Evolutionary ecology
Where do variations come from?
-Mutations. Mutations change the protein and therefore the phenotype. Mutations must act on the phenotype for selection to act upon them Mutations aren't the only way that variation arrives. - Recombinations—crossing over - Migrations.—Mutation in a flower could have been blue at one point where mutation occurred that caused all white. Due to migration of the pollinator, youc an get a mized population of colors.
What are some examples of induced evolution?
Fisheries and big fish. To the selective pressure of humans loving big fish, it isn't the best for fish to be big. So now fish are much smaller and are reproductively mature at a much smaller size. It is seen that with continued human selective pressure, it would take the fish almost 200 years to recover. Without, it would still take 35 years!
What is frequency dependent selection and how many types are there?
Frequency dependent selection is when the fitness of each genotype depends on its frequency in the population (how many times or how many animals have that gene). There are two types, positive and negative.
Define evolution by natural selection
Individuals in a population exhibit variation in heritable traits, and those with traits better suited to their environment tend to survive and produce more offspring that thos with traits less well suited. As a result, populations change over time.
What are similarities and differences between natural selection and drift?
One is biased (natural selection), one is random, both are sampling processes, natual selection depends on random mutation, but it itself is not random.
What are the only changes that can be called evolutionary?
Those that are inherited over generations
If you get a picture with a baby bear and mama bear, does it mean they are fit?
no because you do not know how many offspring and you need to see if that baby will reproduce.
What organisms would recombinations not work? And what are the limits to recombinations
- Asexual organisms. Their recombinations would come from mutations and recombinations only happen during meiotic division. - First limit is that genes on the chromosome are completely independent from one another. Another limitation is inbreeding, not specifically humans but other species. Inbreeding reduces heterozygosity and causes no new variation.
How do gene flow and drift work together?
- Both influence allele frequencies - One leads to recuced genetic diversity and increased population divergence, while to other can increase population divergence.
What are the four mechanisms of evolution?
- Mutation - Natural selection - Gene flow - drift
What are some mutations that could cause variation and give an example of each of there is
- Point mutations is one type. - Chromosomal mutations such as inversions, deletions, duplications, additions, tranversions and translocations—These could have a cascade effect, could impact the entire genome and could possibly be lethal. Chromosomal fusion, polyploidy etc. Plants can be normal and polyolid but humans cannot. Single mutations which can be very important. They saw that a single mutation in the AN2 allele changed the color of the petunia flower to white because the white mutation caused a block of the production of anthocyanin, which cause the pink color. So single mutations matter because they can cause speciation/variation. If you are a pink flower, bumblebees like it more. Hawk moths like white more. Shows how one change in genotype can change ecological interaction
What is the breeders equation and what does it mean?
- R= heritability x selection differential (intensity) - The equation allows us to predict evolutionary change in a population if we already know the heritability and if we can quantify the selection occurring in that population. Using this equation, we can predict which traits are more likey to respond to selection.
Balance between which 3 keys are important for evolution?
- Selection, migration and drift - Drift will tend to make population gene frequencies explore around their present position, could move a population from a local peak to explore the valleys of fitness surface Once it had explored to the foot of another hill, natural selection could start its climb up the hill on the other side if members of a sub-population at he highest peak were better adapted, they could produce more offspring (remember natural selection always pushes species upt he peak). They would also produce more emigrants to the other sub-populations Those other sub-populations would then be taken over by the superior immigrant genotypes by natural selection. Thus, the whole species would evolve to the higher peak.
What is a few ways you can find out if a trait has a genetic basis?
- You can do a common garden study. Go to a bunch of field sites, collect seeds from the same plants and bring them all to one area to grow. If the trait is strictly due to the environment, they would all grow the same, but if there was a genetic basis, then they should retain some of the phenotypes. And for sure, in this study you will see that there is a genetic basis. - You look at finches in common environment "garden and see if they grow the same and found that the beak size was te same due to environment but other traits were gentic.
What does it mean to be the fittest?
-fitness is the measure of potential for an indicidual to contribute to the future gene pool. It is the number of offspring produced which can then also reproduce. So to be fit, you have to be a grandparent. • A trait that confers higher fitness is an adaptive trait, not plastic.
How many evolutionary consequences are there in regards to phenotypic plasticity? What are they ?
3 1) if higher phenotypic values are associated with fitness, the trait that is favored depends on the environment. For example, if we have 3 genotypes in 3 different environments, the genotype (phenotype) designated for a specific environment will do beter than antoer (lecture 5)/ BE ABLE TO DEFINE HERITABILITY IN WORDS. 2) GxE can reduce heritability. The combination of genotype and environment produces a phenotype that cannot be predicted using knowledge about each so you add Vgxe in the equation. 3) Gxe can reduce efficacy of natural selection inducing a slow evolutionary response. There is no response to selection unless a trait is heritable. Environment makes things messy when predicting next generation using additive genetic variance. GxE can reduce heritability. Top right graph—All genotypes are plastic, but some are responding more than others, some are decreasing or increasing. In this example, you have less phenotypic variation because they begin to look similar to each other.
What is stabilizing selection? Give an example
A type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. This means that fitness is higher at the average and fitness works against the extremes. There is a decrease in variance. An example is with light and dark color oysters. Either color oyster might be more frequently preyed upon so selection has decreased the variance ans favored an intermediate color.
What is the difference between adaptation and acclimation? Give example of acclimation.
Acclimation is when an individual has some level fo performance at a time and place. Acclimating to the oxygen levels as you go up everest. Acclimation is when an individual organism adjust to a gradual change in its environment, allowing it to maintain performance across a range of environmental conditions. - adaptation is always genetic anf acclimation may show a value in one trait or gene over another. Adaptation is evolution and occurs over generations. Allows maintenance of performance across a range of conditions. Natural selection is the only evolutionary mechanism that consistently causes adaptive evolution. - Acclimation DOES NOT lead to adaptation.
What is another factor that plays into VG and allows you to predict the effects of alleles?
Additive genetic variance. Phenotype can be predicted. There is also a dominance factor though and this is phentotype that is not predicted by additive effects. Non-additive genetic variance.
What are some of the links between evolution and ecology? What is the common goal?
All the ecological interaction such as interactions between communities, individuals populations, ecosystems, competition, predation, biotic factors, pressures, constraints, all play into the idea of evolution and allow populations/species to macro or micro evolve across generations. The common goal is to understand and describe variation in natural systems and discover its functional basis
In regards to the lip size of chiclids, why might phenotypic plasticity of lip size be adaptive? Why may it not be adaptive?
Could be due to a variable environment, lip size could be more advantageous in specific environments, mechanical stress. May not be adaptive if it can increase fitness or be passed on, there could be trade-offs, and engergy costs.
What is an example regarding phenotypic plasticity in daphnia?
Daphnia display different types of growth in response to a predator que
What is directional selection?
Directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency for a trait to continuously shift in one direction. It is a linear relationship between fitness and the trait. The fitness varied with the trait. There is a change in mean of frequency.
What are the two types of non-additive genetic variance?
Dominance and epistatic. Epistasis is when the phenotype of a gene changes at one locus and it depends on the phenotype at one or more loci (lecture 2 Review!)
What is ecology? What are some factors studied in ecology?
Ecology is the study of how and why organisms interact with their environment in the specific manner that they do. Some of the factors that come into play are those such as competition, predation, energy flow, abiotic, biotic factors etc. Interactions between populations, communities and ecosystems are all taken into account.
what is the difference between evolution and natural selection?
Evolution is change over generations while natural selection is within
What is evolution with regards to gene composition or frequencies of a population?
Evolution is the change in genetic frequencies and the composition of genes in a population
What is disruptive selection and give an example
Extreme values are favored. There is an increase in variance. Continous distribution of lower mandible of finches. Mandible is important for seeds. If there are only large seeds and small seeds, you will get birds only with large and small, not medium. We call this a binodal model.
True or false? Individuals, not populations adapt and evolve?
False. POPULATIONS evolve and adapt, not INDIVIDUALS!
Give an example of how gene flow and natural selection have an impact on population
Found grass species to be growing on both sides. So they wanted to know can this species adapt to the mine tailing toxicity? They found it on both sides of the contaminated pressure, but what causes them not to grow on it? When they looked at the flowering trait, they looked at both sides. They found plants are able to grow in mine area, but look different. They tend to flower at a different stage than others. So they wanted to know if this is adaptive because they are only 10 meters apart. Or are we just seeing plasticity? If you just have plants in pasture, there must hasve been some mutation that allowed plant to handle toxic site. But as long as the mutation doesn't do bad, it will multiply by drift. By chance it could be lost or become more common. So gene flow could cause the seeds show up into the mine and the plant may be able to survive and reproduce. This is an example of extreme selection, where if you dnt have the allele that can handle toxic area, you can die.
what did the researchers of the chichlid lip size experiments conclude?
Found that there was a genotypic and plastic component to lip size and said it was adaptive because they did crosses and created an intermediate. But its only small and big lips so it is disruptive selection.
What are the two special cases of drift? Define each and give examples.
Founder and bottleneck effect. Bottleneck effect occurs through time while the founder effect occurs through space. Bottleneck is when a population is reduced due to an event /disaster than can lead to changes in gene frquency. Founder is when loss of genetic variation occurs when a new population is established by a very small number of individuals from a larger population. - - Bottleneck example : Plants of one species with two variants. Emerge after frost. If you get a freak snowstorm and plants freeze. But of you're under the tree, it can be warmer. So population will look blue after the freeze because they are the ones that survived. So this is a bottleneck and also chance. Those blue are the ones that are left to reproduce. - Another bottleneck effect. Pingelap High percentage of people with this recessive inherited condition that negatively affects you. Cant see color and have some visual loss, etc. in 1700s on this island, there was a huge typhoon and small percentage survived. One of the guys had this recessive allele. He was a carrier. And so in pingelap, he got the population to have 30 percent as carriers and 5-10 percent who have it. Another bottleneck effect. Maladaptive trait, but allele became common because random event. - Amish people are a founder effect. (Look at ppt)
What is difference between direct and indirect selection?
Indirect is when if pollinators favor flower size, color covaries with it. Direct is when color of flower only depends on pllinator preference to color
what is the shade avoidance hypothesis?
It was an experiment done to show how plasticity can be adaptive. this doesnt mean plasticity is always adaptive. Showed how there is a reason why some plastic traits do better in some situations than others and this is due to costs &limits (constraints and trade-offs). Some of the costs are things such as maintenance, genetic costs, energy costs, development instability. Some limits are lag time, small developmental range, information reliability.
• What are two types of evolution?
Macroevolution and Microevolution. Microevolution is within a species while Macroevolution is large scale evolution.
What does it mean if you have a high standard of deviation in an population
Means that there is a ton of variance. Vice versa
What is GxE?
Means that there is variation where the genotype may or may not respond to the environment.
Is mutation the same as drift?
Mutation is at a low frequency when it occurs so it more likely can die off due to drift.
Is plasticity the same as adapting?
No it is similar to acclimating
Can phenotype be predicited solely on genes?
No. For example, daphnia look identical because they are asexual organisms, but when put in the same environment, they look different due to predator cues. So what you look like also depends on the environment.
Is variation in skin color evolutionary significant? Why or why not?
No. It does not influence fitness. Variation needs to have a genetic basis and influence fitness.
True or false. Mutation drives evolution?
No. Mutations is how variation arises, but mutation itself does not drive evolution
Does the phenotype (genotype) determine outcomes of natural selection?
No. While phenotype Genotype may be superior to another, it is OVERALL fitness that determines this.
What is a quantitative trait? (Lecture 2)
One that has a gradient of variation. Continous distribution and variation. Many loci often have a small effect.
Predicting the outcome of natural selection on ecologically important traits depend on being able to determine the quantitative relationships between what three things?
Phenotype, genotype, and fitness.
What are some things that cause plastcity?
Plasticity genes allelic sensitivity: where the same genes control expression in different environments gene regulation: some genes are active only in certain environments, there could be a stimulus that turns a gene on or off to express the phenotypic plasticity.
What is the difference between positive genotype and negative phenotype? What is an example of each?
Positive is when a certain phenotype gains greater fitness as it becomes more common. negative is when a given phenotype gains greater fitness when it is rare and thus maintains genetic variation. Positive frequency dependence example: a lot of monarch butterflies have same black designs because it acts as a warning signal. An example of negative frequency dependence has to do with the orchid. Pollinators come to the flower because of nector. If yellow doesn't have nectar, it is buying fitness off of other flowers. If yellow morph increases, pollinators stop visiting it. So pollen decreases (bottom graph) and fruit set decreases. So when this happens, the red one is going to be more common. Once red becomes more common, is yellow does better. This type of frequency dependent selection can maintain variation in a population.
How can you tell if an organisms trade-off is genetic or environmental
Put it in different environments to see change in litter size and size of offspring. If the graph shows different lines, it means there is also some environmental component.
What is the similarity between gene flow and drift?
They are mechanisms of evolution and can interfere with evolution by natural selection. They can lead to maladptation. But they can also promote evolution by natural selection by saving an allele.
What is the similarity with constraints and trade-0ffs?
They slow down or restrict evolution by natural selection
True or false. More alleles at a locus causes more variation
True
How would you figure out what relation the variation in phenotype has with genetic variation and environmental variation?
Vp= Vg +Ve (work out the equations on a piece of paper on Monday!)
Is plasticity adaptive? Can plasticity evolve?
What are factors required for trait to evolve by natural selection? You need a genetic basis that is due to additive genetic variance, has to be adaptive by increasing fitness, and genotypic variation has to affect a certain phenotype. Some genotypes increase, stay the same, or decrease as shown on the graph. So if you had a graph that had 3 genotypes and they all have a linear relationship with phenotype...is it plastic? Then yes because they are changing in response to the environment, but there is not variation because they are responding the same way. So if we are talking about selection on plasticity, there has to be variation for selection to act on plasticity. So there needs to be genotypic variation in plssticity and plastic genotypes perform better than less plastic ones on average ACROSS environments (variation is non-random). So to be adaptive, your average across generations should be better and should be heritable if you want plasticity to evolve.
What is the noun definition of adaptation?
a trait that enables or enhances the probability of that organism surviving and reproducing (also called adaptive trait. )
Genetic drift occurs in all populations, all the time, tru or false.
agree. For sexual organisms, there is a lot of chance involved. For asexual, random chance of mutation.
What are the three modes of natural selection??
directional, stabilizing, and disruptive
What are some reasons why organisms are not perfectly adapted to their environment? Then name the main 4 reasons, define them and give example if available.
environments are not constant, not all traits do the best in each environment. The same trait could look good for both a pollinator and antagonizer. - the main 4 reasons are constraints, trade-offs, gene flow, and drift . - A constaint is that natural selection only selects from variation that is already present in the population. History development, physiology, physics, and chemistry can limit variation . Arthropods are a huge genus but they are so small. Why? Different circulatory system and they can only get so big, We take up more oxygen than them, which is maybe hwy we are bigger and they are not. Their ecoskeleton is very successful and it takes a long time to molt, so they are smaller so they can molt and mature faster. If youre bigger it limits. - Trade-offs—any case which fitness cannot be maximized because of competing demands on the organisms. For example, a plant could be great in one environment, but not another and this is due to different selective agents like pollinators. Another ecample is how small beaked finches do better in one season versus another and the big ones do better in another. Selection differential could be a reason, which is the difference in mean of population before and after selective event. There could be trade-offs in traits too. For example, if you have more of trait x, you have les of trait y. You have limited resources like energy budget . If you put more energy into defence, you may have to use less for mating. Another example is that it is very difficult for spiders to have a large clutch size because their sac can only hold so many eggs. - - Drift is a game of chance. It is random fixation of alleles and genetic differentiation among subpopulations. Drift reduces the amount of genetic variation which means there is less material for natural selection to act upon. If we have a bag of marbles that represent alleles and phenotypes. We start with 60 white - 40 green marbles. Randomly select marbles. Just by chance, we have a higher chance of grabbing more white marbles. If we keep doing it, the green population has depleted. Once they are lost, the only way they can be reproduced is gene flow or mutation. In the absence of these, drift serves to reduce amount of genetic variation. - Drift is almost stabilizing selection as the population size increases. If you flip a coin 100 times, it will average out and the populations don't lose the alleles. - Gene flow
What is gene flow? What does it do?
gene flow is the movement of individuals and the genetic material they carry from one population to another. Gene flow is the glue that keeps populations together and it homogenizes populations over time. It can add genetic variation to small, inbred populations, increasing fitness through genetic rescue. But, they may introduce a maladaptive allele. It can rescue populations that suffer from drift and it can save or maintain variation. But it cant always be good as it works against natural selection by introducing these maladaptive alleles. - gene flow must be limited in order for populations to diverge
What is phenotypic plasticity?
it is the ability of an individual to change ohenotype in response to an environmental stimulus. If you take species with the same genotype, put them in different spots, they may look differently due to the environment. Think about a graph, phenotype on the y axis and environment on the x axis, it is a linear relationship positive. But,........ o What would this graph look like if the trait was solely determined on phenotype? - it would be a straight line across
Does evolution always result in the best solution?
no
What is meant by opposed selection? Where did we see an example of this?
opposed selection is when the predator and pollinator favor one plant, and plant mutates to keep that benefit. They were trying to see if there was opposed selection of both pollinator and predator that maintained variation, but they found that it does not maintain variatin
heritability
ow much of the genetic diversity of a phenotypic trait in a population is due to genetic differences in that population. In other words, it is the proportion we see in the phenotype due to additive genetic effects. h^2 = Va/Vp Vp= Va+ Vd+Vi+Ve+ Vgxe
Slope is a measure of what?
selection
What is truncation selection?
selection is acting such that only those with a certain phenotype survive to reproduce
What is the verb version of adaptation?
the evolutionary process wherby an organisms becomes better able to live in its habitat Adaptation confers higher fitness
