1. Learning Intention: 8.LS4.3
Science
8th Grade
Standard 11
Learning Intention: 8.LS4.3
Analyze evidence from geology, paleontology, and comparative anatomy to support that specific phenotypes within a population can increase the probability of survival of that species...
Terms/Phases to Investigate
Geological, paleontological, anatomical, phenotypes
Crosscutting Concepts (CCCs)
Cause and Effect, Structure and Function, Stability and Change
Science and Engineering Practices (SEPs)
Analyze evidence, Construct Explanations, Argue from evidence
Success Criteria/I Can Statement
By the end of this unit I will be able to say...
...I can explain how phenotype variations results in species survival.

2. Phenotype Variation in Populations
Variation refers to a variety or diversity of traits
(different kinds) within any given population.
Two causes of phenotype variation
1) Diversity of genetic traits from sexual reproduction.
2) Diversity of genetic traits that result from mutations.
Adapt or Die
Environments always change, sooner or later.
Organisms must adapt to these changes or die.
If too many individuals die, then the species goes extinct.
Those that survive pass on their DNA to their offspring.
When an environmental change occurs, a variety of traits within a population provides the species a chance that at least some individuals will survive the changed conditions.

3. Evidence from Comparative Anatomy Voyage of the HMS Beagle
Scientific expedition from 1831 to 1836
that sailed around the planet.
One expedition member, Charles Darwin,
studied flora (plants) and fauna (animals).
In 1835 Darwin examined life on the
Galapagos Islands. He wrote about his findings
in a famous book titled On the Origin of Species.
Formed by undersea volcanos, all life on the
Galapagos came from elsewhere.

4. Evidence from Comparative Anatomy Life was carried here by
The Galapagos Islands are located in the Pacific Ocean about 600 miles west of Ecuador (see picture below).
Galapagos Islands
18 larger islands
and 3 smaller islands.
Life was carried here by
the wind or the waves

5. Evidence from Comparative Anatomy
At some point in the past, a small population of Finches (birds) were blown from South American to these islands.
South American Finch

6. Evidence from Comparative Anatomy
Each island has a slightly different ecosystem with different food sources. The finches adapted accordingly.
This lead to variation in the shapes and sizes of their beaks.

7. narrow-pointed beak for insects Very wide beak for only eating seeds
The finches developed specialized beak shapes and sizes (phenotypes).
Food Source
Only Bugs
Food Source
Seeds & Bugs
Food Source
Only Seeds
narrow-pointed beak for insects
Moderately wide beak for cracking seeds and sharp point for insects
Very wide beak for only eating seeds
Natural Selection:
On each island, finches with the most effective beaks survived
and reproduced while those with less effective beaks died out.

8. Evidence from Geology and Paleontology
Fossils of extinct organisms such as dinosaurs are found in
rock strata (layers of sedimentary rock).
Iridium, which mainly is found in asteroids, was discovered in the layer of sedimentary rock that is the boundary between the time of the dinosaurs and the time of mammals.
(evidence of extinction caused by a massive asteroid impact).

9. Evidence from Geology and Paleontology
The fossil record shows that non-avian (non-bird) dinosaurs went extinct at the end of the cretaceous period about 65 million years ago
Why did the birds survive?
It may have been their feathers that saved them (their phenotype).
Feathers may have kept them warm in cold conditions after the asteroid strike.
Feathers may have enabled some of the surviving avian dinosaurs to fly to locate limited food sources.