How Does Natural Selection Work

lihotozi's version from 2016-08-21 02:49


Question Answer
What is the correct definition of evolution?the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.
List three different kinds of evolutionary change that can happen in a population Addition of new genotypes. Loss of some genotypes. Change in frequency of genotypes
Name one interesting process that can cause a population to evolveNatural Selection

Natural Selection

Question Answer
What is the source of all genetic variability among individuals in a population? Mutation
How common is it that a population will contain genetic variation? Extremely common
In order for natural selection to occur in a population, what characteristic must the population have? Genetic variability
How common is it for natural selection to affect a population? Very common
What are selective pressures, and what effect do they have on individuals? Aspects of a specific environment that will determine who will surviv ethere and who will not. As a result of selective pressures, some individuals surviv and some die.
List a variety of things that can act as selective pressures Predators, Weather, Competitors
Are selective pressures exactly the same in every environment? No
In a population that is evolving by natural selection, what happens to genetically fit genotypes over time, and what happens to genetically unfit genotypes? Genetically fit genotypes increase in frequency. Genetically unfit genotypes decrease in frequency
In a population that is evolving by natural selection, what happens to genetically fit individuals, over time, and what happens to genetically unfit individuals? Genetically fit individuals will survive become more common. Genetically unfit individuals will die and become less common
Do individuals evolve? No
What two possible “fates” do individuals have in the process of natural selection? Surviv and Reproduce or Die
List three ways in which mutation is random Whether or not it happens. What gene it occurs in. Whether it is fit, unfit, or neutral.
If mutation is random, why isn’t natural selection a random process? Natural selection is about the survival of some mutations over others and survival is not random.
If mutations are considered “genetic lottery tickets”, what picks the “winners”? Selective Pressures
List two common kinds of natural selectionStabilizing selection, Directional selection

Stabilizing Selection

Question Answer
What is stabilizing selection, and how does it change a population over time? Intermediate genotypes are the most genetically fit. Intermediate genotypes survive the best.
discuss sickle cell anemia as a case of stabilizing selection. When is the intermediate genotype (HS) most genetically fit, and why?HS is most genetically fit in areas with malaria because it results in immunity to malaria.

Directional Selection

Question Answer
What is directional selection, and how does it change a population over time? Genotypes toward one extreme are the most genetically fit. Genotypes toward one extreme survive the best.
What major selective pressure acts on the males of many species? Females
Why are females of many species choosy about mates? In many species, males only contribute to their offspring with their DNA so females want to mate with males that have superior alleles in their genes.
Why do female birds often choose males that are brightly colored, and have long tails? These males signify health, agility, strength, and cleverness.
Explain how directional selection can lead to pesticide resistance in insects, and drug resistance in bacteria and viruses. Insects possessing a mutation resistant to pesticides will survive and reproduce while the rest of the population will die. Lucky ones will also survive if they managed to avoid the pesticide sprays. Populations of bacteria and viruses are becoming resistant to pesticides and drugs as a result of mutations.
Do individual insects or germs develop resistance?No
Do useful mutations occur because they are useful to an organism?No, they are random

Populations Change Over Time

Question Answer
Are the genetic characteristics of a population permanently fixed? No
How long does it usually take for natural selection to significantly change a population? Thousands or millions of years.
Under what three conditions can natural selection proceed more quickly than usual? When organisms have rapid generation times. When organisms have rapid mutation rates. When selective pressures are very strong.
What is artificial selection and what is its major selective pressure? Humans purposefully act as strong selective pressures. Humans
Describe, basically, how artificial selection has influenced Brassica oleracea over thousands of years Farmers saved and planted seeds with desired qualities
Describe, basically, how artificial selection has influenced Canis familiaris, over thousands of years Humans selected dogs with specific traits to breed.
What two things are necessary for natural selection to produce changes in populations that are as striking as those seen in artificial selection?Time and strong selective pressures


Question Answer
evolutionchange in the genotypes of a population over time. Changes can include the addition of new genotypes, the loss of old ones, or a change in the frequencies of different genotypes.
populationa group of individuals of the same species living in the same location
natural selectiongreater survival and reproduction of individuals with certain genotypes over others in a population, due to the selective pressures of the local environment. As a result of natural selection, genetically fit genotypes become more common in the population over time, while genetically unfit genotypes become less common in the population over time.
selective pressurea component of an environment that determines who survives there and who doesn’t. Selective pressures vary among different environments. Individuals that are genetically fit will survive the selective pressures of a particular environment, while individuals that are genetically unfit will not survive.
genetic fitnesshaving a genetic makeup that enables survival and reproduction in a particular environment
stabilizing selectionnatural selection in which intermediate genotypes are most genetically fit
directional selectionnatural selection in which genotypes toward one extreme are the are most genetically fit
artificial selectionthe name given to the process of natural selection when humans are a very strong, purposeful selective pressure on a population. Because the selective pressure of humans is so strong, artificial selection can produce significant genetic changes in populations more quickly than natural selection. This process has created all breeds of domestic animals and plants from wild ancestors.
Brassica oleraceathe scientific name for wild lettuce. Over thousands of years, artificial selection has resulted in the development of many crop breeds that are genetically distinct from each other. Examples include cabbage, Brussels sprouts, kohlrabi, kale, broccoli, and cauliflower.
Canis familiaristhe scientific name for the domestic dog. Over thousands of years, artificial selection has resulted in the development of all domestic breeds of dog from one ancestor: the wolf.