9.1 mating

mating system

pattern of male and female paring including monogamy, polygyny, and polyandry

monogamy

one male and one female

polygyny

one male and multiple females

polyandry

one female and multiple males

what is male/female defined by?

the relative size of gametes they produce

what do males produce?

small motile gametes (sperm), large number of gametes, invests little in each gamete

what do females produce?

large gametes (eggs), relatively small number of gametes, invests heavily in each gamete

What does the “underlying asymmetry between females and males” cause?

it causes them to approach mating with differing and sometimes conflicting interests

why do two sexes exist?

because natural selection on gametes favored the extremes: small and large

why were small gametes favored? tradeoff?

because they are fast and could travel quickly, but the trade of was reduced nutrient content

how is the tradeoff in small gametes balanced?

by fertilizing larger, nutrient rich gametes

do medium sized gametes matter?

no

what is this “disruptive selection” ,meaning that it destroyed the middle, though of?

the selective force that resulted in two sexes

what are hermaphrodites?

animals that can produce both eggs and sperm

what are simultaneous hermaphrodites?

male and female at the same time

what are sequential hermaphrodites?

first one sex then the other

sexual reproduction

the process of combining sexual genetic material from two parents through fusion of gametes. offspring are novel combinations of genes.

genetic recombination from meosis

process of removing half of the genes after mixing chromosome pairs (diploid to haploid)

fertilization

gametes fuse to create a zygote (haploid to diploid)

why does sex exist?

benefits outweigh the cost

sex has high evolutionary cost. which is?

the cost of meiosis is that half the genome is lost

high evolutionary cost in sexual reproduction

animals pass only half of their genes to each off spring

high evolutionary cost in asexual reproduction

animals pass all of their genes to each offspring

what is the benefit of reproduction?

genetic recombination and genetic diversity among offspring

what is sexual reproduction most common in?

vertebrates, birds/mammals

asexual reproduction is more common in…

intervertebrates, example is fish

where is asexual reproduction useful?

in environments that change little between generations

where does asexual reproduction sometimes occur?

in pioneering species where single animal migrates to habitat

can some animals switch between asexual and sexual reproduction?

yes

examples of animal that can switch between sexual and asexual reproduction?

sea anemones

in stable environments… sea anemones….

maintain their genetic combination via asexual reproduction

when colonizing new habits (dispersal) sea anemones

use recombination and offspring diversity via sexual reproduction