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Year 11
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Higher

Natural selection at the genetic level

I can explain how natural selection leads to advantageous genetic variants becoming more common over generations.

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New
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Year 11
OCR
Higher

Natural selection at the genetic level

I can explain how natural selection leads to advantageous genetic variants becoming more common over generations.

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Lesson details

Key learning points

  1. Some mutations cause genetic variants that cause advantageous adaptations in phenotype.
  2. Individuals with these genetic variants are better adapted to compete, survive, reproduce and pass them on to offspring.
  3. Natural selection causes advantageous genetic variants to become more common in the population over generations.
  4. This causes advantageous adaptations in phenotype to become more common in the population over generations.
  5. Examples explained at the genetic level using ideas about mutation, genetic variants and natural selection.

Keywords

  • Natural selection - Organisms that are better adapted to their environment are more likely to survive, reproduce and pass on their genes to their offspring.

  • Adaptation - A feature that organisms have that helps them live in a particular place and survive.

  • Genetic variant - A genetic variant is a region of DNA in which the sequence of nucleotide bases has been changed.

  • Phenotype - The observable traits of an organism.

Common misconception

Many students write that organisms change themselves to become better adapted to their environment.

This lesson contains checks for this misconception and challenges it with examples of natural selection explained at the genetic level.

When teaching natural selection, avoid language that makes it seem like the organism is choosing to change itself. Ask students if they can choose to make themselves taller or to change their natural eye colour. Random mutations cause organisms to be better adapted, not choice.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Fossils show that the common characteristics of a species …
are fixed and never change.
Correct answer: change (evolve) over generations.
only change due to selective breeding by humans.
Q2.
Who is correct about the features of organisms?
Lucas: Most features are caused only by our genes.
Jun: All features are caused by the environment.
Correct answer: Aisha: Most features are influenced by both our genes and the environment.
Q3.
If a trait can be passed to an organism’s offspring, it is described as ...
evolution.
Correct answer: heritable.
reproduction.
variation.
Q4.
Match each word to its correct definition.
Correct Answer:adaptation,A trait that helps an organism to survive in a particular place.

A trait that helps an organism to survive in a particular place.

Correct Answer:competition,The struggle for resources that organisms need.

The struggle for resources that organisms need.

Correct Answer:natural selection,Individuals with advantageous traits are more likely to pass them on.

Individuals with advantageous traits are more likely to pass them on.

Correct Answer:reproduction,The process of making a new generation of offspring.

The process of making a new generation of offspring.

Q5.
A mutation in an organism’s DNA creates a genetic ...
copy.
Correct answer: variant.
chromosome.
protein.
phenotype.
Q6.
If a mutation changes the sequence of nucleotide bases in an organism’s DNA, this …
An image in a quiz
always changes the organism’s phenotype.
never changes the organism’s phenotype.
Correct answer: sometimes changes the organism’s phenotype.

Exit quiz

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6 Questions

Q1.
Mutations occur …
Correct answer: at random.
deliberately to help organisms to evolve.
only when organisms need to evolve.
Q2.
Mutations create genetic variants. Who has the correct idea about genetic variants?
Correct answer: Izzy: Genetic variants can be helpful, harmful or neither.
Jacob: All genetic variants must be helpful, otherwise they wouldn’t happen.
Sofia: All genetic variants are harmful because they’re caused by mutations.
Laura: A genetic variant must be either harmful or helpful, it can’t be neither.
Q3.
Match the start of each sentence to its correct ending.
Correct Answer:All genetic variants …,change the organism’s genome.

change the organism’s genome.

Correct Answer:No genetic variants …,happen due to evolution.

happen due to evolution.

Correct Answer:Some genetic variants …,change the organism’s phenotype.

change the organism’s phenotype.

Q4.
Because of natural selection, genetic variants that code for advantageous traits …
become less common over generations.
Correct answer: become more common over generations.
do not change frequency over generations.
Q5.
Put the statements in the correct order to explain how a mutation can affect an organism’s phenotype.
1 - The nucleotide base sequence in DNA is changed.
2 - This creates a genetic variant.
3 - The genetic variant is used as instructions for making a protein.
4 - Because of the mutation, a different sequence of amino acids is joined together.
5 - This may change the shape of the protein.
6 - This may change the activity of the protein.
Q6.
Put the statements in the correct order to explain why the genetic variant that codes for black colouration in the peppered moth became more common when tree bark darkened.
An image in a quiz
1 - Individuals with the genetic variant were better adapted to their environment.
2 - Individuals with the genetic variant were more likely to survive and reproduce.
3 - Individuals with the genetic variant were more likely to pass it onto offspring.
4 - This repeated over many generations.