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!
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!
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. 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.
3. 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.
4. 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.
5. Crash Course Video- If you are a veteran science teacher, chances are you have come across the Crash Course videos. Here is a link to one on the phosphorus and nitrogen cycles. 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.
6. 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. Here is a sample diagram:
7. Biogeochemical Cycles Review Worksheets- Lastly, 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:
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!
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!
I like to use a lot of video clips in my lessons. Video clips keep students engaged and it breaks up the monotony of the notes. After lots of searching on the internet for good videos for my symbiosis lesson, I've found some real winners! Your students will love these videos!
MUTUALISM- (Good for me, good for you) This video clip is from the 1974 Disney movie "Animals are Beautiful People." Don't let the year deter you, it's an oldie but a goodie. This video clip shows a guide bird helping a honey badger find food. Check it out here: www.youtube.com/watch?v=_88SRgOGnVQ
COMMENSALISM- (Good for me, doesn't bother you) This video clip shows beetles falling into the opening of an elephant foot yam plant. The beetles act as pollinators for the plant, and aren't helped or harmed during the process. Check it out here: www.youtube.com/watch?v=hnbiLvzc13g
PARASITISM- (Good for me, harms you) This video clip shows a freshly hatched cuckoo bird in a warbler nest. The cuckoo bird pushes the warbler eggs out of the nest in order to receive all the food and care from the warbler parents. This is also a great time to introduce innate vs. learned behaviors. Check it out here: www.youtube.com/watch?v=YFtY5D_nYW0
I also like this video that goes over all three types of symbiosis. It is a great follow up video for the following day to help refresh student's memory of what they learned. Check it out here: www.youtube.com/watch?v=zSmL2F1t81Q
Want some fun symbiosis posters to hang up in your classroom? --> Take a peek here! <--
Becca of Science Rocks
Hi, I'm Becca! I've been teaching science for 10 years at both the middle and high school levels.