Worksheet #1
1. A paleontological research group is studying fossil deposit from an ancient inland sea. The diagram
below represents the location of various fossil specimens of two extinct species: a fish and a turtle.
Use your understanding of stratigraphy
and relative dating to answer the
following questions.
a. Why were no fossils discovered in rock
layer D?
There is no fossils discovered in rock layer D
because it a magmatic intrusion.
b. Which of the sedimentary rock layers is
the most ancient and how do you know?
The most ancient sedimentary rock layer
is sedimentary layer C because its at the
very bottom.
c. A brand new trainee is unsure which
rock layer was the most important to date
so he ships a sample of each of the four
layers (A, B, C, and D) for direct
radioactive dating with results as
follows: A: 500 million years ago (mya),
B: 200 mya, C: 50 mya, D: 10 mya
Are these radioactive dating results reliable? Explain your answer
The only results that are reliable are the igneous layer D.
Given the reliability of the dates above, when did the fish species go extinct?
The fish species went extinct in less than 200mya
Given the reliability of the dates above, when did the turtle species go extinct?
The turtle species went extinct in less than 500mya
d. A member of the research group finds a non-fossilized organic sample in the soil above the rock
layers, what would be the best approach to get an accurate date for this material and what are the
limitations of this approach?
The best approach to get accurate data for this material trying to determine what is the age of the
organic material that is in the non-fossilized sample. The limitation of this approach is that the carbon
time results is that it will only provide a frame of time which will make the results inaccurate.
2. What is the ultimate source of all the energy that powers your cells (and > 99.9% of all life on earth)?
a. When did this process evolve and how do we know?
The process evolves around 3.4 billion years ago. We know this because that’s when the first
photosynthesis started.
b. When did appreciable levels of oxygen (O2) begin to build up in the atmosphere?
The appreciable levels of oxygen begin to build up in the atmosphere around 2.3 billion years ago.
We know that because the first oxygen traces were found in the atmosphere.
c. Why was there such a long delay between the dates in part 2a and 2b above?
Looking at the dates from parts a and b, we can conclude that there was about 1.1 billion years
delay.
3. Using what you know about the organisms below (and/or the trusty internet) create a matrix of six binary
characters that could be helpful in understanding the phylogenetic relationships of these organism. Code
the character states in the matrix below.
Character 1: hair
Character 2: feathers
Character 3: laying eggs
Character 4: beaks
Character 5: marsupial bags
Character 6: breastfeeding bag
Ch 1:
Chicken
Platypus
Kangaroo
Cat
Sea Lion
No
Yes
Yes
Yes
Yes
Ch 2:
Yes
No
Yes
No
No
Ch 3:
Yes
Yes
No
No
No
Ch 4:
Yes
Yes
No
No
No
Ch 5:
No
No
Yes
No
No
Ch 6:
No
Yes
Yes
Yes
Yes
4. Map your characters onto the two phylogenies below. Using a parsimony criterion which phylogeny is
the best hypothesis about the relationships among these organisms? Why?
-
vi.
•
5. List a physical feature that is a synapomorphy for the group Mammalia.
- Able to produce milk
6. List a physical feature that is a symplesiomorphy for the group Mammalia.
- Complex teeth or losing hair
7. a. Define Homoplasy.
-
Shared character between two or more animals that did not arise from a common ancestor
b. What are the two things that can generate homoplasy?
- similar selection pressures acting on adapting species and the effect of genetic drifts/