lecture 19 Flashcards

sexually

individual that produces both female and male gametes

hermaphrodites and can receive sperm from other slugs, deliver sperm to them, or fertilized their own eggs

reproduction in which the female sex cells undergo meiosis but are not fertilized by sperm

only daughters

asexually, sexually/asexually

more variable offspring

faster than sexual lineages because all progeny produce offspring (sexual lineage, half males that cannot produce by themselves, halving rate of replication)

asexual lineages grow more rapidly each generation, sexual cannot

males and females must locate each other in order to mate, takes time, energy, and risk of predation

sexually reproducing organisms pass half of alleles to offspring from meiosis, halves the relatedness between parents and progeny

mating provides effective means of transmission for many pathogens, asexual avoid this risk

combining alleles of genes can bring separate beneficial mutations together in a single individual faster than would be expected if they had to arise spontaneously in the same genome

thru recombination, meiosis provide chromosomes to cross over, creating gametes with unique combinations of alleles

offspring of sexual parents are more genetically variable than asexual. speed evolutionary response to selection (red queen effect)

sexual populations can purge themselves of harmful mutations, exclude deleterious mutations. asexual cannot, they steadily accumulate mutations until extinct (Muller's ratchet)

genomes of asexual population accumulate irreversible, deleterious mutations over generations

the burden of accumulated deleterious mutations increases over time

either asexually or sexually

fixation in asexual populations but are purged from sexual populations due to recombination

sex beneficial

to maintain relative fitness, coevolving populations must constantly adapt to each other.

more readily when a species' environment changes rapidly

can be favored when selection varies over space, as long as the genetic associations created by migration are locally disadvantageous.

organism both sexually and asexually tend to switch to sex under stressful conditions

with limited number of individuals in population, selection erodes and leaves only hidden variation. recombination then reveals hidden variation, improving response to selection

hidden in the sense that plus alleles at the first site are found with minus alleles at the second site (or vice versa) (this problem is irrelevant in an infinitely large population)

differential investment in reproduction

sexual reproduction involving the fusion of two dissimilar gametes

differ for the sexes

fecundity (number of eggs produced)

number of mates they can obtain

extend past fertilization

male parental care is less common

the probability that a male is the genetic sire of the offspring his mate produces

certain maternity

alters operational sex ratio

a 1:1 sex ration is an evolutionarily stable strategy

ration of males to females capable of reproducing at a given time

competition between members of the same sex (usually males) for access to mates

members of one sex (usually females) choose members of the opposite sex

differential reproductive success resulting from competition for mates (intrasexual and intersexual selection)

males (male biased OSR leads to males outcompete other males for access to females)

attractive traits that incerase mating success

weaponry used to outcompete other individuals

intense sexual selection

territory

benefit the female directly

benefits that affect the genetic quality of the female offspring

male redback spiders will sacrifice their lives to copulate longer with female (higher chance in passing their genes and break the female's reproductive system)

elaborate ornaments

level of advertisement reveals mate quality

females prefer males with handicaps (mating characters that reduce survival chances) because they are indicators of heritable viability

an assemblage of rival males who cluster together to perform courtship displays in close proximity

pre existing sensory bias

certain male traits are advantageous not because they indicate good quality, but but simply because they are attractive to females.

elaborate or bright male ornaments signal underlying good quality (good genes)

alleles for female preferences can coevolve with alleles influencing expression of costly indicator traits in mates

honest signals of better health

one male pairs with one female (sexual: exclusively, social: pair but may cheat)

males mate with multiple females

females mate with multiple males

sexual monogamous

for male traits that increase paternity rates

occurs when females mate multiply and ejaculates from different males overlap and compete for fertilization

larger testes in primates (males testes are larger in species where females regularly mate with multiple males)

a form of sexual selection that arises after mating, when female store and separate sperm from different males and thus determine which sperm they use to fertilize their eggs

traits that confer a fitness benefit to one sex but a cost to the other (traits cevevolve antagonistically)

through sexual conflict

Drosophila were experimentally forced to mate monogamously, had lost their defenses against seminal proteins, so females died at much higher rate when mated with normal males