Edited Invalid date
Chapter 120 -- Part 2: Evidence for Evolution
The minority advantage is a mechanism that preserves variety in a population.
This increases the frequencies of the less common ones and decreases the frequencies of the more common ones.
In predator-prey relationships, a standard representation of prey is developed that allows them to hunt a particular kind of prey effectively.
If the prey individuals are different, the most common type will be preyed upon more often than the less common type.
These rare individuals will become more common for a while, will lose their advantage, and eventually will be selected against.
Evolutionary neutral trait seem to have no advantage.
There are different blood types in humans.
Scientists don't know why they have remained in the human population.
It is possible that they influence survival and reproductive success in ways that are difficult to measure.
The agents of change for a population are genetic drift, nonrandom mating, and natural selection.
Genetic drift is caused by chance.
It is a constant change in the alleles from one generation to the next.
It limits diversity.
The founder effect is one of the two examples.
Small populations can be affected by chance and random events.
Natural disasters, such as fires, earthquakes, and floods, reduce the size of a population, resulting in a loss of genetic variation.
The resulting population is much smaller than the original one.
Some alleles may be overrepresented compared to the original population.
The bottleneck effect is what it is.
There are two examples.
The high rate of Tay-Sachs disease among Eastern European Jews is due to a population problem experienced by Jews in the Middle Ages.
Many Jews were killed and the population was reduced to a small fraction of its original size during that period.
A disproportionate percentage of people who remained alive had the Tay-Sachs gene.
The incidence of the trait remained high because Jews in Europe remained isolated and did not intermarry with other Europeans.
The northern elephant seal was almost wiped out during the 19th century.
Since 1884, when the seal was placed under government protection, the population has increased to about 35,000, all descendants of the original group.
The founder effect is when a small population breaks away from a larger one to colonize a new area.
It is possible that rare alleles may be overrepresented.
The founder effect occurred in the Old Order Amish of Lancaster, Pennsylvania.
A small group of settlers from Germany came to the United States in the 17th century.
One or more of the settlers had extra fingers and toes.
The population has a high incidence of polydactyly due to the extreme isolation and intermarriage of the close community.
If a trait is dominant or recessive, it simply determines if it is expressed or hidden.
The trait is not determined by how common it is in a population.
Genetics can cause an increase or decrease in allelic frequencies of a trait.
Gene flow is the movement of all genes into or out of a population.
It can happen as a result of the migration of fertile individuals.
The wind can carry pollen from one valley to another.
Gene flow increases diversity.
Evolutionary change occurs when there are changes in genetic material.
They make us more diverse.
A new allele can be introduced into a population.
The cumulative effect of all the genes in a population can be significant.
Individuals pick their mates for a specific reason.
The less-fit individuals are eliminated by the selection of a mate.
There are two types of snow geese: white and blue.
White geese tend to mate with blue geese.
If blue geese became more attractive and both blue and white geese began to mate with only blue geese, the population would evolve quickly and favor blue geese.
Natural selection is the main mechanism of evolution.
People who are better adapted to a particular environment have better reproductive success.
They pass their genes on to more offspring.
A stable, nonevolving population is one in which allelic frequencies don't change.
In 1,000 years, if the population is not evolving, the allele will be the same as it is now.
A small change in the gene pool will be mitigated by the large number of people in the population.
There must be no migration of organisms into or out of the pool.
A change in allelic frequencies could be caused by a change in the gene pool.
Those who are better adapted will have a reproductive advantage and the population will evolve.
The equation allows us to calculate frequencies of alleles.
Although it can be applied to complex situations of inheritance, for the purpose of explanation, we will discuss a simple case.
The letter q and the letter p are used by scientists to indicate the frequencies of the dominant and recessive alleles.
The basis for this equation is the mono hybrid cross.
You can use your calculator on the exam in 2020.
The principle is the same even if the problems are not simple.
There are three sample problems.
The blue eyes have a trait that is represented by q 2.
The square root of 0.09 is the solution for q.
If q is less than 0.3, then p is 0.7.
The brown condition is represented by 2 pq.
Substitute values for 2( p )( q ) for the percent of the population that is hybrid.
The percentage of the population that is brown is 42%.
The dominant is represented by p 2.
The percentage of the population that is brown is more than 50%.
The square root of 0.09 is not 0.03.
The percent of the population that is dominant if it's a combination of both genders.
q 2 is 16. q 2 is calculated as.16 and q is calculated as 0.4.
The percentage of the population that is dominant is.36.
The population's allele may change.
The percent of the population that is hybrid is determined by the allelic frequency of the trait.
The value of q is not q 2.
To get the value of p, you need to subtract from 1.
If p + q is 1 and q is 0.5, then p + 0.5 is 1.
The percentage of the population that is hybrid is 50% if both p and q are used.
A species is a group of people who have the potential to interbreed in nature and produce offspring.
In captivity, lions and tigers can be bred but not naturally.
They are considered separate species.
A mule that is not fertile can be produced by horses and donkeys.
The horse and donkey are different species.
A species is defined in terms of reproductive isolation, meaning that one group of genes becomes isolated from another to begin a separate evolutionary history.
Under the pressure of different forces in different environments, the two isolated populations may begin to differ genetically.
Interbreeding would not occur if the two populations were brought back together because they would become so different.
Speciation is said to have taken place at that point.
Speciation may be caused by anything that fragments a population.
The diagrams of allopatric and sympatric speciation can be found in the following.
Speciation may occur when two populations are separated.
Allopatric speciation can be caused by mountain ranges, canyons, rivers, lakes, glaciers, altitude, or longitude.
In certain circumstances, speciation may occur without geographic isolation, in which case the cause of the speciation is sympatric.
Polyploidy, habitat isolation, behavioral isolation, temporal isolation, and reproductive isolation are examples of sympatric speciation.
Polyploidy is when a cell has more than two complete sets of chromosomes.
It can happen naturally or through breeding.
A daughter cell with 4 n chromosomes is formed when gametes with the 2 n chromosomes are fertilized by another abnormal 2 n gamete.
Plants that are polyploid cannot breed with other plants that are not polyploid and are functionally isolated from them.
Habitat isolation is when two organisms live in the same area.
There are two species of snake that can be found in the same area, one of which is in the water.
Sticklebacks, small saltwater fish that have been studied extensively, have elaborate mating behavior.
In response to increased sunlight, the males change in color and form a red belly.
The male builds a nest and courts the female with a dance that causes a complex set of movements between the partners.
No young are produced if either partner fails in any part of the dance.
Male fireflies signal to females of their kind by blinking the lights on their tails.
Females only respond to their own species of males.
If the female doesn't respond with the correct blinking pattern, there won't be sex.
The two animals are not in contact with each other.
A flowering plant colonizes a region that is warm and sunny and cool and shady.
The flowers in the warmer regions are sexually mature sooner than the flowers in the cooler areas.
There are two populations of flowers in the two environments.
Closely related species may be unable to mate because of a variety of reasons.
There are differences in the structure of genitalia.
The shape of the flower may affect pollination.
Prezygotic barriers are things that prevent sex.
A small male dog and a large female dog can't mate because of their large size.
Postzygotic barriers are things that prevent the production of fertile offspring.
There is a chance that a particular embryo is not viable.
Prezygotic and postzygotic barriers result in reproductive isolation.
The evolution of different species is classified into five patterns.
When a population becomes isolated from the rest of the species, they evolve into a new species.
Allopatric and sympatric speciation are examples of diverging evolution.
When unrelated species occupy the same environment, they are subjected to the same pressures.
The whale has a streamlined appearance because it evolved in the same environment as a shark.
The whale's underlying bone structure shows an ancestry to mammals, not to fish.
Two related species have made the same evolutionary changes after diverging from a common ancestor.
The classic example of this is the mammals of Australia and North America.
There are striking similarities between the gray wolf of North America and the marsupial wolf of Australia, both of which evolved in the same environment.
The adaption of two species is called coevolution.
The relationship between the monarch butterfly and milkweed plant is an example of a predator-prey relationship.
The poison in the milkweed plant deters herbivores from eating it.
The butterfly lays its eggs in the milkweed plant and when the caterpillarpillars hatch, they feed on the milkweed and absorb the poisonous chemicals from the plant.
They keep the poison in their tissues.
The poison in the butterfly makes it toxic to animals who try to eat it.
The emergence of many species from a common ancestor is called adaptive radiation.
The newly emerging form specializes in an ecological niche.
The 14 Darwin's finches that live on the Galapagos Islands are all different from the one that existed 10,000 years ago.
There are six ground finches, six tree finches, and one warbler finch.
In Gradualism, organisms descend from a common ancestor in a linear or branching fashion.
There are many small changes that cause big changes.
Fossils should be evidence of every stage in the evolution of every species with no missing links according to this theory.
Scientists rarely find transitional forms or missing links in the fossil record.
Populations of organisms are evolving.
Stephen J developed the favored theory of evolution.
The gradualism theory was not supported by the fossil record.
The theory suggests that new species appear suddenly.
As a new species buds from a parent, it changes little for the rest of its existence.
The allopatric model of speciation can explain the sudden appearance of the new species.
A new species arises in a different place and expands its range.
See it, which shows gradualism and equilibrium.
Chimps walk on four legs in the rainforest, while we walk upright and can send rockets to the moon.
We don't have all the answers.
Some answers can be found in the field of evolutionary developmental biology.
Major changes in body form and function can occur when some genes regulate other genes.
Different species have the same DNA sequence.
The different species might have different outcomes because the genes are up or down regulated by other genes.
Homeotic genes and Heterochrony are examples.
Homeotic genes control spatial organization of body parts.
They determine where the wings or legs will develop on an insect or where the petals will go on a flower.
The Hox gene provides information in the development of embryos.
A change in the location of two Hox genes in crustaceans will make them legs.
Heterochrony is a change in the timing of the development of body parts.
They are very similar as infants.
As the chimp matures, the face becomes more prognathic and the jaw and teeth become larger and more powerful.
The human skull seems to stop development before the same changes happen.
It is possible that the genetic code for the skull in humans and Chimpanzees is the same.
The human skull genes stop developing sooner.
The reduction and eventual loss of hind limbs in whales can be traced back to the slow growth of leg and pelvic bones.
It can change the timing of reproductive development compared to the rest of the body.
The adult aquatic salamander, the axolotl, retains juvenile structures into adulthood.
There wasn't any free oxygen in the ancient atmosphere.
The ancient atmosphere consisted of CH 4, NH 3, CO, CO 2, N 2 and H 2 O.
The primitive atmosphere probably had intense lightning and UV radiation that provided energy for chemical reactions.
Scientists are trying to figure out how the first organic molecule and earliest life developed.
Here is a synopsis of the experiments.
Review flashcards and saved quizzes
Getting your flashcards
Privacy & Terms