Download Evidence of Common Ancestry KEY

Biology
HS/Science
Unit: 09 Lesson: 02
Evidence of Common Ancestry KEY
A Web Exploration Activity
Use the resources provided by your teacher to complete the graphic organizer and to answer the following
questions.
©2012, TESCCC
05/24/13
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Biology
HS/Science
Unit: 09 Lesson: 02
Questions KEY:
Fossils
1. What are the two methods scientists use to date fossils and to determine the age of the earth?
1) Relative dating
2) Numerical dating
2. How are fossils dated using each method?
1) Relative dating: sequence by noting their positions in layers of rocks
2) Numerical dating: using radioactive dating
3. Does the fossil record paint a complete picture of evolutionary history?
No, there are bits missing and things that are still unclear, but it does clearly show that life is old
and has changed over time.
4. Are new fossils still being discovered? If so, give an example.
Yes: ammonite fossils and the duckbill dinosaur Maiasaura
5. What is a transitional form?
A transitional form is a fossil or organism that shows a link between its descendant line and its
ancestral form.
6. What is the significance of transitional forms, and what evidence/information do they provide us about
evolution?
Darwin and other scientists said evolution happens through a process of nature selecting
beneficial traits and pressuring populations of organisms to adapt and slowly change over time
(many, many generations). Transitional forms provide us with information about how this slow
steady change and evolution of new organisms has happened and is happening.
7. Does the fossil record show evolution as a slow, gradual process or as punctuated happening in quick
burst?
There are examples of both types of evolution happening in the fossil record.
8. What term do we use to describe evolution as a slow and steady process?
Gradualism
9. What should we observe in the fossil record if evolution is slow and steady? Draw an illustration.
10. What term do we use to describe evolution happening in “quick burst”?
Punctuated
11. What would we observe in the fossil record if evolution happens in “quick” jumps? Draw an illustration.
12. Does a jump in the fossil record necessarily mean that evolution has happened in a “quick” jump?
No
13. What are four scientific explanations for stasis and the sudden appearance or “burst” of organisms in the fossil
record?
1) There are missing fossils or layers due to erosion or other natural causes.
2) This is an illusion of geology. It appears to be a burst because many years, perhaps 5 million,
have passed between the time when two layers of rock were deposited.
3) “Punctuated Equilibrium”— The sudden appearance of change in the organisms happened
within a short time period. There were transitional forms between ancestor 1 and species 3;
©2012, TESCCC
05/24/13
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Biology
HS/Science
Unit: 09 Lesson: 02
however, they existed for such a short time period that they were not able to be preserved
within the fossil record.
4) “Macromutation”— This type of mutation skips transitional forms because it is such a large
mutation and produces very sudden evolutionary change. This type is actually a “burst”
because there was a large amount of evolutionary change is a very short time period.
Homologies
1. What are homologies, and what do they tell scientists?
Similar characteristics due to relatedness are known as homologies. Homologous structures
derived from a common ancestral form.
2. What are five types of homologies that provide evidence of common ancestry?
Anatomical, developmental (embryological), molecular (genetic), cellular, vestigial structures
3. What do we know about organisms that share many anatomical similarities?
Organisms that share many anatomical similarities are very closely related to each other.
4. What are three to four methods scientist use to study homologies and/or similarities in genetics?
1) Compare protein similarities
2) DNA hybridization
3) Sequencing DNA
4) Comparing epigenetics of species: looking at which genes are turned on and off in organisms.
5. What did testing similarities in antibody proteins among various organisms reveal?
It revealed remarkable similarity between the proteins of humans and those of other great apes.
6. What can DNA hybridization measure?
It measures similarity in the DNA of different species.
7. How does DNA sequencing provide evidence of evolutionary relationships?
Scientists compare DNA sequences of different species to determine similarities and difference in
their genomes. Similarities indicate common ancestry.
8. What are some homologies at the cellular level?
All cells have genetic material, lipids, carbohydrates, salts, proteins, and other substances. All
living things are made of these cells.
9. What does endosymbiosis tell us about the evolutionary history of the eukaryotic cell?
The eukaryotic cell possibly evolved from prokaryotic organisms engulfing (through endocytosis)
other prokaryotes that had specialized functions such as converting solar energy to sugar and
converting sugars to forms of energy that could be used by the cell.
10. What are two examples of organisms that have developmental homologies that suggest common
ancestry between groups of organisms that don’t necessarily seem logical?
Snakes and Baleen whales
11. What did Darwin say about a species embryo developmental program?
It is likely that two closely related species will have similar embryos because the developmental
program is passed down from its ancestors.
12. What is a vestigial organ?
A structure that had a function in the ancestor, but now that function is completely (or mostly
completely) lost within a given species.
13. Why do vestigial organs form?
©2012, TESCCC
05/24/13
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Biology
HS/Science
Unit: 09 Lesson: 02
Future generations are less likely to inherit the “normal” form because the trait’s function is no
longer needed for survival. Sometimes this structure becomes a detriment to the organism.
Biogeography
1. What is biogeography?
The study of species distribution across Earth and the method of distribution
2. What made Wagner think that the continents were connected at one time?
He thought this because identical fossils of animals and plants were found at opposite ends of the
Atlantic.
3. What happens to species when continents separate? Collide?
When continents collide, the species upon those continents will intermingle and potentially create
new species. These new species will go with their respective continents when they separate.
4. What are some examples of organisms that provide evidence that at one point in Earth’s history there was
one large continent?
Land reptiles (Cynognathus and Lystosaurus), ferns (Glossopteris), and freshwater reptiles
(Mesosaurus)
Informational resources used for this answer key:
Unknown. (2010, November 3). Understanding evolution for teachers. Retrieved from
http://evolution.berkeley.edu/evosite/evohome.html
Bar-Yam, S. (2011). Gradualism and punctuated equilibrium. Retrieved from
http://necsi.edu/projects/evolution/evolution/grad punct/evolution_grad punct.html
Fitch, D. (1998, September 8). Evidence for evolution--rudimentary organs. Retrieved from
http://www.nyu.edu/projects/fitch/courses/evolution/html/rudimentary_organs.html
©2012, TESCCC
05/24/13
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