Models can be powerful tools when teaching science. They allow students to visualize concepts that can be difficult to picture in their heads.

If you ask students what the most abundant gas in the atmosphere is, their first guess is usually oxygen. And when you say no, their second guess tends to be carbon dioxide. When we talk about the composition of the atmosphere and the effect of greenhouse gases, students may picture the atmosphere being FULL of carbon dioxide... and rightfully so- statistics estimate that 45 billion tons of carbon dioxide are released every year. But how much is that?

I wanted to build a model of the atmosphere so students could see that there isn't very much carbon dioxide in the atmosphere relative to other gases.

I like that it is easy to see how much nitrogen is in the atmosphere compared to oxygen and other gases. So much easier for students to visualize!

I want to point out that whenever you use models in class, you need to discuss with students any limitations the model might have to avoid misconceptions.

1. This model is limited to 4 types of gases. There are other gases in the atmosphere such as neon, helium, water vapor, and methane, but they are in such trace amounts I left them out of the model.
2. The gases in our atmosphere are more dense near the earth's surface and thin out as you go up in elevation. This is because gravity pulls down on the gases (and why it is difficult for hikers on Mt. Everest to breathe- there is a lot less oxygen up there!)
3. If you teach chemistry, you might want to point out that not all gas molecules are exactly the same size, as they are in this model.
4. It is good to discuss that even though carbon dioxide molecules are few in number, they still play a large role in global climate change.
5. If you teach biology or environmental science and review the biogeochemical cycles, this can be a good time to point out that gases in the atmosphere aren't static- they are constantly moving through cycles. Producers take in carbon dioxide and release oxygen during photosynthesis, consumers take in oxygen and release carbon dioxide during respiration, and bacteria take in nitrogen through nitrogen fixation. But it IS true that we are releasing carbon dioxide to the atmosphere faster than ever before.

Overall, the entire thing only cost me $9 to make and I had enough spheres left over to make another. Pretty cost efficient compared to ordering one from a science supply company!

If you would like to check out other resources I use when teaching about gases in the atmosphere and the biogeochemical cycles, check out this blog post.

If you read my blog post on recommended summer science reads, you saw my confession that I'm not generally a big non-fiction reader. I love to read, but fiction is my go-to.

As I was compiling a science book list for students and teachers, I kept seeing and getting recommended The Serengeti Rules by Sean Carroll (If you've used any HHMI videos in your class, you know who he is). I decided to check it out from the library and I'm so glad I did. The first section of the book discusses cellular rules of regulation. When I first started reading I was thinking "I thought this was an ecology book!" but what's fascinating is he relates cellular rules of regulation to ecological rules of regulation in later sections of the book. So many concepts cross over. For example, cells maintain balance using homeostasis, ecosystems maintain balance with carrying capacity. Cells populations are regulated from the bottom up by food availability, and so are animal populations. Cellular process such as enzyme activity are regulated by  negative feedback, while populations are regulated by negative feedback in the form of trophic cascades. It was cool to see the cross over and I kept thinking "this book is perfect for honors and AP biology students!"

As I set out to look for supplemental student and teacher resources for this book, I came across the official version published by the Princeton Press. There is a ton of great information included in that document, but it didn't suit my teaching style. I wanted students to pull out the main ideas and have clear graphic organizers to fill out as they read the book without getting caught up in the nitty gritty details. So I went back through the book and created my own resource for students that is more user friendly. It includes writing prompts, graphic organizers, chapter discussion questions, and more. Below are some images of what the resource looks like (page borders differ depending on if they are a pre-reading, during reading, or post-reading activity).

HHMI also has some additional resources that supplement the book that you can find on their website. And most exciting.... they are coming out with a Serengeti Rules documentary some time this fall! The trailer looks fascinating and I can't wait to see the full movie. Keep your eyes peeled- the HHMI website  frequently offers free DVD's to classroom teachers.

I hope you enjoy the book!

One of the most common projects for invasive species is for students to make a "Most Wanted" poster. Students do research on an invasive species of their choice and create a wanted poster that includes facts about the species and what they would be "wanted" for. It can be fun, but after doing it for a few years I was looking for something different. Below are some articles, videos, activities, and simulations you can add to your invasive species unit!

This video from Ted is a great introduction to what invasive species are:

This is a fun interactive activity where students act as fish and compete for food and see the effect of invasive species on native species. Requires minimal materials!

This "Fearsome Frog" video from National Geographic is not new (it feels very 90's) but since I'm a local Arizonan my students love watching it since it hits home. This video explores how Bullfrogs are an invasive species that were brought to Arizona by the government and what people have done to try and control the population. At the end of the video I ask students to brainstorm ideas on what we could do to eliminate them from our local ecosystem.

Instead of the go-to "Most Wanted" poster, what about having students create an obituary? In this activity students create an obituary for either an invasive species that has finally been exterminated, or for a native species that has gone extinct in an area due to invasive competition.

Do you have any budding artists in your class? Or students that like to read comics? Check out this lesson plan and comic strip from Oregon State University on invasive crayfish.

If you are looking to include some literacy, newsela.com is always a great source of articles. Here is an article about how technology can be used to combat invasive species. Newsela does require you to sign up and login, but is free to use. Bonus: You can also change the lexile of any article! Great for differentiation.

Have you checked the website of your local fish and wildlife department? Arizona Game and Fish created this poster of our 10 most invasive species. Students enjoy looking at the poster and discussing how many of them they have seen or knew about. Head over to your local site and see what you can find!

In this fun "Invasion Game" from Brainpop, students act as fish competing for food. In part 2 of the game students need to manage invasive species by keeping Carp out of the lake for 25 turns. It's free and does not require a subscription to brainpop.com.

The website "Species in Pieces" is more about endangered species opposed to invasive species, but as we know many species are endangered due to invasives. This website has information about 30 animals that are endangered, gives facts about each animal, and includes a link to a youtube video. Worth checking out! 

If you have the ability to get your students outside, try a citizen science project! Eddmaps.org is a website from University of Georgia built for early detection and mapping of invasive species. You need to register for an account, but you can collect data and report your findings straight from your phone. It would be fun to have your students contribute data to a meaningful and reputable project.

If you live on the east coast, this 5 module curriculum by Maryland's Department of Natural Resources includes a ton of free lessons for all grade levels. It focuses on aquatic invasive species.

I hope those help spruce up your ecology unit! If you have any other favorite lesson ideas for invasive species, feel free to leave them in the comments!

One of my favorite case studies to examine with students is the tragedy that occurred at Lake Nyos. Located in Camaroon, Africa, Lake Nyos is a lake that formed in a volcanic crater. While villagers thought the volcano was dormant, it was slowly releasing carbon dioxide into the lake. One night in 1986 the carbon dioxide built up enough that the lake overturned and all the carbon dioxide was released into the atmosphere. Since carbon dioxide is more dense than air, thousands of villagers and livestock died in their sleep that night of asphyxiation.

While it is a devastating story to learn about, it is good in the sense that it can be applied to so many science concepts. Biology teachers can bring it up when learning about the carbon cycle. Earth science teachers can discuss the story during their volcanoes unit. Physical science teachers can use it to introduce density of gases. It's a phenomena that is so versatile!

I begin the lesson by showing this video clip from National Geographic on Youtube. It gets the students 100% engaged and doesn't reveal why this mystery fog killed the villagers:

Following the video clip I have students read an article I wrote about what happened at Lake Nyos and the science concepts behind it. You can find the article HERE if you would like to download it (appropriate for grades 7-10).


Then at the end of class I like to end with a demo showing how carbon dioxide is truly more dense than air. All you need are 3 birthday candles, some clay or play-doh, a container, baking soda, and vinegar.
Cut two of the candles shorter so all the candles are different heights. Stick them to the bottom of a container with clay. Sprinkle the bottom of the container with baking soda and light the candles. Have students predict what will happen when you pour some vinegar into the container. Students will observe the lowest candle extinguishing first because the dense CO2 that is being formed stays nearest to the bottom of the container. (I do it under the document camera so all students can watch, but if you trust your students with matches you can have them do it in small lab groups instead). 

I hope your students enjoy this lesson- I know mine do! It's simple, engaging, and a story your students won't forget.

I currently live in Phoenix, AZ, which is the 6th largest city in the United States. Considering our large population size and desert climate, we have a huge problem with heat. In the summer it is not uncommon for the temperature to stay above 100F all night. It can be miserably hot! 

An urban heat island is an urban area that has a much higher temperature than the surrounding areas. Students probably haven't heard the term coined before, but can easily explain it to you. If you ask them why downtown Phoenix is hotter than some of the surrounding pockets of town, or ask them why it's cooler to stand under a tree than under a metal awning, they can explain it to you. As I was preparing to teach this concept to my students, I found (and created) a few resources you may want to check out!

Urban Heat Island Lab
In this activity, have your students head out around your school campus and measure the temperatures of different materials. Students will compare surfaces such as cement, asphalt, dirt, and grass in the sun and the shade. Students can brainstorm ways to improve the school campus and lower the overall temperature (and electric bill!) of the school. 

ASU Ecology Explorer Lessons
Arizona State University has a few lessons on urban heat islands that are great! This first lesson uses thermal images to teach students that urban heat islands are a night-time phenomenon, opposed to day time. Students will compare thermal images and try and figure out which ones were taken during the day and which were taken at night. 
This second lesson also uses thermal images, but students have to predict which object in the picture would be the hottest, and which would be the coolest. (If you don't have access to a color printer, you can just project the images on the board). 

Climate Central Interactive
Do you live in an urban heat island? This fun interactive looks at 60 cities across the US and gives you data on each one. Check it out and see if your city is listed!

Citizen Science
Start a citizen science project, where your students collect data about temperatures in your area, brainstorm ideas to mitigate the problem, and reach out to scientists, politicians, or even school board members to try and make a difference! It could be something as simple as planting a tree on campus or taking them to a community garden, to something larger like having students apply for grant money to have solar powered cell phone charging stations installed. If you let the students decide what impact they want to make their work ethic may surprise you! 
​(One great nonprofit organization that plants trees is onetreeplanted.org. They plant a tree for every dollar donated!) 

With climate change being a current global crisis, we have an obligation to teach students how to make more sustainable decisions. If every one of your students made a small change in their front yard we could see incredible results. Who knows, you might have a student in your class that will major in urban planning or sustainability! 

I love teaching about population growth (ecology is one of my favorite subjects to teach). This topic truly leads to so many rich classroom discussions! Pose some questions at your students and see what their thoughts are:

• Should we monitor wildlife populations, or just late nature take it's course?
• Do we have an obligation to try and save endangered species?
• How many humans is too many?
• What happens if we surpass our carrying capacity? Have we already? 
• Are we already in the middle of the 6th mass extinction?

There are many fun ways to dive deeper into population growth with your students, and I've compiled a list of lessons, labs, cartoons, and videos all to help you teach this topic. 

POPULATION GROWTH LESSON
I use this lesson to teach about the two types of growth curves (exponential and logistic), carrying capacity, and limiting factors. Included in this lesson is a 20 slide powerpoint, a writing prompt, student notes page, and exit ticket. 

ST. MATTHEW ISLAND CARTOON
This cartoon by Stuart McMillen is short, sweet, and easy to understand. I use this cartoon as an introduction and have students read it for bell work before we take notes on logistic and exponential growth, and carrying capacity. Best of all is it's a true story! One of my favorite things to discuss is the question he poses at the end- How big is our island? Click on the image to check out this cartoon! 

HUMAN POPULATION GROWTH VIDEO
I love this video clip from NPR because the visual makes human population growth so easy to see. How many humans do we have on Earth?Where do most of the humans on earth live? What made our population skyrocket 200 years ago? Are we reaching carrying capacity? This two and a half minute clip leads to great conversations about our growing human population. 

KAIBAB DEER GRAPHING
I use this activity every year since I teach in Arizona. In this activity from biologycorner.com, students learn about how populations can crash if they have surpassed carrying capacity. They will learn about the deer on the Kaibab Plateau (near the Grand Canyon), and how game and fish department can manage population sizes to avoid another crash. I also like it because students graph the population data- and graphing practice is always good! 

DUCKWEED POPULATION GROWTH LAB
If you have access to duckweed, this lab is easy and fun- no microscopes or fancy equipment needed. Students will examine the population size of duckweed plants over the span of 2-3 weeks, and discuss factors that may limit population size, specifically the addition of an invasive species. You may be able to find duckweed in a pond in your area, so this lab may be free! Click on the image to check out the lab.

YEAST POPULATION GROWTH LAB
In this ADI lab, students have to design an investigation to determine how the size of a yeast population changes over time in response to different variables. It is great practice on designing a controlled experiment and going through the CER process. On the NSTA website, you can download this lab for free, however you must purchase the book in order to get the teacher pages and answer key. 
Warning: In my experience, getting successful data from this lab can be difficult. It is a good idea to have back-up data to provide students that struggle with this lab. 

COMPETITION AND POPULATION GROWTH
In this virtual lab from Glencoe, students observe the effect of competition on population size in two species of protozoa. It is really simple to walk through and students will grasp the idea that competition is a limiting factor. You can also snag a free worksheet from biology corner to accompany the lab by clicking here.

OH DEER! ACTIVITY
In this activity, students act as deer and see how limiting factors affect the population.

INFECTIOUS DISEASE LAB
In this lab, students will see first hand the effects an infectious disease can have on a population. In this lab each student gets a vial with clear liquid (students should wear gloves). One student has the "infected" vial, but it looks the same as all the other vials. As they come into contact with each other, they mix the liquids in their vials. After a few rounds, the teacher adds the indicator solution, and students can see who is infected, and try and deduce which person started the spread of infection. Students always love this lab! Its fun to link back to density dependent vs. independent limiting factors. Click on the image to check out the lab.

I hope you find these resources useful! 

When I moved up from teaching middle school to high school and was looking at my new curriculum I saw the term "keystone species" and scratched my head. It was a term I had never heard before and didn't remember learning in college. After learning about the terms keystone species and trophic cascades I fell in love with ecology a little more (if that is possible). These topics are so fascinating to me and I love teaching them to my students.

If you aren't familiar with the term (like I was) then here is the gist: A keystone species is a species that has an unusually large effect on it's ecosystem. Other species in the ecosystem rely on them to keep everything in balance. When the keystone population is disrupted, trophic cascades can occur. A trophic cascade occurs when predators limit the density and/or behavior of their prey and thereby enhance the survival of the next lower trophic level. I explain to my students that it is like a domino effect- once one part of the food web gets disrupted, everyone else will be effected in some way as well.
I have created and found some really good resources that you can use to introduce or reinforce these concepts:

The presentation I use in my classroom is available for download in my TpT store. I use this after I have already covered food chains and webs. This includes a 16 slide presentation (in both powerpoint or SMART notebook) and 3 writing prompts to accompany the lesson. You can download the lesson HERE.

HHMI Biointeractive's website has some KILLER biology resources. (Side note: If you haven't checked out their evolution resources, please do it now! You won't regret it!) They have a great video on keystone species and trophic cascades that is 19 minutes long. You can find the video HERE and there is a student worksheet that can be downloaded HERE.

Want to include some literacy in your unit? Biology corner has a reading article with questions on keystone species. You can find it HERE. It would be a great homework assignment or sub plan if you are in a pinch.

Another great video for this topic is called "How Wolves Change Rivers." It can be found on Youtube HERE. The video is about the re-introduction of wolves to Yellowstone National Park, and the impact they made on every other species in the ecosystem. It also takes it a step further and talks about how abiotic factors (such as the rivers) were affected as well. This video is only 4 minutes long, but is full of information so I usually show it once, have a class discussion, and then show it a second time to make sure they understand everything.

This is a fun topic to teach, so don't skip it when you are teaching ecology! It brings up great student discussions!

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Ahhh the biogeochemical cycles. They are vital to life, but students don't typically enjoy learning about them. They usually know the water cycle by the time they reach high school, but struggle with carbon, nitrogen, and phosphorus. I've rounded up some resources you can use to spice up your chemical cycles unit. Don't forget to repin this blog post for later by clicking here!

1. Calculate Your Water Usage- Since most students already know the water cycle, don't spend a ton of time on it. Instead I focus on their water usage. Many students will think you are crazy when you tell them it's not sustainable to take 20 minute showers. This website is really user friendly and gives students a break down of their water usage and compares it to the national average.

2. Carbon Footprint Calculator- Similar to the water calculator, this website allows students to calculate their ecological footprint. At the end of the activity it will give students an "earth overshoot day," meaning if everyone on earth lived like they do, that date is when we will run out of resources. Eye opening! You can check out the website here, and if you would like a lesson and worksheet to accompany the activity, click here.

3. Take A Ride Through The Carbon Cycle- In this activity, students will go around the classroom visiting different stations where carbon is found in the carbon cycle. At each station students will grab a tracker (small piece of paper that tracks where they have been) and will roll a cube that will determine where they go next. At the end students will discover where the most carbon is stored in the cycle. Download it HERE.
Students asking for more? I also made versions for the water and nitrogen cycles! Be sure to check them out.

4. Lake Nyos Article- Throw in some science literacy with this article titled "Killer Carbon." Lake Nyos is a lake in Africa that formed inside a volcanic crater. Over time carbon dioxide was building up in the lake. In 1986 the lake eventually overturned, suffocating everyone within a 15 mile radius. This lesson includes a link to a national geographic video that grabs student attention, a close reading article with questions, and a demo demonstrating how carbon dioxide gas is more dense than air (hence the suffocation). All you need are birthday candles, baking soda, and vinegar. Download this lesson HERE.

5. Nitrogen Cycle Interactive- Of all the cycles, nitrogen seems to be the trickiest for my students to grasp. I've found this website to be helpful walking the students through the cycle. I like that it doesn't go into specifics about NH3, NO2, and NO3 but just differentiates between N2 and other usable forms of nitrogen. You can find it here.

6. Crash Course Videos- If you are a veteran science teacher, chances are you have come across the Crash Course videos. I've found Crash Course videos to be GREAT for honors/AP kids, but my lower kids (and especially English language learners) struggle because he speaks fast. Preview it and see if you think it will work for your kids.
Here is one for the water and carbon cycles, and another for the nitrogen and phosphorus cycles.

7. Make a Poster- It is nice for students to understand the cycles individually, but even better if they can link them all together. Put students in groups of 2-3 and give them a piece of butcher paper. Ask them to make a diagram that includes all the cycles. Hopefully by the end of the activity students will see that multiple nutrients cycle through organisms. Below is a sample diagram template that is included in my biogeochemical cycles lesson.

8. Model of Earth's Water- We show students pie charts all the time of how much fresh water is available for human use, but do they really grasp how little it is compared to the total amount of water found on earth? Use this lab activity where students create a scaled model of where earth's water is located. So many light bulbs will turn on and hopefully they will learn why water conservation is so important. You can download the lab here.

9. Biogeochemical Cycles Review Worksheets- It never hurts to review review review. Here is a set of 5 worksheets I created for the cycles. There is one worksheet for each cycle, and the final worksheet is titled "Name That Cycle" where students need to identify the correct cycle it is referring to. You can find them HERE.

Hopefully this helps! If you have any other tips or resources, leave them in the comments!

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:

• Check out this youtube clip that introduces characteristics of living things. Great to get them thinking!
• Great to catch their interest: sometimes called "sewer lice" or "dancing raisins" lab, this activity gets students thinking about what really makes things living or not. Download it free here from Flinn Scientific.
• Hatch some triops! I like having the discussion- are eggs alive? (You'd be surprised at the number of high school students that don't know the difference between eggs that hatch into chickens, and eggs that you eat). You can buy triops online, and I've also found them at our local science kids museum. Your students will love watching them hatch and swim around.
• Another fun question to throw at them- are seeds alive? Ask students if they think popcorn kernels are alive. If so, how could we test it? Your students will be amazed after a week once they have corn plants sprouting in their cups! (see picture below)
• Try my Characteristics of Life Lab. In this activity, students will be given a box of objects and have to classify them as living, nonliving, dormant, or dead. They will also need to find ways to test if they are living or not. For example, if they say a leaf is living, how can they prove it? I like doing this lab before I review the characteristics of life, because it allows students to try and come up with the list of characteristics on their own. You can check it out in my TpT store here.
• I also have a set of task cards in my TpT store, where students have to identify the 8 characteristics. This is a great follow up to your lesson and good review before a quiz. Check it out here.
  
• Here is a free lab where students test if yeast is alive or not.

I hope those are helpful! Any other great ways you teach the characteristics of life? Drop them in the comments!
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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.

Results!
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!

Hear what customers have to say:
"Awesome! The students who really worked to seal the containers with no air in them were richly rewarded with their results." -Susan M.

"This is a great guided inquiry lab. I love giving students freedom in their experiment design while still ensuring the overall concept is understood." -Crystal D.