2i- Costs and benefits of sexual and asexual reproduction

Question 1

What are two costs of sexual reproduction?

Answer 1

• males are unable to produce offspring
• only half of each parents genome is passed onto offspring which disrupts
  successful parental genomes

Question 2

Why do benefits outweigh costs in sexual reproduction?

Answer 2

Due to an increase in genetic variation in the population

Question 3

What does genetic variation provide and why is this important?

Answer 3

The raw materials required for adaptation, this gives sexually reproducing organisms a better chance of survival under changing selection pressures

Question 4

What may co-evolutionary interactions between parasites and hosts select for?

Answer 4

Sexually reproducing hosts

Question 5

What happens if hosts reproduce sexually?

Answer 5

The genetic variation in their offspring reduces the chances that all will be susceptible to infection by parasite

Question 6

What kind of hosts have greater fitness?

Answer 6

Those that are better able to resist and tolerate parasitism

Question 7

What kind of parasites have better fitness?

Answer 7

Those that are better able to feed, reproduce and find new hosts

Question 8

Why can asexual reproduction be a successful strategy?

Answer 8

As whole genomes are passed on from parent to offspring

Question 9

What can happen in asexual reproduction?

Answer 9

Just one parent can produce daughter cells and establish a colony of virtually unlimited size over time

Question 10

When is maintaining the genome of a parent particularly an advantage?

Answer 10

In very narrow, stable niches or when re-colonising disturbed habitats

Question 11

What are two examples of asexual reproduction in eukaryotes?

Answer 11

• vegetative cloning in plants

- parthenogenesis in lower plants and animals that lack fertilisation

Question 12

What can be said about the amount of offspring produced in asexual reproduction?

Answer 12

Offspring can be produced more often and in larger numbers

Question 13

What is parthenogenesis?

Answer 13

Reproduction from a female gamete without fertilisation

Question 14

Where is parthenogenesis more common?

Answer 14

In cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity

Question 15

What is a negative of asexual reproduction?

Answer 15

Asexually reproducing populations are not able to adapt easily to changes in their environment, but mutations can occur that provide some degree of variation and enable some natural selection and evolution to occur

Question 16

What mechanism can organisms that reproduce principally by asexual reproduction also have and why?

Answer 16

Mechanisms for horizontal gene transfer between individuals to increase variation, for example the plasmids of bacteria and yeast

Question 17

Prokaryotes can can exchange genetic material horizontally, what can this result in?

Answer 17

Faster evolutionary change than in organisms that only use vertical transfer