Lab #2 - Scientific Method, Convergent Evolution, and the Tasmanian Wolf story

What’s wrong with this image?

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.

Convergent Evolution

Hawkmoths

Sunbirds

Hummingbirds

Evolution via natural selection

What would happen if all of the trees and dinosaurs were the same size?

Individual variation is necessary for natural selection to occur.

What would happen if all the dinosaurs produced just one offspring?

Differential fitness is necessary for natural selection to occur.

What would happen if offspring never resembled their parents?

Parents:

Offspring:

✖

Traits must be heritable for natural selection to occur

✖Parents:

Offspring:

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.

Convergence on this suite of termite-eating skills has occurred many times around the world!

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!