Earth's oceans are a carbon sink, which is a place where carbon is stored long term. Oceans absorb carbon dioxide from the atmosphere. It reacts with seawater, creating carbonic acid, which in turn lowers the pH of the ocean. This phenomena is known as ocean acidification. It will only get worse as we release more carbon dioxide into the atmosphere. Oceans currently have a pH of around 8.1, but it is projected to lower to 7.7 by the year 2100.

What is the impact of ocean acidification on marine life?
Research is still being conducted on this, but there are a few things we know for sure. First, organisms that rely on carbonate to build their shells and exoskeletons will have less available. These organisms include coral, mollusks, sea urchins, starfish, and zooplankton to name a few. If they struggle to build shells, they are more likely to be eaten by predators and it can create a trophic cascade up the food chain. Other impacts could include lowering the blood pH of fish, changes in reproductive ability of marine life, and impeding with organisms ability to send chemical signals.

Ocean Acidification Lab
An easy way to show students the impact of ocean acidification on marine life is by soaking seashells in ocean water with various pH levels.
For this lab you will need (per group): 3 cups or beakers, 3 seashells, water, salt, vinegar, an electronic scale, and pH paper. Seashells can be purchased at craft stores, and I've even found them at the dollar store in the craft aisle.

Start by mixing up simulated ocean water (3.5% saltwater solution). Students will put ocean water in the first beaker, 75mL of ocean water and 25mL of vinegar in the second beaker, and 50mL ocean water and 50mL of vinegar in the third beaker. Next, have students take the mass of the seashells over the course of 3 days and calculate the percent change in mass. They will see the vinegar eat away at the seashell and a large reduction in mass. You can also have them measure the pH of the liquids over 3 days and see how it changes as carbonate is released (enter discussion on buffers!)

Following the activity you can discuss ways students can lower their carbon footprint so we can slow the rate of acidification in the future. If you are interested in a powerpoint lesson on ocean acidification and a lab write up for this activity, you can find it HERE.

The water cycle is taught starting in elementary school. It seems like in high school biology when I get to the biogeochemical cycles (water, carbon, nitrogen, and phosphorus) the water cycle gets glossed over because we assume the students know it and it's too basic. But water is vital to life! It's important to take some time to dig a little deeper with the water cycle and there are ways to ramp up the rigor. Check out a few activities you can use to take a deep dive into the water cycle:

TAKE A RIDE THROUGH THE WATER CYCLE
Even though this activity is good for younger grades, older kids still enjoy it. In this activity, students roll cubes that tell them how to move through the water cycle. It allows students to review the steps of the process but also realize where more water is stored within the biosphere. You can download the game cubes here.

WATER FOOTPRINT
How much water do students use each day? At watercalculator.org, they can calculate their water footprint.

EVAPOTRANSPIRATION AND URBAN HEAT ISLANDS
In this free lab from ASU, students see first hand how evapotranspiration from trees can cool down an area and have an impact on the urban heat island effect. You will need clay terra-cotta pots and thermometers. You can download the lab for free HERE. If you would like to see more resources dealing with urban heat islands, check out this blog post.

WHERE DID EARTH'S WATER COME FROM?
Water has been around on our planet for a very long time. But where did it come from in the first place? You can students this Ted YouTube video:

SCALED MODEL OF EARTH'S WATER
We tell students that the amount of fresh water we have available is very small compared to the total amount of water on earth, but does it really sink in? In this lab, students create a scaled model of where the water on Earth is located. There are 4 different versions of this lab so you can differentiate based on the amount of inquiry and math you would like your students to do. By the end of the lab, students will see that our freshwater supply is very small and hopefully realize how important water conservation is.

VIRTUAL WATER
What is virtual water? It is the amount of water used to produce a product. In this activity from California Academy of Science, students learn about the hidden water footprint of different products. You can download the lesson here.

THE GRACE SATELLITES
How do scientists monitor groundwater levels? NASA tracks water levels from space using the Grace satellites- super cool! They orbit the Earth and scientists measure the gravitational pull on the satellites in order to monitor how much water is underground (more groundwater = more dense = more gravitational pull).
You can find an article students can read about the grace satellites here, and check out some interactive maps with satellite data here.

ICE CORE LAB
What can we learn from ice cores? In this lab, students learn about how ice cores form, what we can learn from them, and how they are analyzed. It takes about 4 days to set up on your part, but the students love looking at these simulated ice cores. You can read a full blog post on how I made them here.

WATER DOCUMENTARY
There are a ton of documentaries out there on water shortages and conservation. I showed my students one titled "Beyond the Mirage" that is available on YouTube. I chose it because it is centered around Colorado River water, which feeds into my home state of Arizona. If you live in one of the 7 states that uses Colorado River water, I recommend this video. If you would like video questions to accompany the video, click here.

I hope these help and you spend an extra day or two digging a little deeper into the water cycle. If you have any other favorite activities, leave them in the comments!

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.

At the end of every school year we end our life science curriculum with geologic time. It's one of my favorite units because I get to bust out my fossil collection (If you know me, that's a big deal).
It's hard to talk about geologic time, mass extinctions, and evolution of species without bringing up climate change. All these topics are fascinating but there aren't a ton of hands on labs you can do with them. I decided to try something different this year and make my own ice cores for students to analyze. Most students had never heard of ice cores, and when I asked them how we learn about shifts in climate I got a lot of blank stares. It was a great opportunity to bring up a new topic.

Some background on ice cores:

• The best ice cores are taken from places where the snow doesn't melt. Over the years the snow layers on top of each other, compacts, and freezes into thick layers of ice. 
• ​Ice cores are generally drilled from Antarctica and Greenland. The oldest ice cores date back to 800,000 years ago. 
  
• Ice core layers are similar to tree rings- new layers form on top of the last each year.
  
• When analyzing the layers, winter snow layers appear lighter than summer snow layers. This is because the snow melts slightly in the summer, refreezes, and is more dense than the winter layer. When we count years in an ice core, a light band and a dark band make up 1 year of snowfall (see image below).
• As snow falls, particles from the atmosphere get trapped in the snow. We can use this ash, pollen, and even radioactive atoms to make inferences about what occurred during that year. 
• Air bubbles are trapped in ice core layers. Scientists can melt small layers of ice cores, trap the gas that is released, and measure the gas components to infer what the climate was like the past 800,000 years. Higher levels of greenhouse gases such as carbon dioxide and methane mean the climate was warmer.  
  

Overall the students enjoyed looking at their simulated ice cores and I was glad I got to throw in an extra lab during our geologic time unit. If you are interested in checking out the powerpoint and lab worksheet I used for this lesson, click here. If you would like to look at additional ice core information and dig through real data, check out this site. Have fun!

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!

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!

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:

• Glass slides (gridded slides are ideal) 
• Cover slips
• Compound microscopes
• Petroleum jelly or double sided tape
• Cotton swabs
• Optional lab write up can be found here

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. 
​Enjoy! 

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!