Evolution of the sexes and sexual reproduction

Question 1

What is recombination?

Answer 1

combining of genomes such that offspring differ gentically from their parents an siblings

Question 2

What is Reproduction?

Answer 2

can be sexual or asexual can be coupled or uncoupled from recombination

Question 3

what is sexual reproduction( sygnamy)

Answer 3

the fusion of two gametes

Question 4

Sex

Answer 4

is defined by the type of gamete the organism produces. males have small gametes , females have large gametes

Question 5

male and female in biology are defined

Answer 5

by the size of gamete they produce not by morphology, behavior or evene genes

Question 6

what is the benefit of sexual reproduction

Answer 6

• to increase the rate of evolution

Question 7

in what ways does sexual reproductin increase the rate of evolution

Answer 7

• by increasing the rate of beneficial mutations and decreasing the rate of disadvantageous mutations.
• it decreases the rate of extnicition

Question 8

Why is the above argument above sexual reproduction false

Answer 8

-1 only works for large populations
-2 based on group level selection not individual
-3 evolution doesnt anticipate benefits it acts on what’s present
-4 it ignores large costs associated with sexual reproduction

Question 9

What is the cost of sexual reproduction

Answer 9

• Genetic cost ( Break up of advantageous combinations of alleles)
• Ecological ( time, effort, risk and competing for mate
• demographic individuals with mitosis can perform 5-100 times more cell divison than those in meiosis
• the demographic cost of sex- cost of producing males two fold cost of females in the population.

Question 10

what is the Modern hypothsis

Answer 10

muller ratchet

Question 11

what does the muller ratchet theory states

Answer 11

• it states that sex may have evolved to reduce the gradual increase of negative mutattional load.

Question 12

what is mutational load

Answer 12

it s basically the accumulation of deleterious mutation decreasing the fittness of individual.

Question 13

Muller pointed out

Answer 13

if reproduction is asexual then such deletrious mutation willl be rapidly and succesivily be transferered from generation to generation all exipernce loss in fittness.

Question 14

The maximal fitness an individual in mutational load can exipernce is

Answer 14

the individual with the fewest new mildly deleterious mutattion.

Question 15

Sex allows

Answer 15

the population to escape from the rachet and the hatchet by purging deleterious mutations

Question 16

How is the muller ratchet hypothesis different from combinining mutation hypothesis

Answer 16

muller hypothesis works with what’s already present in the population. evolution need not anticipate future benefits.

Question 17

What does the Red Queen hypothesis say ?

Answer 17

• sexual reproduction continually generates new combinations of alleles that the parasite has to asapt to

Question 18

why does sexual reproduction increase variation

Answer 18

-as a way of enagaing in a coevolutionary arm race with another organism often with parasite and pathogens.

Question 19

what is coevolution

Answer 19

• Evolutionary process by which an adaptation in one species leads to the evolution of an adaptation in which it interacts.

Question 20

how does a host body adopt in new enviroment

Answer 20

it increases variation and the resistance form will be favored by selection

Question 21

good example of red queen hypothesis

Answer 21

• The newzeland mud snail parastized by a fluke flatworm called microphallus

the third organism is a duck

Question 22

what is the life cylce of the fluje microphallus

Answer 22

• adult flikes live in duck guts
• duck poops eggs from the fluke enter the water
• they become larvae and and swim to snails and go into their tissue.
• they become cysts
• and then are ingested by ducks when they eat snails, become mature and start the cycle again.

Question 23

what is a definitive host

Answer 23

• host that supports the adult stage of fluke
  ( the duck )

Question 24

what is an intermediate host

Answer 24

• any other host that support other stages of a parasite fluke.

Question 25

comparison between ducks and snails on reactinon with fluke

Answer 25

ducks are not so bothered by it but instead the snails are very much affected their tissues get replaced by the reddish larvae.

Question 26

what do snails do in return

Answer 26

there is a strong selctive pressure for the snails to develop a defense mechanism against the fluke on the other hand there will be a strong selcetive pressure on the fluke to develop a mechanism to overcome the new variation. ( supports the red queen hypothesis)

Question 27

what does it mean by sexual reproduction is costly

Answer 27

- it wastes resource on males who are a waste of time, energy and place beacuse they donnot contribute to an increase in popoulation.

Question 28

what happens to assexually reproducing clone when flukes are absent from the lake

Answer 28

- the assexual clone dont have to be scared of taking over.

Question 29

what happens to assexually reproducing clone when flukes are present from the lake

Answer 29

- as the assexual clone population rise they become an easy target as they all share the same genome - all the clones would have the same defense mechanism. - eventually the fluke will take over as the assexual clones won't be able to change their defense mechanisms.

Question 30

where would you expect to see asexual clones

Answer 30

in deep water becasue the duck poop out and feed on shallow water

Question 31

summarize what happens in newzeland lake ( the Red queen hypothesis theory)

Answer 31

- in low parasite pressure might favor assexual clones but overtime it take over if the assexual clones become common in high parasite pressure the assexual clones get taken out - in either case there is a constant turnover of the asexually reproducing clones with the common ones. the common ones being decimated by flukes and replaced with rare clone with diffrent mechanism Eventually they too get heavily invested and die out

Question 32

what is Daphnia pulex

Answer 32

its a water flea that can switch being sexual and assexual

Question 33

What is synonymous and non synonymous

Answer 33

- many fewer non synoymous changes on asexualy reproducing - similar number of synonymous mutation in sexual and asexual populations.

Question 34

Most non synonymous changes

Answer 34

are very hamful thus we would expect fewer non synonymous changes most likely to be subject to purifiying selection ( elimnated by natural selection)

Question 35

most sysnonymous changes

Answer 35

accumulate because they dont matter to the protein sequence and they can pile up without having an effect. mostly they have the same rate in both asexual and sexual population.

Question 36

strongly vs mildly deleterious mutation.

Answer 36

strongly - they are highly selected against in all individuals because they cause death mildly - tend to presist in asexual population but they are easily elimnated in sexual populations becasue of recombination

Question 37

Purifying selection

Answer 37

ka/ ks less than 1 nonsynonymous/ synonymous nonynonumous have to be smaller than the synonymous or we are cooked.

Question 38

Ka/ ks ( sexual) vs assexual

Answer 38

the ratio smaller in sexual