Lab #2 - Scientific Method, Convergent Evolution, and the Tasmanian Wolf story
Dec 17, 2015
Step 1 is not “observe” …it’s to become an expert, so you can observe critically.
It takes a lot of practice to observe and think of original ideas. Most scientists aren’t even good at it.
“Slow down, look carefully, and things make more sense.” – me.
Conditions required for natural selection to occur:
Individual variation: members of a species differ in their characteristics
Mode of inheritance: parents pass on some of their traits to their offspring
Differential fitness: some individuals leave more offspring than others due to their special inherited traits
Change in population occurs because of differences in reproductive success. Organisms do not evolve because they want or need to change.
How do organisms converge on certain traits?
Change in population occurs because of differences in reproductive success.
Total offspring + future generations = “fitness”
Organisms do not evolve because they want or need to change.
Case study: Thylacines and placental wolves
This is a canid phylogeny.
Notice, there are no Thylacines.
Today you’ll be making predictions based on two hypotheses:1. Both animals were created
similarly
2. The animals underwent convergent evolution and evolved similar traits.
Example:– Cursorial herbivores
pronghorn, capybara, elk, kangaroos, deerIn what ways? …digestive tract, dentition, elongated limbs,
behavior, perception- What other traits have independently evolved?
- Think about the importance of plate tectonics….
CONVERGENT EVOLUTION
Convergent Evolution• Batesian Mimcry– Benign species
resembles a noxious or dangerous species
These bright colorsare signals, or“aposematic traits”
Question: How could aposematism evolve?
Convergent Evolution
• Mullerian Mimicry– Noxious species
resemble each other– Pitohui birds in New
Guinea
Viceroy and Monarch butterfliesboth taste nasty.
Convergent Evolution• Aggressive Mimicry– Noxious or dangerous
species resembles a benign one.
– ex. hawks, vultures, kites
Thylacines and placental wolves
Focus on the following today:
1. The differences between carnivore and herbivore teeth and skull morphologies
2. How do you interpret these differences? Give me focused, specific answers.
e.g. “Based on many skull characteristics, blah blah…”How does ecology affect the organism’s phenotype?What makes the species different ecologically and morphometrically?
3. While you are encouraged to have opinions, try to remain objective and scientific
And don’t forget about your QHPM.
Have fun!