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Grades 6–8. In Unit 8.6 Natural Selection and Common Ancestry, Carolina Certified Version*, students work to answer the Unit Driving Question: "How could things living today be connected to the things that lived long ago?"

In this unit, students investigate the connections between ancient and modern organisms. In the four lesson sets, students develop a model for natural selection and use it to account for patterns between the body structures and behaviors of ancient fossil organisms and similar organisms living today.

The unit begins with students hearing about the surprising fossil of an ancient penguin (nicknamed "Pedro") in a podcast from the researchers who found and identified the fossil. Students also read a photo journal from their research. Students question how penguins living today could be connected to this fossil of a much larger penguin from long ago and record what they notice and wonder about. Students then explore the different species of penguins alive today through a series of videos and data cards. Students develop initial explanations for how today's penguins could be connected to Pedro or other penguins from long ago. Their models need to explain (a) where did all the ancient penguins go? and (b) where did all the different species of modern penguins come from? They expand the range of phenomena by considering other types of organisms that lived long ago and look different from similar types of organisms alive today. Students then develop a Driving Question Board (DQB) to guide future investigations.

In the first lesson set (Lessons 1–6), students investigate the connections between organisms living today and those that lived long ago. Students explore heritable traits in modern penguins (Lesson 2) and examine similar data for ancient penguins (Lesson 3). Students then revise their initial models of how modern penguins could be connected to ancient penguins to account for the time-related and trait-related patterns they have uncovered (Lesson 4). In Lesson 5, students analyze data from ancient and modern species of horses, whales, and horseshoe crabs to see whether these organisms have similar patterns. In Lesson 6, students put together what they have figured out to explain the patterns they uncovered in how organisms change. Their Penguin Timeline model includes the ideas that (a) traits in some modern populations have changed over millions of years from the ancient organisms they are descended from and (b) these changes may be related to changes in the environment from long ago to the present.

In the second lesson set (Lessons 7–11), students work on explaining these patterns to develop and use a model of adaptation by natural selection. In Lesson 7, students begin to investigate five cases in which a trait changed in a population over a few generations. In Lesson 8, they identify common mechanisms that underlie the causes for each of the changes in the populations and develop a model for natural selection that explains all five cases. In Lessons 9 and 10, students use computer simulations to test this model in different environmental conditions and over different lengths of time. An assessment in Lesson 11 then requires students to use their natural selection model to explain how some of the trait differences in a population of lizards could be the result of natural selection.

In the third and fourth lesson sets (Lessons 12–13 and 14–15, respectively), students extend their model of the cause of trait changes in populations over time to include the mechanisms of mutation and sexual reproduction they developed in the earlier material. In Lesson 13, they use their natural selection model to explain how some body structure variations in different species of modern penguins could result from natural selection and how these penguins could descend from a common ancient ancestor penguin population. In Lesson 14, students analyze embryological data from different stages of development for different species to add to their argument about how different types of living things (species) may be connected. Finally, in Lesson 15, students take stock of all the questions they answered in this unit and consider questions they look forward to figuring out in high school.

Through these investigations, students will:

Analyze and interpret data to reveal patterns of connection among modern organisms and between modern and fossil organisms based on anatomical similarities and differences.
Analyze and interpret data regarding the changes that have occurred in different types of organisms and in the environment throughout the history of life on Earth.
Ask questions about the mechanisms that cause changes in the heritable traits in a population of organisms over time.
Obtain, evaluate, and communicate information about structures and how their functions support survival and successful reproduction in new environments.
Develop and use a model of cause-and-effect mechanisms (natural selection) that lead to the predominance of certain trait variations in a population and to the suppression or elimination of others.
Use arguments based on empirical evidence and scientific reasoning to support an explanation for how characteristic behaviors and specialized structures affect the probability of successful reproduction of different species of penguins in different environments.
Construct an explanation for lines of evolutionary descent using evidence for what traits remain relatively stable and which are changing and explain how natural selection could cause these changes.
Argue using data from the physical structures apparent in different types of animals (species) at different stages of embryological development that emphasize new ideas about how different types of living things (species) may be connected.

This 5-Class Unit Kit includes basic teacher access to instructional materials on CarolinaScienceOnline.com, plus the materials needed to teach 5 classes of 32 students per day (160 students).

Building Toward NGSS Performance Expectations

MS-LS1-4: Use argument based on empirical evidence and scientific reasoning to support an explanation for how characteristic animal behaviors and specialized plant structures affect the probability of successful reproduction of animals and plants, respectively.
MS-LS4-1: Analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that natural laws operate today as in the past.
MS-LS4-2: Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.
MS-LS4-3: Analyze displays of pictorial data to compare patterns of similarities in the embryological development across multiple species to identify relationships not evident in the fully formed anatomy.
MS-LS4-4: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals' probability of surviving and reproducing in a specific environment.
MS-LS4-6: Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time.

Science and Engineering Practices

Analyzing and Interpreting Data
Constructing Explanations and Designing Solutions
Engaging in Argument from Evidence

The following practices are also key to the sensemaking in the unit:

Asking Questions and Defining Problems
Developing and Using Models
Planning and Carrying Out Investigations
Obtaining, Evaluating, and Communicating Information

Focal Disciplinary Core Ideas

LS1.B
LS4.A
LS4.B
LS4.C

Focal Crosscutting Concepts

Patterns
Cause and Effect
Stability and Change

*All enhancements to materials and instruction for this Carolina Certified Version of the unit are approved by OpenSciEd to preserve the integrity of the storyline and the instructional model.