How many years separation does each layer in this fossilized stickleback lab represent

Mak Monaco

Laboratory 3 Write-Up: Introduction to Evolution II

Due to the length of this lab, there are no post lab questions. Each question is worth 0.5

points.

II. Stickleback Evolution Virtual Lab

1. Define “model organism.”

A “model organism” is a non-human species that is studied extensively to understand biological

phenomena.

2. Why is the threespine stickleback a model organism for studies in evolution? (List at least two

reasons.)

The three-spine stickleback fish are small and have shorter generations. This makes them easier to

keep in a lab and makes them useful for genetic studies.

3. How do spines protect ocean stickleback fish?

The spines protect stickleback fish by simultaneously flaring out from the pelvic ad dorsal spines.

This makes it a lot harder for predators to swallow them.

4. Describe where its spines are located.

The stickleback fish has three spines on its dorsal side and two spines projecting from the pelvis

on the ventral(front) side.

5. The loss of stickleback pelvic spines is similar to the loss of which body parts in some other four-

legged vertebrates?

It is similar to the loss of hind limbs.

6. Name two other vertebrate animals whose evolutionary histories included the loss of hind limbs.

Snakes and whales evolutionary histories included the loss of hind limbs.

7. In addition to the spines, what is another component of the “armor” of a stickleback fish?

Another component of armor for the stickleback fish are the row of plates on each side of the

body.

8. Explain how the stickleback armor protects the fish from some predators.

The back spines and pelvic spines stick out making it har for predators to swallow. The plates also

make the stickleback fish hard to eat.

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SKILLS TUTORIAL 1

Complete Part 2 of the lab in the window on the left.

1.Looking at the pelvic score data, does the pelvic phenotype differ between Bear Paw Lake

Frog Lake fish? Explain. !

2.After complete the graphing exercise, verify your data. How do your data compare to

those obtained by Dr. Bell and colleagues?!

EXPERIMENT 2

Complete Experiment 1 Quiz. Read the explanation for each correct choice provided.

3.Explain why the stickleback fish in Frog Lake more similar to ocean and sea-run

stickleback than they are to the stickleback fish in Bear Paw Lake.!

4.In addition to predators, what other environmental factors might be responsible for the

differences between Bear Paw Lake and Frog Lake stickleback populations? How would

you test your prediction? !

After completing the quiz, click on Experiment 1 Analysis.

5.For this analysis, what is your null hypothesis? !

SKILLS TUTORIAL 2

1.What score would you assign to a fossil specimen that has only one pelvic spine visible? !

2.A stickleback fossil may show no signs of pelvic structures. What are possible sources of

error associated with scoring the pelvis of such a fossil as “absent”? !

Start Tutorial 2. Continue scoring the fossil specimens until you are confident in your scoring

abilities; then proceed to Experiment 2. (You may have to practice on 20 specimens or more

before you feel you have mastered the technique.)

Stickleback Lab: Evolving Switches, Evolving Bodies

Yes, According to the graph, all fish in Bear Paw Lake have absent or reduced pelvic phenotypes, which means they have

no pelvic spines. All fish in Frog Lake have complete scores, which means they possess pelvic spines.

My data reflected those obtained by Dr Bell and colleagues

The reduced pelvic phenotypes have never been observed in marine and sea-run populations; the pelvic spines protect marine and

sea-run sticklebacks from larger fish that prey on them in the ocean. Most stickleback in Bear Paw Lake have either a reduced or

absent pelvis, while those in Frog Lake have a complete pelvis. There is little variation within each population, and the stickleback in

Frog Lake are more similar to marine and sea-run stickleback.

Fresh water is not rich in calcium and other minerals needed to form pelvic spines. we could test this by

measuring the mineral content of fresh water to ocean water

My hypothesis is that a random sample of stickleback from a population will contain roughly the

same number of individuals with and without pelvic spines

Animals that are preserved as fossils may have been damaged by decay, as a result certain body

structures may not be visible in the fossil

Which layer is older 2 or 5 explain your answer?

What conclusion can you draw from the graph in Experiment 1 stickleback?

What can we infer from the stickleback fossil record about evolutionary processes occurring today?

Why is the three spine stickleback a model organism for studies in evolution list at least two reasons?