1. Heredity and Adaptation Teaching Slides, 2.1 Part 3
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2. Science Log Q3 Week 9: Wednesday 3/8:
What is the function of the digestive system of animals such as Pacific treefrogs?
Heredity and Adaptation Course, 2.1: Lines of Descent

3. Reading
Read “Tree Thinking” in FOSS Science Resources on page As you encounter new information, example, or diagrams about these and other concepts discussed in the article, put on page 71.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 15

4. Discuss time How is time represented on the cladogram?
There is an arrow labeled time on the left side of the cladogram. Older things on the bottom and newer on the top, as shown by the arrow on the left.
Can you tell how much time has passed?
No, only relative time. That is a limitation of this model.
Follow the questions and discussion in steps in the FOSS Investigations Guide.
Heredity and Adaptation Course, 2.1: Lines of Descent
Steps 16-18

5. 17. Find the common ancestor
Determine how common ancestors are represented on your cladogram.
Where do mammals branch off from the other organisms?
This point represents an ancestor of mammals.
That means that from this common ancestor, mammals branched off.
Every intersection on the cladogram represents a common ancestor of some sort.
Circle the intersection on your cladogram where mammals branch off from the other animals. This point is a common ancestor of all mammals
Heredity and Adaptation Course, 2.1: Lines of Descent

6. 17. Common ancestors Return to your model analysis chart.
Add arrows and intersections to the left column, then work in your group to fill in what those parts represent.
Add limitations of time that you just discussed.
Heredity and Adaptation Course, 2.1: Lines of Descent

7. 17 common ancestor
What other animals on the cladogram have this same ancestor?
The bird and the alligator.
What point represents the most recent common ancestor of birds and alligators?
The point where birds and alligators branch off.
How do you know?
There is no other branching between them.
Is the frog an ancestor of humans? Explain.
No, but frog and humans share a common ancestor.
Where would you place a circle to represent an ancestor to all the following animals: frog, human, rabbit, bird, alligator?
Where the frog branches.
There is no direct ancestor/descendant relationship between frogs and humans.
Heredity and Adaptation Course, 2.1: Lines of Descent

8. 18. Discuss Fossils
How might we know what the common ancestor of frogs and humans may have been? Where could we look for information?
The fossil record
What characteristics would the common ancestor of frogs and humans exhibit?
Four limbs, bony skeleton, vertebrae.
Heredity and Adaptation Course, 2.1: Lines of Descent

9. 18. Discuss Fossils
Sometimes there are no fossils that demonstrate the relationship between ancient and current organisms.
Cladograms are considered to be hypotheses based on shared characteristics of current organisms and known extinct organisms.
Each group of cladogram shares specific common characteristics, and each group contains descendants of a common ancestor.
As more information is discovered, it sometimes turns out that organisms are not as closely related as was thought.
Heredity and Adaptation Course, 2.1: Lines of Descent

10. 18. Discuss Fossils
The organisms that share a more recent common ancestor are more closely related, just as a child is more closely related to its parents than it is to its great-grandparents.
Heredity and Adaptation Course, 2.1: Lines of Descent

11. Focus on time Refer to the time arrow
Can you tell how much time may have passed between each bar and tip?
No. The lines show only the sequence of changes. For instance, the shark branched off before the tuna.
Does the cladogram give us information about how much time has passed from the first bar to the present?
No,
Depending upon the cladogram, thousands or millions of years may be represented.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 11

12. Add information to the picture
How do ancestors, including parents, pass on their characteristics to their offspring?
Genetic material, DNA, genes
Heredity and Adaptation Course, 2.1: Lines of Descent
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13. Add information to the picture
Until the 1950’s, scientists were not able to use genetic information to determine relationships.
In the 1950’s, the structure of DNA was pieced together by James Watson (1928-), Francis H. Crick ( ), and Maurice Wilkins ( ).
Now, relationships between groups of living organisms can be determined by how similar their DNA is.
DNA similarities van be used as a vertebrae, amniotic eggs, and hair are used.
Technology????
Heredity and Adaptation Course, 2.1: Lines of Descent

14. 21. Examine
One aspect of a well-developed model is that it helps you incorporate new data and make predictions about new situations.
Sometimes scientists need to revise their model when they get more data.
In this case, we will consider a different species, the dolphin.
Heredity and Adaptation Course, 2.1: Lines of Descent

15. Examine the dolphin
Place the dolphin on the cladogram where you think it belongs. Support your decision with evidence and reasoning.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 21

16. Review embryo development
Where should we place the dolphin on the cladogram?
Dolphins have amniotic egg and hair.
Is it a tetrapod?
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 22

17. Review embryo development
Teacher master T, Dolphin Embryo Development It van be helpful to look at an organism in various life stages, not just when it is an adult. The photographs represent the development of a dolphin embryo before it is born. What do you observe and what inferences can you make? Explain how this image provides evidence that a dolphin is a tetrapod. Where should we place the dolphin on the cladogram? With the mammals.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 22

18. Discuss the reading
Open your notes on “Tree Thinking.” In your group, share one thing you learned from the article.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 23

19. Review vocabulary
Spend a few minutes reviewing the vocabulary for this part. Update the vocabulary index and table of contents in your notebook.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 24

20. Review vocabulary
characteristic a trait that helps identify an organism
cladogram an evolutionary tree diagram based on shared characteristics
common ancestor an organism from the past that is related to all the organisms in the group
descendant an organism related to an organism that lived earlier
limitation the quality of being restricted, such as what information is being shown in a model
most recent common ancestor the first organism from the past that is related to all the organisms in the group
related belonging to the same group or family; connected by common ancestry
species a group of organisms that can interbreed or pass on its genes to following generations
Heredity and Adaptation Course, 2.1: Lines of Descent

21. 25. Summarize
All life is related. We can use diagrams called cladograms to map which characteristics organisms share and determine which species share common ancestors.
Now there are sophisticated tools we can use to examine genetic material (DNA) to collect data and develop cladograms to model how closely organisms are related.
Heredity and Adaptation Course, 2.1: Lines of Descent

22. Answer the focus question page 68
How can a model help us understand the relationships among organisms?
At first I thought ____. Now I think ____ because ____ .
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 26

23. Homework
Teacher master U, Green-Plant Cladogram Notebook sheet 7, Green-Plant Cladogram Questions Answer the questions on the notebook sheet.
Heredity and Adaptation Course, 2.1: Lines of Descent
Step 27

24. Wrap-Up/Warm-Up
“Noticing patterns is often a first step to organizing and asking scientific questions about why and how the pattern occurs.” Brainstorm other examples of patterns in nature. How do those patterns help you better understand and appreciate the world around you?
Quote is from A Framework for K-12 Science Education.
Heredity and Adaptation Course, 2.1: Lines of Descent
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Heredity and Adaptation Course, 2.1: Lines of Descent