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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. 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!
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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!
Okay, so you can tell by the title of this blog post I'm a biologist and not a chemist. (Chemistry teachers, please don't send me hate mail!) Honestly, I don't love chemistry and I don't love teaching it. BUT, I realize how important it is for students to understand biochemistry before I dive into a fun enzyme lab. There have been years where I thought "screw it, I'm just going to talk about macromolecules and cells without reviewing atoms and bonding." Oh was I sorry. Most of my students didn't have a strong enough chemistry background to understand polarity without reviewing bonds. Although most of my students took chem-phys the previous year, they didn't understand how the chemistry they learned prior could apply to biology. So my advice is to take it slow, review the periodic table and bonding, have them build models, and really understand the structure of the 4 macromolecules before moving on in your cells unit. Once you get to membranes, they will understand them so much easier if they understand lipids. Once you get to DNA structure they will understand why it runs from 5' to 3' if they understand the structure of a nucleotide. They will also understand DNA replication and the enzymes involved so much better if they understand protein structure and folding. Have I convinced you yet? I hope so. Here are a list of fun ways to teach macromolecules and deepen student understanding:
1. Build Atomic Models. I'm lucky enough that I have access to model kits. I have my students build models of all the macromolecules. The best is when they can each build an amino acid, link them together, and see dehydration synthesis with their own eyes. Check with the chemistry teacher on your campus and see if they have kits you can borrow for a few days.
2. Emphasize Protein Folding. Lets be honest- of the 4 macromolecules, proteins are the rock star. It's so important that students understand how and why proteins fold, and the consequences of them denaturing. My school purchased a kit called "protein toobers" where students pretend the "toober" is a long chain of amino acids. (The activity can be purchased HERE. I am not affiliated in any way with this company). Students add thumbtacks (side chains) and then have to fold accordingly. For example, if white thumbtacks are hydrophilic and yellow thumbtacks are hydrophobic then they need to fold the toober so the white thumbtacks face out and the yellow thumbtacks face in. It is fun for them to see that each group's protein is folded differently based on the order they placed the thumbtacks. If you aren't able to purchase this kit, I think it could easily be replicated with pipe cleaners and pony beads (click here to check out a similar product from Science with Mrs. Lau!)
3. Use Videos. It is always helpful for students to hear things explained more than once and in a variety of ways. Find videos that will help reinforce concepts already taught. Amoeba Sisters always have great videos and worksheets that go with them. Here is a link to the video on biomolecules and the associated worksheet.
4. Engage with Labs! There are a bunch of fun labs out there on macromolecules, especially enzymes. I love this liver enzyme lab from biology corner. Students will see how changing temperature and pH will affect enzyme reaction rates. It's not the most fun lab to clean up after, but it's inexpensive and fun for the students. You can buy a tub of chicken liver from the grocery store for less than $2 and that will last you the entire day. Tip: I've found I get the best results when I puree the liver in the blender instead of just cutting it into pieces.
5. Use Review Activities and Games. I have never met a student that didn't love puzzles and games. It is way more fun to use these as formative assessment tools opposed to a study guide. I have a few available in my teachers pay teachers store I think you will enjoy! One is a macromolecules tarsia puzzle (pictured) where students have to pair up words with their definitions. Another option is a memory game where students flip over 2 cards at a time to try and find matches. I also have a flip book which is a fun review tool for interactive notebooks. Don't miss my macromolecules bundle where you can buy them all at a discounted price!
What other fun ways do you teach macromolecules? Leave them in the comments!
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Living? Nonliving? Dormant? Dead? Even though teaching living vs. nonliving seems very elementary, you'd be surprised by how often high school students get confused when you throw examples at them. It makes me think of this 90's "J-E-L-L-O it's alive!" commercial:
But in all seriousness....
Teaching characteristics of life is a great way to start off the year in biology. I like teaching it week 1 because it's more fun than the scientific method (which they should know by now anyway) and a great introduction to biology- the study of living things. Here are a few resources you can add to your teacher toolkit for your life unit:
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This is one lab that you don't want to miss! It's easy, the materials are inexpensive (you probably already have them at home), and it ties together multiple concepts. Winner!
In this lab, students will analyze a pedigree of a fictitious family. In the introduction, students read that "Jon and Sue Smith" were in a car accident and need a blood transfusion. The hospital asks family members to donate, but students will need to figure out which family members are able to successfully donate. To complete this lab, students will need to understand blood types, punnett squares, and pedigrees. Its a great end-of-the-unit lab when you are finished with genetics.
One piece of feedback I have gotten from my TpT store is that this lab can take a while to set up. I'm here to give you some tips to save you set up AND clean up time.
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This lab is one of my top sellers in my Teachers Pay Teachers store. It is easy to set up and doesn't require a lot of materials. However, I frequently get questions about the lab so I'm hoping this blog post will be useful to those teachers out there who about to set up this lab.
In this lab, students will be testing whether or not aquatic plants do photosynthesis in the dark or light, and also testing if they do cellular respiration during the dark or light. The plant I usually use for this experiment is called elodea, which is available at any local pet store in the fish area. One nugget of information you will need to know- pet stores call it anacharis, not elodea. It is usually sold in bunches of 4-5 stems for a few bucks. Two big bunches should get you through the day. If they don't have elodea, any other aquatic fish tank plant will work fine, but make sure it is a tall skinny plant that will fit down into your test tubes.
One reason this lab is great is because it can be used in multiple places in your curriculum:
~ Cells unit: When you are teaching cells, chances are you will be talking about chloroplasts and mitochondria. Along with these organelles you will be discussing photosynthesis and cellular respiration. This lab fits in great because it shows that plants not only do photosynthesis, but cellular respiration as well.
~ Ecology unit: During my ecology unit, we cover the 3 major biogeochemical cycles (water, carbon, and nitrogen). What better way to talk about the carbon cycle than to demonstrate the relationship between plants, animals, and gas exchange?
A little background....
This lab uses the chemical bromothymol blue. This chemical is used as a pH indicator. When the pH is above a 7 (basic) it is blue, but when the pH drops below 7 (acidic) it starts to turn yellow.
Image below is courtesy PureySmart on Wikimedia Commons.
Before beginning the lab, I like to demonstrate to the students how bromothymol blue works. I get 2 erlenmeyer flasks (beakers will work just fine too) and fill them 3/4 of the way full with water. Add enough bromothymol blue for the water to be visibly blue. (In a beaker of 200mL of water, I add about 4mL of bromothymol blue). Call up a student, and have them blow through a straw into the beaker. As they blow (it will take 3-4 big breaths) the water will slowly change from blue to yellow. This is because when the carbon dioxide in our breath reacts with the water it forms carbonic acid, lowering the pH.
Inquiry, Inquiry, Inquiry
When I do this lab, I do not tell students how to set up the experiment. I split the class into lab groups, and assign each group one of the following questions:
1. Do plants to photosynthesis in the dark?
2. Do plants do photosynthesis in the light?
3. Do plants do cellular respiration in the dark?
4. Do plants do cellular respiration in the light?
Obviously the group that gets assigned "do plants do photosynthesis in the light" will know the answer, but they will still have to set up a controlled experiment that can demonstrate it. I give each group a big white board and have them set it up like the image below. They will have to fill it out based on the specific question they are assigned. If you don't have whiteboards, butcher paper works great too. Students will know what materials they have to work with because they are listed on their lab worksheet (available in my TpT store).
As we walk around the room and discuss experimental design, students will begin to see that each group will set up their test tubes the same way, the only difference being if their tubes get left in the light or wrapped in foil and put in the dark for 24 hours.
Two notes: I get asked how much bromothymol blue to add to the test tubes. I have each group add 1mL to each tube. If you would like to add more or less that is fine, as they add the same amount to each test tube for consistency. Also- make sure to fill the test tubes to the top and cap them tightly, or use parafilm to cover the tops. We want the gas to stay in the water, not escape.
When students come in the following day they will pick up their test tube rack and fill out their data tables on what happened. They will see that the elodea did photosynthesis in the light, and cellular respiration in the dark.** (see note below)
**One thing you will have to discuss with your students: Plants are doing cellular respiration in the day time as well, but since photosynthesis is also occurring the indicator stayed blue.
A great extension activity is to add aquatic animals to this experiment and see how the added respiration affects the color change. If you can get your hands on some small snails, they will fit great into the test tubes. I had trouble finding snails in Arizona, so I went to my local pet store and picked up two feeder goldfish. I filled up two large erlenmeyer flasks with water and bromothymol blue, and turned one yellow. I added elodea and a goldfish to each flask. Next, I asked my students what will happen when we leave these in the light for 24 hours. The next day we came in and saw both flasks were a shade of bluish green (somewhere in the middle of where the two flasks began). If you don't add a ton of bromothymol blue, and only leave the fish in for 24 hours the fish will not be harmed.
Hopefully you are ready to start this experiment! If you have any questions, drop them in the comments below!
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Need a great inquiry lab? This soda lab is FUN! And I know what you are thinking.... "what a mess it must be!" But I've done this lab multiple times, and never had a spill. Students will get 3 types of soda, and will measure which brand has the greatest amount of carbonation. The best part of this activity is there are 4 different versions included- you can choose which you think is best for your students.
~ EASY~ Great for lower grade levels. Students pour the soda into a cup, and measure the amount of time it continues to bubble.
~ MEDIUM~ (Pictured bottom left) Students cover the top of the bottle with a balloon. After shaking the balloon covered bottle, students will measure the diameter of the balloon with a string.
~ HARD~ (Pictured bottom right) Students will measure the amount of carbonation by putting a tube into the bottle, and catching the gas that escapes into a graduated cylinder. This is the most accurate way to measure the carbonation. I used a tube that was from a fish tank bubbler.
~ EXPERT~ Students will come up with their own experimental design (They may come up with one of the other three ideas already discussed). Great for inquiry, collaboration, and practice writing procedures.
To save money on this lab I buy the smaller bottles of soda, and usually snag them when they are on sale, even if I'm not doing this experiment right away. I love that this lab is a great time to review the scientific method, experimental design, and discuss variables such as temperature, rate of shaking, and other factors that could impact the results. This is a great lab for days before holidays or testing days when the kids are antsy. They will have a blast! Interested? Check it out in my TpT store HERE!
pH.... one of those chemistry topics that us biology teachers get to teach. In biology I don't make my students calculate pH and pOH values, but they need to understand what pH is and why maintaining a healthy pH in your body is so important. You may love biochemistry, or you may hate it, but either way there are plenty of resources to make teaching pH easy!
One of the first things I have my students do is make a pH foldable. As we go through the lesson, they take notes on acids and bases, and label the pH scale at the bottom. Foldables are really easy to have students make on their own, but if you are interested in a template, click here.
After students learn what pH is, I have them complete a pH lab. The lab available in my TpT store is editable, so you can use whatever liquids you have on hand. I try and find a couple acids, a couple bases, and some neutrals (especially water!). A few hints to make your lab go more smoothly: First, don't let the students grab the roll of pH paper themselves. Save yourself some money by making your pH and litmus paper go further by pre-cutting them. I cut the litmus paper in half and cut the pH paper into small strips. Students can use tweezers to dip them into the liquids, so small pieces work great. By cutting them in half I could get through the whole day with one vial of red and one vial of blue. Also, put your pH color keys in a ziplock baggie. Students always hold the wet pH paper up to it for comparison, and if it is in a baggie it won't get ruined.
Since I teach pH right before I dive into cells, this is a great time to talk about enzymes and denaturation. When the pH of our body changes, these enzymes can unfold, or denature. Once enzymes change shape, they no longer function. Enzymes are very specific, so enzymes that are in your stomach will work best at an acidic pH, and enzymes in your bloodstream will work best around a neutral pH. If you have some extra pH paper it is fun for the kids to put a piece on their tongue and measure the pH of their saliva. We talk about how there are enzymes in their saliva that start the digestion process.
Another good topic to talk about is neutralization in the body. I usually start by telling students if I drink orange juice on an empty stomach, I will inevitably get a stomach ache. Why? Students usually recognize that orange juice is an acid and the acid is causing the belly ache. Next, I ask them what do they do when they have a stomach ache? We talk about Tums and Pepto Bismol, and how the alkaline medicine neutralizes the acid in my stomach. It is also fun to talk about bee stings vs. wasp stings. Bee venom is acidic, so putting baking soda on it will help take the pain away. On the other hand, wasp stings are alkaline, so baking soda won't help at all. Instead, putting vinegar or another weak acid should help with the pain. Students are always find these topics engaging and try and come up with other situations where they have needed to neutralize their body pH.
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Is food chains up next in your curriculum? Most students learn food chains in the elementary grades, so how do you make it interesting and rigorous at the secondary level? Here are some great options:
Take the guessing out of creating food chains and webs! Students will create a food chain and web with 36 given organism cards. Each card has an organism, picture, what it eats, and what it gets eaten by. No more "Miss, what does a skunk eat?" Snag this lesson HERE.
This website is a great review of food chains. It is pretty basic, but if you have an interactive whiteboard it’s a quick and easy way to have students come up and show you what they already know. While the order of the animals is pretty obvious, students will need to know where to put them based on the directions of the arrows. I also like that the food chains include the sun, so students recognize that the sun is the source of the energy.
This is a great youtube video on food chains. It shows a food chain in the everglades, and reviews important vocabulary like herbivore, carnivore, producer, and consumer.
This skull lab is always a hit! I take out the skulls before introducing vocabulary words like herbivore, carnivore, nocturnal, or diurnal. Students will analyze the skulls and make inferences about how the animal lived. They have a really fun time trying to figure out which animals they are too! Don't have skulls handy? Don't worry! I have a great paper version of this lab in my teachers pay teachers store. Check it out here.
Last but not least is a lesson that demonstrates why it is important that trophic levels remain in balance. In this activity, students play the role of grass (producer), rabbit (primary consumer), or a coyote (secondary consumer). Throughout the 5 rounds, students will go around the room and pair up with another student. If they find a prey they get to eat it. If they find another organism of the same species, they reproduce. If they don't eat or get eaten that round, they are out. Students will quickly learn that there needs to be few secondary consumers and a lot of producers for a community to be sustainable. Check it out in my teachers pay teachers store here.
When you make ecology hands on and interactive, students will have a blast. What other activities do you do with your students when teaching food chains? Leave ideas in the comments below!
It's the beginning of the year, and chances are you are starting off teaching or reviewing the scientific method. If you've looked around on the internet for scientific method labs, you will notice that the majority are not biology related. Don't get me wrong- building paper airplanes, measuring bubbles, and seeing how many water drops can fit on the surface of a penny are fun labs, but not directly related to biology. In my class I want students to understand from the get-go that we are learning about living things, so I want my first lab to reflect that. Here are a few labs that can start your year off right:
1. Pulse Lab- This is a great lab because there are almost no supplies required other than a stopwatch. In this lab students measure their resting pulse, and compare it to their pulse standing up and holding their breath. It is a great way for students to practice writing hypotheses, and identifying independent and dependent variables. Before beginning the lab I start with a class discussion about what your pulse is, why blood needs to be pumped through the body, and where blood cells are made.
2. Firework Milk Lab- I have seen this lab done at ALL ages. Even preschool teachers love this lab. But the beauty of this lab is that high school students still love it, and they can finally start to understand the concept behind the fun swirling colors. In this lab students pour milk into a petri dish, add some food coloring, and put a drop of soap in the middle of the dish. Once the soap enters the dish the food coloring starts swirling and creating "fireworks." The reason the soap begins to mix the food coloring around is because of the chemical structure of the soap. The soap molecule has a polar portion that likes to mix with water, and a nonpolar portion that doesn't like to be around water. The soap molecules react with the fat molecules in the milk and start swirling around, which is visible from the movement of the food coloring. The fattier the milk, the better a reaction you will get. It is fun to have students test whole milk and skim milk and compare the results.
3. Testing the 5 Second Rule- This is my favorite lab to begin the year with, but it requires a little prep work. While you can order sterile agar plates from any science supply site, it is much cheaper to pour your own. If you haven't poured your own plates before, there are a ton of youtube tutorials available to walk you through it. In this lab students get to design their own experiment that would test whether or not food is really safe to eat after being on the ground for 5 seconds. When you purchase this lesson from my TpT store you will get two versions. In the high school version students design their own experiment, write their own procedures, and choose their own independent variable (food type, surface that they drop the food on, etc.) In the middle school version the procedures are given and it walks the students through the lab step by step. If you have an incubator the plates can be ready in 1 day, if not then let the plates sit over the weekend. Students will love seeing how much bacteria is on their food! You can even take it a step further and have students try and kill the bacteria with different cleansers (soap, bleach, 409, etc.) and see which is the most effective.
What other scientific method experiments do you love? Leave them in the comments below!
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Becca of Science Rocks
Hi, I'm Becca! I've been teaching science for 10 years at both the middle and high school levels.