2.3a Costs and benefits of sexual and asexual reproduction Flashcards
Why isnt sexual reproduction the best?
Males unable to produce offspring,
Only half of each parents genome passed onto offspring, disrupting successful parental genomes.
Benefits of sexual reproduction
Benefits outweigh the costs due to an increase in genetic variation in the population.
What does Genetic Variation provide?
Genetic variation provides the raw material required for adaption, giving sexually reproducing organisms a better chance of survival under changing selection pressures.
Red Queen hypothesis: persistence of sexual reproduction
The red queen hypothesis states that co-evolutionary interactions between parasites and hosts may select for sexually reproducing hosts.
Hosts better able to resist and tolerate parasites have greater fitness. If hosts reproduce sexual = increased genetic varability of offspring, so less likely to be infected with parasite.
Parasites with increased virulence, better at feeding, reproducing and finding new host have greater fitness. If parasites reproduce sexually = genetic variation in population, so some will be able to better exploit their hosts.
So sexual pressures drives ecah to keep evolving.
Co evolutionary interactions - parasites and hosts
Co evolutionary interactions between parasites and hosts may select for sexually reproducing hosts.
Hosts are better able to resist and tolerate parasitism have greater fitness. Parasites better able to feed, reproduce and find new hosts have greater fitness.
Sexual reproduction
The production of new living organisms by combing genetic information from two individuals of different types (sexes)
Why is hosts reproducing sexually beneficial?
If hosts reproduce sexually, the genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasite.
Asexual reproduction
A type of reproduction by which the offspring arise from a single organism, and inherit the genes of that parent only. It does not involve the fusion of gametes.
Why is asexual reproduction successful
Asexual reproduction can be successful reproductive strategy as whole genomes are passed on from parent to offspring.
Examples of asexual reproduction in eukaryotes
Vegetative cloning in plants and parthenogenesis in lower plants and animals that lack fertilization.
Where is asexual reproduction advantageous
Maintaining the genome of the parent is an advantage particularly in very narrow, stable niches or when re-colonizing disturbed habitats
Offspring can be produced more often and in larger numbers.
Definition of parthenogenesis
Parthenogenesis is the reproduction from a female gamete without fertilization.
When is parthenogenesis most common?
It is more common in cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity.
Why isnt asexually reproduced populations great?
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.
What do organisms which reproduce by asexual reproduction have to increase variation?
Organisms that reproduce principally by asexual reproduction also often have mechanism for HGT between individuals to increase variation, for example plasmids of bacteria and yeast.
