Key Area 3 - Variation & Sexual Reproduction Flashcards
Costs & Benefits of Sexual & Asexual
Reproduction
Explain the costs of sexual reproduction
Costs of sexual reproduction: males unable
to produce offspring; only half of each
parent’s genome passed onto offspring,
disrupting successful parental genomes.
Why do benefits outweigh costs?
Benefits outweigh costs due to an increase in genetic variation in the population.
What does genetic variation provide?
Genetic variation provides the raw material
required for adaptation, giving sexually
reproducing organisms a better chance of
survival under changing selection pressures.
What can be used to explain the
persistence of sexual reproduction?
The Red Queen hypothesis to explain the
persistence of sexual reproduction.
What interactions between
parasites and hosts may select for sexually
reproducing hosts?
Co-evolutionary interactions between
parasites and hosts may select for sexually
reproducing hosts.
Hosts better able to resist and tolerate
parasitism have greater fitness. Parasites
better able to feed, reproduce and find new
hosts have greater fitness.
If hosts reproduce sexually, the genetic
variability in their offspring reduces what
chances?
If hosts reproduce sexually, the genetic
variability in their offspring reduces the
chances that all will be susceptible to
infection by parasites.
Why can asexual reproduction be a successful reproductive strategy?
Asexual reproduction can be a successful
reproductive strategy as whole genomes are passed on from parent to offspring.
Explain asexual reproduction
In asexual reproduction, just one parent can produce daughter cells and establish a
colony of virtually unlimited size over time.
Where is maintaining the genome of the parent an advantage?
Maintaining the genome of the parent is an
advantage particularly in very narrow, stable niches or when re-colonising disturbed habitats.
Name examples of asexual reproduction in eukaryotes
Vegetative cloning in plants and
parthenogenesis in lower plants and animals that lack fertilisation are examples of asexual reproduction in eukaryotes.
Explain parthenogenesis
Parthenogenesis is reproduction from a
female gamete without fertilisation.
Give an advantage of asexual reproduction
Offspring can be reproduced more often and in larger numbers with asexual reproduction.
Where is parthenogenesis more common?
Parthenogenesis is more common in cooler
climates, which are disadvantageous to
parasites, or regions of low parasite density
or diversity.
Explain variation in asexually reproducing populations
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.
Organisms that reproduce principally by
asexual reproduction also often have
mechanisms for what type of transfer?
Organisms that reproduce principally by
asexual reproduction also often have
mechanisms for horizontal gene transfer
between individuals to increase variation, for example the plasmids of bacteria and yeasts.
Explain how prokaryotes exchange genetic material
Prokaryotes can exchange genetic material
horizontally, resulting in faster evolutionary
change than in organisms that only use
vertical transfer.
Meiosis
What is meiosis?
Meiosis is the division of the nucleus that
results in the formation of haploid gametes
from a diploid gametocyte.
How do chromosomes appear in diploid cells?
In diploid cells, chromosomes typically
appear as homologous pairs.
What are homologous chromosomes?
Homologous chromosomes are
chromosomes of the same size, same
centromere position and with the same
sequence of genes at the same loci.
