What is required within a population for natural selection to occur?

Genetic variation within the population.

Define the term selection pressure.

An environmental factor that affects the survival and reproduction of individuals with certain phenotypes.

What happens to the proportion of individuals with advantageous characteristics over many generations?

The proportion of the population possessing advantageous characteristics increases.

Explain how pesticide resistance evolves in insect populations.

Random mutations confer resistance; resistant individuals survive pesticide application and reproduce, passing resistance alleles to offspring, increasing their frequency in the population.

Explain how antibiotic resistance evolves in microorganisms.

Random mutations confer resistance; resistant individuals survive antibiotic treatment and reproduce, passing resistance alleles to offspring, increasing their frequency in the population.

OCR A-Level Biology H420

Cell Structure

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Classification and Evolution

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Classification and Evolution

Natural selection and resistance

2 things to know
Components 02 and 03

Overview

What natural selection requires, selection pressure and the resulting change in allele frequency, and how pesticide and antibiotic resistance evolve.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

Explain natural selection.

Process

Explain how natural selection leads to changes in allele frequency.

Questions from this subtopic

Each one with the model answer underneath.

1
What is required within a population for natural selection to occur?
Model answer
Genetic variation within the population.
2
Define the term selection pressure.
Model answer
An environmental factor that affects the survival and reproduction of individuals with certain phenotypes.
3
Explain how natural selection leads to changes in allele frequency.
Model answer
Individuals with advantageous characteristics have greater reproductive success, passing their alleles to more offspring.
4
What happens to the proportion of individuals with advantageous characteristics over many generations?
Model answer
The proportion of the population possessing advantageous characteristics increases.
5
Explain how pesticide resistance evolves in insect populations.
Model answer
Random mutations confer resistance; resistant individuals survive pesticide application and reproduce, passing resistance alleles to offspring, increasing their frequency in the population.
6
Explain how antibiotic resistance evolves in microorganisms.
Model answer
Random mutations confer resistance; resistant individuals survive antibiotic treatment and reproduce, passing resistance alleles to offspring, increasing their frequency in the population.

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