MS-LS4-4: Genetic Traits and Survival

MS-LS4-4
Genetic Traits and Survival

Middle School

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Learning Objectives

• Describe how genes and alleles are responsible for the traits that can be inherited.

• Explain how genetic variation from mutations provides the raw material for new adaptations.

• Explain how natural selection causes certain traits to become more common in a population.

• Use simple probability to show how traits affect an organism's survival and reproduction.

• Analyze how environmental changes cause shifts in the traits of a population.

Key Vocabulary

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Gene

A gene is the basic unit of heredity that is passed from parent to child.

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Allele

An allele is a specific version or form of a gene, like different options for a trait.

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Mutation

A mutation is a permanent alteration or change in the DNA sequence of a cell’s genome.

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Adaptation

An adaptation is a beneficial trait that helps an organism survive and successfully reproduce in its environment.

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Natural Selection

Natural selection is the process where organisms with favorable traits are more likely to survive and reproduce.

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Genetic Variation

Genetic variation refers to the diversity in gene frequencies or the differences in genes between individuals.

Key Vocabulary

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Inheritable Trait

An inheritable trait is a specific characteristic or feature that is passed down from a parent to its offspring.

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Advantageous Trait

An advantageous trait is a characteristic that increases an organism's chances of survival and successful reproduction.

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Disadvantageous Trait

A disadvantageous trait is a characteristic that decreases an organism's chances of survival and successful reproduction.

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The Stages of Mendel's Experiments

• Gregor Mendel studied inheritance using pea plants, which had many different traits.

• He first created pure-breeding parent plants (P generation) through self-pollination.

• Cross-pollinating these created an F₁ generation where all offspring were tall.

• Self-pollinating the F₁ plants produced an F₂ generation with a 3:1 ratio.

• This experimental learning laid the foundation of modern genetics.

Multiple Choice

What was the primary contribution of Gregor Mendel's experiments with pea plants?

• They established the foundations of modern genetics.

• They proved that all plants grow at the same rate.

• They discovered how to create different colors of flowers.

• They showed that all offspring are identical to their parents.

Multiple Choice

What happened when Mendel cross-pollinated the pure-breeding parent plants?

• All offspring in the F1 generation were tall.

• The offspring had a mix of tall and short plants.

• All offspring in the F1 generation were short.

• The parent plants did not produce any offspring.

Multiple Choice

What is the best conclusion that can be drawn from the fact that the F1 generation was all tall, but the F2 generation had both tall and short plants?

• A trait from the parent generation can be hidden in the F1 generation and reappear later.

• The F1 generation was not healthy enough to pass on traits.

• The tall trait is always stronger and eliminates the short trait completely.

• Self-pollination creates entirely new traits not seen in parent generations.

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Mendel's Breakthrough: Genes and Alleles

Dominant Alleles

• ​Genes come in different versions called alleles, and you inherit one from each parent for every trait.

• ​​A dominant allele is a version of a gene that masks the effect of another allele.

• ​For example, the allele for tallness in pea plants is dominant over the allele for shortness.

Recessive Alleles

• ​A recessive allele is a version of a gene that is hidden by a dominant allele.

• ​​This trait is only seen when an organism inherits two copies of the recessive allele.

• ​For instance, the allele for short plants is recessive and is only expressed with two copies.

Multiple Choice

What is the relationship between a gene and an allele?

• Alleles are different versions of the same gene.

• Alleles are cells inherited from one parent.

• Alleles are traits that are always visible.

• Alleles are the physical appearance of an organism.

Multiple Choice

How does a dominant allele affect a recessive allele when both are present for a single trait?

• The dominant allele's trait is expressed, and the recessive allele's trait is hidden.

• The recessive allele's trait is expressed, and the dominant allele's trait is hidden.

• Both the dominant and recessive traits are expressed together.

• Neither the dominant nor the recessive trait is expressed.

Multiple Choice

A pea plant shows the trait for shortness. What can be concluded about the alleles it has for the height gene?

• It inherited two recessive alleles for shortness.

• It inherited one dominant allele for tallness and one recessive allele for shortness.

• It inherited two dominant alleles for tallness.

• It inherited only one allele for shortness from one parent.

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How Adaptations Arise from Mutations

• Mutations, or errors in DNA, are a main source for new adaptations.

• These mutations can be passed on to an organism's offspring through reproduction.

• A beneficial mutation that helps an organism survive is called an adaptation.

• A macaw’s sharp beak and a penguin’s beak are examples of adaptations.

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Multiple Choice

What is a main source for new adaptations in a species?

• Errors in DNA called mutations.

• The environment where the organism lives.

• The food an organism eats during its lifetime.

• Learned behaviors passed from parent to child.

Multiple Choice

What makes a mutation an adaptation?

• It helps an organism survive in its environment.

• It occurs in the organism's DNA.

• It can be passed on to the organism's offspring.

• It changes the physical appearance of an organism.

Multiple Choice

A penguin is born with a mutation that results in a sharper beak, which helps it catch fish more easily. For this trait to become a common adaptation in the penguin population, what must also be true?

• The penguin must be able to pass the trait on to its offspring.

• The penguin must live longer than all other penguins.

• The mutation must also change the color of the penguin's feathers.

• The penguin must teach its offspring how to use the new beak.

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The Process of Natural Selection

• Organisms with beneficial traits are more likely to survive and reproduce.

• For selection to occur, traits must vary, be heritable, and affect reproduction.

• For example, antibiotic-resistant bacteria survive treatment and pass on the resistance trait.

• A changing environment is a major driving force for natural selection.

Multiple Choice

What is the primary role of natural selection?

• It helps adapted organisms survive and reproduce more successfully.

• It causes all organisms in a population to become identical.

• It prevents environments from changing over time.

• It creates new traits in an organism on purpose.

Multiple Choice

Why is the variation of traits a required condition for natural selection?

• Because there must be a variety of traits for selection to act upon.

• Because all organisms must reproduce at the same rate.

• Because the environment must always remain stable and unchanging.

• Because traits acquired during a lifetime must be passed on.

Multiple Choice

If a changing environment leads to the frequent use of a new antibiotic, what is the most likely long-term effect on a bacteria population with some resistant members?

• The population of resistant bacteria will likely increase over time.

• The antibiotic will become stronger to combat the bacteria.

• All the bacteria will be completely eliminated by the antibiotic.

• The bacteria will evolve to no longer need the resistance trait.

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Genetic Variation and Survival Probability

• Genetic variation means a population has many different inheritable traits.

• Some traits are advantageous, helping an organism survive and reproduce.

• For example, thicker fur helps an animal survive in a cold environment.

• Advantageous traits increase the probability of survival, but do not guarantee it.

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Multiple Choice

What is genetic variation?

• The variety of different inheritable traits within a population.

• A single trait that guarantees an organism will survive.

• A trait that an organism learns during its lifetime.

• The process of an organism reproducing in its environment.

Multiple Choice

What is the role of an advantageous trait?

• They guarantee that an organism will live a long life.

• They help an organism survive and reproduce in its environment.

• They prevent an organism from being able to reproduce.

• They are traits that are acquired and not inherited.

Multiple Choice

An animal in a cold environment is born with thicker fur, which is a variation in its population. Which statement best describes this situation?

• The thicker fur guarantees that the animal will survive the cold.

• The thicker fur is a disadvantage because it is different.

• The thicker fur increases its probability of surviving the cold.

• The animal will be unable to reproduce because of its fur.

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Natural Selection and Trait Proportions

Advantageous Traits

• ​These traits help individuals survive and reproduce, so they are more likely to be passed on.

• ​​Over many generations, the proportion of individuals with advantageous traits will increase in a population.

Disadvantageous Traits

• ​These traits make it difficult for individuals to survive, so they are less likely to be passed on.

• ​​Over many generations, the proportion of individuals with disadvantageous traits will decrease in a population.

Multiple Choice

What is the overall effect of natural selection on a population over many generations?

• The proportion of certain traits in a population changes over generations.

• All individuals in a population develop the same traits.

• Traits are passed on randomly without any pattern.

• Individual animals can choose to change their traits.

Multiple Choice

Why does a trait that helps an organism survive and reproduce become more common in a population over many generations?

• Because these traits make an individual stronger than all others.

• Because these traits are guaranteed to be passed on to all offspring.

• Because these traits improve an individual's ability to survive and reproduce.

• Because individuals with these traits actively help others survive.

Multiple Choice

Based on the principles of natural selection, what is the most likely outcome for a population that has both advantageous and disadvantageous traits?

• The proportion of individuals with the advantageous trait will increase, while the proportion with the disadvantageous trait will decrease.

• Both traits will become more common as the population grows.

• The disadvantageous trait will disappear in a single generation.

• Individuals with disadvantageous traits will learn to adapt and survive.

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Common Misconceptions

Misconception	Correction
Individuals can choose to adapt.	Adaptations are from random genetic mutations over generations.
Natural selection gives organisms what they 'need'.	Natural selection acts on existing, advantageous genetic variation.
A recessive allele is weaker or less common.	A recessive allele is just masked by a dominant one.
All mutations are harmful.	Mutations can be harmful, neutral, or beneficial.

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Summary

• Traits are determined by genes and alleles, which can be dominant or recessive.

• Genetic variation from random mutations is the origin of new traits.

• Adaptations are beneficial traits that improve an organism's survival and reproduction.

• Natural selection makes advantageous adaptations more common over many generations.

Poll

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

• 1 (Not confident)

• 2 (A little confident)

• 3 (Mostly confident)

• 4 (Very confident)