We finally cleaned up our room and had a chance to really figure out what our dissections revealed to us. We're still trying to figure out the cause(s) behind the fluctuating trout population, and we feel that we've gotten a handle on things.

But some of the things we figured out about bony fish and the sea lamprey don't really hit home until we look at the evidence mathematically. Since sixth graders have studied ratios and proportions in math, it seemed like a great way to compare these two organisms!  
 
Using research and evidence from the dissections, students created a mathematical model to represent various features of both the trout and the lamprey.  From some of models, it seems like the lamprey totally had an advantage over the trout. In other models, the trout looks overpowering to the sea lamprey.  

Which models best represent the results of an invasive species' effect on an organism in an ecosystem?  You be the judge!

After exploring the simulator and seeing what happens to another invader as it relates to the ecosystem it enters, we're beginning to think that an invader is absolutely organism #3 on our graphs.

But it would be really helpful to see both the trout and sea lamprey in person, to get a first hand account of what these two organisms are like.

Field trips and scuba diving were suggested early on in our unit, and while these ideas are certainly great ways to see these organisms, it's hard to do and risky.

So Mrs. Brinza is bringing the organisms to us!  The trout wasn't available, so we're using another bony fish--the perch, as a comparison.  We'll be looking at both external and internal parts, to compare how these two organisms eat, swim, breathe, and reproduce. 

On Day 1 of our dissection, we looked at the external parts of the bony fish.  

On Day 2, we looked at external parts of the sea lamprey.

And on Day 3, we looked at the internal parts of both organisms to figure out the most about reproduction.  Look at all those eggs!  

So all of our research helped us figure out the following things:

1.  The Great Lakes and the Atlantic Ocean became connected in the 1920s, when canals connected the St. Lawerence Seaway and the Great Lakes.

2.  Around this time, fisherman began noticing large fish, like the trout and salmon, begin to have quarter-sized wounds appear.  They also caught wind of an invasive organism, known as the sea lamprey, to have entered the Great Lakes.  A journal entry from a fisherman in the 1930s revealed this to us.

So we set off to find out more about the sea lamprey, and figured we should compare it to the trout.  We decided to return to our Driving Question Board, and answer questions we had about reproduction, movement, and habitat, for not only the trout, but this new organism, too.

We discovered a whole bunch of things!

1.  The sea lamprey can live in both fresh and salt water, while the trout can only survive in fresh water.

2.  The sea lamprey have FAR more offspring than a trout.

3.  Despite trout being good swimmers, it seems as if sea lamprey's body made of cartilage and s-like swimming ability make it even faster and more agile than the trout.

4.  The sea lamprey has absolutely no predators, while the trout has many.

While we have lots of strong evidence that organism #3 on our graphs is the sea lamprey, but we're using a computer model to help gather even more evidence for what an invasive does to an ecosystem.  

What do you notice when an invasive arrived in this ecosystem?  How is this related to what happened to the trout?  And the trout's prey?

So we've figured out that organism #2 is prey to the trout.  In fact, it's chub--a smaller fish the trout consumes.

But we got this other organism...organism #3, and after graphing it, we had a lot of concerns.  We immediately couldn't call it a predator or a prey to the trout since it seems to break some "rules" we established about what happens to each type of population in terms of increasing/decreasing.

The most astounding part was what happened between 1930-1945.  For one thing, it didn't exist in 1930--it's total population was ZERO!  We had a lengthy discussion about what this means (extinct versus new species?!?!?!) and clarified that organisms of different species couldn't mate with one another, and that if an organism is extinct it can't come back.  We certainly had lots of wonderings!

So after some really intense conversation in class, we figured out that our second organism had to be prey to the trout.  While we recognized that while the predator population decreases, the prey population would increase, we also determined that a prey population compared to a prey's population would always be larger.  This is because a predator must consume more prey to get the matter and energy it needs.

From there, we looked at the graph to realize that the trout always had enough food to consume, yet its population continued to plummet in 1970.  This drove us to consider that prey's availability could NOT be the reason for the trout's decline.

The request for MORE data set in...

And lo and behold, Mrs. Brinza got another set of data.

But what does this data reveal?  What new questions arise?