Unit 2 - Variation and Sexual Reproduction Flashcards
What are the costs of sexual reproduction?
Males are unable to produce offspring.
Only half of each parent’s genome is passed onto offspring, disrupting successful parental genomes.
Why do the benefits outweigh the costs of sexual reproduction?
Sexual reproduction increases genetic variation.
What does genetic variation provide?
Provides the raw material required for adaptation, giving organisms a better chance of survival under changing selection pressures.
Why can asexual reproduction be a successful reproductive strategy?
Whole genomes are passed on from parent to offspring so a successful parental genome is not disrupted.
One parent can produce daughter cells and establish a colony of virtually unlimited size over time.
When is maintaining the genome of the parent (in asexual reproduction) particularly advantageous?
In very narrow, stable niches or when re-colonising disturbed habitats.
What is an advantage of asexual reproduction?
Offspring can be produced more often and in larger numbers with asexual reproduction compared to sexual reproduction.
What is parthenogenesis?
Reproduction from a female gamete without fertilisation.
What does the Red Queen hypothesis state?
In a co-evolutionary relationship, changes in the traits of one species can act as a selection pressure on the other species as both species must adapt to avoid extinction.
What may co-evolutionary interactions between parasites and hosts select for?
Sexually reproducing hosts.
What hosts have greater fitness?
Hosts that are better able to resist and tolerate parasitism.
What parasites have greater fitness?
Parasites that are better able to feed, reproduce and find new hosts.
What is the advantage of parasite hosts reproducing sexually?
The genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites.
Give two examples of asexual reproduction in eukaryotes.
Vegetative cloning in plants
Parthenogenesis in lower plants and animals that lack fertilisation.
When is parthenogenesis more common?
In cooler climates, which are disadvantageous to parasites, or regions of low parasite density or diversity.
In asexually reproducing environments, what can occur that provides some degree of variation and enables some natural selection and evolution to occur?
Mutations.
What do organisms that reproduce principally by asexual reproduction often have to increase variation?
Mechanisms for horizontal gene transfer, eg plamids of bacteria and yeast.
What does the ability of prokaryotes to exchange genetic material horizontally result in?
Faster evolutionary change than in organisms that only use vertical transfer.
What is meiosis?
The division of the nucleus that results in the formation of four haploid gametes from one diploid gamocyte.
In diploid cells, what do chromosomes typically appear as?
Homologous pairs.
What are homologous chromosomes?
Chromosomes of the same size, same centromere position and with the same sequence of genes at the same loci.
What does meiosis I start with?
Interphase.
