Origin Of Sex And Sexual Selection

Question 1

Anisogmy

Answer 1

Differential investment in reproduction
F: produces few, well-provisioned eggs
M: produce many cheap gametes

Question 2

Sex costly

Answer 2

-sexual behavior is time-consuming, dangerous, not all mating results in fertilization

Question 3

Sex dangerous

Answer 3

• male tree frogs: Call to attract mates, also attracts carnivorous bats which come in on calling mate and eat
• calling cricket males

Question 4

Contributed to evolution and diversification of eukaryotes

Answer 4

• increased O2 concentration, switch to aerobic respiration
• global climate change- major ice age
• evolution of sexual reproduction

Question 5

Incoming mutations

Answer 5

-most are deleterious : decreases population mean fitness by 1-2% each generation

Question 6

Benefit of Sex

Answer 6

Recombination provides a mechanism for genomic repair, eliminating deleterious mutations
-parents can produce offspring that have higher fitness genotypes than themselves

Question 7

Red Queen hypothesis of evolution of sex

Answer 7

Without constant evolution, pathogens, competitors, change and would eliminate species
-sex and recombination provide neccassary variation that keeps evolution going

Question 8

Evolutionary arms race

Answer 8

Natural enemies, predators, parasites etc of any species evolve every generation to better exploit their hosts, capture their pray and push aside their competitors
-red queen, a natural outgrowth of evolutionary arms race

Question 9

Sex advantageous in face of

Answer 9

Environmental change. Man species switch between sexual and asexual repro. Turn to sex when faced with an imminent change in environment your

Question 10

Sexual selection

Answer 10

Accounts for many elaborated traits and behaviors
-occurs only when access to one or other sex is limiting (when there is competiton for mates or offspring)

-individuals with favorable traits experience increased success at attracting mates and breeding: they “win” the struggle for mates

Question 11

Parental investment

Answer 11

Any investment by parent that increases offspring chance of surviving and reproductive success at the cost of the parents ability to invest in other offspring

Question 12

Intrasexual selection

Answer 12

Direct competition for mates between members of the same sex, usually male-male competition

Question 13

Intersexual

Answer 13

Differences in attractiveness to the opposite sex, usually non-random mate choice by females

Question 14

Assymetric nature of sexual selection leads to dramatic..

Answer 14

Sexual dimorphism in characters

Question 15

Male-male competition

Answer 15

• sex sel can be v strong and often opposes NS this lead to maladaptive male traits
• can explain many morphological and behavioral traits (exaggeration of body size and horn size )
• often does stop with successful mating
• there is often post-copulatory competition (SPERM)

Question 16

Nuptial gifts

Answer 16

Male hanging flies present female partners with insect food items
-“size of gift” correlated with duration of copulation and number of sperm transferred

Question 17

Male provisioning can go a little too far

Answer 17

• males mate just once

- transmit sperm while being eaten (but more likely to mate successfully)

Question 18

Reasons for female choice/ preference

Answer 18

Direct benefits;
-increased nutrition, provisioning, paternal care that increase their reproductive output or offspring quality

Indirect:

• good genes hypothesis
• sexy son hypothesis

Question 19

Good genes

Handicap principle

Answer 19

Elaborated male traits, indicators of heritable genetic quality

Handicap principle:

• some males may have a heritable trait that reduces viability
• only males with good genes can survive despite handicap
• bigger handicap, higher genetic quality
• female choice evolves and handicap spreads and becomes elaborated

Question 20

Sexy son

Answer 20

• assortative mating between males with most exaggerated trait and females with strongest preference can lead to a genetic correlation between trait genes and prefernece genes
• female preference genes will hitchhike onto successful male genes
• evidence for a genetic correlation between trait and preference from three-spine sticklebacks

Question 21

Maladaptive traits

Answer 21

• when trait and preference are genetically correlated then trait can evolve way beyond the point where it indicates overall genetic quality
• runaway of male trait can proceed to a point if exaggeration