Download Evidence for Evolution

Evidence for
Evolution
Archaeopteryx
Main lines of evidence for evolution come from:
1. Fossils
2. Embryology
3. Geographic Distribution of
4. Artificial Selection
5. Homologous Structures
6. Vestigial Structures
7. Comparative Analysis of DNA
1
Fossils:
Fossils are _________________________________________________________.
Scientists determine the age of fossils by :
1. Examining the ___________ above and below the fossil’s ______________.
2. Radiometric Dating is….
3. Earth is ________________________ years old.
Transitional Fossils
are important because:
Whale evolution example:
Below are just a few of the transitional fossils between modern whales and their terrestrial
(land-dwelling) ancestors.
Modern Whale - ___________________________
 Tail evolved into flipper
 Ears modified to hear underwater

Basilosaurus -______________________________
 Sturdy Flippers
 Still has small weak hind legs

Ambulocetus - _________________________________
 Forelimbs with fingers/small hooves
 Hind feet and tail adapted for swimming

Mesocynids - _________________________________
 Limbs adapted to moving on land
 Ears adapted to hearing in air

Scientists combine evidence from fossil record with other lines of evidence to provide the most
complete understanding of the change in organisms over time as possible. As more evidence
is accumulated, this understanding is continuously modified. Sometimes this involves heated
debates!
2
Embryology Activity:
Organize the cards on the chart:
Q 1: How did you decide which card went in which area of the chart?
Q 2: Where did you struggle deciding the correct place for embryos? Why?
AFTER THE TEACHER SHARES THE ANSWERS
Q 3: Which organisms do you think are more related? Why?
Embryology: Study of early ___________ developmental stages of organisms
 Early developmental stages of related animals are ____________________.
 More ____________ = more ____________________________________.
Example:
Analyzing Geographic Distribution of Organisms around the world
Similar environments around the world contain organisms that are DIFFERENT species but
have similar anatomies and/or behaviors because:
______________________________________________________________________________
Example:
Artificial Selection: When ________________________ with a desired _____________
repeatedly until the trait becomes _____________ in the population
Examples:
Homologous Structures: A shared _____________________ that provides evidence
that the organisms had a ______________________ with that trait.
Example:
3
Vestigial Structures: A trait that was useful to an ______________ and has been
________________, but is not useful to the current __________________
Examples:
Comparative Analysis of DNA: If all _______ evolved from the same ______________
(3.5 bya), then all should share some common ______________.
The greater the __________________between 2 species = more recent they have a _________
Analysis Questions:
Use your notes and the book (esp. pages 382-385) to answer the following questions.
1. Fill in the description of the whale trait we find in each of the transition fossils:
Mesochynids
Ambulocetus
Basilosaurus
Modern cetaceans
Location of nostrils
Why are transition fossils important in understanding evolution?
2. Compare and contrast artificial selection with natural selection.
3. How do homologous structures provide evidence for evolution?
4. What is a vestigial structure? Give an example of a vestigial structure and its former
function in the ancestral organism.
5. Why do the early stage embryos of vertebrates look strikingly similar?
6. Would you expect the DNA of 2 species that share an ancestor 1 million years ago to be
more or less similar than 2 species that share an ancestor 100 million years ago? WHY?
4