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.
stages of selective breeding
- Humans breed individuals with desired trait
- Alleles for desired trait passed to next generation
- Number of alleles for desired trait in population increases
- Gene pool contains high frequency of desired alleles.
negatives of selective breeding
selective breeding makes the poplation more susceptible to diseases and natural disasters
selective breeding prompts the production of individuals with the same alleles
little variation in alleles
unlikely for plants to have different genes allowing them to survive the disease.
changes in the environment could kill the entire population.
selective breeding has an increased chance of inbreeding due to recessive alleles, which are only noticable when expressed.
what is being manipulated in selective breeding
In selective breeding, humans are creating selection pressures to favour a particular trait!
define selection pressure
abiotic and biotic factors can exert pressures on organisms that live in an ecosystem. when these pressures affect the ability of an organism to survive, they are called selection pressures.
effects of selection pressures
selection pressures make some characteristics favourable and others unfavourable, driving the evolution of the species towards the favourable trait. individuals with favourable trait are more likely to live longer, fuck more.
what is the process of natural selection
- natural selection exists because genetic variation exists.
- genetic variations means some individuals are more suited to an environment than others, and more likely to survive.
3.
why is genetic variaiton a thing
genetic variation may arise due to:
random mutations in DNA
different alleles being introduced into a population
individuals with beneficial allele are more likely to:
survive -> reproduce -> pass on genes
increasing the proportion of individuals in the next generation with the beneficial allele
these individuals are more likely to:
survive -> reproduce -> pass on genes
leading to the frequency of the beneficial allele increasing even more.
importance of natural selection in evolution
natural selection helps species become more adapted to their environments, increasing their chances of survival.
natural selection can also change gene pools so much that new and distinct species form.
what does genetic variation refer to?
Genetic variation refers to the differences in genetic information between individuals.
Why is genetic variation so important in the process of natural selection?
Genetic variation means that some individuals will be better suited to selection pressures than others, and survive more easily. These differences are the basis of natural selection!
Explain how genetic variation is linked to natural selection.
Genetic variation implies that every individual within a species is genetically different. Because of this, different individuals may be either more susceptible or more adapted to particular environments or environmental changes. Therefore, genetic variation is important in natural selection as the environment will ‘select for’ favourable characteristics within a genetically varied population.
Explain how selection pressures are relevant to evolution.
Selection pressures refer to anything that affects the behaviour, survival, and reproduction of an organism and therefore can be biotic or abiotic factors. Therefore, a tropical climate or the introduction of a new species into an environment can constitute selection pressures.
Organisms with traits favourable for their survival under a particular selection pressure, or set of selection pressures, are more likely to survive. Those organisms that survive will reproduce and pass on their favourable trait to their offspring, increasing the number of organisms in the next generation that possess the favourable trait. Therefore, selection pressures are drivers for evolution.
what does sexual selection emphasise?
sexual selection emphasises that an organisms chances of reproducing depend on its ability to attract the opposite sex.
what determines an organisms chances of reproudcing
combination of survival (natural selection) and ability to attract another individual (sexual selection)
where is genetic drift more common
genetic drift is more common in smaller populations since alleles can disappear from a population by chance.
is sexual selection applied to evolution of all organisms.
Sexual selection can’t apply to all organisms, since some organisms reproduce asexually.
Explain how genetic drift contributes to changes in allele frequency in a population gene pool.
Genetic drift is when random events occur within the population, such as births and deaths, that lead to changes in allele frequency. This is more common in smaller populations because alleles appear and disappear by chance when an individual dies or fails to reproduce. These alleles are not necessarily harmful or beneficial, and therefore genetic drift causes changes in allele frequencies completely by chance.
Compare natural selection and sexual selection.
Sexual selection occurs when an organism’s chances of reproducing depend on their ability to attract a member of the opposite sex. Individuals with a particularly attractive trait will be more likely to reproduce, and more likely to pass on their allele for that trait to the next generation. Over time, the allele for the attractive trait will accumulate in the population.
Natural selection is process whereby organisms better adapted to their environment tend to survive and produce more offspring.
In natural selection, selected for characteristics are beneficial for survival in certain environments, which contrasts with sexual selection as selected for characteristics in sexual selection are not necessarily beneficial for survival. Moreover, characteristics selected for with sexual selection are often to do with sex-specific features, which is not the case in natural selection.
Both processes do not occur at random, and therefore are not due to chance.
define evolution
every organism shares a common ancestor. a change in the genetic composition of a population during successive generations. the changes in proportions of different alleles in a gene pool over time.
Describe how microevolution occurs.
Microevolution is the small-scale variation of allele frequencies in the gene pool of a species. Allele frequency can change due to four main factors:
Gene flow: the movement of alleles between populations, due to the movement of individuals, leading to changes in allele frequency.
Genetic drift: when random events occurring within the population, such as births and deaths leads to changes in allele frequency.
Mutations: a change in an organism’s DNA, which can act as a source of new alleles.
Selection pressures: where organisms with favourable traits are more likely to survive, reproduce, and pass on their genes to the next generation.
Explain how microevolution leads to macroevolution .
Macroevolutionary changes occur from an accumulation of microevolutionary changes. Over time, a species might accumulate so many genetic changes that they are unable to successfully reproduce with their original ancestor. At this point, there has been a macroevolutionary change because a variation in an allele frequency beyond a singular species has occurred.
Relate the concept of natural selection to microevolution and macroevolution.
Natural selection is the evolutionary process by which the environment ‘favours’ certain characteristics. These characteristics are favoured because they promote survival in a specific environment, and are therefore more likely to be passed onto the next generation.
Microevolution refers to changes in allele frequency in the gene pool of a species. Due to natural selection, certain alleles will be ‘selected’ by the environment and are therefore more likely to be passed on, leading to microevolutionary changes over time. The speed of these changes will be in proportion to how rapidly the environment itself changes. Over time, these microevolutionary changes (caused also by genetic drift, gene flow, and mutations) will themselves be ‘selected for’ by the environment, leading to the production of a new species (macroevolution). This new species will therefore have adapted to their environment due to microevolutionary changes, formed by natural selection.
what are the major differences in new populations
selective pressures
gene pools
when has speciation occured
when orgnaisms in one population are unable to breed with organisms from other population, speciation has occured.
what are the three types of speciation
allopatric
sympatric
parapatric
when does allopatric speciation occur?
allopatric speciation occurs when populations of a species become geographically (separated by a physical barrier) or spatially (inhabit different areas) isolated from each other.
when does sympatric speciation occur?
sympatric speciation occurs when organisms become live in the same place but are reproductively isolated. This may occur due to breeding patterns.
when does parapatric speciation occur?
parapatric speciation occurs where populations are capable of interbreeding, but individuals are more likely to mate with individuals geographically close.
when does parapatric speciaition occur
its very rare. when selection pressures undergoi a large change across a small area. speciaiton involves a lack of gene flow across the population
Explain how speciation relates to natural selection.
Speciation is the formation of a new and distinct species in the course of evolution. Evolution occurs because of natural selection, meaning that the environment ‘selects’ favourable characteristics in a genetically diverse species.
Outline the role of reproductive isolation in speciation.
Speciation is the formation of a new and distinct species in the course of evolution. When organisms are unable to breed, reproductive isolation occurs. This means that the allele frequencies in the two populations will change independently of each other due to exposure to different selection pressures. Over time, when the organisms in one population are unable to successfully breed with organisms from the other population, speciation has occurred and a new taxonomic group has been formed.
when does extijction occur?
when species fail to adapt to environmental changes, or are outcompeted for resources, they may die out and cease to exist entirely.
why is genetic divesirty good for helping to prevent extinction
populations with high genetic diversity have a greater variation in alleles. advantageous in terms of selection pressures. if individuals in a population are different, theres a higher chance that a few individuals will be able to survive an environmental change.
describe the bottleneck effected
as the population size of a species decreases and the species becomes closer to extinction, genetic diversity is continually lost. if you decrease the size of a population, the total number of alleles and the diversity of alleles in the gene pool will decrease.
Define extinction. In your answer, provide ONE possible mechanism of extinction.
Extinction occurs when individuals in a species die out over time and therefore a species ceases to exist. This can occur from a change in environmental conditions, for example the introduction of a deadly disease.
Genetic diversity is vital for the survival of a species.
Evaluate this statement.
Genetic diversity is the variation of alleles, so versions of genes, in a population. A population with a high genetic diversity will have a greater variation in alleles. A population with a low genetic diversity will have a smaller variation in alleles.
A high variation of alleles is advantageous under changing environmental conditions. If the individuals in a population are all slightly different, there’s a chance that at least a few of the individuals will be able to survive an environmental change. If a new disease is introduced, for example, individuals with alleles allowing them to survive the disease will be more likely to survive, reproduce, and pass on their genetic information on to their offspring. This is a process known as natural selection, and it determines the survival of a species. So the more genetic variation, the greater the likelihood that a species will survive.
Therefore, genetic diversity is indeed vital to preventing extinction and ensuring the survival of a species.
