lesson 5 evolution of sexual reproduction

asexual

1 parent, n→n or 2n→2n ploidy level, no gametes involved, clone, faster, all members produce viable offspring

sexual

2 parents or 1 if hermaphrodite, n→2n, gametes involved, variation, slower, only female can produce viable offspring

very costly compared to asexual reproduction
its maintenance is due to the advantages it provides
improves the fitness of the offspring produced (increases quality of progeny)

why have sex

creates variation
provides mechanisms to improve genome at the molecular level

advantages of sexual reproduction that drives its maintenance

creates variation

-combine the effexts of two beneficial mutations in the same indiv
-creates new gene combi that may be more fit than prev ones, or may simply lead to reduced competition among relatives.
-bring together currently deleterious mutations to create severely unfit indiv that are then eliminated from the population

muller’s ratchet

the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner; demonstrates the advantage of sexual reproduction over asexual reproduction

hermann joseph muller

proposed the muller’s ratchet mechanism

muller’s ratchet

a mechanical device that permits movement in one direction but not the opposite direction; the steady and irreversible accumulation of mutations.

recombination

muller’s ratchet does not apply to sexual organisms because of

recombinational dna repair, complementation

mechanisms to improve genome at molecular level

recombinational dna repair

repair genetic damage via homologous recombination of chromosomes during meiosis; an adaptation for repairing the genomic dna, which is passed on to progeny

complementation

masking of deleterious recessive mutations

hybrid vigor or heterosis

complementation is also known as

most primitive form of sex

may have been one organisms with damaged dna replicating an undamaged strand from a similar organism in order to repair itself

selfish parasitic genetic elements

sex evolved from ancient haloarchaea through a combination of jumping genes and swapping plasmids

non random mating

could be partly due to sexual selection

sexual selection

favors one mate at the expense of others, some traits promote their own passage into the next gen by helping bearers win mating opportunities

selfish gene

gene centered view of evolution in that genes that are passed on are the ones whose evolutionary consequences serve their own implicit interest in being replicated, not necessarily those of the organism

Richard dawkins

selfish gene is proposed by ___ as a buildup from george william’s theory on adaptation and natural selection

charles darwin

sexual selection is originally proposed by

sexual selection

can be thought of as two special kinds of natural selection by competing or preferring

sexual dimorphism

differences in form between males and females abound

isogamy

gametes are identical in appearance; microalgae and protists

anisogamy/ heterogamy

male and female gametes are distinct in size and shape

male contest, female mate choice, male mate choic

sexual selection in humans is driven by the ff

male contest

larger, stronger and more aggressive males are characteristic of species with ___; function in threatening rivals

female mate choice

dom males are more likely to be chosen by females bc dom males had access to better resources or territory; intelligence and creative displays

genetic quality

women also choose mates partly on ____; good genes mate choice

geoffrey miller

leading proponent of a theory that men’s brains and creativity are designed to attract females; diplays of neurophysiological efficiency advertise heritable fitness

mating-mind hypothesis

offers explanations for the evolution of large human brains and behaviors such as humor, music, and poetry that do not have obvious survival value

creative displays

represent an alternative mating tactic to male contests

male mate choice

expected to have been more important in shaping women’s traits; women compete to look attractive and possess anatomical traits that appear to have been shaped by