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 nonhuman species that is vigorously studied to further an understanding of
a biological phenomena.
2. Why is the threespine stickleback a model organism for studies in evolution? (List at least two
reasons.)
It is a model organism for studies in evolution because they are easy to study due to their short
generation time and their small demeanor.
3. How do spines protect ocean stickleback fish?
Spines protect ocean Stickleback fish sticking out its pelvic spines and dorsal spines so predators
have a hard time swallowing it.
4. Describe where its spines are located.
Three spines are on its dorsal side, and two spines are on its ventral side. The spines on its ventral
also help protect it from its pelvis.
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.
Two other vertebrate animals are manatees, snakes, and whales.
7. In addition to the spines, what is another component of the “armor” of a stickleback fish?
Another component of the armor is the row of plates on both sides of its body.
8. Explain how the stickleback armor protects the fish from some predators.
The spines stick out in almost a 90-degree angle making it really hard for predators to swallow
them. The plates stick out a little too and makes it extra hard for the predators to swallow it.
9. How did ancestral populations of ocean-dwelling fish come to live in freshwater lakes?