Biol 1001 midterm study

Relate Lamarck's major contributions to evolutionary thought to Darwin's evolution by natural selection, explaining which of Lamarck's hypotheses were integral to Darwin's idea, and which were not, providing reasons. [Comprehension]

Relate Lamarck's major contributions to evolutionary thought to Darwin's evolution by natural selection, explaining which of Lamarck's hypotheses were integral to Darwin's idea, and which were not, providing reasons. [Comprehension]

Lamarck stated that organisms change over time based on challenges in the environment and that they pass these on to offspring - Darwins idea states that organisms have variation in their traits and that they pass these on to offspring so theyre heritable. This helped shape his idea. Darwin states theyre passed on if theyre better for survival and Lamarck states something similar, that if an organism is using his trait and if its "of use" then its passed on.
What did not contribute: Lamarck states that the first organisms were spontaneously created.
- Buffon and lamarck influenced his idea because they showed that variation in a population is important

convergent evolution involves unrelated species that develop similar characteristics over time, divergent evolution involves species with a common ancestor that change to become increasingly different over time.

convergent vs divergent evolution

Explain why lamarcks hypothesis of use and disuse and inheritance of acquired characteristics are not supported. [Comprehension]

His hypotheses are not supported because:
Use and disuse: an organism can acquire new traits to lose existing traits based on its use and disuse of certain body parts. Ex giraffe neck. However this hypothesis is incorrect as traits acquired during an organism's LIFETIME are not passed on to its offspring because there was no change to the gene for that trait, without a change at the genetic level, the trait cannot be passed on.
Inheritance of acquired characteristics: organisms can pass on traits acquired during their lifetime to their offspring. Ex. strong muscles. However, traits are determined primarily by genetic info that is passed on and inherited, not by acquired characteristics.
Lamarck also did not account for the role of natural selection in evolution.

lamarcks hypothesis of use and disuse

Use and disuse: an organism can acquire new traits to lose existing traits based on its use and disuse of certain body parts. Ex giraffe neck.

Explain the influence of gradualism and uniformitarianism, and Malthus's ideas of population growth and food supply on Darwin's ideas of natural selection
and evolution. [Comprehension]

Gradualism's influence: it states that slow processes occur over long geological periods and small changes over a long period can lead to a BIG change.
Uniformitarianism's influence: processes of change and the rate that they occurred at - in present are same as past meaning past and present are a key to each other
They influenced his idea because they show that organisms are changing and not static and they change over time - this is part of the definition of evolution.
Malthus: struggle for survival = survival of resources: theres a limit to a sustainable pop. size because there are limited resources in each pop. and if each individual lived to reproduce and survive the pop. would inc. exponentially but food supply only inc. arithmetically, so this would lead to famine and so there is a struggle to survive. This influenced his idea that some individuals survive better because of a trait that they have - so they essentially win this struggle.

Gradualism's influence:

it states that slow processes occur over long geological periods and small changes over a long period can lead to a BIG change.

Uniformitarianism's influence

processes of change and the rate that they occurred at - in present are same as past meaning past and present are a key to each other

Malthus: struggle for survival

survival of resources: theres a limit to a sustainable pop. size because there are limited resources in each pop. and if each individual lived to reproduce and survive the pop. would inc. exponentially but food supply only inc. arithmetically, so this would lead to famine and so there is a struggle to survive.

Summarize Darwin's five observations and three inferences that encompass the logic of his theory of evolution by natural selection.

Observations:
1. Pop. have the potential to inc. exponentially
2. They dont tho, and instead become stable after a certain point
3. Natural resources are limited
4. individuals in a pop. are not identical and they vary in many characteristics
5. Many of these characteristics are heritable
Inferences:

1. Not every individual in a pop that is produces, lives to survive and reproduce
2. Some reproduce and survive better than others because of certain heritable traits
3. Differences in survival and reproduction are non-random - these traits inc. at a higher rate in the population and are passed on at a higher proportion to the next population.

Summarize Darwin's five observations and three inferences that encompass the logic of his theory of evolution by natural selection.

1. Pop. have the potential to inc. exponentially
2. They dont tho, and instead become stable after a certain point
3. Natural resources are limited
4. Individuals in a pop. are not identical and they vary in many characteristics
5. Many of these characteristics are heritable


Inferences:
1. Not every individual in a pop that is produces, lives to survive and reproduce

2. Some reproduce and survive better than others because of certain heritable traits

3. Differences in survival and reproduction are non-random - these traits inc. at a higher rate in the population and are passed on at a higher proportion to the next population.

Explain the link between the two inferences. [Knowledge, Comprehension]

Some traits will help the organisms survive better and they are able to reproduce more, thus being able to pass on these traits more relative to the individuals without this trait that dont have a survival advantage. As they are better able to pass on this trait, because it is heritable it will be seen in their offspring increasing the frequency of that trait.

evolution

change in the characteristics of a population over time through different mechanisms like natural selection

Microevolution

Microevolution is the small changes that happen within a species over a short period of time, like a few generations.

macroevolution

Macroevolution is the process of big changes that happen over a long time, like millions of years.

Natural selection

due to a certain trait that is heritable, some individuals survive better and able to reproduce.. More offspring with that trait in the next generation

typological vs. population thinking

typological: organisms are static and dont change, variation is unimportant - created thru special creation
Population thinking: species change over time and variation is significant

Scala Naturae/ladder of nature:

lamarck.. Spontaneous creation of the first organism.. Evolved over time based on use and disuse and adaptation to environment.. Acquired characteristics bc of challenges in environment

inheritance of acquired characteristics

parents passed on characteristics that they acquired due to adapting to challenges in the environment

Describe briefly the general process of fossilization (including conditions ideal for fossilization), types of bias in the fossil record (& reasons for them)

Process:
Organism dies in an area like a swamp and is quickly buried by sediments
There is no oxygen/bacteria and fungi that can quickly decompose the organism and so it slowly decays and rots
Over time it is buried in more sediment as erosion occurs and the habitat will also dry
Conditions:
Need to have hard structures like skeletal structure etc so that it doesnt decay quickly
Anoxic area with no oxygen, or fungi, bacteria etc to quickly decay it
Have to have active sedimentary deposits to go on top and bury the organism
Need quick burial
Biases:
Temporal bias: fossil record contains more fossils of recent organisms rather than earlier ones, more exposed to crushing, melting and heating over time so less likely to be found
Tissue and taxonomic bias: need slow decay so need hard parts not soft tissue like worms
Habitat bias: need environments where sediments are being actively deposited etc ex. Swamps, beaches, mud flats but not deserts, dry forests etc
Abundance bias: the organisms that are more widely spread and found, more of these are found in record vs those that are rare and isolated populations

Describe how continental drift & chance catastrophic events could affect the evolutionary history (patterns of speciation & extinction) of a species.

Continental drift and pangea: changed temperatures and climates - changed characteristics of species over time as natural selection occurred. This also led to speciation and diversification as they encountered new environments (some survived better)
Catastrophic events like mass extinctions can wipe out whole lineages and if its not an extinction than if its a natural disaster then only the small population that survived would be reproducing so the offspring would all be similar to them

Distinguish between structures similar via common ancestry (homology) & convergent evolution, justifying your choices, & explaining how both phenomena result. Identify examples of each, including the different types of homologies (vestigial trait, genetic/developmental/structural homology).

Homology: similarities found among two or more species due to shared ancestry (same source)
Example of homology: human hand, bat wing, horse leg etc all these limbs have similar number of bones and arrangement but different or same functions - ex. Lilies and roses are homologous because of..


Homoplasy: similarities found among species due to any other reason than shared ancestry (same form)
Example of homoplasy: convergent evolution: where species individual evolution of similar traits of distantly related organisms because of adaptation similar characteristics due to similar lifestyles and environment - their sister groups dont have these traits and neither do their distant common ancestor but they do!


Genetic homology: same genetic structure - dna, rna etc so they make same proteins bc of same amino acid sequence ex. Eyeless gene in fruit flies and anirdia gene in humans

Developmental homology: seen in embryo - animals may have pouches and tails but disappear soon after and for some of them they remain because their common ancestor had them.
Structural homology: similarities in adult morphology or form - hands, wings etc so an ancestral tetrapod had similar arrangement of bones

Vestigial traits: reduced or non functioning traits/structures in organisms, but clearly similar to a closely related species functioning organ or structure ex. Human tailbone and monkey tail

Homology

similarities found among two or more species due to shared ancestry (same source)

Homoplasy

similarities found among species due to any other reason than shared ancestry (same form)

Vestigial traits

reduced or non functioning traits/structures in organisms, but clearly similar to a closely related species functioning organ or structure ex. Human tailbone and monkey tail

Explain how homologies (including vestigial traits), the fossil record, and biogeography support hypotheses of common ancestry/descent with modification and formulate predictions regarding these hypotheses.

- Biogeography - geographic distribution - more similar species are found in the same area so some species are only found in certain areas
- All of these things show that there is change over time in species - fossils found of species living in an area and extant species have similar traits so they must have a common ancestor and related to each other, but may also have changed a little - shared common ancestry AND some change over time in the species
- Vestigial traits show there was a common ancestry between the organism with functioning and nonfunctioning trait but for one organism its been changed over time so its evidence of both once again

descent with modification (darwin)

all living organisms are desencded from earlier species and overtime changes occurred and accumulated in the characteristics of species.

transitional fossil

a fossil that exhibits intermediate traits of both its ancestral groups and its descendants. They provide evidence of evolutionary change.

Morphology

study of the form and structure of organisms

habitat bias

organisms that live in beaches, mudflats, swamps, and bogs are more likely to form fossils than organisms that live above ground in dry forests, grasslands, and deserts.

taxonomic and tissue bias

organism with hard parts such as bones or shells are more likely to leave fossil evidence ex. Clams, snails

temporal bias

recent fossils are much more common than ancient fossils
abundance bias - weighted toward common species

transitional feature

trait in a fossil species that is intermediate between those of ancestral and derived species

extant vs. extinct

"extant" and "extinct" are used to describe the current status of a species or group of organisms in relation to their existence. Extant species are currently alive and have living members, while extinct species are no longer alive and have no living members.

background vs. mass extinction

background: lower avg rate of extinction is observed when a mass extinction is not occurring; mass extinction: rapid extinction of a large number of lineages scattered throughout the tree of life

Explain why individuals do not evolve, and why evolution is considered a population process. [Comprehension]

Individuals do not evolve, rather natural selection acts on individuals and evolution acts on populations. This is because the process is defined as a change in the characteristics of a population over time, meaning a change in allele frequencies in the population over time and allele frequencies change at the population level, not at the level of individuals.
Evolution is a process that occurs at the population level over multiple generations. These changes occur through mechanisms such as mutation, genetic drift, gene flow, and natural selection. Even though organisms may exhibit different variations in their traits, it does not mean they are evolving at the stage of the individual. It is instead changes in the frequency of those traits within a population. IF a trait becomes more or less common in a population overtime, then evolutionary change may be occurring.

Justify the importance of genetic variation in populations to the process of evolution, explaining the ways in which variation is generated. Given a scenario/graph, classify: the degree of variation for that character; variation as qualitative or quantitative. [Comprehension, Application, Analysis]

Genetic variation is very important to the process of evolution because there are some mechanisms like genetic drift and natural selection which NEED variation in order for evolution to occur. Mutation is the ultimate source of genetic variation because its the only mechanism which adds NEW alleles to the population, without it, if there was no variation then evolution would just stop. This is because natural selection would select for a trait (an allele) and eventually genetic drift would cause that allele to become fixed, then evolution would just stop!
Also it helps to have variation in case of selection pressures, disease outbreaks etc where some individuals have a trait that allows them to survive better so that the entire species does not go extinct.

Explain the significance of Hardy-Weinberg equilibrium in the context of evolution (i.e., how the HW principle acts as a null hypothesis/model for evolution), relating the assumptions/conditions of HW to the mechanisms of evolution, and populations to which HW is applicable. Given a scenario, indicate which (if any) assumptions have been violated and how. [Comprehension]

A null hypothesis predicts that there are no changes in the treatment groups in an experiment. HWE explains what would be observed if the four processes were not occurring, so it will determine the genotypic frequencies at a genetic equilibrium. If the results observed are different to the predicted frequencies, then this means that there is a violation of one of the four processes, this could mean an evolutionary mechanism has had an effect on the population and evolution has occurred.

Describe the mechanism of evolution by natural selection, explaining why evolution is not progressive (i.e., moving towards 'perfection'), how natural selection is non-random and results in adaptations. [Comprehension]

Natural selection is not progressive because it does not necessarily lead to an "end goal" or a "perfect organism". It is that certain traits become more or less common over time. Natural selection occurs through variation, competition, selection, and/or adaptation. The traits that are most advantageous in an organism are usually what allow them to survive, and allow them to reproduce and eventually pass those traits to their offspring through genetic DNA. Also, natural selection is non-random, meaning that it is based on the interaction between the organism's particular trait and its environment. If the trait works well in its environment, it will survive.

a. Describe how natural selection acts on phenotypic variation to alter the genetic structure of a population. [Comprehension]

Natural selection acts on phenotypic variation by selecting for the most advantageous phenotypic traits of an organism. If an organism's phenotypic traits allows and helps it to survive, the individual will have a higher chance of reproducing and passing its genes to its offspring and so on and so forth. As generations pass, the variation of phenotypic traits may decrease as one trait may dominate the others.

b. Relate natural selection to the concept of fitness and explain how it results in adaptation. [Comprehension]

Natural selection acts on the variation within a population to favor individuals with traits that increase fitness, resulting in adaptations that allow and help species to survive and reproduce in a particular environment. Individuals with traits that increase fitness are more likely to survive and reproduce, and overtime, can lead to evolution through the process of adaptation, where traits are specialized for a particular function in an environment.

Compare and contrast the various types of selection (e.g., directional) and their effects (e.g., genetic variation, mean character value) on a population over a period of time. Given a scenario, determine the type(s) of selection acting and predict the effects on the population. [Knowledge, Comprehension, Application, Analysis]

Directional Selection: one phenotype in the population is favoured causing the average phenotype of the population to move in one direction.
It reduces genetic variation and if it continues in one direction then genetic drift can cause the advantageous allele to become fixed and the recessive deleterious allele to be lost
Fitness trade-offs: a result of directional selection: two competing selective forces that make a compromise on a trait that cannot be optimized simultaneously, which will lead to the intermediate trait to be selected for.
Stabilizing Selection: the average phenotype is selected for - both extremes in the population are reduced.
Reduces genetic variation
Disruptive Selection: it is the opposite of stabilizing selection and it favours the two extreme phenotypes.
Genetic variation is (increased acc. to textbook) maintained (acc. to Dr.Kelly)
It plays a role in speciation and diversification because large finches will mate with large ones and small finches will mate with small finches
Balancing selection: where the phenotypes of the population are maintained as selection acts on a few phenotypes because no one phenotype has an advantage over the others. (the other types of selection act on one specific trait, but this one does not.)
1. This occurs when:
Heterozygotes in the population have an advantage over the homozygotes. So genetic variation is maintained
2. Over time the environment varies for example by temperature etc or different geographical areas are occupied by the population over time. This allows for no one specific trait to have a clear advantage over the others. Thus genetic variation is maintained over time.
3. Frequency-dependent selection is occurring in the population; some traits are selected against when they are common and the rare traits are selected for, then the rare traits become common and they will be selected against. So selection is based on the frequency of the genotype! This will maintain genetic variation over time, as traits go thru a cycle of being selected for and against.

Directional Selection + effect on genetic variation overtime

one phenotype in the population is favoured causing the average phenotype of the population to move in one direction.
- It reduces genetic variation and if it continues in one direction then genetic drift can cause the advantageous allele to become fixed and the recessive deleterious allele to be lost
- Fitness trade-offs: a result of directional selection: two competing selective forces that make a compromise on a trait that cannot be optimized simultaneously, which will lead to the intermediate trait to be selected for.

Stabilizing Selection + effect on genetic variation overtime

the average phenotype is selected for - both extremes in the population are reduced.
Reduces genetic variation

Disruptive Selection + effect on genetic variation overtime

is the opposite of stabilizing selection and it favours the two extreme phenotypes.
Genetic variation is (increased acc. to textbook) maintained (acc. to Dr.Kelly)
It plays a role in speciation and diversification because large finches will mate with large ones and small finches will mate with small finches

Balancing selection

where the phenotypes of the population are maintained as selection acts on a few phenotypes because no one phenotype has an advantage over the others. (the other types of selection act on one specific trait, but this one does not.)

Describe various mechanisms by which natural selection does not lead to elimination of genetic variation. Given a scenario, determine/identify the process, justifying your choice. [Comprehension]

1. Mutation is a process that introduces new genetic variation into a population. Mutations are random changes to an organism's DNA sequence, and they can create new alleles that may be beneficial, neutral, or deleterious in their effects on an organism's fitness. Because mutations occur at a low rate, they can maintain genetic diversity within populations.
2. Migration, or gene flow, is the movement of individuals or gametes between populations. When individuals with different genetic backgrounds interbreed, they can introduce new alleles into the population or prevent the loss of existing ones. This can help to maintain genetic variation within populations.
3. Genetic drift is the random fluctuation of allele frequencies within a population due to chance events. In small populations, genetic drift can be a significant factor in maintaining genetic diversity, as rare alleles may become more or less common simply by chance. Genetic drift is especially important in populations that have undergone a bottleneck, where the population size has been drastically reduced, as it can lead to the fixation or loss of alleles.
4. Balancing selection refers to the processes by which natural selection maintains multiple alleles at a locus. This can occur when different alleles confer advantages in different environmental conditions or when heterozygous individuals have higher fitness than homozygous individuals. Balancing selection can help to maintain genetic variation within populations.

Discuss adaptations, explaining why: there are limits to adaptation; not all traits are adaptive; why adaptation is not 'universally good'; and how an organism's phenotype represents a compromise or trade-off between the adaptive value of multiple traits. Identify/provide an example of a fitness tradeoff. [Comprehension, Application]

While adaptations provide many advantages for organisms, not all traits are adaptive and can be limited. An example of a limitation to adaptation is the availability of genetic variability. The potential for adaptation is limited by the amount and nature of genetic variation. Adaptation is not universally food because they come with some costs, for example, if an individual has a larger body size, they may succeed in strength or defense, but it may require more effort to maintain its invulnerability to predators. An organism's phenotype also represents a trade-off, for example, a plant species may allocate resources to growth and defense, but if these functions conflict, one may not be able to function while the other is in play. As a result, an organism's phenotype represents a balance between the costs and benefits of different traits in its environment.

Differentiate between the different types of evolutionary mechanisms; the conditions under which they occur; their effects on a population's genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects. Given a scenario, determine the type(s) of mechanism(s) acting, and predict the effects on the population, justifying your choices. [Knowledge, Comprehension, Application, Analysis]

1. Gene flow: the flow of alleles from one source population to another population by individuals immigrating and emigrating, individuals must leave, breed and reproduce in over for them to have an effect on the genetic structure of the population.
- It is random with respect to fitness
- It homogenizes allele frequencies between populations because as individuals from one pop. move to another, they become more alike rather than different.
- It can increase or decrease fitness because as individuals leave, they could be decreasing variation in the original population but they could be increasing variation when the other population might have undergone genetic drift.
2. Genetic drift: is the random fluctuation of allele frequencies within a population due to chance events. In small populations, genetic drift can be a significant factor in maintaining genetic diversity, as rare alleles may become more or less common simply by chance. Genetic drift is especially important in populations that have undergone a bottleneck, where the population size has been drastically reduced, as it can lead to the fixation or loss of alleles.
3. Nonrandom mating: in nature mating may not be random with respect to the gene in question. Organisms may look for a mate with a specific trait (which is essentially coded by a specific genotype). There are different forms of nonrandom mating such as inbreeding which is mating between relatives. Inbreeding increases homozygosity, but it is not an evolutionary mechanism because it only increases genotype frequencies not allele frequencies, the number of each allele will stay the same. (more stuff on inbreeding like inbreeding depression - heterozygote advantage is essentially lost). Another example of nonrandom mating is assortative mating, there are two types: positive and assortative.
Positive assortment: looking for a mate with the same trait as you
Negative assortment: looking for a mate that differs in a specific phenotypic trait
4. Natural selection:
5. Mutation: is a process that introduces new genetic variation into a population. Mutations are random changes to an organism's DNA sequence, and they can create new alleles that may be beneficial, neutral, or deleterious in their effects on an organism's fitness. Because mutations occur at a low rate, they can maintain genetic diversity within populations.

GENE FLOW: the conditions under which they occur; their effects on a population's genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects.

Gene flow: the flow of alleles from one source population to another population by individuals immigrating and emigrating, individuals must leave, breed and reproduce in over for them to have an effect on the genetic structure of the population.
- It is random with respect to fitness
- It homogenizes allele frequencies between populations because as individuals from one pop. move to another, they become more alike rather than different.
It can increase or decrease fitness because as individuals leave, they could be decreasing variation in the original population but they could be increasing variation when the other population might have undergone genetic drift.

Genetic drift: the conditions under which they occur; their effects on a population's genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects.

Genetic drift: is the random fluctuation of allele frequencies within a population due to chance events. In small populations, genetic drift can be a significant factor in maintaining genetic diversity, as rare alleles may become more or less common simply by chance. Genetic drift is especially important in populations that have undergone a bottleneck, where the population size has been drastically reduced, as it can lead to the fixation or loss of alleles.

non random mating: the conditions under which they occur; their effects on a population's genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects.

in nature mating may not be random with respect to the gene in question. Organisms may look for a mate with a specific trait (which is essentially coded by a specific genotype). There are different forms of nonrandom mating such as inbreeding which is mating between relatives. Inbreeding increases homozygosity, but it is not an evolutionary mechanism because it only increases genotype frequencies not allele frequencies, the number of each allele will stay the same. (more stuff on inbreeding like inbreeding depression - heterozygote advantage is essentially lost).
- Another example of nonrandom mating is assortative mating, there are two types: positive and assortative.
Positive assortment: looking for a mate with the same trait as you
Negative assortment: looking for a mate that differs in a specific phenotypic trait

Mutation - the conditions under which they occur; their effects on a population's genetic structure (e.g., variation, and mean character value); their relative effects on evolution; and factors that can impact their effects.

is a process that introduces new genetic variation into a population. Mutations are random changes to an organism's DNA sequence, and they can create new alleles that may be beneficial, neutral, or deleterious in their effects on an organism's fitness. Because mutations occur at a low rate, they can maintain genetic diversity within populations.

Describe the random nature of mutations; how mutations are passed from one generation to next (vertically and horizontally); the role of mutation in evolution; and describe how a mutation in DNA has a wide range of possible evolutionary consequences. [Comprehension]

Mutation: is a process that introduces new genetic variation into a population. Mutations are random changes to an organism's DNA sequence, and they can create new alleles that may be beneficial, neutral, or deleterious in their effects on an organism's fitness. Thus they are random with respect to the fitness of the organism. Often it can be deleterious as most organisms are already well adapted to their environment. Mutations are changes to the genetic info of the organism therefore they are heritable and can be passed on from parent to offspring.

Mutations are essential to the evolutionary process and without it evolution would just stop. This is because it's the only mechanism that only increases genetic variation because it makes NEW alleles, the other mechanisms can increase or reduce. But with no genetic variation, if selection acted on one trait, then drift fixed that allele, there would be no variation for evolution to continue. Thus, because mutations occur at a low rate, they can maintain genetic diversity within populations.
However mutations alone dont have a significant impact because the process is much slower and more rare, so combined with the other mechanisms like natural selection it can have an evolutionary impact.

Mutations can either have a beneficial, deleterious or neutral effect on organisms. If it is a point mutation, this could change the dna which codes for rna, which is essential to making proteins that result in phenotypic traits, so this could lead to changes in the phenotypes. It can beneficial for organisms when hiding from predators, or it can be deleterious by making them more noticeable.

Describe the impact of gene flow between two populations. [Comprehension]

- It homogenizes allele frequencies between populations because as individuals from one pop. move to another, they become more alike rather than different.

- It can increase or decrease variation because as individuals leave, they could be decreasing variation in the original population but they could be increasing variation when the other population might have undergone genetic drift.

- Gene flow may have a significant impact on the conservation of endangered species, because if a population is isolated, then theres a decline in gene flow, which could make them more vulnerable to extinction if genetic diversity is reduced.

- Gene flow can reduce, increase or have no effect on the fitness of the recipient population because if a captive population with a reduced fitness is released among a wild population, then over generations this can reduce the fitness of the whole population. However it can have the exact opposite effect if the captive population had a higher fitness!

Explain how drift (and its effects) is largely dependent upon population size; relate these effects to conservation biology. [Comprehension]

- Genetic drift: is the random fluctuation of allele frequencies within a population due to chance events. In small populations, genetic drift can be a significant factor in maintaining genetic diversity, as rare alleles may become more or less common simply by chance. Genetic drift is especially important in populations that have undergone a bottleneck, where the population size has been drastically reduced, as it can lead to the fixation or loss of alleles.

- There are important consequences of drift for species conservation: drift can cause even harmful alleles to rise in frequency by chance alone, especially in small populations, and smaller populations are less likely to evolve adaptively to new environmental challenges.
- Genetic drift acts faster and has more drastic results in smaller populations. This effect is particularly important in rare and endangered species.
- Genetic drift can contribute to speciation. For example, a small isolated population may diverge from the larger population through genetic drift.

Compare founder and population bottleneck events (causes and outcomes). Given a scenario identify which is occurring. [Comprehension]

- Founder effect occurs after a founder event, which is when a small RANDOM sample of the original population moves, and establishes a new population. This is a random sample so its unlikely that the new population will be genetically similar to the original population. And this difference will be elevated the smaller the population is. It is by chance that these individuals emigrated and established a new population. The outcome is that the new population itself has reduced genetic diversity because they are much smaller.

- Population bottleneck events are drastic reduction in the size of the population and a genetic bottleneck is a sudden reduction in the number of alleles in the population due to some event like a natural disaster. This will cause a change in the allele frequencies of the population. This can cause the population's genetic diversity to be reduced.

. Compare genetic drift and natural selection in terms of: how they work; their potential outcomes with respect to fitness, adaptation, and genetic variation; and random vs. non-random processes. [Comprehension]

Genetic drift: is the random fluctuation of allele frequencies within a population due to chance events.

fitness: Random: can increase, decrease or have no effect on fitness. May be devastating for bottleneck populations

Adaptation: Can reduce potential for adaptation by limiting genetic variation or removing beneficial alleles by chance

genetic variation: Random - usually decreasing bc ur losing alleles

random vs non random: random


Natural selection

fitness: Increases fitness

adaptation: Increases adaptation

genetic variation: Losing variation as one allele is selected for. But it depends. It can be lost or maintained!

random vs. nonrandom: Nonrandom

Compare gene flow and the founder effect (causes and outcomes). [Comprehension]

The main difference between gene flow and founder effect is that gene flow is between two populations, so a small population emigrates to another population and begins to breed and reproduce. The founder effect is when a small sample of the original population establishes a NEW population. Both events can reduce the genetic diversity of the original population as they leave the population, but as for the new population, gene flow homogenizes the two populations and the founder effect will decrease it because it's much smaller than the original one.

Compare inbreeding and sexual selection, and their potential effects on a population; given a scenario, determine which is acting. [Comprehension, Application, Analysis]

There are different forms of nonrandom mating such as inbreeding which is mating between relatives. Inbreeding increases homozygosity, but it is not an evolutionary mechanism because it only increases genotype frequencies not allele frequencies, the number of each allele will stay the same.
Inbreeding depression: when the average fitness of the population declines due to inbreeding:

Causes:
1. It increases homozygosity and many recessive alleles are loss-of-function mutations which have an effect in homozygotes but little or no effect in heterozygotes, so if inbreeding is increasing the number of homozygotes the avg. fitness will decline
2. Many genes (specifically the ones involved in fighting diseases) are under pressure from different selection forces for heterozygote advantage, if inbreeding is decreasing the number of heterozygotes then the fitness will decline

Describe the impact of inbreeding on a population's genetic variation, phenotypes, and heterozygosity; explain how non-random mating may not result in evolution. [Comprehension]

Inbreeding does not have an effect on allele frequencies but it has an impact on genotype frequencies. It decreases genetic variation because it increases homozygosity.
It wont result in evolution because it does not change allele frequencies.

Explain how sexual selection has resulted in showy structures in males, commenting on what this indicates about the males (relating to fitness trade-off, handicap hypothesis, honest signals, etc.); provide examples of male traits/behaviours to explain it. [Comprehension]

.

Differentiate between inter- and intra-sexual selection; given a scenario, identify which is acting, which sex will show the greater variation in reproductive success, and the extent of sexual dimorphism, justifying your answer. [Comprehension, Application, Analysis]

intrasexual selection: individuals of a gender competing with one another to obtain a mate
intersexual selection: the selection of an individual of one gender for mating by an individual of the other gender
Sexual dimorphism: "two forms" - refers to any trait that differs between males and females

Describe the phenomena of assortative mating (positive and negative) and its potential impact on a population. [Comprehension, Analysis]

Positive assortment: looking for a mate with the same phenotypic trait
Negative assortment: looking for a mate that differs in a specific phenotypic trait
Could result in directional selection for certain traits

Positive assortment

looking for a mate with the same phenotypic trait

Negative assortment

Negative assortment: looking for a mate that differs in a specific phenotypic trait

- Could result in directional selection for certain traits

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

population bottleneck

a type of genetic drift in which population size is sharply reduced due to some catastrophic event

Mutation

is a process that introduces new genetic variation into a population.

are random changes to an organism's DNA sequence, and they can create new alleles that may be beneficial, neutral, or deleterious in their effects on an organism's fitness. Thus they are random with respect to the fitness of the organism. Often it can be deleterious as most organisms are already well adapted to their environment.

are changes to the genetic info of the organism therefore they are heritable and can be passed on from parent to offspring.

Intra vs intersexual selection

Intrasexual selection happens within the same sex (ex: males fighting),

intersexual selection happens between sexes (ex: female choice)

The fitness trade-off hypothesis

suggests that the showy structures in males are indicative of genetic quality. Females select mates with these traits because they are more likely to produce offspring with higher fitness.

The handicap hypothesis

suggests that showy structures need more effort to maintain and only the males that most genetically fit can maintain and display them. This shows females that although it is difficult to maintain, the males are able and capable of surviving.

The honest signals theory

suggests that showy structures in males are honest and true indicators of their genetic quality/fitness because they cannot be fakes. If a female chooses a male with these indicators, they will have offspring with good genes because the male has a high genetic fitness.

Explain the adaptive value of sexual cannibalism and self-sacrifice. [Comprehension, Analysis]

Sexual cannibalism is the act of eating one's partner after intercourse. There are some adaptive advantages.
1. Nutritional benefits: if food is scarce the female can eat the male when she needs energy to lay eggs and needs extra nutrition
2. Reduced competition: the female can reduce competition from other males for her eggs by eating the male.
3 . Protection against predators: the male may sacrifice himself to the female to escape frim a predator. For ex. spiders

Self sacrifice:
1. Protection of offspring: parents may sacrifice themselves to protect their offspring from predators, etc.
2. Benefits to the group: ex bees work hard and may sacrifice themselves to protect the hive

Relate and justify characteristics of an organism to their suitability as model organisms in evolutionary studies. [Comprehension, Analysis]

Genetic tractability: A model organism should have a well-understood genome and genetic tools available for manipulation. This allows researchers to study the effects of specific genetic changes on evolution and provides a better understanding of the genetic basis of evolution.

Short generation time: A short generation time allows for the rapid accumulation of genetic variation and the observation of evolutionary change over a relatively short period. This is particularly important for studying evolutionary processes that occur over a few generations, such as adaptation to new environments.

High reproductive capacity: A high reproductive capacity allows for large populations to be studied and for the observation of rare evolutionary events that may occur randomly. This also allows for the study of the evolution of mating systems and sexual selection.

Availability of resources: A model organism should be easy to obtain, maintain, and study. It should have well-established laboratory protocols for breeding, housing, and experimentation. This reduces the cost and time required for research and ensures that the results are reproducible.

Phylogenetic position: The model organism should be phylogenetically informative, meaning that it is representative of a diverse group of organisms and can provide insights into evolutionary processes across multiple taxa.

List 3 characteristics of model organisms useful for evolutionary studies.

Short generation time
Availability of resources
High reproductive capacity

Predict how genotype frequencies differ from Hardy-Weinberg proportions under directional selection when allelic phenotypes are codominant.

Under directional selection, the fitness of certain genotypes can change which may lead to a deviation from HWE. Since directional selection favors one genotype, there will be an increase or decrease in the frequency of the allele overtime. However if the allelic phenotypes are codominant, the homozygous genotype will have different fitness values and the heterozygous genotype will have an intermediate fitness value.

What does it mean when an allele reaches 'fixation'?

- When an allele reaches fixation, it means that it has become the only allele at a particular locus in a population. The individuals in the population are homozygous for that allele and no other alleles exist at that locus.
- Rmbr that genetic drift can lead to the fixation of an allele by chance, even if its disadvantageous.
-If an allele has reached fixation, it will be permanent unless a new mutation is introduced or the pop. undergoes an event such as bottleneck effect or migration.
- Fixation can have effects such as loss of genetic diversity, increased homozygosity, and decreased potential for adaptation.

Why is mutation the ultimate source of genetic variability?

Mutation is the only process that brings brand new genetic info into a population. They are random changes in the DNA sequence which can create new alleles that were not present before (disregarding recombination, genetic drift because they don't create NEW genetic info).

If the antibiotic rifampin was banned, would the mutants with the rpoB allele have lower or higher fitness in the new environment. What would happen to the numbers of individuals carrying the mutation - would they increase, decrease, or stay the same in M. tuberculosis populations?

If the antibiotic rifampin was banned, mutants with the rpob allele would have lower Fitness in the new environment compared to Wild type strains of M.tuberculosis that do not carry the mutation. This is because the rpob mutation comes with the fitness cost and it reduces the overall reproductive success of the bacteria in the absence of the antibiotic. There would no longer be a selective pressure that favors the rpob mutants and the wild type strains would have a fitness advantage this means that the numbers of individuals carrying the rpob mutation would decrease in population over time as they would be out competed by the non-mutant strains.

allele

a specific version or variant of a gene that can differ in its DNA sequence from other alleles of the same gene.

gene

regions of DNA that contain the information needed to produce a functional molecule, such as a protein or RNA molecule.

genotype

refers to the genetic makeup of an organism, specifically the set of alleles that an individual carries for a particular gene or gene.

Phenotype

refers to the observable characteristics or traits of an organism that are the result of both genetic and environmental factors

genotypic variation

differences in the genetic makeup of individuals

phenotypic variation

differences in appearance or function that are passed from generation to generation

Heritability

measure of the proportion of variation in a particular within a population that is due to its genetic factors.

gene pool

The gene pool refers to all of the genetic information (alleles) present within a particular population or species. It includes all of the different versions of genes (alleles) that are present in individuals within the population, as well as the frequencies at which those alleles occur

genotypic frequency

refers to the proportion of individuals in a population that have a particular genotype for a given gene or set of genes. It is often expressed as a decimal or percentage.

how to calculate genotype frequency

To calculate genotypic frequency, the number of individuals with a particular genotype is divided by the total number of individuals in the population.
For example, suppose a population of 100 individuals contains 25 individuals with the homozygous dominant genotype (AA), 50 individuals with the heterozygous genotype (Aa), and 25 individuals with the homozygous recessive genotype (aa). The genotypic frequencies for each genotype can be calculated as follows:
AA genotype frequency = 25/100 = 0.25 or 25%
Aa genotype frequency = 50/100 = 0.5 or 50%
aa genotype frequency = 25/100 = 0.25 or 25%
p+q=1
The sum of these genotypic frequencies should always equal 1 or 100%

allele frequency

refers to the proportion of a particular allele (one of the possible versions of a gene) in a population. In other words, it is the percentage or proportion of individuals in a population who carry a specific version of a gene.

Hardy-Weinberg principle

The principle states that if certain conditions are met, the frequencies of alleles and genotypes in a population will remain constant from generation to generation.

The conditions required for the Hardy-Weinberg principle to apply are:

1. No mutation: the alleles at a particular locus do not mutate from one form to another.
2. No migration: there is no migration of individuals into or out of the population.
3. No selection: all genotypes have an equal probability of survival and reproduction.
4. Large population size: the population is large enough that random fluctuations in allele frequencies are negligible.
5. Random mating: individuals mate randomly, without regard to their genotype.

Hardy-Weinberg equilibrium/Genetic equilibrium

the proportion of individuals with a particular genotype is the same in each generation, and the frequencies of alleles do not change over time.

loci/locus

location of a gene on a chromosome

acclimation

refers to a reversible, short-term physiological adjustment that an organism makes in response to a change in its environment.

adaptation

a long-term evolutionary process that occurs over many generations.
cheater/selfish alleles,

Pleiotropy

a single gene can affect multiple traits or phenotypic traits. In other words, a single gene can have multiple effects on the phenotype of an organism. For example, sickle cell anemia is a disease caused by a single gene mutation that results in abnormal hemoglobin protein production. This gene mutation not only causes sickle cell anemia, but it can also provide some resistance to malaria

assortative mating

refers to a type of mating pattern where individuals tend to choose mates with similar or dissimilar traits to their own, rather than choosing mates randomly.

Non-assortative mating

refers to a mating pattern where individuals mate randomly, without regard to their own traits.

Positive assortative mating

occurs when individuals with similar traits tend to mate with each other