Why the stickleback fish in Bear Paw lake are now so different from the ocean and sea

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?

If a lake is cut from the ocean and has no large fish as predators (only dragonflies), then the sticklebacks will have a better chance at surviving and reproducing because the sticklebacks will be better adapted to the environment (presence/absence of a pelvic bone) and have little to no predators. The hypothesis was supported.
Before the experiment started, background knowledge was collected to better the knowledge of the lakes. Bear Paw Lake is an enclosed lake, meaning no predators could get into the lake. However, Frog Lake is connected to a water system by a small stream, thus allowing predators such as salmon to enter the lake. Twenty fish were collected from each lake and then put into a solution that stains the fish's bones. This makes…show more content…
Natural selection is the process by which evolution occurs where organisms that are better suited to the environment (‘fittest’) survive and pass on favorable traits to the offspring. Organisms must adapt to the environment in order to survive. The stickleback fish adapted to the environment by keeping/removing the pelvic structures. For example, in Frog Lake, the all of the sticklebacks had complete pelvic structures because the lake was connected to a system of streams that allowed predators into the lake. The sticklebacks in Bear Paw Lake had reduced or absent pelvic structures because little/no predators are present in the lake. The pelvic structures on the fish are similar to the legs of four-legged vertebrates. With this said, the pelvic structures are a very important to the survival/defense of a stickleback. The stickleback fish experiment was well designed for many reasons. First, the experiment contained all the variables of a well-designed experiment. The independent variable is the water source (lake) and the dependent variable being the amount of complete, reduced, or absent pelvic structures found in the fish. Also, the experiment contained a constant: the number of fish collected per lake (20). Secondly, the experiment contained lots of data and is

Why the stickleback fish in Bear Paw Lake are now so different from the ocean and sea

How do Oceanic stickleback differ from freshwater stickleback in Bear Paw Lake?

How are ocean and lake sticklebacks different?

How did sticklebacks change as they adapted to their new environment?