Subject
Molecular biology
Objectives
In this lesson students will understand the way that salmon are able to live in both freshwater and saltwater, they will understand the physical adaptations and the behavioral adaptations that salmon have in order to go through the smoltification process.
Materials
Background
Salmon are anadromous fish, this means that they hatch in freshwater, live the majority of their lives in the saltwater ocean and migrate back to the freshwater to spawn. Salmon can survive in both freshwater and saltwater. There are behavioral adaptations as well as physical adaptations that make this possible.
The first thing that has to be understood is osmosis. Osmosis is the process by which molecules of a solvent pass through a semipermeable membrane from a less concentrated solution into a more concentrated solution, thus equalizing the concentration on each side of the membrane. When talking about saltwater or freshwater, water will move through the semipermeable membrane to the side that has a higher salt concentration. This means that salmon in freshwater have to have an adaptation to prevent over hydration, and in saltwater they need an adaptation to prevent dehydration.
Behaviorally salmon will prevent over hydration (in freshwater) by drinking less or no water, and having diluted urine (more water than salt). In saltwater they do the opposite, they will hydrate by drinking water and they will have concentrated urine (more salt than water).
Salmon also have a physical adaptation to prevent dehydration and over hydration. This adaptation is on the cellular level. These are called active transport and passive transport proteins, they act as doors in the cell membrane to move salt in and out. In passive transport salt (the solutes) will move with the concentration gradient. In active transport the cell will use energy (ATP) to move salt (the solute) against the concentration gradient.
Procedure
- Look through the Osmoregulation Slideshow and familiarize yourself with the content
- Hand out the Osmoregulation Vocab Sheet
- Let the students fill in the Vocab sheet as you present the information
- Once you have finished presenting the slideshow hand out the Osmoregulation Worksheet and let the students work through it alone or with partners.