allele became abundant

A: mutations

• new alleles can only come from mutations
• it's not random, however, there are factors that make mutations more or less likely
• a lot of mutations have no effect on fitness
• mutation rates are generally low
• the environment does not have any effect on getting 'good' mutations

A: migration, moves alleles between populations

• introduces new alleles to a population
• often opposes selection

A: False. Gene flows operate in opposition to natural selection. 

Natural selection wants less variability, while gene flows promotes variation.

• involves a single trait
• eye colour, hair colour, height, etc

• mating of individuals having traits more dissimilar to one another
• aggressive bird with a calm bird

• inbreeding
• inbreeding avoidance
• assortative
• disassortative

• AA with AA will produce AA
• aa with aa will produce aa
• Aa with Aa will produce Aa, but also AA and aa
• increases the number of homozygous individuals

• dominance status of alleles
• frequency dependence
• time
• available genetic variation
• trade offs (attracting mates with colours vs. trying to survive)

Genetic recombination

• single celled organisms have sex without reproducing
• binary fission --> share genetic information without dividing
• parasexuality
• a lot of organisms reproduce asexually
• a lot of organisms can do both

• means 'two houses'
• male and female gametes are from two different 'houses'
• have to have a male and a female

• both male and female parts housed together
• hermaphrodites

• every individual belongs to one sex and then at some point switches to the other sex
• bluestreak wrasse, clownfish

• if you have less to lose by being a male, you will be born as a male first
• after a certain point you may have more to gain by being the opposite sex, so you will change

• You have more to gain by being born a female, but may change to male

• Asexually
• pretty much everything but plants and animals

• 99.9%

• Mutations bring different allele combinations together
• population evolves faster
• increases the speed of harmful mutations being weeded out
• increases the speed of good mutations being added
• decreases the likelihood of extinction! :D 

• says that the number of harmful mutations increases over time
• in asexual organisms, these harmful mutations increase over time
• there is no way of completely losing them
• sexually reproducing breaks this ratchet-ass ratchet
• introduces more scatter in these results

Discussion Question:

Dandelions have bright colouration, this is an adaptation from sexual reproduction

Still produces pollen à vestigial traits that reflect that they evolved from an ancestor that reproduced sexually

Why did the dandelion evolve to reproduce asexually?

Selection on individuals is always stronger than selection on species.

Sexual. The variation of offpsring provides better odds to have the genotype required to survive the change.

• 'running to stay in the same place'
• co-evolutionary arms race
• new and rare genotypes have high fitness
• when parasites are common, producing new combinations of alleles is advantageous
• worms can do both kinds of sex, but reproduce sexually when there are many parasites

Long term:

-removes harmful mutations and combines good mutations

Short term:

-Bet hedging in a changing environment, out racing natural enemies

-Ecological explanations are the main reason why sex persists moreso than asexual 

Asexual. Sexual is really costly.

• Female choice
• choose who has the best displays
• one sex chooses the other

• Large size, appendages etc, decides who gets to mate with the opposite sex

Yes. With the Satin bauerbird (bowerbird?) example MacShack did in class, the female bird looks at the bauer the male made and evaluates it for the pretty colour blue (intersexual), but other male birds can come in and place other colours in it or mess it up in general (intrasexual).

Spreading their genes to as many women as possible.

Males.

Neither, they are exactly the same between males and females.

It costs more to make eggs, while sperm are cheaper to produce.

Male seahorses take fertilized eggs from the female and care for them. Because of this, the female seahorses compete for the males that are larger in size. (sex role reversal)

More in parental care= limiting resource

• The prisoner's dilemma refers to the example of, when two people are in prison, they can either look after themselves and out the other person (get out scott free), or they can wait and hope that the other person waits too.
• If both defect to maximize their fitness, they get 8 years.
• If they both wait, they get 0 years.
• If one dude outs the other, the other dude gets 10 years.
• What do you do?
• In terms of cooperation, it's irrational to only look out for yourself (get you 8 years)
• Because of this, species cooperate to make sure their genes are safe

-Someone makes a rational, selfish decision and as a result, the groups suffers

-Ex, everyone shares the pasture that the cows graze in

If you keep adding more cows, the pasture will be overgrazed and no one gets the benifits 

-its better to cooperate

• Small groups. This way individuals interact many times, and acts are more likely to be reciprocated.
• In larger groups, individuals come and go, and it's harder to get the bond needed for altruistic behaviour.

Random thing to know: 

Whenever there is divergence in interest, there is potential for conflict.

• The Biological Species Concept
• just because individuals may look alike does not mean they will produce viable offspring
• must freely produce offspring with fitness

1. Cannot use it on bacteria or other unicellular organisms that reproduce asexually

2. Extinct species

3. Allopatric populations that aren't in the same geographical area

True. A lot of species like to reproduce together, although they're of two different species. 

A population becomes isolated and gene flow stops because there is a physical barrier in the way

(river, earthquake, big drift)

This results in :
1. Isolation

2. Divergence

3. Drift

 Peripatric Speciation

(subset of allopatric)

Still a physical barrier, but instead of both populations changing, only one does. (Not a large enough group isolated to change bigger population)

-population sizes are small

-genetic drift happens very quickly

-different selection pressures on island compared to the mainland

No, it depends on how diverged they are. If they're not far diverged, they can resume interbreeding.

-one male and one female raise offspring

-males compete against males

-females compete against females

-does not mean you reproduce with that one mate forever

-on the side seek out short term mating opportunities while keeping your long term mating opportunities

-resource holding potential (wealth and financial stability)

-kindness to children

-physical attractiveness

-athletic ability

-cues indicating health

-physical attractiveness

-youth

-health

-fertility

-child bearing years

-small waist in proportion to hips

-facial features indicating a lot of estrogen

-facial and bodily symmetry

-symmetry is wanted across all cultures, because it indicates disease resistance

-they have each other's backs

-bring down prey together

-help raise young

-division of labour

(all examples of cooperation)

If they don't need the survive, they won't wait around to be highly virulent. 

If the pathogen is very young in evolutionary time, it hasn't had enough time to find the right balance of being harmful.

There's a cost and a risk of parsites being too harmful

However, there are benefits to high virulence

If highly virulent, it's much easier to transmit the virions

Depends on how easily the virus, or parasite, can colonize itself within the host

Direct Contact --> need the host to be alive and moving around, so the virulence will be fairly low

Indirect Contact --> surivorship of host doesn't matter (infected water, insects) so the virulence will be fairly high

This is a result of the modern day environment being different from the environment we are adapted to because of our ancestors.

Ex: -myopia because ancestors didnt need to close up as much as far away

-diabetes because ancestors weren't exposed to as many sugar rich foods

-auto immune disorders because ancestors lived in dirtier conditions

One gene has multiple effects.

Selection maintains a harmful trait because it benefits fitness in another context.

-temporal 

-ecological (different habitat)

-behavioural (not attracted to each other's behaviour)

-mechanical (prevents the physical transfer of sperm)

-hybrid inviability: hybrid is born dead

-hybrid sterility: hybrid cannot produce young

-hybrid breakdown: first generation of hybrids are viable and fertile but further hybrid generations are sterile

pressure put on females because they run the risk of producing hybrids

favours prezygotic isolation

anything that allows females to discriminate between populations is favoured

speeds up speciation

Two extreme phenotypes, each with high fitness, mate with each other but not with the intermediate phenotype.

--> formation of two separate species

2 equally likely explanations

-common ancestor didnt have it, it came in lineage

-common ancestor had it, and it was lost in lineage

two equally likely explanations

-common ancestor had the trait and it was lost

-common ancestor didn't have the trait and it appeared

A population of pigs has 3 different alleles: B, W and R. How many different genotypes are possible?

3

6

8

9

How does selection influence the amount of genetic variation in a population? (eg, number of alleles maintained at a locus?)

a) no effect

b) reduces variation by weeding out harmful alleles

c) increases variation, by enhancing production and spread of beneficial alleles

d) depends on which genotypes/phenotypes are favoured and under what conditions

A population of birds colonizes an area in which the insects upon which they feed live inside trees. Which of the following events accounts for an observed increase in average beak size in the bird population over time?

a) increased fitness of large-beaked birds, leading to natural selection

b) increased fitness of the large-beaked birds, creating a new species

c) decreased fitness of small-beaked birds, creating a new species

d) decreased fitness of the insects, allowing the birds to catch them more easily

Cladograms (a type of phylogenetic tree) constructed from evidence from physical characteristics are based on similarities in

a) mutations to homologous genes

b) the pattern of embryological development

c) biochemical pathways

d) morphology

Which of these conditions should completely prevent the occurrence of natural selection in a population over a period of time?

a) the population lives in a habitat where there are no competing species present

b) the population size is large

c) the environment is changing at a relatively slow rate

d) all variation between individuals is due only to environmental factors

Adaptive radiation is thought to be the process by which the diversification of mammals occurs, such as at the end of the Cretaceous Period, when dinosaurs became extinct and mammals become more prevalent. Rates of adaptive radiation typically are at their highest in which of the following situations?

a) in very large, randomly mating populations that are isolated

b) when new niches become available

c) when many species are competing for the same resource

A cell with a diploid number of 12 chromosomes undergoes meiosis. What will be the product at the end of meiosis?

a) 2 cells each with 12 chromosomes

b) 4 cells each with 6 chromosomes

c) 2 cells each with 6 chromosomes

d) 4 cells each with 12 chromosomes

In humans, the gene for polydactyly (extra fingers and toes) is dominant over the gene for the normal number of digits. If two parents that are both heterozygous for polydactyly produce four children, what is the probability that they could have a child with a normal number of fingers and toes?

a) 3/4

b) 1/2

c) 1/4

d) 4/4

The allee for red flower colour (R) in a certain plant is co-dominant with the allele for white flowers (R'). Thus a plant with the genotype RR' has pink flowers. Tall (D) is dominant to dwarf (d). What would be the expected phenotypic ratio from a cross of RR'dd plants with R'R'Dd plants?

a) 9:3:3:1

b) 50% pink, 50% white, and all tall

c) 1:1:1:1, in which 50% are tall, 50% dwarf, 50% pink and 50% white

d) 3:1

Of the mutation types below, which one is least likely to affect the function of the protein corresponding to to the gene where the mutation occurs?

a) deletion of a single base

b) base-pair substitution 

c) insertion of a single base

d) nonsense mutation 

A cell in the testis (LOLZ) of a male chimpanzee (Pan troglodytes) contains 48 chromosomes. It is about to undergo meiosis. How many molecules of DNA will be present in the nucleus of the sperm cells just after the second meiotic division?

a) 96

b) 48

c) 24

d) 12