Heredity and Adaptation

Heredity and Adaptation

Middle School

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Learning Objectives

• Describe how the fossil record documents changes in life on Earth over time.

• Model how gene mutations can result in beneficial, harmful, or neutral traits.

• Explain how genetic variation and natural selection can change a population over time.

• Describe how humans use technologies to influence the inheritance of traits.

Key Vocabulary

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Fossil

Fossils are the preserved remains or traces of ancient organisms, providing evidence of past life on Earth.

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Heredity

Heredity is the process by which genetic traits are passed down from parents to their biological offspring.

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Gene

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

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Mutation

A mutation is a permanent alteration in the DNA sequence that makes up a particular gene.

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Protein

Proteins are complex molecules, built based on gene instructions, that determine an organism's specific traits.

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Allele

An allele is a specific version or variation of a gene, found at a particular chromosome location.

Key Vocabulary

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Genetic Variation

This term describes the variety of different genes that can be found within a population.

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Adaptation

An adaptation is a special trait or characteristic that helps an organism survive in its environment.

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Natural Selection

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

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Artificial Selection

Artificial selection is when humans intentionally breed plants or animals for specific, desirable traits.

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Evolution

Evolution is the process of how species gradually change and develop over very long periods of time.

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Cladogram

A cladogram is a diagram that scientists use to show the evolutionary relationships between different species.

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Fossil Dating and Geologic Time

Relative Dating

• Compares the age of fossils based on their position in the layers of sedimentary rock.

• The principle of superposition states that older fossils are found in lower, deeper rock layers.

• This method determines if one fossil is older or younger than another, but not its exact age.

Absolute Dating

• Provides a more specific, numerical age for a fossil or the rock it is found in.

• This method measures the decay of radioactive isotopes, which act like a natural, steady clock.

• A half-life is the set time it takes for half of a radioactive isotope to decay.

Multiple Choice

What is the main principle of relative dating?

• To determine the age of fossils by comparing their positions in rock layers.

• To find the exact, numerical age of a fossil using radioactive decay.

• To understand how long it takes for half of a radioactive isotope to decay.

• To prove that fossils found closer to the surface are always older.

Multiple Choice

What is the key difference between the results from relative and absolute dating?

• Relative dating uses radioactive isotopes, while absolute dating uses rock layers.

• Relative dating is for young fossils, while absolute dating is for old fossils.

• Relative dating compares fossil ages, while absolute dating provides a numerical age.

• Relative dating is more precise than absolute dating.

Multiple Choice

A scientist needs to determine the most precise, numerical age possible for a fossil. Which method should be used and why?

• Relative dating, because it can determine if the fossil is older than the rock around it.

• Absolute dating, because it can provide a specific age by measuring isotope decay.

• The principle of superposition, because it can show the fossil is in the top layer of rock.

• Relative dating, because it is the only method that works on fossils found in rock.

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Anatomical Similarities and Evolutionary Evidence

• Similar body parts, like forelimb bones, suggest species share a common ancestor.

• Homologous structures are inherited from a common ancestor despite different functions.

• Scientists compare living and fossil anatomies to build evolutionary family trees.

• More anatomical similarities mean two species diverged from their ancestor more recently.

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Multiple Choice

What do significant anatomical similarities, like the bone structure in the forelimbs of different species, suggest to scientists?

• The species live in the same environment.

• The species share a common ancestor.

• The species evolved at the same time.

• The species eat the exact same food.

Multiple Choice

Which statement best describes homologous structures?

• They are structures that have the same function but evolved independently.

• They are structures inherited from a common ancestor that may have different functions.

• They are structures that only appear in the fossil record, not in living animals.

• They are structures that are identical in both shape and function in all species.

Multiple Choice

If scientists determine that Species X and Species Y have far more anatomical similarities than Species X and Species Z, what is the most logical conclusion they can draw?

• Species X and Y are less related than Species X and Z.

• Species X and Y share a more recent common ancestor than Species X and Z.

• Species Z must have evolved from Species Y.

• Species X, Y, and Z are not related to each other at all.

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Evidence for Evolution: Fossils and Cladograms

Transitional Fossils

• Fossils like Acanthostega show features of both ancestral and descendant groups, providing evidence for evolution.

• Acanthostega had fish-like traits but also had limbs with fingers and toes, called digits.

• This fossil illustrates the transition of four-limbed animals from living in water to living on land.

Reading a Cladogram

• A cladogram is a diagram that models relationships between species based on shared inherited traits.

• A branch point represents the most recent common ancestor shared by the connected organisms.

• Cladograms show the order in which new traits appeared, not that one living species is an ancestor of another.

Multiple Choice

What is the main purpose of a cladogram?

• To show that one living species is the ancestor of another.

• To model relationships between species based on shared traits.

• To prove that all animals once lived in the water.

• To list every trait an individual animal possesses.

Multiple Choice

What makes the Acanthostega fossil key evidence for an evolutionary transition?

• It is the oldest fossil ever discovered.

• It has features of both fish and land-dwelling animals.

• It shows that animals with limbs could only live on land.

• It is a complete skeleton with no missing parts.

Multiple Choice

On a cladogram showing the evolution of four-limbed animals from fish, where would a transitional fossil like Acanthostega most likely be placed?

• At the very beginning, before the common ancestor of fish.

• On the branch leading only to modern fish.

• Near the branch point where land animals split from fish.

• On a separate branch that is not connected to fish or land animals.

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The Basics of Heredity

• Heredity is the passing of traits from parents to their offspring through genes.

• Chromosomes are coiled DNA structures that transfer hereditary information to the next generation.

• DNA holds the genetic information for an organism in a double helix structure.

• Genes are sections of DNA that control protein production to determine traits.

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Multiple Choice

What is heredity?

• The passing of traits from parents to their offspring through genes.

• The process by which an organism grows and develops over time.

• The way an organism gets energy by breaking down food molecules.

• The coiled structures that hold hereditary information for the next generation.

Multiple Choice

What is the relationship between genes and traits?

• Genes are sections of DNA that control the production of proteins to determine traits.

• Traits are sections of DNA that control the production of proteins to determine genes.

• Genes and traits are separate parts of a chromosome that do not interact.

• Traits are passed from offspring to their parents through their genes.

Multiple Choice

Which statement best describes the structural organization of genetic material?

• Chromosomes are made of coiled DNA, and genes are specific sections of that DNA.

• DNA is made of coiled chromosomes, and genes are specific sections of those chromosomes.

• Genes are made of coiled DNA, and chromosomes are specific sections of that DNA.

• Chromosomes, DNA, and genes are all separate structures within a cell.

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How Gene Mutations Affect Proteins

• A gene mutation is a random change in the structure of a gene.

• Genes provide instructions for making proteins, so a mutation can change a protein.

• A protein’s function is determined by its shape, which a mutation can alter.

• These changes to proteins can result in harmful, beneficial, or neutral traits.

Multiple Choice

What is a gene mutation?

• A random structural change to a gene.

• The process of a cell creating a new protein.

• A predictable change in a protein's shape.

• A temporary change to a chromosome's function.

Multiple Choice

How can a change in a gene affect the protein it creates?

• It can alter the protein's shape, which changes its function.

• It always destroys the protein immediately.

• It makes the protein larger and stronger.

• It has no effect on the protein's structure or function.

Multiple Choice

If a gene mutation results in a protein with a new shape and function, what is a possible outcome?

• The new function might be beneficial, harmful, or have no noticeable effect.

• The change in function will definitely be harmful to the organism.

• The protein will no longer have any function at all.

• The gene will quickly change back to its original structure.

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Mendelian Genetics and Punnett Squares

• Gregor Mendel experimented with pea plants to understand the principles of heredity.

• Genes have different forms called alleles, which can be dominant or recessive.

• A dominant allele (T) is expressed over a recessive allele (t).

• Punnett squares predict the potential genotypes and phenotypes of offspring.

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Multiple Choice

What is the relationship between a dominant allele and a recessive allele when both are present for a single trait?

• The dominant allele is expressed.

• The recessive allele is expressed.

• Both alleles are expressed equally.

• A new, blended trait is created.

Multiple Choice

What is the main function of a Punnett square in genetics?

• To count the total number of genes an organism has.

• To describe Gregor Mendel's experiments with pea plants.

• To predict the potential genotypes and phenotypes of offspring.

• To determine if an allele is dominant or recessive.

Multiple Choice

If a pea plant has one dominant allele for tallness (T) and one recessive allele for shortness (t), what conclusion can be drawn about its appearance?

• The plant will be tall because the dominant allele is expressed.

• The plant will be short because the recessive allele is stronger.

• The plant will be a medium height between tall and short.

• The plant's height cannot be predicted with this information.

Human Influence on Inheritance

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Artificial Selection

• Humans choose organisms with desired traits to be parents for the next generation.

• This process has been used by us for many centuries.

• It created different breeds of dogs, cattle, and various crops.

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Genetic Engineering

• This modern technology directly modifies an organism's genes to change its characteristics.

• Soybean genes can be modified to make them resistant to weed-killers.

• This modification helps protect the plants and can increase crop yields.

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Gene Therapy

• This is an experimental technique to treat or prevent genetic diseases.

• It works by inserting a healthy copy of a gene into cells.

• The goal is to correct problems caused by faulty or missing genes.

Multiple Choice

What is the main goal that connects artificial selection, genetic engineering, and gene therapy?

• To intentionally change the traits of organisms for a specific purpose.

• To study how organisms behave in their natural environments.

• To create entirely new species that have never existed before.

• To help wild animals adapt to changes in the climate.

Multiple Choice

What is the key difference in the process between artificial selection and genetic engineering?

• Genetic engineering directly alters genes, while artificial selection uses breeding to pass on traits.

• Artificial selection is used on plants, while genetic engineering is only used on animals.

• Genetic engineering is an ancient practice, while artificial selection is a modern technology.

• Artificial selection changes an organism's traits, while genetic engineering does not.

Multiple Choice

A scientist wants to cure a genetic disease in a dog by replacing a single faulty gene with a healthy one. Which approach is the most specifically designed for this task?

• Gene therapy, because it aims to correct health problems by inserting a healthy gene.

• Artificial selection, because it is the fastest way to create new breeds.

• Genetic engineering, because it is mainly used to help plants resist weed-killers.

• A combination of all three methods would be required to be successful.

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Adaptation: Traits for Survival

Adélie Penguin

• They have a compact body shape to reduce heat loss in the extreme cold of Antarctica.

• Dense feathers and a thick layer of body fat provide excellent insulation against freezing temperatures.

• Their wings have evolved into flippers, perfect for swimming and hunting for food underwater.

Wandering Albatross

• Its enormous wingspan allows it to soar on wind currents for long distances with minimal effort.

• It possesses a strong sense of smell to locate prey across the vast and open ocean.

• Special glands in its head allow this bird to drink salt water by filtering out excess salt.

Multiple Choice

What is the primary purpose of an adaptation?

• A trait that helps an organism survive in its environment

• A feature that makes an organism appear more colorful

• A behavior that helps an organism change its environment

• A part of an organism that has no specific function

Multiple Choice

Which statement correctly compares an adaptation of the Adélie penguin to an adaptation of the Wandering albatross?

• The penguin's dense feathers provide insulation, while the albatross's large wingspan allows it to soar.

• The penguin's flippers are for flying, while the albatross's wings are for staying warm.

• The penguin's strong sense of smell helps it stay warm, while the albatross's compact body helps it fly.

• The penguin's salt glands help it swim, while the albatross's dense feathers help it find food.

Multiple Choice

Consider a new environment that is extremely cold, has only salt water, and where prey can only be located by smell over vast distances. Which bird is fully adapted to survive here?

• Neither bird, because each one lacks critical adaptations needed for this specific environment.

• The Adélie penguin, because it is adapted for the cold temperatures.

• The Wandering albatross, because it can find prey by smell and drink salt water.

• Both birds would be able to survive, as they are both seabirds.

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Genetic Variation and Natural Selection

Low Survival Fitness

• A white mouse is easily seen by predators on a rocky, brown background.

• This coloration leads to a lower chance of surviving and having offspring.

• Inherited traits that are not suited to the environment decrease an individual's survival.

High Survival Fitness

• A brown mouse is well-camouflaged from predators on the same rocky, brown background.

• This camouflage gives it a higher chance of surviving to reproduce and pass on its genes.

• The environment selects for advantageous traits that increase the probability of survival and reproduction.

Multiple Choice

What is the most likely consequence for an individual whose inherited traits are not well-suited to its environment?

• Its chances of surviving and having offspring decrease.

• It will quickly learn to find a new, safer environment.

• Its inherited traits will immediately change to match the environment.

• It will have more offspring than better-suited individuals.

Multiple Choice

What is the relationship between a mouse's coloration and its environment?

• The brown mouse is better camouflaged from predators in that environment.

• The brown mouse can run faster than the white mouse to escape danger.

• The rocky environment causes the mice to change their color to brown.

• Predators in the area prefer not to eat brown-colored mice.

Multiple Choice

Based on the principles of natural selection, what is the most likely long-term outcome for the mouse population in the rocky, brown environment?

• The population of brown mice would likely increase over time.

• The population of white mice would likely increase over time.

• The white mice would learn to hide from predators more effectively.

• Both mouse populations would decrease at the same rate.

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What is Natural Selection?

• Natural selection is how organisms with beneficial traits are more likely to survive and reproduce.

• For it to occur, traits in a population must vary and be heritable.

• These traits must affect an organism's chances of surviving and having offspring.

• For example, some bacteria have mutations that help them survive antibiotics and reproduce.

Multiple Choice

Which statement best describes the process of natural selection?

• Organisms with traits best suited to their environment are more likely to survive and reproduce.

• Organisms can choose to develop new traits during their lifetime to help them survive.

• All organisms in a population survive and reproduce at the same rate.

• The environment changes to better suit the organisms living in it.

Multiple Choice

For natural selection to cause a change in a population over time, what must be true about the traits in that population?

• The environment must remain perfectly stable and unchanging.

• All individuals in the population must be genetically identical.

• There must be inherited variation in traits among individuals.

• Organisms must learn new behaviors from their parents.

Multiple Choice

A certain type of bacteria is often killed by an antibiotic. However, due to a random genetic trait, a few bacteria are resistant to the antibiotic and survive. What is the most likely outcome for this bacterial population over many generations?

• The entire population of bacteria will be killed by the antibiotic.

• The bacteria will learn how to fight off the antibiotic.

• The resistant bacteria will reproduce, and the trait for resistance will become more common.

• The antibiotic will become weaker over time.

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Population Changes Over Time

• Natural selection changes the distribution of traits in a population over generations.

• Traits supporting survival and reproduction become more common, while others become less common.

• Scientists track these changes with mathematical models, such as graphs and charts.

• Environmental changes drive trait adaptation, but rapid shifts can lead to extinction.

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Multiple Choice

What does natural selection change in a population over many generations?

• The number of new species

• The distribution of traits

• The speed of environmental changes

• The types of mathematical models

Multiple Choice

What is the main reason that traits supporting survival and reproduction become more common in a population?

• These traits are the only ones that can be tracked with graphs.

• These traits are caused by sudden environmental changes.

• These traits are passed on to the next generation more frequently.

• These traits make extinction impossible for a population.

Multiple Choice

If a scientist's model shows that a population's traits are not helping it survive after a rapid environmental change, what is the most likely conclusion?

• The population will quickly adapt to the new environment.

• The scientist needs to use a different type of chart.

• The population is at a high risk of extinction.

• The environment will soon return to its previous state.

What Makes a Scientific Theory?

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What is a Theory?

• ​A scientific theory is not just a simple guess or a hunch.

• ​​It is a broad explanation for a range of natural observations.

• ​It is supported by many lines of evidence and makes accurate predictions.

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Darwin's Observations

• ​He observed that different but similar species exist in similar global habitats.

• ​​He also noticed different, yet related, species living in the same area.

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

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Theory of Evolution

• ​Species are descended from common ancestors and have changed over vast time.

• ​​He identified natural selection as the main mechanism for this evolutionary change.

• ​The theory of evolution is the unifying principle of all biology.

Multiple Choice

What is a scientific theory?

• A broad explanation for a range of natural observations that is supported by evidence.

• A simple guess or a hunch that has not yet been tested.

• An observation of a single event in nature.

• The main mechanism for evolutionary change.

Multiple Choice

How did Darwin's observations of fossils provide evidence for the theory of evolution?

• They showed that extinct animals resembled modern species, suggesting a common ancestor.

• They proved that natural selection is the only mechanism for change.

• They revealed that different, yet related, species could not live in the same area.

• They showed that species never change over vast periods of time.

Multiple Choice

Which statement best explains why the theory of evolution is considered a strong scientific theory?

• It is a broad explanation for the diversity of life that is supported by multiple lines of evidence.

• It is based only on the observation that similar species exist in similar habitats.

• It is considered a unifying principle because it was Darwin's main idea.

• It identifies natural selection as a possible guess for how change happens.

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Common Misconceptions

Misconception	Correction
A scientific theory is only a guess.	A theory is tested, evidence-supported explanation.
Evolution is a straight ladder with humans on top.	Evolution forms branching tree; no species is universally highest.
Individual organisms adapt their bodies when needed.	Adaptation occurs in populations across generations, not within one individual.
All mutations are harmful mistakes.	Mutations may be harmful, neutral, or beneficial for adaptation.

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Summary

• Fossils and anatomy show life changes and shares common ancestors.

• Genes on chromosomes code for proteins that determine traits.

• Mutations change genes, which can be helpful, harmful, or neutral.

• Natural selection favors adaptations, changing populations over time.

Poll

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

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