Mechanisms of Evolution

"Survival of the Fittest" refers to ​ (a)   , which causes​ (b)   ,

• Natural Selection
• Evolution
• Gene Flow
• Genetic Drift

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What is the definition of Genetic Drift?

• Random fluctuation in allele frequency.

• Natural selection process.

• Mutation in DNA sequence.

• Gene flow between populations.

Answer explanation

Genetic drift refers to random fluctuations in allele frequencies within a population, often due to chance events. This distinguishes it from natural selection, which involves differential survival and reproduction.

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What is the definition of Nonrandom mating (inbreeding)?

• Mating occurs between similar individuals.

• Mating occurs randomly in a population.

• Mating occurs between different species.

• Mating occurs only during specific seasons.

Answer explanation

Nonrandom mating, or inbreeding, occurs when individuals that are similar genetically mate with each other. This choice correctly defines inbreeding, while the other options describe different mating scenarios.

Randi is studying a small population of butterflies on an isolated island. What effect does Genetic Drift have on genetic variation in this population?

• Lowers genetic variation (small populations).

• Increases genetic variation (large populations).

• Has no effect on genetic variation.

• Causes genetic variation to fluctuate randomly.

Answer explanation

Genetic drift tends to lower genetic variation, especially in small populations, as random events can lead to the loss of alleles. This reduces the overall genetic diversity within the population.

In a remote arctic community of polar bears, how does Genetic Drift affect the community's overall fitness?

• Usually lowers population fitness as populations are less able to adapt to environmental change.

• Increases genetic diversity leading to higher adaptability.

• Has no effect on population fitness.

• Improves population fitness by selecting advantageous traits.

Answer explanation

Genetic drift usually lowers population fitness because it can lead to the loss of beneficial alleles and reduce genetic variation, making populations less adaptable to environmental changes.

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What effect does Nonrandom mating (inbreeding) have on genetic variation?

• Lowers genetic variation (small populations).

• Increases genetic variation.

• Has no effect on genetic variation.

• Leads to the creation of new alleles.

Answer explanation

Nonrandom mating, such as inbreeding, typically lowers genetic variation, especially in small populations, by increasing the likelihood of homozygosity and reducing the diversity of alleles.

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Select the best answer based on the image.

• Gene Flow

• Genetic Drift

Answer explanation

Genetic Drift refers to random changes in allele frequencies in a population, especially in small populations, leading to significant evolutionary changes over time. This distinguishes it from Gene Flow, which involves the transfer of genes between populations.

Match the following

• Genetic Drift

• Changes in genetic traits due to a chance event

• Gradualism

• Rapid changes contrasted with long periods with little chage

• Gene Flow

• Changes in genetic traits due to migration

• Punctuated equilibrium

• Long periods of time with slow changes and diversity

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A population of squirrels on one side of the Grand Canyon change so much over a period of time that they can no longer breed with the squirrels on the other side of the Grand Canyon. This is called _________________.

• Genetic Drift

• Speciation

• Gene Flow

• Vestigial Structures

Answer explanation

This is called speciation because the population of squirrels has evolved to the point where they can no longer interbreed with the other population, leading to the formation of new species.

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