Lecture 13. Evolution of Sex and Sexual Selection

Question 1

What were Darwins two worries about natural selection ?

Answer 1

1. Altruism

2. Sexual selection

Question 2

What are the two problems with sex ?

Answer 2

1. How could sexual reproduction evolve in the first place

2. How such mal-adaptively showy males could evolve

Question 3

Does asexual or sexual reproduction get the most genes into the next generation ?

Answer 3

Asexual

Question 4

Does asexual or sexual species populate a new environment more quickly ?

Answer 4

Asexual - sexual needs a mate

Question 5

What was John Maynards Smiths idea called ?

Answer 5

The two fold cost of sex

Question 6

What is the two fold cost of sex ?

Answer 6

Sexual reproduction is less efficient as

1. only half the individuals genes are present in each offspring
2. males dont produce offspring directly

Question 7

What are some other negatives to sexual reproduction mentioned by John Maynard Smith ?

Answer 7

1. Courtship and mating takes times, energy and is dangerous
2. Finding a mate of the right age, species, sexual state can be difficult
3. Courtship is showy which attracts predators and takes time
4. Letting another individual that close carries danger or parasites and disease as well an injury

Question 8

What are the advantages of sexual reproduction at an individual level ?

Answer 8

More variation in offspring leads to:

1. Sibling competition reduced
2. Better protection against predators

Question 9

What are the advantages of sexual reproduction at a population level ?

Answer 9

1. Mullers ratchet
2. Hill Robertson Effect
3. Sexual species survive longer

Question 10

What is sexual reproduction at an individual level necessary for ?

Answer 10

Evolution of sex

Question 11

What is sexual reproduction at a population level necessary for ?

Answer 11

Help with maintenance but not original evolution of sex

Question 12

Why do we need to consider individual benefits not population ones when explaining the evolution of sex ?

Answer 12

1. Evolution depends on selection between individuals
2. The first mutant from asexual to sexual had to outcompete the asexuals in the population
3. Benefits only obtained by the population wouldn’t spread a new allele for sex at the expense of the asexual alleles
4. Its not for the good of the population that traits evolve

Question 13

Why do aphids switch from being asexual to sexual just before winter ?

Answer 13

Future conditions are uncertain so variable offspring are a good bet

Question 14

When do asexual produced offspring do well ?

Answer 14

When environment is stable

Question 15

What does increase variation mean for siblings ?

Answer 15

Reduced competition meaning offspring survive in many different habitats and offspring compete less as fewer in any one patch

Question 16

What was better protection against parasites also called ?

Answer 16

Red Queen Hypothesis

Question 17

What is the red queen hypothesis ?

Answer 17

Evolutionary arms race between hosts and parasites which sexual reproduction can help the hosts win

Question 18

What is the benefit to the individual parent concerning red queen hypothesis ?

Answer 18

Relief from parasites for some offspring, at least briefly

Question 19

What is Miller’s Ratchet ?

Answer 19

Gradual accumulation of deleterious mutation

Question 20

What does Mullers Ratchet effect

Answer 20

Asexual reproduction

Question 21

What is the Hill Robertson effect ?

Answer 21

Getting multiple mutation into one individual is easier in sexuals

Question 22

What species survive longer ?

Answer 22

Sexual

Question 23

What are the two types of sexual selection ?

Answer 23

1. Intersexual

2. Intrasexual

Question 24

What is inter sexual selection ?

Answer 24

Female choice

Question 25

What is intra sexual selection

Answer 25

Male - male competition

Question 26

What is the result of inter sexual selection ?

Answer 26

Ardent males and reluctant females

Question 27

What does honest mean ?

Answer 27

Anything difficult for poor quality, sickly males to maintain

Question 28

What does female choice create ?

Answer 28

A directional selection pressure towards even bigger and more costly displays in males

Question 29

What are the two theories to explain extreme males ?

Answer 29

1. Fishers Run Away Process | 2. Zahavis' Handicap Principle

Question 30

What is fishers run away process ?

Answer 30

The trait will continue until the detrimental effect is so strong that the extra chance of breeding is not enough to make it up

Question 31

Why dont females stop preferring extreme males ?

Answer 31

Sexy sons hypothesis

Question 32

What is Zahavi's handicap principle ?

Answer 32

Male is displaying uncheatable signal of good genes as he survived despite handicap of excessive tail

Question 33

What does evolution not produce ?

Answer 33

What is best for the species

Question 34

What does selection favour ?

Answer 34

Whoever breeds best and this does lead to mal-adaptively extreme results