Lecture 6

Question 1

Reproductive Models

Answer 1

1. Reproductive system: asexual vs sexual
2. Sexual system: sexual: dioecious vs hermaphrodite
3. Mating system: hermaphrodite: crss fretilization or self - fertilization

Question 2

Definition of Sexual Reproduction

Answer 2

2 parents contribute genetic material to offspring; meiotic, reducive division to form gametes; fusion of gametes

Question 3

Definition of Asexual Reproduction

Answer 3

1 parent contributing genetic material to offspring: no meiotic reductive division, offspring are genetic replicas, clones of parent

Question 4

Costs of Meiosis

Answer 4

1. Compared to the asexual, the sexual female contributes only 50% of her gene copies to the next generation
2. Favoring of asexual in competing with sexual females: maintenace of favorable combinations of alleles
3. Sexual reproduction can continually recreate unfavorable combinations of alleles

Question 5

Costs of Sex

Answer 5

• Time and energy to find and attract mates
• Increased energetic costs of mating
• Risk of predation and infection
• Cost of producing males
• Breakup of adaptive gene combinations: segregation, recombination

Question 6

Benetifs of Sex

Answer 6

Favorable combinations of mutations brought together more rapidly by sex; eliminating harmful mutations; genetic variation in unpredictable environments

Question 7

Does sex increase or decrease in homogenous/heterogenous environments

Answer 7

Decreases in homogenous environments, increase in heterogeneous environments

Question 8

Parthenogenesis

Answer 8

Growth and development directly from an egg, without need for fertilization

Question 9

Characteristics of Asexual Species

Answer 9

• Higher extinction rate
• Low chance of long - term evolutionary persistence
• Extremely low genetic variation and accumulation of deleterious mutations

Question 10

Out breeding vs inbreeding

Answer 10

Outbreeding: mates less closely related to each other, etc.

Question 11

Self fertilization vs asexual reproduction

Answer 11

Selfing: fusion of gametes from one parent, derived from meiotic reductive division

Question 12

Inbreeding Avoidance Traits in Flowering Plants

Answer 12

• Timing offset between male and female reproduciton
• Pollen vs ovule maturation
• Opening time
• Diverse morphologocal and physiological mechanisms to avoid selfing

Question 13

Inbreeding Avoidance Behaviors in Animals

Answer 13

Dispersal by one sex, delayed maturation, extra pair copulation, kin recognition and avoidance

Question 14

Population Genetic Effects of Inbreeding

Answer 14

Changes genotype frequencies, increases homozygosity, decreases heterozygosity, doesn’t directly change allele frequencies or polymorphism

Question 15

Inbreeding Depression

Answer 15

• Reduction in fitness of inbred offspring compared to outcrossed offspring

Question 16

How inbreeding reduces fitness

Answer 16

Homozygosity of recessive deleterious alleles

Question 17

2 Models for Advantages of Sex

Answer 17

1. Lottery model: benefits of gnetic vairaiton invariable or unpredicable environments: organism doesn’t know where the progeny will end up, wants it to be able to adapt to any variety of possible environments
2. Red Queen Hypothesis: like the temperate nature of the Red Queen in Alice in Wonderland, environments change ove rtime, are temporally heterogeneous and also unpredictable

Question 18

Sex persisted at a much higher level with _____

Answer 18

Spatial heterogeneity, to incrase likelihood and amount of positive alleles

Question 19

Asexual species ar eusually at the tips of phylogenies because….

Answer 19

Macroevolutionary pattern indicates higher extinction rate as there is a low change of long - term evolutionary persistence. Probably due to extremely low genetic variation and accumulation of deleterious mutations

Question 20

Clonal propagation

Answer 20

Multiplication of genetic copies

Question 21

Outbreeding: mates are ___ closely related than random

Answer 21

Less

Question 22

Inbreeding: mates are ___ closely related than random

Answer 22

More

Question 23

Self - fertilization vs inbreeding

Answer 23

Selfing is the most extreme form of inbreeding, but not the same as asexual reproduction. It is the fusion of gametes from 1 parent, drvied from meiotic reductive division

Question 24

Inbreeding is desirable or undesirable?

Answer 24

Undesirable

Question 25

Inbreeding avoidance traits in flowering plants

Answer 25

Timing offset beween male and female reproduction, e.g. pollen and ovle maturation time within a flower and when male vs female flowers open Diverse morphological and physiological mechanisms to avoid selfing: self - incompatibility, spacing of anther and stigma

Question 26

Inbreeding avoidance behavior in animals

Answer 26

DIspersal by one sex (different sexes geographically separate), delayed maturation to prevent parents from mating with their offspring, extra pair copulation (cheating), kin recognition

Question 27

Population genetic effects of inbreeding

Answer 27

Increases homozygosity, decreases heterozygosity, doesn't change polymorphism

Question 28

2 consequences of inbreeding depression

Answer 28

Lower viabilty and fertility. Homozygosity of recessive deleterious alleles surface

Question 29

Selfing variant has a ___ advantage

Answer 29

Transmission

Question 30

Short term and long term effects of selfing

Answer 30

Short term: selfing may spread via natural selection, low in inbreeding depression Long term: low diversiity, inefficient selection, higher extinction rates