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NATURAL SELECTION Students use beads to mimic  natural selection in a population

LIZARD ACTIVITY  Students use actual data to try and determine ancestral connections between lizard populations

NATURAL SELECTION LAB

THINGS YOU WILL NEED:
Copy paper box lids- 2 per group of 3-4 students
2 COLORS of pony beads (enough for each group to have 75 of each color)
Colored fabric that each of the two bead colors will blend in with
    (You will need enough to cover a box lid X number of groups)
Plastic cups (1 per group)
Spray adhesive

AHEAD OF TIME:
Cut fabric to fit box lids.
Use spray adhesive to attach fabric to inside of box lids.

           
Images by Riedell

Count out 75 beads of each color and place in cup
Copy off Natural selection data sheet (1 for each student)
Copy off Natural selection lab ?'s

class data table

ACTIVITY:
Students count out beads and put 50 of each color on the fabric in the box lid and fill in “At start” column on tally sheet. One student acts as the box shaker and “swirls” the box being careful to keep beads in box!  Others in group are “predators looking for food”. When the box stops, predators quickly look in box and grab first bead they see.

SLIDE SHOW DIRECTIONS

RULES:
You must take first bead you see.
No picking your favorite colors.
Don’t look around in box for “a good one”

Box shaker mixes beads again and predators quickly pick one bead each again. Continue swirling and feeding until predators have picked 20 beads from box. Count up beads and enter numbers in “After first feeding” column on tally sheet.

REPRODUCTION:
For every two beads in box add another of that color.
Ex: if there are 42 black beads and 38 pink beads in the box after feeding, you will add 21 more black beads and 19 pink beads to the box.

FEED & REPRODUCE AGAIN:
Repeat feeding and reproduction procedures described above and remove 20 more beads and add offspring beads, filling in the appropriate columns on their tally sheet.

Have groups put their data on board or projector and fill in class data sheet with data from other groups and answer questions.

LIZARD EVOLUTION ACTIVITY This activity was modified from http://www.ucmp.berkeley.edu/fosrec/Filson.html Lizards Activity  Lizard lab      Lizard cladogram Lizard map blank Lizard map with DNA data DNA sequences Phylogeny solutions

LIZARD LAB
Use the Lizards Activity  slideshow as you walk through the activity. 
Read/discuss general info in Lizard lab about how islands are colonized.

Have students measure distances from each island to African mainland. Fill in the map in the Lizard lab showing the path you think the lizards moved as they colonized the islands.
Give students a copy of the cladogram handout and have students fill in the first cladogram showing their idea about how the islands were colonized and how the lizards are related.
EX: If you think the lizards on Gran Canaria migrated from Lanzarote then Atlantica lizards are the ancestors of the Stehlini lizards and Stehlini should appear as a branch off the Atlantic line on your cladogram.

PART II: Follow sequence in Lizard lab packet. Look at geologic data. 
"Does your story and cladogram relationships fit with the geologic date about when the islands appeared. If not, you must change your cladogram.
EX: If you said the lizards on Palma migrated from Hierro, that probably didn't happen since Palma is older than Hierro. If you need to, make a new cladogram that is supported by the evidence.

PART III.
Look at the morphology of the lizards. Does this evidence support your relationship story and your cladogram. EX: As lizards evolved, you would probably see a gradual progression; not, increasing then decreasing then increasing again in size.
Do you want to change your relationship story/cladogram?

PART IV.
Compare DNA sequences. 
HINT: It is easier to count differences if you cut apart the sequences, attach them in order, and laminate the strips so students don't have to jump from page to page.
Divide up the comparisons so each student only has to compare DNA between several lizards. Post answers for students to write down all the data
Hand out Lizard map and have students draw lines between islands to show differences between lizard DNA (See Lizard map with DNA data)

Is your story/cladogram supported by the DNA evidence?
Most students will probably have said Stehlini lizards on Grand Cananary island descended from Atlantica lizards that migrated from Lanzarote. DNA evidence does NOT support this theory. Stehlini DNA is DIFFERENT from all the other lizards. If students said they thought lizards split and moved from to Palma and Hierro from Gomera, this is NOT supported by DNA evidence either. Palma lizard DNA is most like Tennerife lizards.
The split probably happened at Tennerife. See possible Phylogeny solutions

Scientists think the Stehlini lizards came from another migration possibly carried down on a current from the north

Bioteacher help         Biology other units          APBIOteacher help      Riedell Science Home       APBIO other units        Zoology other units       

sphynx moth: http://www.exploringnature.org/wordpress/?p=21

Lizards: http://www.ucmp.berkeley.edu/fosrec/Filson.html

Cartoon from: http://www.cartoonstock.com/newscartoons/cartoonists/rbr/lowres/rbrn15l.jpg

Finch image: http://focus.hms.harvard.edu/2006/090106/images/Nature_finches.jpg