Biology Unit 4: Evolution
Evidence For Evolution Worksheet
Name _____________________________
Date __________________ Per ________
The following questions cover ideas and concepts that we have learned throughout our
study of evidence for evolution. Use your note sheet to answer each question thoughtfully.
1. Fruit fly embryos and frog embryos differ from each other more than frog embryos and
human embryos do. What does this tell us about how the three species are related?
Frogs are more closely related to humans than fruit flys are to frogs. Ambphians
and humans are animals, fruit flys are insects.
2. The mouthparts of an adult horsefly are modified for biting. The mouthparts of a
mosquito are modified for piercing skin and sucking blood. Are the mouthparts of the
two species homologous or analogous? Explain your answer.
The mouthparts are homologous…same structure, different function. Suggests
that they shared a common ancestor.
3. Changes have occurred through time that have in some cases reduced or removed
the function of some body structures or organs. These are called vestigial structures
and the penguin’s wings and leg bones or snakes are examples of this phenomenon.
Listed below are several human vestigial structures. Suggest a possible function for
each and explain why the structure may have become vestigial.
a. Ex: Appendix
i. Probable Function: Used to digest plant material
ii. Why Don’t We Use It Anymore: Omnivorous diet of humans make us rely
less heavily on plants for nutrition.
b. Wisdom Teeth
i. Function:
ii. Why Vestigial:
c. Coccyx (Tail Bone)
i. Function:
ii. Why Vestigial:
d. Muscles That Move Ears
i. Function:
ii. Why Vestigial:
Answers will vary…
4. What can you conclude if you find identical examples of a fossilized organism in two
adjacent geologic layers (layer A and B)?
The animal lived successfully through both time periods.
5. 60 grams of a sample is found. If the half-life of the sample is 2,000 years, how much of
would be left after 6, 000 years?
Three half-lives, so divide three times. 7.5 grams.
6. Phosphorus-32 has a half-life of 14 days. How many days will it take for a radioactive
sample to decay to one-eighth its original size?
1/8 = 3 half-lives (1 to ½, ½, to ¼, ¼ to 1/8 ) so 14 x 3 = 42 days old
7. The half-life of radium is 1,500 years. If 18 grams of radium are present in a sample, how
much will be present in 6,000 years?
1,500 goes into 6,000 4 times. So, four half-lives, or cut 18 g in half four times.
1.125
8. After the recent snow storm, a snowman was built outside of Arapahoe. Unfortunately,
the snowman was taken and brought inside the building and started to melt. The
teachers wanted to know what time the snowman was actually taken inside. They did
this by measuring the rate of melting water. At 8:00, there was already 5 ml of water
melted. 1 additional ml of water dripped every 5 minutes. After 60 minutes, the
snowman was completely melted. They used this data to create a line graph. By
extending the line backwards, you should be able to determine exactly what time the
snowman started to melt.
Melted Water (ml)
Rate of Melting In Snowman
20
18
16
14
12
10
8
6
4
2
0
Water…
Time Of Day
a. What time did the snow man start to melt? 7:35
b. If the time when the snowman started to melt represents the time when a living
organism died, explain how this activity would be an analogy about carbon
dating.
The start of melting represents the death of the organism. By measuring the rate
of decay, scientists can work backwards to determine when the organism
began to decay.