The Process of Evolution

The Process of Evolution

Middle School

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Learning Objectives

• Describe how natural selection changes the traits of a population over many generations.

• Explain how a gene mutation can create a beneficial, harmful, or neutral trait.

• Explain how genetic variation helps a population survive and reproduce in its environment.

• Define coevolution and give examples of how interacting species can evolve together.

Key Vocabulary

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Gene

A gene is a segment of DNA that holds the instructions for building a specific protein.

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Protein

Proteins are large molecules that perform most of the work in cells and determine our traits.

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Trait

A trait is a specific characteristic of an organism, like eye color, height, or blood type.

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Mutation

A mutation is a permanent change in the DNA sequence of a gene, possibly altering a protein.

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Chromosome

A chromosome is a thread-like structure located inside the nucleus that contains tightly coiled DNA.

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Genetic Variation

Genetic variation refers to the diversity in gene frequencies between individuals or populations within a species.

Key Vocabulary

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Natural Selection

The process where organisms with helpful traits are more likely to survive, reproduce, and pass them on.

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Adaptation

A physical or behavioral trait that helps an organism better survive and reproduce in its environment.

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Fitness

A measure of how well an organism can survive and reproduce in its specific environment.

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Population

A group of organisms of the same species that live together in the same geographical area.

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Coevolution

The process where two or more species evolve in response to changes in each other over time.

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From Genes to Traits

• Genes on chromosomes hold instructions to build specific proteins.

• A protein's structure determines its function, like carrying oxygen.

• The functions of proteins determine an organism's observable traits.

• Therefore, the connection is: Genes → Proteins → Traits.

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Multiple Choice

What is the primary function of a gene?

• To hold the instructions for building specific proteins

• To create the observable traits of an organism directly

• To determine the structure of a chromosome

• To carry oxygen throughout the body

Multiple Choice

What is the relationship between a protein's structure and an organism's traits?

• A protein's specific structure determines its specific function, which creates a trait.

• A protein's main purpose is to copy the instructions from a gene.

• All proteins have the same function, regardless of their structure.

• Traits are determined by the number of chromosomes an organism has.

Multiple Choice

If a gene's instructions are changed, what is the most likely effect on the protein and the resulting trait?

• The protein's structure would change, likely altering its function and resulting in a different trait.

• The organism would create more chromosomes to correct the error.

• The protein would still function correctly, but the trait would disappear.

• The gene would automatically repair itself without affecting the protein.

Mutations and Their Effects

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Beneficial Mutations

• These mutations increase an organism's chance of survival and reproduction.

• They provide an advantage in the organism's current environment.

• An example is bacteria developing resistance to antibiotics over time.

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Harmful Mutations

• These mutations decrease an organism's chance of survival and reproduction.

• They can lead to genetic disorders or other harmful diseases.

• Sickle cell anemia is an example of a disease from a mutation.

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Neutral Mutations

• These mutations do not have an observable effect on the organism.

• The change in the DNA does not alter the protein’s function.

• An example is a different eye color that doesn’t affect vision.

Multiple Choice

What is the primary factor that determines whether a mutation is classified as beneficial, harmful, or neutral?

• Its effect on the organism's survival and reproduction.

• The specific part of the DNA that is changed.

• The speed at which the mutation appears in a population.

• Whether the organism is a plant or an animal.

Multiple Choice

What is the underlying reason why a neutral mutation does not have an observable effect on an organism?

• The mutation does not result in a significant change to a protein's function.

• The mutation helps the organism find more food.

• The mutation leads to a serious genetic disorder.

• The mutation is impossible to detect in an organism.

Multiple Choice

Based on the information provided, which statement best analyzes the different impacts of mutations?

• A mutation that helps bacteria resist an antibiotic is beneficial, while one that causes a disease like sickle cell anemia is harmful.

• All mutations related to diseases are harmful, but all mutations in bacteria are beneficial.

• A mutation for antibiotic resistance is neutral, while a mutation for sickle cell anemia is beneficial.

• Any mutation that changes an organism will eventually become harmful to its survival.

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Genetic Variation in Populations

• Genetic variation is the difference in traits like color among individuals in a population.

• Some traits provide an advantage, helping individuals survive and reproduce more successfully.

• Natural selection leads to advantageous traits becoming more common in the population over time.

• This process is how a population adapts to its environment and evolves.

Multiple Choice

What is genetic variation?

• The differences in traits found within a population.

• The process where all individuals in a population become identical.

• The changes that occur in an ecosystem over a long period.

• The way an individual organism learns new behaviors to survive.

Multiple Choice

What is the relationship between an individual's traits and its survival?

• An individual's traits do not affect its chances of survival or reproduction.

• Individuals with advantageous traits are less likely to have offspring.

• Only individuals that learn new skills can survive, regardless of their traits.

• Individuals with advantageous traits are more likely to survive and pass those traits to their offspring.

Multiple Choice

A population of bears has variation in fur thickness. If the climate in their habitat becomes significantly colder over many generations, what is the most likely outcome?

• The bears will all learn to hibernate, making fur thickness irrelevant.

• The trait for thinner fur will become more common as it requires less energy.

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

• The entire bear population will migrate to a warmer climate.

Natural Selection and Adaptation

• Natural selection favors traits that help a species survive and reproduce.

• An organism's fitness is its ability to survive and pass on traits.

• Adaptation is when helpful traits become more common in a population over time.

Multiple Choice

Which statement best describes the process of natural selection?

• A process that favors traits that improve a species' chances of survival and reproduction

• A process where an individual organism changes its traits to fit its environment

• A process where species choose to develop new, helpful features

• A process that ensures all individuals in a population are identical

Multiple Choice

What is the relationship between an organism's 'fitness' and the process of natural selection?

• Higher fitness means an organism is more likely to survive and pass on its traits.

• Higher fitness is achieved by the strongest and fastest organisms, regardless of reproduction.

• Fitness is a measure of how well an organism can change its own traits.

• An organism's fitness has no effect on the process of natural selection.

Multiple Choice

A population of lizards lives on brown soil. Most are brown, but some are gray. If a new predator that hunts by sight arrives, what is the most likely long-term result for the lizard population?

• The trait for brown coloration will become more common in the population over time.

• The gray lizards will learn to hide more effectively from the new predator.

• The entire lizard population will be eliminated by the new predator.

• The brown lizards will begin to produce more gray offspring.

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Coevolution and Species Interactions

Cooperative Evolution

• ​Coevolution is when species with close interactions influence each other's evolution over a long time.

• ​​Acacia trees and ants show cooperation; the tree offers shelter and food, while the ants offer protection.

• ​These interactions can be cooperative, competitive, or predatory, driving evolutionary changes in the species involved.

Mimicry

• ​Mimicry is an outcome of coevolution where one species evolves to look like another species.

• ​​For instance, some non-toxic butterflies evolved wing patterns that closely resemble those of toxic butterflies.

• ​This resemblance protects them as predators that have learned to avoid the toxic species also avoid them.

Multiple Choice

What is the definition of coevolution?

• A process where two species with close interactions influence each other's evolution.

• A process where a single species changes its appearance to attract a mate.

• A process where animals compete for resources within the same species.

• A process where one species actively hunts another for food without any changes.

Multiple Choice

How does mimicking a toxic butterfly benefit a non-toxic butterfly?

• It helps the non-toxic butterfly find more food.

• It allows the non-toxic butterfly to attract more mates.

• It helps the non-toxic butterfly avoid being eaten by predators.

• It makes the non-toxic butterfly stronger than the toxic one.

Multiple Choice

If the ants that protect an acacia tree were removed, what would be the most likely consequence for the tree based on their coevolutionary relationship?

• The tree would be harmed by herbivores.

• The tree would grow faster without the ants.

• The tree would not be affected.

• The tree would find a new protector insect.

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Common Misconceptions

Misconception	Correction
All mutations are harmful.	Most mutations are neutral; some can be beneficial or harmful.
Individual organisms adapt during their lifetime.	Populations adapt over generations through natural selection.
Evolution is just 'survival of the fittest.'	Evolution also includes traits that increase reproductive success.
Adaptation is always successful.	Rapid environmental change can lead to extinction if a population can't adapt.

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Summary

• Genes on chromosomes code for proteins that determine traits; mutations are random gene changes.

• Mutations create genetic variation by causing beneficial, harmful, or neutral effects on traits.

• Natural selection allows individuals with higher fitness to pass on traits, leading to adaptation.

• Coevolution occurs when two species with close interactions influence each other's evolution.

Poll

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

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