One of my favorite parts of the cell unit is teaching about membranes. If you ask me, they are by far the most important part of the cell. Everything the cell does is because it is responding to signals received by the membrane. While many students think the nucleus is in charge, it is in fact the membrane that is directing cell processes. (You can read a blog post about why the cell membrane is more of the control center than the nucleus by clicking HERE).
There are a ton of lab options you can do for students to understand the structure and properties of the cell membrane. Check out these 10 resources you can implement in your classroom:
MEMBRANE PROPERTIES & STRUCTURE
1. Visualizing the Membrane: Using analogies really helps students visualize the cell membrane in their head. I read this analogy a few years ago in a book by Dr. Bruce Lipton and have been using it ever since. I tell the students the cell membrane is like a bread and butter sandwich. If I poured water on top of the sandwich, what would happen? Students can recognize that the water would only soak through the bread and stop at the butter layer. Since students already learned about lipids being hydrophobic from our macromolecule unit we circle back to that discussion. Click here if you would like to check out a worksheet that goes with this analogy.
2. Bubble Lab: Who doesn't love to play with bubbles?! Bubbles are a fun way to examine properties of membranes because they are similarly made of molecules that have a hydrophobic side and a hydrophilic side. In this lab students learn how membranes are flexible, can self repair, how materials move in and out, and more. Materials are inexpensive and the fun is endless. You can find it FREE HERE.
3. Interactive Website: Check out this website that walks students through the structure of the cell membrane. This website is great for high school students. I like that it shows the actual molecular structure instead of just head and tail blobs... this allows students to really comprehend the structure. While you are there check out some of his other interactives- they are all great!
MEMBRANE TRANSPORT (Many of these labs demonstrate the same concepts. Pick one or two that you like!)
4. Carrot lab: This lab is great for middle school students to understand osmosis. In this activity, students will soak a baby carrot in fresh water and salt water overnight and observe any changes to it's physical appearance and mass. (You can use celery, potatoes, or any other vegetables you have on hand). I prefer using vegetables over gummy bears (Which is a teacher favorite) because vegetables are actually made out of cells.
5. Egg Lab: In this classic lab, students dissolve an egg shell with vinegar and are able to observe a "naked" egg. Once the shell is dissolved you can soak the eggs in different liquids such as distilled water or corn syrup and observe the effects on the egg size and mass. This lab is fun, but I don't do it every year because there are always messy casualties. You can read more specific directions HERE.
6. Dialysis tube lab: In this ADI lab, students need to design an experiment to determine the effect of solute concentration on the rate of osmosis. (Note: ADI labs are available for free online, but the hard copy books must be purchased if you want the answer key). This is a great lab for high school students who are ready to think critically and design their own experiment. Sugar can also be used instead of salt. When I had students complete this experiment I pre-mixed the solute concentrations and we discussed how dialysis tubing works but had students figure out their own experimental set up.
7. Onion Skin Lab: Have you already taught students how to use microscopes? If so, this lab is fool-proof. In this lab, students observe a thin layer of purple onion under the microscope. They make wet mounts with fresh water and salt water, and observe what happens to cells placed in a hypertonic environment. You can read a blog post with some tips HERE. It's great because it's easy (no dye needed) and really inexpensive.
8. Osmosis Tonicity Worksheet: I created this quick 2 page worksheet to use as a formative assessment before I tested students on osmosis. It includes a handful of scenarios and students have to identify how the cells will respond and if the solution is hypertonic, hypotonic, or isotonic. You can download it here.
9. Amoeba sisters: Do you want to enrich your lesson with some videos? Amoeba sisters videos on youtube are great for review and reinforcement. There are two video clips that cover topics relating to the cell membrane, one titled "Inside the cell membrane" and another titled "Cell Transport."
Don't forget that many of the amoeba sisters videos have worksheets to accompany the lesson. They can be found here.
10. Cell membrane close reading: One thing students tend to struggle with is understanding how the cell receives and responds to signals. When we use the term "environment" students think about the outdoors... but the environment for a cell is the conditions inside our bodies. I wrote this close reading article to help students understand how the cell receives and responds to signals, and how genes can be turned on and off. It is a great segue into genetics because it introduces the topic of epigenetics.
I hope you have a great cells unit and your students have a blast with some of these labs!
Getting out the microscopes is one of the best parts of teaching biology. I love hearing the ooh's and aah's when they finally get the specimen into focus. But if you've taught biology before you know it can also be one of the most exhausting units- constantly running around the room because "Mrs, I just don't see anything!" or they end up drawing dust, air bubbles, or their eyelashes. After a decade of tweaking my microscope unit, I've come up with some tips to help save your sanity.
1. Don't get them out until it makes sense.
While it may be tempting to get microscopes out the first week of school, it just doesn't make sense. If you aren't going to use them regularly until later in the year, why are you teaching them the names of the microscope parts in week 1? They will forget the information and you will find yourself reteaching. Hold off until you get to cells (or whichever unit you need them regularly).
2. Make sure they know the names of all the microscope parts.
It can be really frustrating when you are trying to help a student, tell them to adjust the fine focus, and they look at you like you are speaking another language. Because of this I don't let students start using the microscope until they can tell me the names of all the parts. We take notes on it and I give them a short quiz at the beginning of the unit. If you want to check out the worksheets I use for teaching parts of the microscope, click here.
3. Try a virtual lab first
Virtual labs are a way to provide students extra practice on the methods of using a microscope before getting out the real deal. Extra practice never hurts, especially for your SPED or ELL students who would really benefit from some visual practice.
For practice going through the process of using a microscope, check out this activity from Brainpop. (This site is great for middle school). For some higher level practice, check out this site from University of Delaware.
4. If your scopes have a single ocular, teach them which eye to use.
The microscopes in my room have a single ocular lens, so students often ask me which eye to use. This video shows an easy and quick way to teach them which of their eyes is dominant.
5. Start with prepared slides.
I always begin with prepared slides. I put 4 different prepared slides at each lab group, and have students practice focusing and drawing. The first day of prepared slides you will hear a lot of "I don't see anything!" but eventually they get the hang of it. Not all of your students are going to be great artists, but I make sure they know when they turn in their drawings they must a) be drawn to scale, and b) be neat. No scribbles allowed. I should be able to look at the drawing and easily tell what slide it is. I use these lab templates for prepared slides. Don't have access to prepared slides? You can make your own! Check out this blog post on how to easily make a classroom set.
6. Encourage peer help
There is only 1 of you and 30 students. It is physically impossible for you to be running around helping every single student. One day when I was about to rip my hair out I made this poster and hung it up on the whiteboard. Students were not able to call me over for help unless they had checked all of these items off the list. Most of the time their neighbor can help them resolve the issue before you need to be called over. If they still needed help after going down the checklist, then they could call me over. It has helped greatly! You can download this for free in my TpT store here.
7. After they have mastered prepared slides, then move on to wet mounts
Wet mounts can be much more exciting than prepared slides because you can have students look at their own cells (if your school allows you to do a cheek cell swab) or watch microorganisms swimming around. Protists are an absolute blast to watch, but students need to have mastered focusing the microscope and scanning relatively quickly in order to see the protozoa zooming around. You don't have to spend money ordering protists from a supply company, you can easily get your own culture going. Check out this blog post on how to set up a hay infusion. During this lab, I allow students to take pictures or videos with their phones. It takes a steady hand, but they can line up their smart phones with the ocular and get a decent video.
It can be really frustrating when the bell is about to ring and students try to walk out of the classroom without cleaning up. General microscope clean up procedures should include:
a) Removing your slide and returning it to where the teacher directs
b) Turn the objective to low power
c) Turning off the light
d) Putting the dust cover back on
e) If you are putting microscopes away for the day, unplugging and winding the cord around the arm.
I have this poster hanging on my microscope cabinet- it is a freebie from my friend Bethany Lau. You can find it in her TpT store.
I hope these tips help your microscope unit run more smoothly! Have fun!
Why are cells so small? And why are we made of so many? It seems like it would be easier to be made of 100 or even 1,000 cells instead of trillions. One of the reasons we teach students that cells are small is because they need a large surface area to volume ratio. The larger the ratio, the more efficient the cell is at moving materials in and out of the cell.
I've seen cell size labs that use different sized agar cubes prepared with a pH indicator. The cubes start pink and lose their color as they soak. Frankly with 3 preps a day this year, I didn't have the time or energy to pour agar cubes. Instead I found a quick and easy way for students to see the same concept- using beets and bleach.
In this experiment, cut different sized beet cubes, a small, a medium, and a large. The students soak the cubes in bleach for roughly 30 minutes (I had them doing some practice SA:V calculations while they waited). Tip: if you use tupperware containers with lids you won't have to smell bleach fumes all day, or you can put parafilm over the beakers.
After 30 minutes of soaking, students remove the beets, cut them open, and measure the amount of red pigment remaining. It is an easy way to see that small cells are more efficient at moving materials in and out. If you are interested in seeing the lab write-up I wrote, you can view it here.
I hope your students enjoy it!
Air pollution is a topic that fits into almost all science content areas. Teach biology? You teach the water and carbon cycles. Environmental science? Climate change and smog. Earth and space science? Layers of the atmosphere and ozone. Chemistry? Water + CO2 = carbonic acid. (Side note: My students recently tested the pH of different water sources, and were blown away that the pH of our rainwater sample was 5.4). I think it is telling that our air and atmosphere are woven into so many different sciences. Air is vital, so let's talk about it with our students!
I recently did a mini unit with my students on urban ecology. We were learning about the effects of urbanization on ecosystems, and pollution and urban heat islands came up in our discussions. (You can read my blog post about urban heat islands here). Here in Phoenix it is relatively easy to see how polluted our air is, all you have to do is drive up a hill and you will see the layer of haze that sits over our city of 1.6 million people. We discussed the health effects of air pollution and I wanted my students to have a visual of what they were breathing in. You can buy fancy (and expensive) sensors that will give you data readings of all the particles in the air, but I found an easy way for students to see the particulate matter floating around.
You will need:
This lab is super easy. All you have to do is have students smear a thin layer of petroleum jelly across the center of a glass microscope slide with a clean cotton swab. If you want your students to have quantitative data at the end of the experiment, gridded slides are ideal (See image). No worries if you only have plain slides.
Students got to choose where they wanted to leave their vasaline-covered slide for 24 hours. I had some students leave the slides in the classroom and others left their slides outside. (Tip: I had students set them in a petri dish and label them with their initials so we could track them down easier the next day. Also, if students choose to leave them outside, find a location on your school campus where they won't get disturbed). In the next 24 hours, any particulate matter floating around will land on the slide and stick to the petroleum jelly. If you want easier cleanup, you can also try putting a piece of double sided tape on the slide instead.
The next day, students retrieved their slides and viewed them under the microscope. I had them switch slides with their neighbors so they could compare indoor vs. outdoor slides. As you can see from our results pictured below, there was generally a lot more particulate matter on the outdoor slides. I had students draw what they observed and do a little math to calculate the particle deposition rate. If you are interested in checking out the lab write up, click here.
Remember when I said there was generally more particulate matter outside than inside? Are you ready to be completely grossed out? I had a student that decided to hang his slide from the ceiling by the classroom air vent... and this is the image that ensued. Can you say "time to change the air filter?"
I hope your students enjoy this lab as much as mine did! It was definitely eye opening for them to see the microscopic matter going into their lungs.
At the beginning of every school year I can bet that you review the scientific method. While there isn't necessarily a specific set of steps that we follow in all branches of science, we want our students to be able to use inquiry and think through the scientific process. One great way to get our students thinking like scientists is by using the CER method.
What is CER?
CER stands for claim, evidence, and reasoning. After being posed with a question or observation, students have to make a claim (similar to forming a hypothesis), provide evidence to support their claim, and explain their reasoning. Getting students to understand CER is important because it helps them think through the scientific process. All claims must have supporting evidence, and students should be able to explain the reasoning behind their thoughts. CER is science literacy for the win!
CER can be applied so many different methods of teaching. It doesn't just have to be for labs! Here are a few ideas on how you can implement the process:
1. Video clips: Find a video clip that poses some sort of question or claim. Have students identify the claim, evidence, and reasoning given in the video. If only a claim is given, have students come up with evidence and reasoning on their own following the clip.
2. Labs: CER is great to implement within the lab process. Students are posed with a question they will test, write out their claim (hypothesis), provide evidence (their data), and reasoning. If you haven't checked out NSTA's ADI books (arguement driven inquirty), they follow the CER process and have a lot of great lab ideas. Many of the labs can be found free online, but you have to purchase the book to get the accompanying teacher information. Some free resources can be found at the following links: Biology labs, Chemistry labs, Middle school life science
3. Socratic Seminars: If you aren't familiar with what a socratic seminar is, it is essentially a class discussion where the facilitator asks open ended questions and encourages class discussion. For me it works best when the class sits in a circle facing each other, and every student is required to contribute to the conversation at least once (give them a grade for speaking). Pose a question to your class, give them time to come up with CER speaking points, and get them talking! Make sure your question is open ended so students don't all come to the same conclusions. A sample question you could pose is "Do you think humans could ever survive on Mars?" While there are only 2 answers to this question (yes or no), there will be a lot of discussion regarding their evidence and reasoning.
4. Whiteboard sessions: CER works well on mini-whiteboards. I have studentes set up the whiteboards as pictured below. After groups fill out their whiteboard, have the class face each other in a circle, review the boards, and have a "whiteboard session" where they discuss what other groups came up with. This could supplement a lab or be done as a stand alone activity. It takes some training to get students to give constructive feedback to other groups, but after a few tries they get the hang of it. A sample is shown below.
5. Analyzing journal articles: We all want our students to be better readers. At the high school level, I try and get my students reading journal articles. They can be a lot to digest and asking students to read and summarize them can be daunting. I give students the CER graphic organizer (found below) and have them fill it out as they read. It is a great way for them to organize information as they read.
This is a great inquiry lab for your physics unit! In this activity students will be asked to figure out which of the following variables affect the period of the pendulum swing: the mass, the length of the string, or the angle the pendulum is released from.
All you need for this lab is: string, a ring stand (or other object to hang the string from) a stopwatch, a protractor, and some hanging masses. Don't have hanging masses? You can hang a cup instead and add pennies or marbles for weight (see the images below).
I gave the students 2 days to complete this lab. The first day they just played around with the pendulums and tried to figure out which variable affected the pendulum swing. The second day I had them time the swings, record data, and make conclusions. It was a great introduction to my unit on motion! If you'd like to check out the 2 day lab write-up I made, it is available in my TpT store.
I hope your students enjoy this lab as much as mine did!
Physics is really exciting to teach because there are so many fun labs you can do. After teaching students about speed, velocity, and acceleration I wanted to do a STEM lab to follow up the unit. I decided to have students build a parachute out of a plastic grocery store bag and gave them a goal of keeping it in the air as long as possible. It was not only fun for them but the materials were super inexpensive! I supplied string and tape, and they had to supply the bag and any other materials they wanted to add. You are welcome to set size or material restrictions but I chose not to. I gave them one class period to build (if they didn't finish they had to finish at home) and we tested the following day. When testing the parachutes I tied a GI Joe to the bottom to add some mass but you are welcome to use whatever you have handy (metal washers work great too).
Our school is 2 stories so the students dropped their parachutes from the 2nd story. When they went to drop the parachutes they had 1 rule: No throwing the parachute up in the air. They had to hold their hands straight out horizontal and drop straight down.
Each group got to drop their parachute 2 times. They had to calculate the speed of the drop (distance / time) and acceleration (Vf - Vi) / t. Overall they had a blast and I had some silly prizes for the winner of each class period. If you would like to check out the lab worksheet I used CLICK HERE. Have fun!
Virtual labs are a great tool to try if you have computer access. I love them because:
I've compiled a list of websites that have virtual labs. Many require Flash or Java software, so be sure your computers have it before trying with students. If any of the links are broken or out of date, please leave a blog comment and I will update.
Enjoy! If you know of other sites, please share in the comments!
I'm excited to share with you an EASY PEASY way for students to see osmosis in plant cells! In the past, I always used elodea leaves for this lab. Elodea can be hard to find at pet stores and is a little temperamental to keep alive. This year I decided to use onion skin from a purple onion and we got awesome results!
I used this lab BEFORE I taught any vocabulary such as osmosis, equilibrium, hypertonic, hypotonic, or isotonic. I wanted students to visually see what happens to cells in fresh water vs. salt water before I threw any vocabulary at them. Students were really excited to see the cells change within a matter of 60 seconds. Here are a few tips when doing this lab for the first time:
1. You cannot use the dry layers of the onion skin. You need to use the very top of the purple fleshy layer. It can be a little bit tricky to get a specimen that is thin enough, so I decided to do it myself and hand each kid a piece. I took metal tweezers, gently pushed them under the purple layer, and slid the tweezers out so a small flap of onion skin was loose. I peeled it off, handed it to each kid, and they set up their own wet mounts. No dye needed!
2. Have students make drawings using fresh water first. After they finished their drawing, they switched to salt water. To do this they do not need a new piece of onion, just leave it directly on the slide. Add a drop or two of salt water directly to the slide, no need to pre-soak the onion. Make sure your salt water solution is pretty saturated.
3. Tell students to wait at least 2 minutes before drawing the salt water image, because sometimes it takes a little time for the cytoplasm to shrivel up. Below are images of the onion cells in fresh water (left) and salt water (right) on 100x magnification. We had a discussion on whether or not the cell wall shriveled as well. Students automatically said yes, because the cell wall is almost transparent and harder to see. Once I told them to switch to high power (400x) they were able to see the cell wall more clearly and realize that the cell walls were still intact, while the membrane and cytoplasm shriveled.
Tomorrow we are going to follow up with the discussion of what happened and why. Students will take notes on osmosis and we will relate it to real world situations such as: Why can't I drink salt water if I'm stranded on a boat in the ocean? Why is my contact lens solution saline instead of pure water? Why do grocery stores spray the produce with water? If you want a quick worksheet to use as a formative assessment to follow this lesson, check out my tonicity and osmosis worksheet in my TpT store HERE.
I hope your students enjoy the lab as much as mine did! Other than having my classroom smell like onion for a day, it was a total win! Want more ideas? Check out this blog post that has 10 resources for teaching cell membranes!
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As fun as prepared slides are, students always LOVE looking at living organisms under the microscope. I generally order mixed protist specimens from Wards or Carolina Biological, but this year I didn't get an order put in on time (if your district is like mine it often takes months to get things ordered and delivered...) Since I didn't have anything for my students to look at, I decided to make a hay infusion. It turned out great for what I needed.
Overall, here are the pros and cons of doing a hay infusion:
Before using the hay infusion, have your students practice using the microscope with prepared slides. If students are comfortable with how to focus and scan, it makes it much easier when they are looking for things that are swimming around. We began the class with learning how to set up a wet mount slide using an elodea leaf. Once they got the hang of it, they cleaned their slide and took a sample of the pond water.
Here is a video I took under 40x magnification:
and 100x magnification:
Although there weren't a variety of species to see, students were still pretty excited to see them swimming around. I wasn't able to identify which type of protists we had- if you had honors or AP students it might be fun to give them a protist dichotomous key and see if they can figure out which species they find. Overall it was a success and didn't cost me a cent!