After a week of re-learning cell organelles and observing cells under the microscope, today students learned about how the cell membrane works. The primary focus of the lesson was to provide students with the vocabulary to explain the concepts of osmosis and transport of water across the membrane via the membrane protein channel aquaporin. Students should review the Membrane Functions PowerPoint slide deck and commit the vocabulary terms to memory. The aquaporin claymation video included in the slide deck is also provided below for easy access:
Every now and then we have to take a day of class to “sit and get” – a day of class where students learn and review important science concepts designed to help them make sense of their lab observations and use science to explain what they saw. Today was one of those days. Students learned about how the cell membrane works, focusing on the concepts of osmosis and transport. Students should review the Membrane Functions PowerPoint slide deck and commit the vocabulary terms to memory. The aquaporin claymation video included in the slide deck is also provided below for easy access:
I was at a district-wide high school biology teacher meeting this morning during periods 1-3. Below is the lesson plan my substitute shared with the students:
Yesterday we learned about how the construction of a causeway across the Great Salt Lake dramatically affected the ecosystem of the Great Salt Lake.
Entry Task: In your lab notebook, describe how the causeway resulted in the north arm of the lake appearing purple compared with the blue south arm. You have 5 minutes.
Group work: Working with your extreme environment group, your job is to solve the problem of the GSL railroad causeway. Your team must devise a solution to undo the ecological changes of the causeway on the ecosystem of the Great Salt Lake. Your group’s report must include the following:
- A model of how altering the causeway will affect the populations of each of the 8 GSL organisms.
- Application of the concepts of osmosis, diffusion, and active transport in your model.
- Initial ideas on how GSL organisms will be immediately affected by a change in the salinity of the GSL upon changing of the causeway. You must include a discussion of water and/or salt moving across cell membranes for full credit.
- Research! Slides 15-20 from yesterday’s lesson (on the class website) may be a useful starting point. Be sure to cite any references used when making claims about GSL salinity (before and after causeway changes) and any references used to learn which organisms can survive at the salinities found in the GSL after the causeway is removed. Please use electronic resources appropriately.
- Your analysis should include a written discussion of the risks and benefits of altering the causeway, both to the railroad and to the organisms that live in the Lake.
Exit Ticket: Turn in group work with names of all students who actively engaged in the work for the entire class period.
In lesson 10, we continued with our study of osmosis, focusing on the extreme environment of the Great Salt Lake. Students learned that a railroad causeway was built across the lake more than 60 years ago, physically separating the lake into two sides. Only the south side of the lake receives a continuous supply of freshwater, causing the salinity of the south side to be much lower than the north side. As a result, the ecosystem of the south side of the lake is much more robust than the north side which is inhabited primarily be halobacteria. Considered extremophiles because of their unique ability to live in extremely salty water, halobacteria are present in such abundance that they color the water in the north side of the lake purple (because of the rhodopsin protein they produce). As evidence of their learning, students completed a case study worksheet and hypothesized what might happen to the existing Great Salt Lake ecosystem if the causeway were removed.
In lesson 9, our first lesson of the week, we circled back to osmosis, a concept students learned about early in the school year. We connected the theme of “Water Follows Salt” with the reality that cell membranes contain pores and channels that regulate the flow of everything across the cell membrane. We discussed the vocabulary of osmosis in the context of blood, recognizing that blood cells in plasma (isotonic) behave much differently than blood cells in water (hypotonic) or in saltwater (hypertonic). We then thought about how salmon might be able to transition from freshwater to saltwater during their life cycle. By connecting pore protein expression (via the Central Dogma) with evolution, students now have the foundation necessary to explain how salmon can hatch from an egg fertilized in a freshwater stream, migrate through the brackish waters of an estuary out into the Puget Sound, travel for years in the salty Pacific Ocean, and eventually find their way back to the steam from which they were born to complete their life cycle. We wrapped up with a video about ice cave exploration, in which the concept of extremophiles was presented. Students then transitioned to Work Time where they read an article and answered questions about extremophiles.