Evolution

Evolution

Middle School

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Learning Objectives

• Explain how gene mutations can change proteins, resulting in different traits.

• Describe how natural selection leads to advantageous traits becoming more common.

• Use models and data to explain how traits change in a population.

• Compare and contrast natural selection with artificial selection by humans.

Key Vocabulary

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Adaptation

A special trait that helps an organism successfully survive and reproduce in its environment.

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Mutation

A permanent change in the sequence of an organism's DNA, which can create new traits.

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Natural Selection

The process where beneficial traits become more common in a population over several generations.

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Evolution

The scientific theory that describes how species of organisms change over very long periods of time.

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Artificial Selection

The process where humans choose organisms with desirable traits to breed for specific, targeted outcomes.

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Gene

A specific unit of heredity that is transferred from a parent to its offspring through reproduction.

The Impact of Gene Mutations

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Beneficial Mutations

• ​Gene mutations can sometimes give organisms a survival advantage in their environment.

• ​​This change can result in a new and improved protein function.

• ​It helps the organism adapt better to its changing surroundings.

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Harmful Mutations

• ​These mutations negatively affect an organism's ability to survive and reproduce.

• ​​The altered protein may be less effective or completely non-functional.

• ​They can often lead to various diseases or genetic disorders.

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Neutral Mutations

• ​A neutral mutation is a gene change with no observable effect.

• ​​The function of the altered protein remains exactly the same as before.

• ​It does not affect the organism's survival or its ability to reproduce.

Multiple Choice

What is a harmful mutation?

• A gene change that provides a survival advantage to an organism.

• A mutation that always leads to a new and improved protein.

• A gene change that has no observable effect on the organism.

• A mutation that negatively impacts an organism's ability to survive and reproduce.

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What is an Adaptation?

Adélie Penguin

• ​Its wings have evolved into flippers, which are used for swimming through the water.

• A thick layer of fat and dense feathers provide insulation to keep the penguin warm.

• Its black-and-white feathers provide camouflage, helping it hide from predators and sneak up on prey.

Wandering Albatross

• ​A massive wingspan allows it to glide over the ocean for days without flapping.

• ​​Tubular nostrils give it an excellent sense of smell to locate fish from far away.

• ​It produces a rich stomach oil that provides energy during its long flights at sea.

Multiple Choice

What is an adaptation?

• A behavior that an organism learns during its lifetime.

• An inherited trait that helps an organism survive and reproduce.

• A temporary physical change in response to the environment.

• A random illness that affects an organism.

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Natural Selection Changes Populations

• Natural selection drives evolution using genetic variations that are passed down.

• Traits that improve survival and reproduction become more common over time.

• A change in the environment can cause a population's traits to shift.

• For example, antibiotic-resistant bacteria survive treatment and then multiply.

Multiple Choice

What is the main outcome of natural selection?

• It ensures all offspring are identical to their parents.

• It makes certain traits more common over time.

• It causes all genetic variations to disappear.

• It allows individual animals to change their traits.

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Artificial Selection: Human's Influence

Selective Breeding

• Humans choose organisms with desirable traits to be the parents of the next generation.

• Different dog breeds have been created by selecting for traits like size or temperament.

• Farm animals are also bred to produce more milk or meat for consumption.

Genetic Modification

• This modern technology allows scientists to directly change an organism's genes for a desired outcome.

• This technique is often much faster and more precise than traditional selective breeding.

• Crops can be genetically modified to become resistant to pests and diseases.

Multiple Choice

What is the key difference between selective breeding and genetic modification?

• Selective breeding is a faster process than genetic modification.

• Genetic modification changes genes directly, while selective breeding relies on choosing parents with desired traits.

• Genetic modification is an ancient practice, while selective breeding is a modern technology.

• Selective breeding is used for plants, while genetic modification is used for animals.

Darwin's Key Observations

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Species Vary Globally

• ​Darwin saw different species lived in similar habitats across the globe.

• ​​For instance, rheas live in South America and ostriches in Africa.

• ​Both are large, flightless birds that live in similar grasslands.

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Species Vary Locally

• ​Darwin observed related species differed within a local geographical area.

• ​​He found unique finch species across the Galápagos Islands.

• ​Each finch had a distinct beak shape adapted to its diet.

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Species Change Over Time

• ​Darwin found fossils of extinct animals that resembled modern species.

• ​​He found fossils of the Glyptodon, an ancient armored mammal.

• ​The Glyptodon shared many features with the modern armadillo.

Multiple Choice

Which statement best summarizes Darwin's key observations about life on Earth?

• Animals on different continents are always the same species.

• Species can vary in different places and have changed over time.

• Related species are only found in the exact same type of habitat.

• All species around the world are identical to their fossil ancestors.

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What's the Difference Between a Guess and a Theory?

Everyday 'Theory'

• In everyday language, a 'theory' is often just a hunch or a guess about something.

• For instance, you might say, 'I have a theory that it is going to rain today.'

• It is a casual idea that has not been tested in a systematic or structured way.

Scientific Theory

• A scientific theory is a well-tested explanation for why things happen in the natural world.

• It is supported by a large amount of evidence and many confirmed facts from experiments.

• Theories can be used to make accurate predictions about a wide range of natural events.

Multiple Choice

What is a scientific theory?

• A well-tested explanation for how nature works that is supported by evidence.

• An idea that has not yet been tested or observed.

• An opinion that is shared by many people.

• A guess or a hunch about a single event.

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Common Misconceptions

Misconception	Correction
Organisms choose to adapt.	Adaptations come from random mutations, not by choice.
Individuals evolve during their lifetime.	Populations evolve over generations, not individuals.
A scientific theory is just a guess.	A scientific theory is a well-tested explanation with lots of evidence.
Natural selection is always very slow.	Natural selection can happen rapidly, like in antibiotic-resistant bacteria.

Multiple Choice

If a region's climate becomes significantly colder, which rabbit mutation would most likely become more common over time due to natural selection?

• A mutation for thicker fur.

• A mutation for longer ears to release heat.

• A mutation for a smaller body size.

• A mutation for brown fur in a snowy environment.

Multiple Choice

What is the key difference in how advantageous traits are selected in natural selection versus artificial selection?

• Natural selection is driven by environmental pressures, while artificial selection is driven by human choices.

• Natural selection only applies to animals, while artificial selection only applies to plants.

• Artificial selection happens over millions of years, while natural selection is very fast.

• Artificial selection is random, while natural selection is purposeful.

Multiple Choice

A scientist discovers a new species of bird on a remote island where the primary food source is insects inside tree bark. What adaptation, based on Darwin's observations of finches, would you predict this bird species has developed?

• Large, powerful wings for long-distance flight.

• A long, thin, pointed beak for probing into bark.

• A short, strong beak for cracking hard nuts.

• Webbed feet for swimming.

Multiple Choice

A farmer selectively breeds corn for the largest size. A side effect is that this corn is also less resistant to drought. What does this scenario demonstrate about artificial selection?

• It is a perfect process with no downsides.

• It always results in organisms that are better adapted to their natural environment.

• Focusing on one desirable trait can lead to unintended and potentially negative consequences.

• It is a completely random process with no goal.

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Summary

• New traits from gene mutations are selected by nature for survival.

• In artificial selection, humans choose desirable traits to be passed on.

• Darwin's observations provide strong evidence for the scientific theory of evolution.

• Entire populations evolve over generations, not individual organisms during their lifetime.

Poll

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

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