Evolution: Sexual Selection and Molecular Evolution

Gender

a social construct and may be comprised of gender identity and gender expression

Sex is Multivariate: Yes or No

Yes: gamete, genetics/chromosome, gonads, anatomy, physiology, reproductive role, Behavior

Sex chromosomes and determination vary widely across animals: Yes or No

Yes

advantages of sexual reproduction

1. increases genetic variation

2. gives them a survival advantage: can now adapt

3. disease is less likely to effect the population due to the genetic variation

disadvantages to sexual reproduction

1. takes time and energy to find mates

2. difficult for isolated members of the same species to reproduce

costs of sexual reproduction

1. breaks up a good thing

   1. you could have a cat who is meek but has long claws and a cat who is aggressive but has short claws

2. population growth

   1. sexual reproduction occurs much slower than asexual reproduction for example

Males make what:

A large amount of low resourced sperm

Females make what:

A small amount of high resourced eggs

females are limited by:

1. the number of offpspring they can raise

2. the number of eggs they can produce

Males are limited by:

1. access to females

simultaneous hermaphrodite

possess ovotestes that produce both egg and sperm

• they produce egg or sperm depending on the sex around them

• ex: golden hamlet (fish)

sequential hermaphrodite

animals begin life as one sex but then change to the other as adults in response to social, environmental or genotypic factors

ex: nemo (should have)

Sex role reversal

Hyenas (competitive social system)

• females present with pseudo penis’s so they do not get attacked by males

sexual selection

differential success in aquiring mates

Things needed for natural selection to occur

1. trait needs to be heritable

2. trait needs to have with reproduction or survival of the individual

sexual selection focuses on:

The reproductive success idea of natural selection

batemans rule says:

sexual selection will be stronger in males because the more partners they have the more offspring they have

• a steeper slope indicates stronger sexual selection

Members of the sex with stronger sexual selection with be

competative

Members with weaker sexual selection will be

choosy

INTRAsexual selection

competition between members of the same sex for access to mates

• aggressive males

male to male competition (intrasexual selection)

males using weaponary (fangs or antlers) to attack other males so they don reproduce with that female

Sperm competition

form of post-copulatory sexual selection where males sperm simultaneously physically compete to fertilize a single ovum

• male damsel flys penises act as bottle brushes to clean out the competitors sperm

sperm cooperation

sperm works together to help the females ovum be ferilized

• ex: European Wood Mouse, they have hooks on their sperm and those can grab onto other sperms of the same individual and aid in their swimming speed

mating strategies determine what:

The strength of sexual selection in males and females

monogamy

One male: One female

• with parental investment

polygyny

One male: Multi females

• with parental investments

polyandry

Multi Male: One female

• with parental investment

polygynandry

• Multi male: multi female

  • with parental investment

promiscuity

Multi male: multi female

• without parental investment

when should males be monogamous

1. when females are widley distributed

2. taking over a new territory with females is too costly

3. mate guarding

4. increase fitness by helping to raise young (parental care)

when should females be monogamous

• resources between mating territories are balanced

• when the pressure to provide parental care is on the male

INTERsexual selection

involves individuals of one sex choosing among members of the opposite sex based on the attractiveness of certain traits they possess

• choosy females

resources defense polygyny

When one male controls the resources needed by multiple females

Female (harem) defense polygyny

• males will choose a harem or plot of land and defend it

• ex: in seals, females give birth on land and become sexually active afterwards so males are defending one harem so that female is more inclined to come back and mate in that spot

Resource based mate choice

1. resource based defense polygyny

2. female (harem) defense polygyny

non resource based mate choice or examples of intersexual selection

1. good gene hypotheis

2. fishers runnaway selection

3. sensory exploitation

good gene hypothesis

physical traits (plummage coloration or weaponary) are an advertisement for something you cant see

ex: good health, good genetics

fisher runaway selection

female preference and a males traits co evolve together in a positive feed back loop

sensory expolitation hypothesis

female preference evolves before males trait exists

non resource based male dominance polygyny

males have to dance to attract females because males cannot easily monopolize either the dispersed resources or the females

Hamilton - Zuk hypothesis (parasite-mediated good gene hypothesis)

exaggerated sexual ornaments indicate a males additive genetic immunity to parasites

feedback loop leads to what

genetic correlation between female preference and male trait

if preference and trait coevolve together you get assortative mating

ex: short eye females prefer short eyed males and long eye females prefer long eye males

sexual conflict

reproductivee traits can evolve in response to conflicts between sexes over reproductive decisions

ex: duck genitlia

Scrambles

ability to quickly find mates early in the breeding season

ex: horseshoe crabs, they well developed sensory organs and are able to latch onto females as they approach the beach

endurance rivalry

ability to remain reproductively active for longer time in breeding season

contests

the ability to win fights for access to mates or development of alternative mating tactics for inferior individuals

mate choice

1. non-resource based behavioral or morphological traits that attract mates

2. offering of nutrition, territories, nest sites, or other resources needed by the mate for breeding

primary sex characteristics

organs or structures that are required for successful reproduction

secondary sex characteristics

phenotypic traits that differ among males and females that are indirectly used for successful reproduction

corecion

morphological or physiological adaptations that allow for forced copopulation

infanticide

the intentional killing of young offspring by a mature animal of the same species

four mechanisms of evolution

1. natural selection (non random)

2. mutations (random)

3. genetic drift (random)

4. gene flow (random)

missense mutation

adds a new amino acid that encodes for a new protein

nonsense mutation

adds a new amino acid that encodes for a premature stop codon

silent (synonymous mutations)

a new amino acid is added that encodes for the same protein

synonymous mutations

dont change the protein being made

non synonymous

changes the protein being made

neutral theory

the idea that evolution is purely based on the random mechanisms of evolution

• mutations

• genetic drift

• gene flow

neutral theory of evolution =

random substitution of one allele to another

mutation =

appearance of a new allele

substitution =

once that new allele becomes fixed (completely replaces what it arose from)

evidence that supports neutral theory

1. synonymous base substitution > non synonymous base substitutions

2. mutation rate is higher in non coding sequences

3. pseudogenes evolve at higher rate than functional genes

pseudogenes

a DNA sequence that resembles a gene but has been mutated into an inactive form

molecular clock

DNA and protein sequences evolve at a rate that is relatively constant overtime and among different organisms

pseudogenes have a higher or lower rate of molecular evolution

higher rate of molecular evolution

highly constrained genes have:

lower rate of molecular evolution because a mutation in these critical regions of a protein could be detrimental to an organism

weakly constrained genes have:

higher rate of molecular evolution because these amino acids are not crucial to the survival of the organism so a mutation here wouldn’t rlly hurt the animal

genome size in prokaryotes

there is a correlation between the number of genes and the size of the genome in prokaryotes

what percent of the human genome is coding

about 1%

gene duplications (definition)

the process where an extra copy of a gene is made leading ot mutiple copies of the same gene

gene duplication creates what:

Redudancy

• where the same portion of a gene is duplicated and put into the same portion of the chromosome (right next to each other)

subfunctionalization

both copies accumulate degenerative mutation and the functional parts of the gene are distributed among the two copies

neofunctionalization

• one of the two copies mutates to develop a different function and the other copy maintains the orginal function

what causes gene duplication

1. retroposition by transposons

2. unequal crossover during meiosis

3. chromosome duplication

partial gene duplication- transposable elements

transposons or jumping genes

• they can move from one location to the another on the genome and take whole or parts of genes with them

partial gene duplication- exon shuffling

exon

• via mistakes in crossing over

• coding region of a gene and those apparently move around

chromosomal duplication -polyploidy

ploidy

• means copy number of chromosomes

• so this an entire copy of the chromosomes or the genomes

unequal crossing over

when non homologous point on a chromosome cross over

horizontal gene transfer

passing of one or more genes through routes other than parent to offspring

types of horizontal gene transfer

transformation

• introduction, uptake and expression of foreign genetic material

conjugation

• transfer of DNA via a plasmid from a donor cell to a recepient cell

transduction

• bacterial DNA is moved from on bacterium to another by a virus