Bio H - Evolution
Diagramming Evolutionary Relationships
As we talked about in class, evolutionary history can be represented in a sort of “family tree” that shows which
organisms are most closely related to each other. There are two basic types of trees that can be created:
Phylogenetic trees and Cladograms. Both are similar in many respects but have some specific differences.
Let’s start with phylogenetic trees.
Phylogenetic trees
The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of
that ancestor. As you move from the root to the tips, you are moving forward in time.
When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation event
occurs, a single ancestral lineage gives rise to two or more daughter lineages.
Phylogenies trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is
unique to it alone and parts that are shared with other lineages.
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with other
lineages — common ancestors.
Bio H - Evolution
Cladograms:
Represent an ancestor and all its descendents. It is based on derived characteristics, or characteristics that are
shared by a group of descendents. For example, in the tree below, Fur and mammary glands are derived
characteristics of the mouse and chimp because it is believed that both received those traits from their common
ancestor.
The table below will be used to create a cladogram.
Step 1: Compare the amino acid sequence of each organism to the human. Count the number of different
amino acids and record these values in Data Table I.
Step 2: Compare each of the nine vertebrates to the others. Determine the number of different amino acids
in the sequence. Record these values in Data Table II.
Step 3: Create a cladogram for these nine vertebrates. Remember the greater the number of differences the
less related the organisms are.
Step 4: At each fork in the cladogram created, identify the trait or characteristic that is different. Add the
specific trait to the cladogram at the appropriate forks.
Bio H - Evolution
Organism
Zebra
Turkey
Catfish
Frog
Great White Shark
Loggerhead Sea Turtle
Rhesus Monkey
Rabbit
Data Table I: (Comparing to Human amylase)
# of Differences
Bio H - Evolution
Data Table 2. Compare the amino acid sequence of each organism to all the other organisms. Record the number of
differences in the chart below.
Zebra
Turkey
Catfish
Frog
Great
White
Shark
Loggerhead
Sea Turtle
Rhesus
Monkey
Rabbit
Human
Zebra
0
8
11
8
11
7
7
6
6
Turkey
8
0
7
3
12
4
13
6
7
Catfish
11
7
0
8
13
9
10
10
9
Frog
8
3
8
0
12
5
8
6
8
Great
White
Shark
Loggerhead
Turtle
Rhesus
Monkey
Rabbit
11
12
13
12
0
12
13
12
14
7
4
9
5
12
0
9
8
8
7
13
10
8
13
9
0
5
1
6
6
10
6
12
8
5
0
5
Human
6
7
9
8
14
8
1
5
0
Zebra
Turkey
Catfish
Frog
Great
White
Shark
Loggerhead
Sea Turtle
Rhesus
Monkey
Rabbit
Human
Zebra
0
8
11
8
11
7
Turkey
8
0
7
13
6
7
Catfish
11
7
0
8
13
10
10
9
Frog
8
8
0
12
8
6
8
Great
White
Shark
Loggerhead
Turtle
Rhesus
Monkey
Rabbit
11
13
12
0
12
13
12
14
12
0
9
8
8
0
Human
12
7
12
9
9
13
10
8
13
9
6
10
6
12
8
7
9
8
14
8
Use the data chart above to draw your cladogram below.
0
0
Bio H - Evolution
Part II Your Mission: You must analyze several species and fossils that you find and propose an evolutionary
history for life on this fictitious planet. We will be using types of candy as our species. Yes, this is pretend,
candy does not evolve, but you are too young to have dead imaginations. And if I give you real species you’ll
just google it and copy it onto your paper….
Directions:
1. Begin by establishing which species was the common ancestor of all candy. Think about what
characteristics it should have. What the origin of all life simple or complex? Have species gained or
lost characteristics over time? Do species today maintain most of the characteristics of the original
organisms?
2. Then begin making your tree. I strongly suggest using a pencil. Changes WILL need to be made!
Requirements for your tree are as follows:
a. Your tree must consist of a minimum of 15 species total
b. Transitions should be plausible. In other words, the common ancestor of us and chimps was a
human/chimp like organism, not a pterodactyl.
c. Your species may become extinct (not every organism that once lived is still alive today)
3. You may work in partners on the TREE ONLY. Each person must create their explanations of the 5
phenomena.
4. Now using your tree find examples that represent each of the following phenomena. Keep in mind that
much of it will depend on the “story” you use to explain why one species changed into another.
i. Convergent evolution – including descriptions of the specific analogous structure and a
Rational explanation of why this structure evolved in two separate species (what was the
selecting force the two species shared?)
Ex: body shape shared by penguins and dolphins because both were advantageous to
swimming in water.
ii. Divergent evolution - including descriptions of the specific homologous structure
Ex: ancestor of bat and dolphin had a body part with a certain structure, but because
flying was selected for in one group and swimming in the other, the body part
changed into a wing and a flipper.
iii. Endosymbiosis – including the advantage to each species that the endosymbiosis provides
Ex: Mitochondria were once free living prokaryotes. They were engulfed by a large
cell and each species (the large cell and the mitochondria) benefitted from each other.
Mitochondria got protection, Large cell got more efficient energy production.
iv.
v.
Adaptive Radiation: including a description of how different environmental characteristics
caused the same species to diverge in several directions.
Ex: On the Galapagos, one parent species of finches existed. As smaller groups
migrated to neighboring islands, each island created its own natural pressures or
challenges. There for different variations succeeded under each set of conditions and
the groups of birds each evolved into different species.
Vestigial Organs: including an explanation of what the organ was once used for, what changed
such that the organism no longer needs that organ
Ex: Once upon a time the diet of humans was such that an appendix was considered
necessary. As the diet and lifestyle of the human changed, eventually there was no
need for an appendix. Once the need was gone, mutations that popped up making the
appendix dysfunctional were no longer a disadvantage and therefore “stuck.”