Station #1 – Similarities in Early Development
Scientists also make inferences about evolutionary
relationships by comparing the early development of different
organisms. Look at the development of a fish, human, pig,
chicken, and turtle pictured to the right. At the adult stage,
each animal looks quite different. However, during early
development, these five organisms all have a tail and a row of
tiny slits along their throats (gill pouches). Both of these
similarities are indicated by the red arrows. These similarities
suggest that these backboned animals ALL share a common
ancestor.
1. What are two similarities shared by the animals during early
development. HINT: Look back in the text to find the answer.
2. What are at two differences you observe in early
development? HINT: Analyze the picture to come up with an
answer.
3. Which two animals do you think are most closely related based
on the images of their development?
Station #2 – Similarities in Body Structure
Look closely at the structure of the bones in the whale flipper, bat wing, cat leg, and human arm. Notice that the
bones in the forelimbs of these animals are arranged in a similar way. These similarities provide evidence that
these three organisms ALL evolved from a common ancestor. Similar structures that related species have
inherited from a common ancestor are known as homologous structures.
1. Write the definition for the term “homologous structures” on your answer sheet.
2. Color the homologous bones of the human, cat, whale, and bat on your answer sheet the same color appearing in the
picture above. Use your colored pencils.
3. What other animals do you think would have forelimbs similar in structure to those above? List at least two other
animals.
Station #3 – Similarities in DNA
Recall that genes are made of DNA. By comparing the sequence of nitrogen bases in the DNA of different species,
scientists can infer how closely related the species are. The more similar the DNA sequences, the more closely
related the species are. Analyze the sequences of the human, chimpanzee, and gorilla to see which species are
most closely related.
DNA Sequences
Chimpanzee
A
A
T G
T C
C
C
A
T A G G C C A T
Human
A
A
T G
T G
C
C
A
A A G G G C A C
Gorilla
A
A
T G
T A
A
A
G C
A C C C C
A T
1. Compare the DNA sequences of the following animals and write down how many bases are in common between the two.
a. chimpanzee and the human.
b. human and the gorilla
c. chimpanzee and the gorilla
2. Which two animals are most closely related? In other words, which two animals have the MOST bases in common?
3. Which two animals are least closely related? In other words, which two animals have the LEAST number of bases in
common?
Station #4 – Fossils
Remains of organisms that lived in the past are called fossils. Most fossils are found in rocks and can help link the
past to the present. Fossil evidence supports the hypothesis that whales evolved from land dwelling ancestors who
had 4 limbs (legs). Baliosaurus is one of these early whales with hind limb bones.
1. Watch the clip on whale evolution from the following website and answer the questions below. Don’t worry if you can’t
watch the entire clip in one station. There are two stations dedicated to this topic.
http://www.pbs.org/wgbh/evolution/l ibrary/03/4/l_034_05.html
a) Is a whale a mammal: yes or no?
b) Basilosaurus is an early ancestor of the
modern whale. This whale had certain
bones that provided evidence that it
evolved from a land dwelling creature.
What types of bones were found?
c) How did whales evolve to breathing in the
water? Remember that they are NOT
fish so they do not have gills.
d) How does whale movement (swimming)
reveal that it evolved from land mammal?
Station #5 – Fossils
Remains of organisms that lived in the past are called fossils. Most fossils are found in rocks and can help link the
past to the present. Fossil evidence supports the hypothesis that whales evolved from land dwelling mammals that
had 4 limbs (legs). Baliosaurus is one of these early whales with hip bones.
1. Watch the clip on whale evolution from the following website and answer the questions below. Don’t worry if you can’t
watch the entire clip in one station. There are two stations dedicated to this topic.
http://www.pbs.org/wgbh/evolution/l ibrary/03/4/l_034_05.html
a) Is a whale a mammal: yes or no?
b) Basilosaurus is an early ancestor of the
modern whale. This whale had certain
bones that provided evidence that it
evolved from a land dwelling creature.
What types of bones were found?
c) How did whales evolve to breathing in the
water? Remember that they are NOT
fish so they do not have gills.
d) How does whale movement (swimming)
reveal that it evolved from land mammal?