Name: _________________________________________ Period: _________ Date: ________________

1.21 Mechanism of Evolution

1. Mutation

Change in the ____________ (Deoxyribose Nucleic Acid)

A mutation could cause parents with green alleles have an offspring with brown alleles.

Allele = different version of a ___________, ex: green eyes, brown eyes, blue eyes; can roll tongue, cannot roll tongue

__________________ variation (diversity)

2. Natural Selection

Organisms best __________ for their environment are more likely to _____________________, _________________, and pass on genes

Birds prefer to eat green beetles, so the brown beetles are more likely to survive, reproduce, and pass on the brown allele.

frequency __________________

Population Prediction in Natural Selection

3. Artificial Selection

Process in which __________________ select certain traits

This could be in the form of seeds or animals for reproduction in order to influence the ______________ inherited by the next generation.

4. Gene Flow

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A. Directional Selection

B. Diversifying Selection

C. Stabilizing Selection

Selects for ________ of the extreme variations of a traitDecreases variation (diversity)

Selects for __________ extremes of a trait’s variationSelects against average (middle) phenotypes

Selects for ____________ (middle) individuals

Decreases variation (diversity)

Phenotype - _______________ characteristics

Name: _________________________________________ Period: _________ Date: ________________

_____________________ of genes from one population to another

Important source of __________________ and variation

Some brown beetles join a population of green beetles.

Genetic variation ___________________

5. Genetic Drift

The change of traits in a population due to ________________ ____________

Beetles were killed – by _____________, more green beetles were killed than brown. (It had nothing to do with being best fit.)

Genetic variation ____________________

CFU 1 - Do each of the following mechanisms tend to increase (I) or decrease (D) genetic variation in a population____ Mutation____ Natural Selection____ Gene Flow____ Genetic Drift

CFU 2 - What is the difference between genetic drift and natural selection?A. Natural selection occurs randomly; genetic drift does not.B. Genetic drift does not require the presence of variation.C. Genetic drift does not select for specific traits in the population.D. Genetic drift never occurs in nature; natural selection does.

CFU 3 - There are two populations of salamanders living on nearby islands. If some of the salamanders from Island A were able to reach Island B, which of the following would result?

A. An increase in genetic variation on Island A due to gene flow.B. A decrease in genetic variation on Island A due to genetic drift.C. Genetic drift on Island A.D. Natural selection on Island A.

CFU 4 - Which of the following occurs when migrating individuals breed with a new population?A. Genetic DriftB. Natural SelectionC. Gene FlowD. Artificial Selection

Mini Mind Map for Mechanisms of Evolution

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Name: _________________________________________ Period: _________ Date: ________________

Independent Practice1. During a storm, two male and two female seagulls are blown 300 miles due west to an isolated

island uninhabited by seagulls. By chance, all four original colonists were white-colored gulls. They reproduce and form a new population. The difference in color between the new population and old population is due to which evolutionary phenomenon?

A. Stabilizing selectionB. Artificial selectionC. Gene FlowD. Genetic Drift

2. All of the following tend to decrease genetic variation in a population EXCEPTA. genetic driftB. reproductive isolationC. natural selectionD. gene flowE. artificial selection

3. In a small group of people living in a remote area, there is a high incidence of “blue skin”, a condition that results from a variation in the structure of hemoglobin. All of the “blue-skinned” residents can trace their ancestry to one couple, who were among the original settlers of this region. The unusually high frequency of “blue skin” in the area is an example of -

A. mutation.B. genetic drift.C. gene flow.D. sexual selection.

4. Allele frequencies in a population would most likely change due to

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Name: _________________________________________ Period: _________ Date: ________________

A. Random matingB. A stable environnementC. A large populationD. An increase in birth rateE. Mutations

5. The guppy is a species of small freshwater fish. Scientists observed that the average size of guppies in a pond decreased over a few years after a guppy predator was introduced in the pond. Which of the following best explains the change in guppy size?

A. natural selectionB. artificial selectionC. recombinationD. genetic shufflingE. genetic drift

6. A harmless scarlet king snake and a venomous eastern coral snake have similar banding patterns, as shown below. For the scarlet king snake, the adaptation of having a banding pattern like the eastern coral snake’s is known as mimicry.

The outcome of this adaptation in the scarlet king snake is to--A. make it easier for the scarlet king snake to attract prey.B. make it easier for the scarlet king snake to interbreed with the other snake.C. protect the scarlet king snake from predators.D. allow the scarlet king snake to blend in with its environment.

7. A population of salamanders, 50% of whom were spotted, decreased from 500 to only 100 in just a few months when a drought dried up much of the lake they inhabit. The remaining population had a much higher frequency of spotted than non-spotted salamanders compared with the original population. The most likely cause for this change is --

A. genetic drift.B. gene flow.C. mutation.D. artificial selection.

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