Chapter 9: Mechanisms of Evolution of Speciation Flashcards
what is a gene pool?
total colleciton of alleles for all genes in a population. the gene pool retains all of the genetic information of the population, including the number of genes, number of alleles, and the allele frequency. genes pools are dynamic
what can genes pools be used for
to compare populations
factors effecting gene pools
gene flow
genetic drift
mutations
selective presssures
how can gene flow affect gene pools
if gene flow between populations remains high, then the population’s gene pools will be similar.
define gene flow
movement of alleles between populations, due to the movement of individual organisms
define genetic drift
random events that occur within the population (such as births and deaths) that can lead to changes in the gene pool and allele frequency.
define mutations
they are a source of new alleles, so that the size of the gene pool is increased. large gene pool means the population has a greater genetic diversity.
define selective presssures
any external factor which affects an organisms ability to survive. selection pressures change the allele frequency in a population, as organisms with advantagous alleles are more likely to survive.
how are selective pressures categoried
postivie = increases the frequency of an allele in a gene pool
negative = decreases the frequency of an allele in a gene pool
why does variation exist
Variation exists in a population because individuals have different alleles.
Define selective breeding.
Selective breeding is the intentional reproduction of individuals with desirable characteristics in order to produce offspring with desirable characteristics. also known as artificial selection.
Explain how an increase in production of cow’s milk could be achieved by farmers over many generations of cows.
The farmers would identify the cows that produce the most milk and then breed these cows to produce offspring with high milk production. If this process is continued over many generations, the offspring will gradually have higher milk production.
Explain how selective breeding impacts the gene pool.
Selective breeding can cause the frequency of the desired trait to increase. Due to this, the size of the whole gene pool may decrease, because there may be a decrease in the number of different alleles (genetic variation), as the undesirable traits may be bred out.
Explain how gene flow affects the gene pool of a population.
Gene flow is the exchange of genetic material between populations, due to individuals entering and leaving the populations. Gene flow can bring new alleles into the gene pool of a population, increasing the size of the gene pool and the genetic diversity and can also alter the current allele frequencies in a population.
Large numbers of Australian herring fish inhabit estuaries on the south coast of Western Australia. The genetic compositions of the groups of individuals in the different estuaries are the same.
Identify a plausible explanation for why this is so.
Gene flow between the populations could be causing the different estuaries containing the same genetic composition. If many individuals are migrating between the estuaries, this would cause similar allele frequencies between the groups.
Describe the effect of selection pressures on a gene pool.
A selection pressure refers to any external factor which affects an organism’s ability to survive in its environment. Selection pressures mean that individuals with traits that are advantageous to coping with the pressure are more likely to survive. These individuals will then be able to reproduce and pass on these beneficial alleles to their offspring, altering the allele frequency in the gene pool.
Compare the founder effect and bottleneck effect.
The bottleneck effect refers to when a species experiences an event that suddenly and significantly reduces its population and gene pool. The founder effect refers to when a small group of individuals are separated from their original, larger population, and move to a new location to establish a new population. Both the founder effect and the bottleneck effect are forms of genetic drift, meaning they both involve random events occurring within a population that lead to changes in the gene pool. Both forms of genetic drift also result in an initial smaller population size.
Zebra populations are suffering from a reduction in their gene pools due to habitat
destruction and increasing isolation. This has led to an increase in the number of
offspring born with coat patterns different to that of their parents.
Explain possible reasons for the increase in these offspring.
A reduction in gene flow occurs as populations become smaller and more isolated. This results in inbreeding, a reduction in the gene pool and the accumulation of mutations. Many mutations are recessive and when offspring receive two copies of a mutation it is expressed (and offspring will appear different to their parents). Inbreeding with close relatives results in increased risk of phenotype being affected by mutations.
Analyse the advantages of selective breeding.
Can be used to increase the frequency of a desired trait, making a population more useful.
Can be used to prevent species from going extinct in conservation efforts.
Analyse the advantages of selective breeding.
Decreases genetic diversity which may cause problems, like making a population more susceptible to disease.
The traits selectively breed for may not be advantageous for the species itself, which can lead to health problems.
Biologists are breeding malleefowl in captivity to assist in the recovery of wild populations. Explain TWO ways in which captive breeding can assist in the recovery of wild populations.
Captive breeding can assist in the recovery of wild populations by boosting the population size. Captive breeding programs are designed to meet the needs of the individuals and increase the population size. These individuals can then be released into the wild to increase the size of the wild population.
Captive breeding can assist the recovery of wild populations by increasing the genetic diversity of the population. Releasing genetically diverse individuals can boost the genetic diversity of wild populations, reducing their susceptibility to selection pressures, thus aiding their recovery.
Explain how TWO processes that affect the gene pool of populations can lead to
evolution.
Gene flow is the movement of alleles into or out of a population. For example, a migrant animal may add new alleles when it reproduces with individuals in the original population.
Genetic drift is a change in allele frequency as a result of random selection of alleles. This is especially marked in a small, remnant population. The few remaining individuals that survive carry a small sample of the alleles in the original population.
Explain how a consideration of biogeography can assist conservation planning to assist the continuation a vulnerable species.
Bioeography
Biogeography refers to how a species is naturally distributed. Scientists can take data about the climate from these locations to determine the conditions that allow that species to survive, grow and reproduce. A consideration of these factors can allow conservationists to identify appropriate areas which have similar conditions or even recreate these conditions to build reserves or restoration sites that provide an appropriate habitat in order to assist the continuation of a vulnerable species.
Explain how a consideration of population dynamics can assist conservation planning to assist the continuation a vulnerable species.
Population dynamics refers to information such as population size, sex ratios and age distribution. A consideration of these factors can assist conservation planning, as they can identify trends in population size. Small population sizes pose the most risk to gene pool or population as they are most at risk from selection pressures. Therefore, conservation efforts can be planned to boost the population size when there is a small population that deviates from what is the normal trend for a certain population. Additionally, by monitoring population size changes, it is possible to identify potential causes of decline for a vulnerable species, and thus there is the option to manage these factors.