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.