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Living things can be single-celled or multicellular. They could be plants, animals, fungi,bacteria, or archaea. All life is related. Millions of years of evolution have shaped each of Chapter Outline these organisms into the forms we see today, according to Evolutionary theory. Evolution is considered a key concept by scientists. One of the most dominant evolutionary forces is it.

The traits and behaviors that are detrimental to the organisms are evolution. Natural selection cannot create.

Genetics change populations and species. The world of life we see today is the result of 19 processes.

The idea of natural selection was being developed by Alfred Russel Wallace. It was difficult to understand many aspects of evolution because of the lack of knowledge. Blending inheritance made it difficult to understand how natural selection might work. Darwin and Wallace were not aware of the Austrian monk's "Experiments in Plant hybridization", which came out after Darwin's book, On the Origin of Species. In the early 20th century, scholars rediscovered Mendel's work, which helped geneticists understand the basics of inheritance. The discovery of particulate nature of genes made it difficult for biologists to understand gradual evolution. The relationship between natural selection and genetics was understood by the 1940s. Today, this concept is generally accepted. Evolutionary processes, such as natural selection, can affect a population's genetic makeup and result in the gradual evolution of populations and species, according to the modern synthesis.

The media starts reporting on flu vaccinations in the fall. Scientists, health experts, and institutions determine recommendations for different parts of the population, predict optimal production and inoculation schedules, create vaccines, and set up clinics to provide inoculations. The annual flu shot may be seen as media hype, an important health protection, or just a brief uncomfortable poke in your arm.

The media hype of yearly flu shots is based on our understanding of evolution. Scientists try to predict the flu strains that will be the most widespread and harmful in the coming year. This knowledge is based on how flu strains have evolved over time. Scientists work to create the most effective vaccine to fight the selected strains. In order to provide vaccinations to key populations at the optimal time, pharmaceutical companies produce hundreds of millions of doses in a short period.

The challenge is due to the fact that viruses evolve very quickly and in evolutionary time. The vaccine developed to protect against last year's flu strain may not be enough to protect against the coming year's strain. Adaption to survive previous vaccines is one of the ways evolution of these viruses ensures survival.

A character's genes may have several alleles, or variant, that code for different characteristics. In humans, there are three alleles that determine the blood type on the surface of red blood cells. Each individual in a population of diploid organisms can only carry two alleles for a particular gene, but more than two may be present in the individuals that comprise the population. As all genes were passed down from parent to offspring, Mendel followed them.

Evolution is a change in the characteristics of a population of organisms, but behind that is genetic change. The term evolution is defined in population genetics as a change in the allele's frequencies. The number of copies of the IA allele divided by the number of copies of the ABO gene in the population is the ABO blood type system example. A study in Jordan found a Frequency of IA to be 26.1 percent.

All of the frequencies added up to 100 percent, with the IB and I0 allelesconstituting 13.4 percent and 60.5 percent of the alleles respectively. Over time, a change in this Frequency would be considered evolution in the population.

Certain alleles become more widespread than others during the natural selection process because of environmental factors. Natural selection can change the population's genetics.

An example is if a given allele allows an individual to have more offspring. Because many of those offspring will carry the beneficial allele, and often the corresponding phenotype, they will have more offspring of their own that also carry the allele, which perpetuates the cycle. The allele will spread throughout the population over time. Every individual of the population will carry at least one of the alleles, meaning that if a dominant allele is found in the gene pool, it will be quickly fixed.

Sometimes, allele frequencies within a population change with no advantage to the population over the existing frequencies. This phenomenon is called genetic drift. Natural selection and genetic drift are not isolated events. It's difficult to determine which process dominates because it's hard to determine the cause of change. Changes in a population's genome can be caused by natural selection, random drift, and founder effects.

The principle of equilibrium was stated in the early twentieth century by English and German mathematicians. The principle of equilibrium states that a population's allele and genotypic frequencies are stable unless some kind of evolutionary force is acting on the population. The principle assumes conditions with no genetic changes, migration, emigration, or pressure for or against a particular group. The principle offers a model against which to compare real population changes.

Population geneticists use this theory to represent different alleles as different variables in their mathematical models. The variable q and the variable p are used to represent the frequencies of all the genes that make up the color green. If these are the only two possible alleles, then p + q is the number. In other words, all of the p and q alleles are in the same place in the population.

We can only observe the phenotype if we have the allele's genotype. An estimate of the remaining genotypes is provided by the calculations. Predicting the genotypes' frequencies is a simple calculation if we draw two alleles at random from the gene pool. In the above scenario, an individual pea plant could produce yellow peas, pq, also yellow, or qq, and thus produce green peas. The frequencies of pp individuals are simply p; the frequencies of pq individuals are 2pq; and the frequencies of qq individuals are q2. If p and q are the only two possible alleles for a trait in the population, these frequencies will sum to one: p2 + 2pq + q2

When populations are in the equilibrium, the allelic frequencies are stable from generation to generation and can be determined from the equation. Scientists can use the allelic frequencies measured in the field to figure out what evolutionary forces are at play.

In plants, violet flower color is more dominant than white.

In theory, if a population is at equilibrium, there are no evolutionary forces acting on it--generation after generation would have the same gene pool and genetic structure, and these equations would all hold true all of the time. No natural population is immune to evolution. Populations in nature are constantly changing due to drift and other factors. The only way to determine the exact distribution of phenotypes in a population is to count them. The Hardy-Weinberg principle allows scientists to compare evolving populations with a mathematical baseline of a non-evolving population. The population is evolving if the frequencies of all genes don't match the values expected from the equation.

The calculator can be used to determine a population's genetic structure.

Scientists refer to individuals in a population as polymorphisms, because they display different phenotypes or alleles of a particular gene. Populations are called if they have two or more variations of the same characteristics. Understanding the sources of variation in a population is important for determining how a population will evolve.

Population variation is shown by the distribution of phenotypes in this litter of kittens. Natural selection and some of the other evolutionary forces can only act on an organisms genetic code.

Because alleles are passed from parent to offspring, those that confer beneficial traits or behaviors may be selected, while those that do not may not. Most of the acquired traits are not heritable. If an athlete works out in the gym every day and builds up their muscles, their offspring may not grow up to be a body builder. A child may be given the ability to run fast if there is a genetic basis for it.

Jean-Baptiste Lamarck believed that organisms could inherit trait from one another. Some scientists have recently begun to realize that Lamarck was not completely wrong, despite the fact that the majority of scientists have not supported this hypothesis. To learn more, visit this site.

The evolutionary forces that act on heritable variation are more susceptible to heritability.

When scientists are involved in the breeding of animals in zoos and nature preserves, they try to increase the population's genetic variation to preserve as much of the diversity as possible.

A disease that is caused by a rare, recessive allele might exist in a population, but only if an individual carries two copies of it. Only 25 percent of offspring of two carriers will inherit the disease from both parents, because the chance that two carriers will mate is low. Natural selection won't be able to eliminate the allele from the population quickly because it won't happen frequently.

Changes in allele frequencies can shed light on how a population is evolving. There are other evolutionary forces that could be involved in natural selection.

Natural selection is based on the idea that some people in a population are more likely to live longer and have more children than others. A big, powerful male gorilla is more likely to become the silverback, the leader of the group, than a smaller, weaker one. Half of the pack leader's genes will be passed on to his offspring, who are likely to be bigger and stronger than their father. The population will grow larger on average as the population's genes for bigger size increase in frequency. The selection pressure might be caused by better camouflage or a stronger resistance to drought.

By chance, some individuals will have more offspring than others, just because one male was in the right place at the right time, or the other one was in the wrong place.

It is possible to eliminate an allele from a population by chance. rabbits with the brown coat color allele are more dominant over rabbits with the white coat color allele. In the first generation, the two alleles occur with equal frequencies, resulting in p and q values. A second generation with p and q values of.7 and.3 was created by only half of the individuals. Two individuals in the second generation are dominant for brown coat color. The b allele is lost in the third generation.

Small populations are more vulnerable to genetic drift. Large populations are not affected by chance. All of the population's genes will be lost if one of the 10 individuals dies before the next generation is born.

You can watch an animation of random sampling and genetic drift on this site.

A large portion of the population can be affected by a natural disaster. The survivors' genetic structure becomes the entire population's genetic structure at once, which may be very different from the pre-disaster population.

The genetic variability within a population can be reduced by a chance event.

If a portion of the population leaves to start a new population in a new location or if a physical barrier divides the population, there is a chance of a strong influence of genetic drift. The founder effect occurs when those individuals are an unlikely representation of the entire population. The founder effect occurs when the genetics of the new population match those of the founding fathers and mothers. The founder effect is believed to be a key factor in the genetic history of the Afrikaner population of Dutch settlers in South Africa. A higher proportion of the founding colonists carried these genes.

There is a short video to learn more about the founder and bottleneck effects.

The Fanconi Anemia Families of the Afrikaner Population of South Africa have evidence of a founder effect.

When a big earthquake or storm wipes out a lot of people, the survivors are usually a random sample of the original group. The population's genetic makeup can change a lot. The phenomenon is called the bottleneck effect.

Each time one runs this experiment, the results will vary.

Use different colored beads to count out the original population. There are red, blue, and yellow beads. After recording the number of each individual in the original population, place them all in a bottle with a narrow neck that will only allow a few beads out at a time. Put 1/3 of the bottle's contents in a bowl. A majority of the population is killed by a natural disaster. Place all of the beads back in the bottle and repeat the experiment four more times.

The populations resulted from the experiment. The populations all came from the same parent.

The five resulting populations are likely to differ a lot. Natural disasters kill and spare people at random. Think about how this might affect a population.

Some populations are stable. Many plants send their pollen far and wide, by wind or bird, to other populations of the same species some distance away. A pride of lions can experience immigration and emigration as developing males leave their mothers to seek out a new pride with genetically unrelated females.

Variable flow of individuals in and out of the group can change the population's gene structure and introduce new genetic variation to populations in different geological locations and habitats.

Gene flow occurs when an individual travels from one location to another.

Diversity in populations is influenced by changes to an organisms' genes. Over time, the species evolve. Novel genotypic and phenotypic variance can be introduced by the appearance of new genes. Natural selection eliminates unfavorable or harmful genes from the population. Others will spread through the population. Whether or not a genetic change is beneficial or harmful depends on whether the change helps the organisms survive to sexual maturity and reproduce. Natural selection can cause some genes to linger unaffected in the genome. There are some genes that can have a dramatic effect.

The result can be a changing population if individuals don't randomly mate with each other. Simple mate choice is one reason. Peahens may prefer peacocks with bigger tails.

Natural selection picks characteristics that lead to more sexual selections for an individual.

Physical location is a cause of nonrandom mating. In large populations spread over vast geographic distances, not all individuals will have equal access to one another. Some might be miles apart through the woods or over rough terrain.

Population variation can be determined by more than just genes. A city dweller is more likely to have darker skin than a beachgoer due to regular exposure to the sun. Some species have major characteristics determined by the environment.

Some turtles and other reptiles have sex determinations that are dependent on temperature. If females are at a different temperature range than males, they will develop into males.

The American alligator's (Alligator mississippiensis) produce females and males when the eggs are at 30 and 33 degrees.

There can be differences in the variation between populations. Smaller bodies in the cooler climates closer to the earth's poles allow species of warm-blooded animals to better conserve heat.

This is aitudinal line. Depending on where they are along a mountain slope, flowering plants bloom at different times. This is aitudinal line.

The individuals will show gradual differences in their phenotype if there is gene flow between the populations.

Alterations, even speciation, can be caused by restricted gene flow.

By the end of this section, you will be able to explain the different ways natural selection can shape populations. If an individual carries an allele that results in a fatal childhood disease and also carries a beneficial genotype that increases the ability to reproduce, that fecundity phenotype will not pass to the next generation.

Individuals with greater contributions to the gene pool of the next generation are selected.

Scientists measure fitness in the field. It isn't an individual's fitness that counts, but how it compares to the other organisms in the population.

Stabilizing selection is one of the ways that selection can affect population variation. Individuals can become more or less genetically similar and the phenotypes can become more similar as a result of natural selection.

Natural selection is likely to favor mice that blend in with the forest floor and are less likely for predators to spot them. If the ground is a shade of brown, the mice that have fur that is close to that color will be more likely to survive and reproduce. The lighter the mice are, the more likely they are to fall victim to a predator. The population's genetic variance will decrease as a result of this selection.

The evolution of the peppered moth in England in the 18th and 19th century is a classic example of this type of selection. Prior to the Industrial Revolution, the moths were mostly light in color, which allowed them to blend in with the trees and lichens in their environment. As soot began to come from factories, the trees darkened and the light-colored moths became easier to spot. The moth's melanic form increased in frequencies because they had a higher survival rate in habitats that were affected by air pollution. If something were to cause the forest floor to change color, the mouse population could evolve to take on a different color. The result of this type of selection is a shift in the population's genetics.

Some things in science are true and new information can change our understanding. Some scientists have questioned the facts behind the selection of the peppered moths. You can read this article to learn more.

Sometimes two or more distinct phenotypes can each have their advantages for natural selection. Large, dominant alpha males use brute force to obtain mates, while small males can sneak in for furtive copulations with the females in an alpha male's territory. Medium-sized males who can't overtake the alpha males and are too big to sneak copulations are selected against the alpha males. When environmental changes favor individuals on either end of the spectrum, diversifying selection can happen. Imagine a mouse population living on a beach with sand and grass. Light-colored mice that blend in with the sand would be favored, as well as dark-colored mice that can hide in the grass. Medium-colored mice would not blend in with either the grass or the sand, and thus would most likely be eaten by a predator. The population becomes more diverse as a result of this type of selection.

Natural selection can affect the distribution of phenotypes. An average phenotype is favored in stabilizing selection. The spectrum of observed phenotypes can be shifted by a change in the environment. Two or more extreme phenotypes are selected for, while the average phenotype is not.

In the last few years, factories have become cleaner and less harmful to the environment.

An example of this type of selection can be seen in a group of Pacific Northwest lizards. There are three throat-color patterns for male common side-blotched lizards. The reproductive strategy of each form is that orange males are the strongest and can fight other males for access to their females. Medium-sized blue males form strong bonds with their mates.

Yellow males look a bit like females, which allows them to sneak copulations. Like a game of rock-paper-scissors, orange beats blue, blue beats yellow, and yellow beats orange in the competition for females. The big orange males can fight off the blue males to mate with the blue's pair-bonded females, the blue males are successful at guarding their mates against yellow sneaker males, and the yellow males can sneak copulations from the potential mates of the large.

A yellow-throated side-blotched lizard is smaller than either the blue-throated or orange-throated males and appears a bit like the females of the species, allowing it to sneak copulations.

When blue males dominate the population, natural selection favors orange males. When the population is mostly yellow males, blue males will thrive, while yellow males will be selected for when orange males are the most populous. In one generation, orange might be the dominant color, and then yellow males will start to rise in frequencies. Blue males will be selected when yellow males make up a majority of the population. When blue males become common, orange males will once again be favored.

Positive and negative frequencies are used to increase the population's genetic variance by selecting for rare phenotypes.

The differences between males and females of certain species are not limited to the reproductive organs. The peacock's tail is one of the elaborate colors and adornments displayed by males, while females tend to be smaller and duller in decoration. Some males get the majority of the total matings, while others don't. The males are better at fighting off other males or females will choose to mate with the bigger or more decorated males. The evolution of bigger body size and elaborate ornaments to attract the females' attention is a result of the variation in reproductive success. Females are more likely to select more desirable males if they achieve a few selected matings.

Some species have sex-role reversed. In such cases, females tend to have a greater variation in their reproductive success than males and are usually selected for the larger body size and more elaborate characteristics of males.

In peacocks and peahens, the female spider is larger than the male one, and in wood ducks, the female spider is larger than the male one.

The selection pressures on males and females are what we call them. Secondary sexual characteristics that do not benefit the individual's likelihood of survival can result in maximized reproductive success.

Sexual selection can be so strong that it can damage an individual's survival. While it is beautiful and the male with the largest tail is more likely to win the female, it is not the most practical appendage. It makes the males slower in their attempts to escape. Females like the big tails because of the risk. The larger the tail, the more fit the male is.

Females choose males with the most impressive features because it signals their genetic superiority, which they will pass on to their offspring. One may argue that females should not be picky because it will reduce their number of offspring, but if better males father more fit offspring, it may be beneficial. The chances of survival may be increased by fewer, healthier offspring.

Ronald Fisher proposed a model of sexual selection in 1915, which suggests that selection of certain traits is a result of sexual preference.

Natural selection can create populations that are better adapted to survive and reproduce in their environments. Natural selection can't produce perfect organisms. Natural selection is limited to existing variation in the population. It doesn't create anything from scratch. It is limited by a population's existing genetic variation and any new alleles that arise through gene flow.

Natural selection is limited because it works at the individual level and some alleles are linked due to their physical proximity in the genome, making them more likely to pass on together. Some individuals may carry some beneficial and unfavorable alleles. Natural selection can act upon the alleles' net effect. Good alleles can be lost if people also have bad alleles.

Good alleles can be kept if they result in an overall fitness benefit.

Natural selection can be constrained by the relationships between different polymorphisms. One morph may confer a higher fitness than another, but may not increase in frequency because going from the less beneficial to the more beneficial trait would require going through a less beneficial phenotype. There are mice at the beach. Some are light-colored and blend in with the sand, while others are dark and blend in with the grass. The dark-colored mice may be more fit than the light-colored mice, and one might expect the light-colored mice to be selected for a darker color. The medium-colored coat is bad for the mice because they can't blend in with the sand or grass.

Not all evolution is adaptive. Natural selection often results in a more fit population, but other forces of evolution, including genetic drift and gene flow, often do the opposite. Evolution isn't changing a population into an ideal. It is the sum of the various forces that we have described in this chapter and how they affect the population's genetics.

Evolutionary theory grew out of the fact that both genetic and environmental factors can affect a population. The more modern study of confer different phenotypes and different environments can population genetics. The evolution causes individuals to act differently. Only those populations and species from small-scale changes among differences in an individual's genes can individuals to large-scale changes over paleontological time pass to its offspring. Scientists can selection to understand how organisms evolve. Natural selection works by selecting alleles that track populations' frequencies over time. Scientists can conclude that those for deleterious qualities are those who differ from each other. The population is not in equilibrium with the genes, and this leads to genetic drift.

Gene flow can change frequencies when individuals leave or join the population. New variation into a population may be caused by genetic changes.

Natural selection acts to increase the frequency of selection, in which individuals with positive beneficial alleles and traits while decreasing the frequency of frequency- dependent selection, or negative frequency deleterious qualities, is adaptive evolution. The selection is natural dependent. Sexual selection acts at the individual level, selecting for those that results from one sex having more variation in their fitness compared to the rest of the reproductive success than the other. If the fit phenotypes are similar, females experience different pressures, which can natural selection result in stabilizing selection, and an often lead to the evolution of phenotypic differences, or overall decrease in the population's variation.

Microevolution describes the evolution of organisms that came from Europe. The had polydactyly, a rare dominant trait, was one of the evolutions of the ship's captain.

Microevolution describes the evolution of organisms in the Amish population. This is over their lifetimes, while macroevolution describes the evolution of organisms over multiple generations.

Natural selection offspring of two unrelated individuals are often not as good as offspring of closely related individuals.

Close relatives are not compatible.

People of one sex develop impressive offspring because their genes react negatively in the d.

An example of a trait that may have evolved as a flower is undergoing evolution. bees seem to think that there is a result of the handicap principle.

Population blue flowers can be affected by evolution. In a separate experiment, you discover variation and describe how they affect the color of the flower.