Biology Module 1.3: Natural Selection

Questions and Answers

What are the requirements for evolution by natural selection? (Select all that apply)

Individuals with different alleles have the same survival and reproduction.

There must be a struggle for existence. (correct)

The trait under selection must be heritable. (correct)

The trait under selection must be variable in the population. (correct)

What is fitness?

The idea that the organisms that best match their environment will have greater survival and reproduction of their alleles.

When does natural selection occur?

When the environment pressures a population so that only some phenotypes survive and reproduce.

What does stabilizing selection result in?

A narrowing of the normal distribution. Signup and view all the answers

What does directional selection result in?

A shift toward one end of the normal distribution. Signup and view all the answers

What does disruptive or diversifying selection result in?

Separation of the normal distribution into two distributions. Signup and view all the answers

When does balancing selection occur?

When multiple phenotypes are maintained in the population. Signup and view all the answers

What are two common types of balancing selection? (Select all that apply)

Heterozygote advantage Signup and view all the answers

What is frequency-dependent selection?

Where fitness depends on how common the phenotype is. Signup and view all the answers

What is heterozygote advantage?

Where the heterozygote has higher fitness than either homozygote. Signup and view all the answers

Does evolution of bigger, sexually reproducing organisms happen on time scales faster than geologic time?

True Signup and view all the answers

How does natural selection explain how bacterial populations evolve resistance to antibiotics?

Rare, resistant mutant bacteria in the population survive antibiotic treatment. Signup and view all the answers

What conditions lead to evolution by natural selection? (Select all that apply)

Competition for limiting resources Signup and view all the answers

Which of the following statements is/are accurate? (Select all that apply)

Natural selection works on variation already present in a population. Signup and view all the answers

Which statement describes the canary with the greatest biological fitness?

Canary that lives to be 2 years old and has four offspring, all of which survive to reproduce. Signup and view all the answers

Study Notes

Requirements for Evolution by Natural Selection

Population must display VARIABLE traits, meaning there are multiple alleles for a given gene.
Traits must be HERITABLE, allowing them to be passed from one generation to another.
A STRUGGLE FOR EXISTENCE exists as more offspring are produced than can survive.
Individuals with different alleles exhibit VARIED SURVIVAL AND REPRODUCTION rates based on environmental fitness.

Concept of Fitness

Fitness refers to the ability of organisms that match their environment closely to achieve higher survival rates and reproductive success.

Occurrence of Natural Selection

Natural selection occurs when environmental pressures favor certain phenotypes, leading to a non-random shift in allele frequencies between generations.

Stabilizing Selection

Results in a narrower normal distribution by favoring individuals with average phenotypes, allowing them to produce more offspring than those at extremes.

Directional Selection

Shifts normal distribution toward one phenotypic extreme, favoring individuals at that end to have more offspring than those at the opposite extreme.

Disruptive or Diversifying Selection

Leads to the division of a normal distribution into two separate distributions, as individuals with extreme phenotypes outperform those with intermediate phenotypes.

Balancing Selection

Occurs when multiple phenotypes or alleles are maintained in a population without a single phenotype having a consistent advantage.

Types of Balancing Selection

Commonly includes frequency-dependent selection and heterozygote advantage.

Frequency-Dependent Selection

The fitness of a phenotype or allele is influenced by its frequency within the population.

Heterozygote Advantage

The heterozygote possesses a combined phenotype from both alleles, granting it a higher fitness compared to either homozygote.

Evolutionary Time Scale

Evolution of larger sexually reproducing organisms can occur faster than geological time, exemplified by rock pocket mice adapting to different environments.

Bacterial Evolution and Antibiotic Resistance

Evolution of bacteria's antibiotic resistance is driven by rare mutant bacteria surviving antibiotic treatments, rather than adaptations being passed from individual bacteria.

Conditions for Evolution by Natural Selection

Key conditions include competition for limited resources and heritable variation in the population. Unlimited resources do not support natural selection.

Accuracy of Statements on Natural Selection

Natural selection acts on pre-existing variation in populations. Evolution by natural selection results solely from selection on heritable traits.

Biological Fitness of Canaries

The canary with the highest biological fitness is one that produces the most surviving offspring, emphasizing the importance of both longevity and reproductive success.

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Description

Test your knowledge on the key requirements for evolution by natural selection. This flashcard quiz covers essential concepts like variability, heritability, and the struggle for existence. Enhance your understanding of evolutionary biology through these engaging questions.