All of the organisms we see today were created earlier.
Evolution can be described as a change in a population over time.
Natural selection operates on the level of the individual.
Evolution is defined in terms of individuals, but not in terms of populations.
Charles Darwin's work is the basis of what we know about evolution.
Darwin was a 19th-century British scientist who sailed the world in a ship.
Darwin's theory of evolution was based on natural selection and he studied animals in the Galapagos Islands.
The beaks of finches and tortoises differed in length, but there were similar animals on the islands.
Animals in different areas have different characteristics.
It was impossible for the finches and tortoises of the Galapagos to grow long beaks or neck as needed, according to Darwin.
They were passed on from generation to generation.
He decided that there must be a way for populations to evolve and change their characteristics.
He thought that there must have been a variety of beak lengths, but only the longest one was helpful.
The finches were more likely to contribute offspring to the next generation since they could eat better, survive better and reproduce better.
On the first Darwin island, there must have been short-necked tortoises.
These tortoises died off because they couldn't reach higher vegetation.
Evolution is thought of as the survival of the fittest, because only the most fit organisms will survive and reproduce.
The book On the Origin of Species was written by Darwin.
Each species has more offspring than can survive.
The offspring compete for limited resources.
The offspring with the most favorable traits are the most likely to survive and produce a second generation.
Darwin wasn't the first to propose a theory about life on Earth.
Jean-Baptiste de Lamarck proposed one of the most widely accepted theories of evolution in Darwin's day.
Lamarck proposed in the 18th century that acquired traits were passed on to offspring.
Lamarck's giraffes had long necks because they were constantly reaching for higher leaves while feeding.
giraffes have long necks because they use them a lot.
Lamarck's theory that changes at a "macro" level in body cells will not show up in gamete cells is incorrect.
Children wouldn't inherit this trait if you lost one of your fingers.
The gametes that your body makes include copies of your regular old genome, not a new version of a genome that is determined by how careful you are with a table saw.
Lamarck was wrong.
Do not take a Lamarckian position on the test.
Nature selects which living things survive and reproduce.
The major lines of evolution and the great variety of organisms have been revealed by paleontology.
The study of the distribution of flora and fauna in the environment is called biogeography.
Darwin observed that animals in the Galapagos have similarities to animals on the mainland of South America.
A common ancestor is a possible explanation for the similarities.
There are other explanations for the same trait.
It's pretty safe to say that organisms shared a common ancestor.
Humans show fishlike features called gill slits in their bodies.
Scientists have discovered that some animals have similar structures that serve different purposes.
A human's arm, a dog's leg, a bird's wing, and a whale's fin are the same appendages, though they have different purposes.
Sometimes animals have the same function but are different in appearance.
A bat's wing and an insect's wing are used to fly.
They have the same function, but they have evolved differently.
Similar structures are called analogous structures.
The eye is an example of an analogous structure.
Humans, insects, and scallops all have different types of eyes, which are thought to have evolved independently of one another.
They are similar structures.
The most compelling proof of all is the similarity at the molecular level.
Scientists can look at the sequence of organisms.
We found that organisms that are closely related have more of the same sequence in common than distantly related species.
Humans don't look like Chimpanzees.
As many as 99 percent of our genetic code is similar to that of a chimp, according to some estimates.
The genes that contain introns are found in all the eukaryotes.
There is evidence that evolution is happening constantly.
Changes in the fossil record can be seen with consistency.
The evolution of resistance to antibiotics, pesticides, herbicides, or chemotherapy drugs can be seen.
It is possible to see how fast replicating pathogens evolve and cause diseases never before seen.
There are universal structures across every domain.
There are many pathways that are conserved between species.
Scientists can get a good handle on how evolution of certain species occurred by using the evidence mentioned above.
It all depends on who has common ancestors.
Life began somewhere.
Where things went from there can become quite convoluted.
A cladogram is a chart used to study relationships between organisms.
The data from the fossil record can be used to build phylogenetic trees.
The amount of change is shown by trees but not by cladograms.
In other words, cladograms are drawn with even spacing between species, but phylogenetic trees are often drawn with different distances between species and as a result they look more like a tree with odd branches.
As more data is uncovered to establish the relationships between species, the hypotheses change as well.
They always start with a common ancestor.
A fork in the road is called a common ancestor.
The common ancestors are the point at which evolution went in two different directions.
One direction eventually led to one species, and the other led to another.
We have a common Ancestor with Chimpanzees.
This doesn't mean that our great-great...great-grandfather was a chimp.
We have the same great-great...great-grandfather, who was neither a human nor a chimp.
His species was split and evolved in different directions, so he was a completely different species.
Both of the linage became humans.
This is an example of a tree.
The three main domains of life are visible in the tree.
Plants, animals, and fungi are much more closely related to each other than are tobacteria.
There are two common ancestors of Archaea and Eukarya, one thatbacteria doesn't have, and one thatbacteria does.
species A is an out-group because it is the least related to all of the other species.
The species B, C, D, and E all have the same number of legs.
Wings are a shared character for species D and E, but they could also be considered a derived character since they separate species D and E from the rest of the species that don't have wings.
No two people are the same.
Genetic variability is the difference in each person.
All this means that there are no two individuals in a population with the same allele.
The genetic variation allows a species to survive in a changing environment.
The same weaknesses and strengths would befall a population if they were all the same.
Some individuals have more evolutionary fitness and can be selected for natural selection.
The more variation there is among the population, the more likely it is that there will be a perfect lifesaver.
There is a famous example of Rudolph the Red-Nosed Reindeer.
His red nose was a random change, but it became the best nose to have.
A more diverse population is more likely to survive and evolve.
The simple answer is that random changes happen all the time.
Errors by DNA polymerase, changes to DNA caused by transposons, or other types of DNA damage can be the reason for this.
New variations and alleles can be created by either way.
There is a lot of genetic variation in a population.
Sexual reproduction contributes to genetic variation.
When chromosomes are packaged further, they add to the genetic uniqueness of each gamete.
It's hard to think of genetic variation in this way, but it's the foundation of evolution.
We can refine our definition of evolution now that genes have been reintroduced.
Over time, the population's genes change.
An example can be looked at.
There was a large population of flying insects in England in the 1850s.
Half of them were dark and the other half were light.
The other half was light and had alleles.
The ratio of phenotypes was observed until air pollution changed the environment.
Both of these cities had unpolluted environments before the Industrial Revolution.
Both dark and light moths lived side by side.
Let's say our proportions were a perfect fifty-fifty, half dark and half light.
At the height of the Industrial Revolution, our northern city was heavily polluted, whereas our southern city was unchanged.
In the north, all the trees and buildings were covered in soot.
As a result, the predators devoured light-colored moths just as fast as they could reproduce, sometimes even before they reached an age in which they could reproduce.
The dark moths had dark alleles.
With all the soot around, the predator couldn't see them; the dark moths continued reproducing.
They had more and more offspring carrying the dark allele when they reproduced.
After a few generations, the pool of genes in City 2 changed.
The population's genetic makeup was changed because of excessive predator activity.
90 percent of the genes were dark and 10 percent were light.
The light moths didn't stand a chance in an environment where they were easy to spot.
The dark moths were just as fast as they could be.
There was very little pollution in the southern city.
Things were pretty much the same.
The population had roughly the same proportions of light and dark moths.
Natural selection is an evolutionary mechanism that selects which members of a population are best suited to survive and which are not.
The direction of evolution can be affected by biotic and abiotic factors.
Depending on environmental fluctuations, different traits might be selected for each generation.
Some individuals have an advantage due to genetic variation and environmental pressure.
Humans have a great influence on many species.
An example of artificial selection is what we pick for.
The colors of plants and dogs are influenced by humans who are orchestrating breeding to create certain characteristics that we want.
If they are not increasing the reproductive fitness of their species, they will be selected.
Let's take a look at how this process unfolds in nature.
The answer is random.
A dark-colored winged insect was born one day before coal was burning.
The next generation may inherit a certain amount of a certain type of mutations if it doesn't kill an organisms before it reproduces.
There were offspring over time.
The environment changed all that when the dark and light-colored moths lived side by side.
The initial variation was a result of chance.
The dark moths were given an edge by this variation.
It wasn't apparent until something made it obvious.
Coal burning intensive pollution was what it was in our case.
The abundance of soot made it easier for predator to spot light-colored moths.
Dark color is an adaptation favored by natural selection.
The name of the game is survival of the fittest, and any trait that causes an individual to reproduce better gives that individual evolutionary fitness.
These are things that help to survive.
For reproduction to occur, survival is essential.
Strength, speed, height, camouflage, and many other things can be useful.
Odd things can be helpful.
For example, a peacock's tail has been selected because females choose to mate with males that have a large and beautiful tail.
The tail doesn't help them to survive because it makes it easier for predators to catch them, but it is essential for the females to find them attractive.
Sexual selection is an example.
Evolutionary fitness should not be confused with physical fitness.
Strength and speed will increase evolutionary fitness, but anything that increases survival and reproduces will add to it.
It's important to remember that fitness depends on the environment.
It is possible that a trait is beneficial in one circumstance and detrimental in another.
One moment at a time, one environment at a time.
We're going to go back to our example.
There were different genes in the two populations.
Over time, the two populations might change so much that they could no longer reproduce together.
We could say with certainty that the moths had evolved at that point.
The population was put under pressure by an environmental change that resulted in evolution.
Natural selection and adaptation can be accelerated by catastrophic events.
Sometimes odd variations are selected for when the rules change.
Several mass extinction events have taken place on Earth.
If these events had not happened, the tree of life would look different.
Natural selection is not the cause of genetic drift.
Random events reduce the number of people in a population.
The founder effect is when only a few individuals are left to mate and grow a population.
If those individuals were the only survivors due to random luck, the alleles that are present to regrow the population are random.
They are not the best.
Even if only 4 birds are left on an island, the traits that they have will be the ones that the population will use in the future.
Gene flow can occur if people migrate from one population to another.
The genetic diversity will change as new alleles enter and exit.
Large populations are more susceptible to this type of change.
It can be selected for or against.
It isn't the genotype.
Only the phenotype will be exposed to the environmental pressures because genotypes are hidden away inside the DNA.
An example of directional selection is the situation with our moths.
At one of the extremes of the normal distribution, one of the phenotypes was favored.
One of the phenotypes is "weeded out" by directional selection.
Light and dark moths were eliminated in our case.
If the appropriate allele is present in the population, directional selection can happen.
stabilizing selection and disruptive selection are two other types of selection.
Stabilizing selection means that organisms in a population are eliminated.
This type of selection favors organisms with average or medium characteristics.
The phenotypes that are less adaptive to the environment are "weeded out" by it.
The birth weight of human babies is a good example.
A large baby will have a challenge in terms of a safe birth delivery, while a small baby will have a higher chance of having birth defects.
Disruptive selection does the reverse.
It favors the extremes and dislikes the common ones.
Females are selected to be small and males to be large in elephant seals.
Female and male of intermediate size are rare.
A dog and bumblebee can't produce offspring.
They are different species.
At least in theory, a chihuahua and a Great Danes can reproduce.
They are simply different breeds.
To become different species of dogs, they would have to become reproductively isolated from each other.
The two groups would be able to undergo natural selection.
They could change in different ways and no longer be able to mate with each other.
This is called evolution.
There is a rapid evolution that occurs after a period of stasis.
This can be a result of a major event.
It can take hundreds or millions of years for a change to come about after many smaller changes.
When a species rapidly diversifies due to an abundance of available ecological niches suddenly opening up, you should be aware of adaptive radiation.
To be considered the same species, two individuals must be able to mate and produce viable offspring that will be capable of producing offspring.
Our example shows that these species often originate from a common ancestor.
The "engine" of evolution is often environmental change such as pollution.
Factors in the process of evolution include geographic barriers, new stresses, and disease.
Pre- and post-zygotic barriers prevent the reproduction of two different species.
There are pre-zygotic barriers that prevent fertilization.
Temporal isolation occurs when two species reproduce at different times of the year.
The inability of a hybrid to produce offspring is related to a post-zygotic barrier.
A horse and a donkey can mate to produce a mule, but mules are sterile and cannot produce a second generation.
The process of convergent evolution is when two unrelated species come to have the same characteristics, often because they have been exposed to the same pressures.
Aardvarks, anteaters, and pangolins are examples of convergent evolution.
They all have long snouts with sticky tongues, but they evolved from three completely different mammals.
There are two types of speciation.
Allopatric speciation means that a population becomes separated from the rest of the species by a geographic barrier so that they can't interbreed.
A mountain separated two populations of ants.
The populations might evolve into different species in the future.
If a new species forms without a geographic barrier, it is called sympatric speciation.
In plants, this type of speciation is common.
Two species of plants can evolve in the same area.
Plants get doubles of their chromosomes when they undergo speciation due to polyploidy.
The laws can be extended to the population level.
You could catch a bunch of fruit flies.
The ratio of red-eyed to green-eyed fruit flies would not change if the flies were allowed to mate and count the next generation.
The allele frequencies would remain the same.
The relative frequencies of genes in a population are constant over time according to the law.
Alleles are not lost in the shuffle.
The dominant and recessive genes don't disappear.
According to the law, a population will be in genetic equilibrium only if it has a large population, no mutations, no immigration or emigration, and no natural selection.
The gene pool in a population is stable when these five conditions are met.
If a small group of fruit flies move to a new location, the allele frequencies may be altered.
The allele for red eyes is more dominant than the one for green eyes.
There are red-eyed fruit flies.
The fruit flies have green eyes.
The equation below shows the frequencies of the alleles.
It must be either R or R. Let " p" and " q" represent the frequencies of the R allele in the population.
It must add up to one.
If you know the value of one of the alleles, you will also know the value of the other one.
It makes sense that this works for populations with 2 alleles that have normal dominant-recessive behavior.
If you know that 70% of the alleles are the dominant one, then the remaining 30% must be the recessive one.
The following equation can be used to determine the number of genotypes in a population.
In this equation, p 2 is the dominants, pq is the Heterozygotes, and q is the recessives.
The number of individuals with the dominant phenotype includes those with the same or different genes.
The AP Biology Equations and Formulas sheet has the equations listed.
You can use proportions in the population to figure out both frequencies.
Let's figure out how many green-eyed fruit flies there are.
If 9% of the fruit flies are green-eyed, the genotype frequency is 0.09.
This value can be used to figure out the frequencies of the alleles in the population.
The square root of 0.09 is equal to the allele frequencies for green eyes.
The dominant allele has to be 0.7.
That's because 0.2 + 0.7 is equal to 1.
The second equation can be used to calculate the genotypes of the dominants.
The frequencies for the dominants are 0.7 x 0.7 and 0.49.
The Frequency for the Heterozygotes is 2 x 0.2 x 0.7.
The numbers add up to 1.
There have been many extinctions.
During ecological stress, the rate of extinction can vary.
Humans have contributed to extinction events.
A population with high genetic diversity is more protected from extinction events because there is a higher chance that an individual will have the characteristics required to survive the ecological stress leading to the extinction event.
The niche that a species occupied can become available to other species when it becomes extinct.
Around 4.5 billion years ago, the Earth formed.
The Earth was hostile prior to 3.8 billion years ago.
Scientists are still debating this topic.
Most scientists believe that the earliest beginnings of life were in the primitive oceans of the earth.
The theory took shape in the 1920s.
The primitive atmosphere was rich in methane, ammonia, hydrogen, and water, according to B. S. Haldane.
There was almost no free oxygen in this atmosphere.
They believed that the gases produced chemical reactions that led to the organic compounds we know today.
The theory didn't receive much support until 1953.
Stanley Miller and Harold Urey did a simulation of primitive Earth.
An alternative hypothesis is that organic Molecules were transported to Earth on a meteorite.
No one was around to witness the process, so no one knows how it happened.
The original life-forms are likely to have been made ofRNA.
This is a hypothesis.
It is not restricted to being a double helix because it can take many shapes.
It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 Dehydration synthesis must have formed complex organic compounds.
Simple cells used organic molecule as their source of food.
Simple cells evolved into complex cells over time.
Define a few more key terms.
This can be done in two different ways.
Heterotrophs are living organisms that rely on organic molecules for food.
The earliest Heterotrophs were simple unicellular life-forms.
Heterotrophs hydrolyze them as sources of free energy.
Some life-forms found a way to make their own food.
These organisms are called autotrophs and capture free energy in the sun.
The early autotrophs are responsible for the oxygenated atmosphere.
The hypothesis states that the first cells would have fed on organic molecules that had been made without cells.
These cells are likely to have survived by performing similar processes.
Aerobic respiration followed once autotrophs were producing and releasing oxygen.
Refer to Chapter 6 for a primer on biochemical processes.
Each species produces more offspring than can survive.Offspring compete with each other for limited resources.
Evidence for evolution includes:fossilsbiogeographycomparison of developmental embryologycomparative anatomy, including homologous and analogous structuresmolecular biology (sequences of genes are conserved across many types of species) Members of a species are defined by the ability to reproduce fertile offspring.
Environmental pressures favor certain characteristics that allow survival and reproduction of selected individuals in a varied population.
It is possible that the favored traits will evolve to cause convergent evolution.
Random variations in a trait are selected for later in the population.
When a population's traits change due to random events, it's called genetic drift.
If an average phenotype is preferred, disruptive if the extremes are preferred, and directional if one extreme is preferred, selection can be stabilizing.
The equations can be used to determine genetic variation.
The equations are as follows:p + q + 2pq + q2
Chapter 15 contains answers and explanations.
The eye structures of mammals and squid are very similar.
The mass production and deposition of ash and soot around cities and factories caused a major change in insect species.
The spotted moth population was one of the most famous instances.
In 1802, the number of spotted moths and longtail moths were counted in 8 different urban settings over a square kilometer.
100 years later, a repeat experiment was performed.
The results of the experiment are shown.
The Upper Galilee Mountains of Israel are home to the Middle East blind mole rat.
Scientists discovered that there is a 40% difference between the two groups of mole rats.
The rats don't seem to interbreed in the wild.
The following scenarios are referred to in questions 7 and 8.
They decided to stay because they like the island so much.
There is a small group of people with red hair.
Red hair does not increase fitness.
Evolution doesn't happen when a population is said to be in equilibrium.
Peacock males have large tails and large eye spots.
When you are running from a predator, long, colorful tails are hard to carry.
Peahens have been shown to mate with males with more eye spots and longer tails, despite the fact that the males are more susceptible to predation.
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