2.3a Costs and Benefits of Sexual and Asexual Reproduction

Question 1

What are the costs of sexual reproduction?

Answer 1

• males unable too produce offspring
• only half of each parent’s genome passed onto offspring - disrupting successful parental genome

Question 2

explain benefits and costs of sexual reproduction

Answer 2

benefits ought weigh the cost due to an increase in genetic variation in the population

Question 3

What does genetic variation provide and what is the benefit of this?

Answer 3

• the raw material required for adaptation
• giving sexually reproducing organisms a better chance of survival under changing selection pressures

Question 4

What explains the persistence of sexual reproduction?

Answer 4

the red queen hypothesis

Question 5

Wha may coevolutionary interactions between parasites select for?

Answer 5

sexually reproducing hosts

Question 6

What means a host has better fitness?

Answer 6

better able to resist and tolerate parasitism

Question 7

What means a parasite has greater fitness?

Answer 7

better able to feed, reproduce and find new hosts

Question 8

What happens if hosts reproduce sexually?

Answer 8

the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites

Question 9

Why is asexual reproduction successful?

Answer 9

• whole genome is passed from parent to offspring
• maintaining genome of parent is an advantage particularly in very narrow, stable niches or when recolonising distributed habitats

Question 10

What are examples of asexual reproduction in eukaryotes?

Answer 10

• negative cloning in plants
• parthenogenesis in lower plants and animals that lack fertilisation

Question 11

what is parthenogenesis?

Answer 11

reproduction from a female gamete without fertilisation

Question 12

Explain offspring numbers with asexual reproduction

Answer 12

offspring can be produced more often and in larger numbers

Question 13

When is parthenogenesis more common and what is the effect of this?

Answer 13

• more common in cooler climates
• this is disadvantageous to parasites
• or in regions of low parasite density or diversity

Question 14

Explain the downsides of asexual reproduction

Answer 14

• not able to adapt easily to changes in their environment
• mutations can occur that provide some degree of variation and enable some natural selection and evolution to occur

Question 15

Explain HGT in organisms that reproduce by asexual reproduction

Answer 15

• often have mechanisms for HGT to increase variation
• ## such as plasmids of bacteria and yeast

Question 16

Explain HGT in prokaryotes

Answer 16

can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer