The Evolution Of Sex

Question 0

Asexual reproduction

Answer 0

Cloning, vegetative propagation from group of somatic cells

Question 1

Sexual reproduction

Answer 1

Recombination, meiosis with crossing over, union of gametes of different individuals

Question 2

Recombination

Answer 2

The recombining of alleles to form a new individual, results from meiosis and crossing over as well as sexual reproduction, shuffles allele combinations and can lead to better combos of beneficial alleles across loci

Question 3

Parthenogenesis

Answer 3

Offspring develops from unfertilized eggs (diploid)

Question 4

Costs of sexual reproduction relative to asexual reproduction

Answer 4

1. Searching for a mate costs time, energy and increases predation rate
2. Sexually transmitted diseases
3. Cost of meiosis
4. Cost of males or two-fold cost of sex

Question 5

Cost of males

Answer 5

Because males must be involved fewer offspring are created (8 grandchildren vs 16 grandchildren)

Question 6

Cost of meiosis

Answer 6

With asexual parthenogenesis, meiosis is suppressed and all offspring share 100% of mothers genes, pass on more copies of alleles when asexual so have higher fitness

Question 7

Benefits of sex

Answer 7

1. Brings beneficial mutations that appear in two different individuals together in their offspring
2. Muller’s ratchet
3. New combinations of alleles may be beneficial in a changing environment if offspring are variable, at least some might survive (tangled bank and red queen hypotheses)

Question 8

Muller’s ratchet

Answer 8

Idea that asexuals accumulate “genetic load” (deleterious alleles), prevents going backward, sex rids lineage of this genetic load, cloning means mistakes are cloned and passed ok so deleterious recessives add up and there is no way to get rid of them (benefits of sex argument)

Question 9

Tangled bank hypothesis

Answer 9

Changing or variable physical environment, argument for benefit of sex, need to adjust to changing environment means changing genes has more likelihood of some surviving

Question 10

Red queen hypothesis

Answer 10

Changing biotic (living) environment (example: evolving parasites or predators), arms race between parasites and hosts so changing environment favors sex, see more sexual reproduction in presence of competition/predator