Natural and Artificial Selection

Natural and Artificial Selection

Middle School

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Learning Objectives

• Describe how natural selection leads to changes in populations over many generations.

• Describe artificial selection and provide examples of how humans use it.

• Compare and contrast the processes of natural selection and artificial selection.

• Explain the role of mutations and inheritance in how traits are passed on.

Key Vocabulary

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Natural Selection

A process where organisms better suited to their environment are more likely to survive and reproduce.

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Artificial Selection

This is a process where humans breed plants and animals to produce specific and desirable traits.

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Mutation

A mutation is a change in an organism's genetic material which can be inherited or random.

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Inheritance

This is the process of passing down genetic traits from parents to their offspring through genes.

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Generation

It refers to a single step in the line of descent from an ancestor.

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What is Natural Selection?

• Natural selection helps organisms with useful traits survive and reproduce in their environment.

• Random changes in genes, called mutations, can create new and helpful traits.

• For example, better camouflage can help a mouse hide from predators like owls.

• These helpful traits are passed to offspring, making them more common over time.

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Multiple Choice

According to the principles of natural selection, which statement best explains why a helpful trait becomes more common in a population?

• The environment causes all new offspring to be born with the helpful trait.

• Mutations stop occurring in the population once a helpful trait appears.

• All organisms in the population decide to develop the helpful trait at the same time.

• Organisms with the helpful trait are more likely to survive and pass it on through inheritance.

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What is Artificial Selection?

• In artificial selection, humans choose which organisms get to reproduce.

• The goal is to encourage specific desirable traits in species.

• Over generations, this makes the selected trait more common.

• Charles Darwin studied this process in many different pigeons which led to the central concept in his theory of evolution.

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Multiple Choice

Darwin used the results of artificial selection in pigeons as an

analogy to explain which central concept in his theory of evolution?

• Hybridization

• Mutation

• Acquired characters

• Natural selection

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Natural vs. Artificial Selection

Natural Selection

• It is a slow, natural process that happens in wild populations over many generations.

• Only traits that are favorable and help an organism survive are passed on.

• This process helps in creating biodiversity and allows for the evolution of species.

Artificial Selection

• It is a rapid, man-made process that happens in domestic populations like farm animals.

• Humans select desirable traits to be passed on, regardless of their survival value.

• This is used for breeding animals, like cows that can produce more milk.

Multiple Choice

What is the key difference in the traits passed on through natural selection versus artificial selection?

• Natural selection reduces biodiversity, while artificial selection increases it.

• Natural selection is a rapid process, while artificial selection is a slow one.

• Natural selection only occurs in domestic populations, while artificial selection occurs in nature.

• Natural selection passes on traits selected by nature for survival, while artificial selection passes on traits selected by humans for desirability.

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Common Misconceptions About Evolution

Misconception	Correction
Organisms can evolve during their lifetime.	Evolution happens to populations over generations, not to one organism.
All genetic mutations are harmful.	Mutations can be harmful, neutral, or helpful for survival.
Artificial and natural selection are unrelated.	Artificial selection is a model Darwin used to explain natural selection.
Organisms get new traits because they ‘need’ them.	Traits come from random mutations, not from need.

Multiple Choice

Why is artificial selection considered important evidence for the theory of natural selection?

• It proves that all species were created by humans.

• It happens much faster than natural selection.

• It only works on domesticated animals like pigeons and dogs.

• It shows that populations can change over generations based on selected traits.

Multiple Choice

A population of birds has a variation in beak size. After a change in the environment where only large, hard seeds are available, birds with larger, stronger beaks become more common over generations. Which process does this describe?

• Random mutation

• Artificial selection

• Inheritance alone

• Natural selection

Multiple Choice

A farmer wants to breed a new type of sheep that has both soft wool and is resistant to a common disease. How would the farmer need to apply the principles of selection to achieve this goal?

• They should cross-breed many different types of sheep and see what happens.

• They should hope that random mutations create the desired traits.

• They should find sheep with soft wool and others with disease resistance, then selectively breed their offspring with the best combination of traits.

• They should only select for one trait at a time, as it's impossible to select for two.

Multiple Choice

If a dog breeder only ever selects for a specific physical trait, like a very short snout in pugs, what is a potential unintended outcome for that dog population?

• The population may suffer from health problems related to that trait, like breathing difficulties.

• The dogs will eventually be born with long snouts again.

• The dogs will become more intelligent.

• Natural selection will no longer have any effect on the dogs.

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Summary

• Natural selection helps organisms with environmental advantages survive and reproduce.

• In artificial selection, humans choose organisms with desirable traits to breed.

• Mutations are random gene changes that create variations in a population.

• Nature drives natural selection, while humans direct artificial selection.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4