Candy Phylogeny Lab

Materials

· Candy Bars (2 each)

· Baby Ruth

· Reeses Pieces

· Hershey’s Cookies and Cream

· Snickers Cruncher

· Snickers

· M&Ms Peanut

· M&Ms Plain

· Hershey’s

· Hershey’s Almond

· Skittles

· Pictures of Candy Bars (Multiple Copies; 2 sets per group – smaller sizes for Venn Diagram, larger sizes for tree)

· Pens

· Card stock

· Giant Sticky Notes

· Plates

· Data table

· Tape

· Markers

· Scissors

Set Up:

· Print copies of the candy bar pictures and data table

· Cut out the candy bar pictures

· Cut the card stock into nested sizes; should have one set per group

· Example (each box represents a separate sheet of paper):

·

· Open 1 set of the candy bars (except for skittles) and cut each into halves to view the internal features

· Place the cut pieces on plates, label and set at the front of the room (can cover with additional plates so students can’t see the candy, until you are ready)

· Place sheets of the blank Giant Sticky notes around the room, spaced out enough so each group will have space to work.

Procedure:

1. Introduce group to phylogenetics and phylogenetic relationships.

a. Phylogenetics allow for the reconstruction of evolutionary history by depicting possible historical relationships between species.

b. The major goals of constructing phylogenetic relationships are to:

i. Clarify evolution of a group

ii. Aid in the classification of the group

2. Discuss the methods utilized for constructing phylogenies

a. Phenetics

i. an attempt to classify organisms based on overall similarity, usually in morphology or other observable traits, regardless of their evolutionary relation.

ii. the study of relationships among a group of organisms on the basis of the degree of similarity between them, be that similarity molecular, phenotypic, or anatomical. The aim is consider as many characteristics as possible to classify orgs to produce a variety of named groups

iii. Produces A tree-like network expressing phenetic relationship, a phenogram. It links organisms by estimates of overall similarity as evidenced by an analysis of characters

b. Evolutionary Taxonomy

i. Traditional taxonomy

ii. Classifies orgs using a combo of phylogenetic relationships, recency of common descent, and degree of evolutionary change

iii. Considers the whole taxa as opposed to single species in such a way that groups of species can be inferred as giving rise to new groups.

c. Cladistics

i. The study of the pathways of evolution, particularly the recency of common descent

ii. Interested particularly in the branching – how many branches among groups of orgs, which branches connect to which other branches; what is the branching sequence

iii. Unlike phenetics, which considers all characteristics, it only considers a restricted set of characteristics. Orgs are assigned to a group because they share unique derived characteristics not found in other organisms

iv. Seeks to determine the order in which the evolutionary lines diverged or branched

v. Creates a ladder-like network that expresses ancestor-descendant relationships – a cladogram

3. Explain the following :

a. phylogenetic trees serve as a visual representation of the possible historical relationships between species

b. This is the “phylogeny”

c. These trees are constructed using a cladogram

4. Show an example of a phylogenetic tree

a. How to read:

i. Species at the tips or end represent species, genera, or taxa living today (extant species) or are extinct

ii. Branches of trees represent ancestral populations of species through time

iii. Nodes designate points where one species splits into 2 or more descendant populations

iv. Shared derived characteristics are shown along the branches

b. The tree helps to show that the more derived characteristics 2 organisms share, the closer their evolutionary relationship is

i. Close relationships shown by a recent fork from the supporting branch

ii. The closer the fork in the branch between 2 organisms, the closer their relationship

5. Walk the group through the steps in creating a phylogenetic tree

a. Choose taxa

b. Determine the characteristics/character states for each organism

c. As you observe the different characteristics, fill out a data table to indicate the character stated for each

i.

d. Use the data table to sort your organisms into bins based on the characters used to compare them. Venn diagrams are helpful for this

i. Start with the characteristics that all the organisms share (Vertebrae)

ii. Select the next common characteristic (2 pairs of limbs) and create they next venn diagram.

iii. Move all the organisms with this character into this bubble. This should leave sharks in the first, larger bubble and everything else in the smaller bubble.

iv. We can read this as “sharks have vertebrae; Bullfrogs, kangaroos, and humans have vertebrae and 2 pairs of limbs.”

v.

vi. Continue until you have placed all the organisms in appropriate bins.

e. Now use the Venn Diagram to draw a cladogram. (see example below)

i.

6. Inform the group they will now determine the phylogeny of common chocolate candy.

a. Show students the 9 wrapped chocolate candies.

b. Ask them to consider how the candies are similar or different and choose a couple students to answer.

i. For students in lower grades: hand out the copies of the data sheet with characteristics you want them to focus on already listed.

ii. For students in higher grades (or for those students needing a challenge): hand out blank copies of the data sheet – they will determine what characteristics to look at in their groups.

c. Explain that they will now get the chance to see if they can categorize the chocolates and create a cladogram like we did together in the example.

7. Place the students into small groups (2-5 students per groups)

8. Give each group a set of the small candy bar pictures.

a. Instruct the groups to complete the data sheets based on the characteristics of each candy, by placing “x”’s or check marks in the corresponding boxes.

b. Let the students know that if they can’t remember what is inside the candy, they can send a representative to the front of the room to view the internal features of the candy (this can also be likened to doing “genetic analysis”)

9. As groups complete the data table, give them a set of nested card stock sheets.

a. They can use these sheets and the candy bar pictures to create their Venn diagrams.

10. Instruct students that once their Venn diagrams are completed, they can turn over their data sheets and make a sketch or draft of their cladogram/phylogenic tree.

a. Once the group is sure of the structure of their tree, let them go to their giant sticky sheet and give them a set of the larger candy bar pictures and tape.

b. Have them construct their final phylogenetic tree on the wall sticky.

11. Once all the groups have finished, allow the groups to present their trees and to explain their groupings to the class.

12. After all groups have presented, ask the following discussion questions:

a. Were the trees all the same? Why or why not?

b. What things were the same? What things were different?

c. What do you think looking inside of the candies represents?

d. Show the group the bag of Skittles.

i. How would this fit into your trees?

ii. What would need to be changed and/or added?

13. For an additional challenge, display the following data sheet and ask students if they think they can repeat this process with actual organisms and their characteristics like biologists do.

a.

b. Have students construct a new Venn diagram and tree.

c. This can also be done as a race, with the fastest team receiving first choice of the candy to share amongst their group.

d. If time is limited, this can be assigned as a homework practice.

Data Sheet:

Characters

Hershey’s

Hersey’s w/Almond

Hershey’s C&C

Baby Ruth

Snickers

Snickers Cruncher

Reeces Pieces

M&M’s Plain

M&M’s Peanut

Totals

Chocolate

Bar Shape

Nuts

Caramel

Rice Crispies

Blank Data Sheet:

Characters

Hershey’s

Hersey’s w/Almond

Hershey’s C&C

Baby Ruth

Snickers

Snickers Cruncher

Reeces Pieces

M&M’s Plain

M&M’s Peanut

Totals