Evolution of Sex

Question 1

what is sex?

Answer 1

recombination (genetic material is broken down and shuffled to create unique offspring genetic profile)

reproduction (sexual or asexual, coupled or not with recombination)

Question 2

sexual reproduction

Answer 2

reproduction that has:
- production of haploid gametes via meiosis
- fusion of gametes to produce diploid zygote
- new genetic combination in zygote via crossing over

Question 3

asexual reproduction

Answer 3

production of new individuals without creating new genetic combination (parthenogenesis). Doesnt need meiosis or fertilization, just one parent. much faster.

Question 4

which form of reproduction came first?

Answer 4

asexual

Question 5

4 costs of sex

Answer 5

1. cost of breaking up co-adapted genes: if genes adapted to be together, recombination may break them up.
2. cost of making males: males cant produce eggs, but use up a gamete
3. cost of STDs
4. cost of finding a mate and mating: predation risk, time, energy

Question 6

why have sex?

Answer 6

1. sex clears deleterious mutations: recombination allows new, potentially advantageous combinations of genes to come together, and harmful mutations can be eliminated or masked
2. sex helps create wider range of offspring genotypes: allows response to environment, increased rate of evolution or adaptation.

Question 7

red queen hypothesis

Answer 7

constant arms race between predator and prey, each tries to gain the upper hand

Question 8

2 reasons why sex must be advantageous

Answer 8

evolution: sex is very common, ancient asexual lineages are rare
ecological time: some species that are asexual will flip into sexual reproduction sometimes

Question 9

new zealand mud snails parasites + lifecycle

Answer 9

parasitic worms infect snails, but the worms need ducks to complete life cycle. they reproduce sexually where there are lots of parasites, near edge of river. but asexually away from parasites, at bottom

Question 10

dimorphic gametes

Answer 10

gametes of males vs. females look different

Question 11

isogamy

Answer 11

equal sized gametes

Question 12

2 assumptions in the model for evolution of dimorphic gametes:

Answer 12

1. trade off between size and number (more gametes = smaller gametes)
2. zygote fitness increases with size.

Question 13

type of selection on dimorphic gamete evolution

Answer 13

disruptive selection, as males and females went to opposite ends of the spectrum. females have few large gametes, males have many small gametes.

Question 14

fitness benefits of dimorphic gametes

Answer 14

large gametes (female) lead to increase fitness
small gametes (males) are selected because theres more of them to compete for fertilization.

Question 15

anisogamy

Answer 15

gametes of different sizes

Question 16

gametic investment with anisogamy

Answer 16

males have smaller gametic investment since their gametes are smaller and devoid of nutrients. have many of them.

females have larger gametic investment since their gamete are large and nutritionally rich. have few of them.