Evolution

Evolution

Middle School

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Learning Objectives

• Explain how gene mutations can change proteins, resulting in beneficial, harmful, or neutral traits.

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

• Explain how the distribution of traits in a population changes using models and data.

• Compare and contrast natural selection with artificial selection, where humans influence trait inheritance.

Key Vocabulary

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Adaptation

An adaptation is a special trait or characteristic that helps an organism successfully survive and reproduce.

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Mutation

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

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Natural Selection

Natural selection is the process where beneficial traits become more common in a population over several generations.

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Evolution

Evolution is the scientific theory that describes how species of organisms change over very long periods of time.

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Scientific Theory

A scientific theory is a thoroughly tested and well-supported explanation for observations of the natural world.

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Gene

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

Key Vocabulary

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Protein

A molecule built from gene data that plays a crucial role in determining an organism's traits.

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Chromosome

A structure found inside the nucleus of a cell that carries genetic information in genes.

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Trait

A specific characteristic or feature of an organism, like its eye color, height, or behavior.

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Genetic Variation

The variety of different genes and traits that exist within a single population of a species.

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Artificial Selection

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

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Selective Breeding

The practice of mating two organisms to produce offspring with specific and desirable genetic traits.

The Impact of Gene Mutations

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Beneficial Mutation

• A gene mutation can sometimes provide a survival advantage to an organism.

• This change can lead to a new and improved protein function.

• It helps the organism adapt better to its surrounding environment.

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Harmful Mutation

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

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

• This can often lead to various diseases or genetic disorders.

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Neutral Mutation

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

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

• It does not affect the organism's survival or its reproduction.

Multiple Choice

What is a harmful mutation?

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

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

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

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

Multiple Choice

How does a gene mutation affect the protein it codes for?

• It can make a protein less effective or non-functional, or create an improved protein.

• It only happens in organisms that are unable to reproduce.

• It always causes the function of the altered protein to remain the same.

• It only occurs in response to a change in the environment.

Multiple Choice

A rabbit living in a snowy region is born with a mutation that changes its fur color from brown to white, making it harder for predators to spot. How would this mutation be classified and why?

• Beneficial, because it provides a survival advantage in a snowy environment.

• Harmful, because any change to an organism's genes is a disorder.

• Neutral, because the change in fur color has no effect on the rabbit.

• Neutral, because the protein's function must have remained the same.

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What Is an Adaptation?

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

• These traits arise from random genetic changes, known as mutations, in an organism.

• A beneficial trait helps an organism to live longer and produce more offspring.

• Over generations, this helpful trait becomes more common in a population.

Multiple Choice

What is an adaptation?

• An inherited trait that helps an organism survive and reproduce

• A behavior that an organism learns during its lifetime

• A temporary physical change in response to the environment

• A random illness that affects an organism

Multiple Choice

According to the principles of adaptation, how does a random genetic change become a beneficial trait?

• It is a change the organism chooses to make

• It occurs in all members of a population at once

• It helps the organism live longer and have more offspring

• It makes the organism physically stronger than all others

Multiple Choice

If a species develops a new inherited trait that provides better camouflage in its environment, what is the most likely outcome over many generations?

• The trait for camouflage will likely become more common in the population over time.

• The entire population will immediately develop camouflage.

• The original trait will become more dominant to fight the change.

• The organisms will decide to stop the genetic changes from happening.

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Adaptations: Penguin vs. Albatross

Adélie Penguin

• Their wings have evolved into flippers, making them powerful swimmers instead of flyers, perfect for hunting underwater.

• A compact body shape, a layer of fat, and dense feathers provide excellent insulation in cold waters.

• Black-and-white feathers offer camouflage in the water, while living in large groups reduces the risk from predators.

Wandering Albatross

• A massive wingspan of up to 3.5 meters allows it to glide on wind currents for days without flapping.

• It has tubular nostrils on its beak that give it an excellent sense of smell to find fish.

• It produces an energy-rich stomach oil for long flights and as a nutritious food source for its chicks.

Multiple Choice

The unique features of the Adélie Penguin and the Wandering Albatross, such as the penguin's flippers and the albatross's large wingspan, primarily help them to do what?

• Survive in their specific environments

• Communicate with other animals

• Change their habitats to suit their needs

• Find mates more easily

Multiple Choice

How do the wing adaptations of the penguin and the albatross relate to their different lifestyles?

• The penguin's wings are for swimming to hunt, while the albatross's wings are for gliding to travel far.

• The penguin's wings help it fly low, while the albatross's wings help it dive deep.

• Both birds use their wings primarily for balance on land.

• The penguin's wings are for defense, while the albatross's wings are for finding fish.

Multiple Choice

An albatross is on a long journey over the ocean, far from any land. Which two adaptations are most crucial for helping it find food and sustain its energy during this flight?

• A keen sense of smell to locate fish and stomach oil for energy.

• A compact body for warmth and black-and-white feathers for camouflage.

• Dense feathers for insulation and living in a large group for protection.

• Powerful flippers for diving and a thick layer of fat for insulation.

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What Is Natural Selection?

• Natural selection drives evolution, making some traits more common than others.

• The process requires genetic variations that can be passed to offspring.

• Some traits give a higher probability of surviving and reproducing.

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

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Multiple Choice

What is the main outcome of natural selection?

• It makes certain traits more common over time.

• It allows individual animals to change their traits.

• It ensures all offspring are identical to their parents.

• It causes all genetic variations to disappear.

Multiple Choice

For a trait to be affected by natural selection, what must be true about it?

• They are learned during an organism's lifetime.

• They can be passed down from parents to offspring.

• They make an organism weaker than others.

• They are only present in bacteria.

Multiple Choice

When an antibiotic is used, most bacteria are killed, but some may survive and multiply. Which statement best explains why some bacteria survive?

• The antibiotic was not strong enough to kill any bacteria.

• The bacteria learned how to fight the antibiotic and taught others.

• A few bacteria had a genetic trait that allowed them to survive the antibiotic.

• All bacteria were able to change themselves to become resistant.

Changing Traits in a Population

• Natural selection changes traits in a population over many generations.

• An environmental change can cause a shift in the distribution of traits.

• Traits that help survival in the new environment become more common.

Multiple Choice

What is the primary effect of natural selection on a population?

• The traits found in the population change over time.

• Individual organisms can choose to change their traits.

• The traits of a population remain stable forever.

• All changes in traits happen within a single generation.

Multiple Choice

Under what conditions does the distribution of traits in a population typically begin to shift?

• When the environment changes, making certain traits more advantageous for survival.

• When individual animals decide it is time to change their traits.

• When a population becomes too large for its habitat.

• When new animals move into the habitat from another place.

Multiple Choice

If a giraffe population lives in an area where a disease suddenly wipes out all the low-lying plants, leaving only tall trees for food, what would be the most likely long-term effect on the population?

• The proportion of giraffes with longer necks would likely increase.

• All the giraffes would instantly grow longer necks.

• The giraffes would learn to eat grass instead of tree leaves.

• The length of giraffes' necks would not change.

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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.

• For example, different dog breeds have been created by selecting for specific traits like size or temperament.

• Farm animals are also bred to produce more milk or meat, a practice that is thousands of years old.

Genetic Modification

• Modern technology allows scientists to directly change an organism's genes to produce a desired outcome.

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

• For instance, crops can be genetically modified to become resistant to pests and diseases.

Multiple Choice

What is the primary purpose of artificial selection?

• To create new species from scratch.

• To help organisms survive in the wild without human help.

• To produce organisms with specific, desirable traits.

• To study the natural evolution of animals and plants.

Multiple Choice

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

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

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

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

• Selective breeding is a faster process than genetic modification.

Multiple Choice

A farmer wants to grow corn that is resistant to a new, rapidly spreading pest. Why would the farmer most likely choose genetic modification over selective breeding?

• Because selective breeding cannot be used on crops like corn.

• Because genetic modification is a more precise and faster way to introduce a specific trait like disease resistance.

• Because selective breeding takes thousands of years to show any results.

• Because only selective breeding can create pest-resistant crops.

Darwin's Key Observations

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Species Vary Globally

• ​Darwin noticed similar habitats on different continents were home to different species.

• ​​For instance, he saw large, flightless birds like rheas and ostriches.

• ​They lived in similar grasslands in South America and Africa respectively.

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Species Vary Locally

• ​Darwin observed that related species often occupied different habitats in a local area.

• ​​He noticed several unique species of finches across the Galápagos Islands.

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

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Species Change Over Time

• ​Darwin collected fossils of extinct animals that looked like modern species.

• ​​He uncovered fossils of the Glyptodon, a giant, ancient armored mammal.

• ​This extinct animal shared many features with the modern-day armadillo.

Multiple Choice

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

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

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

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

• Animals on different continents are always the same species.

Multiple Choice

Based on Darwin's observations of finches in the Galápagos, what is the relationship between a species and its local habitat?

• Each finch species had a beak shape that was suited for a different food source.

• All the finches on the islands were identical to each other.

• The finches' beaks were similar to fossils Darwin found.

• The finches flew from South America to Africa.

Multiple Choice

Darwin found fossils of the extinct Glyptodon, which resembles the modern armadillo. What conclusion does this evidence support?

• Evidence suggests that modern species may be related to extinct species from the same region.

• Animals with similar features always live in similar habitats on different continents.

• All ancient animals were much larger than the animals that are alive today.

• Flightless birds like rheas and ostriches do not change over time.

What is a Scientific Theory?

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Everyday 'Theory'

• In common language, a theory can often be just a hunch.

• It is sometimes used to describe a guess about something.

• For example, "I have a theory it might rain today."

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Scientific Theory

• A scientific theory is a well-tested explanation for how nature works.

• It is built on a wide range of evidence and facts.

• Scientific theories can be used to make predictions about the world.

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Examples of Theories

• The Theory of Plate Tectonics explains how continents have moved.

• The Germ Theory of Disease states that microbes can cause illnesses.

• The Atomic Theory of Matter says everything is made of atoms.

Multiple Choice

What is a scientific theory?

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

• A guess or a hunch about a single event.

• An opinion that is shared by many people.

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

Multiple Choice

What is the main difference between a scientific theory and an everyday theory?

• A scientific theory is supported by evidence, while an everyday theory is often just a guess.

• A scientific theory is a guess, while an everyday theory is a well-tested explanation.

• A scientific theory cannot be changed, while an everyday theory can.

• There is no real difference between the two types of theories.

Multiple Choice

A scientist proposes a new idea that everything in the universe is connected by invisible strings. According to the principles of scientific theories, what would need to happen for this idea to be accepted as a theory like the Atomic Theory of Matter?

• It must be repeatedly tested and supported with a wide range of evidence.

• It must be a popular idea that many people agree with.

• It must explain a single event, like why it might rain today.

• It must be named after the person who first thought of it.

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Common Misconceptions

Misconception	Correction
Organisms choose to adapt or change.	Adaptations arise from random mutations.
Individuals evolve during their lifetime.	Populations evolve, not individuals.
A scientific theory is just a guess.	A scientific theory is a well-tested explanation backed by extensive evidence.
Natural selection happens very slowly.	Natural selection can occur rapidly, as seen in antibiotic-resistant bacteria.

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Summary

• Genes determine traits, and mutations can create new ones.

• Natural selection favors traits that aid survival and reproduction.

• Humans choose traits to be passed on in artificial selection.

• The Theory of Evolution is a strong, evidence-based explanation for life’s diversity.

Poll

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

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