It's February ... And That Means Daphnia Love is in the Air!

This is the PERFECT lab for a high school biology class on Valentine's Day!

I soooo look forward to this lab each and every year.  Measuring the heart rate in Daphnia is FUN, is fairly easy to do, allows our biology students to work with living organisms in the lab, and perhaps most importantly, it provides an outstanding situation for having our students design and implement their own experiment.

Are you nervous about "student-designed experiments"?  Don't be!  If properly trained and instructed on the front end, the students will surprise you with their creativity and passion for designing an experiment.  But I am getting ahead of myself.  Let me go back to the beginning....

Daphnia are tiny crustaceans, closely related to a shrimp. They are often called "water fleas." They are small, but not microscopic.  They can be seen with the naked eye, but you will need a dissecting microscope to view the beating heart. Daphnia can be purchased from any of the companies that sell lab supplies and equipment. Since Daphnia are arthropods, they demonstrate the three major arthropod characteristics: exoskeleton, jointed appendages, and segmented body. The exoskeleton is clear, allowing the student to easily view the heart. Daphnia are ectotherms and their body temperature changes with the surrounding environment.  This further means that there is a direct relationship between the internal body activities and the external temperature of the water in which it lives.

This sets the stage for the first part of our experiment.  I have my students carry out an experiment where they measure the change in heart rate when Daphnia are exposed to different temperatures.  I provide the procedure, and the student simply follows the instructions and carries out the lab.  The Daphnia are exposed to three different temperatures, and the student counts the number of heart beat per minute in each environmental condition.

Students carry out my procedure, graph their results, and answer my questions.  On Day 2, the fun begins!  It is time for the students to design their own experiment!  They are asked to design an experiment to test the effect of caffeine on the heart rate of Daphnia.  The students must state a hypothesis, describe their experimental and control groups, carry out the experiment, collect their data, graph their data, and come to a conclusion based on their data. 

The student-designed experiment will take some time.  I require my students to write their experiment and submit it to me for approval before they begin. Once approved, they carry out their experiment and write a formal lab report. The best learning occurs as the student is carrying out their experiment.  They invariably realize that their procedure is flawed, and they must revise, revise, and revise until they get it right.

For my honors and AP students I require that they also complete a worksheet on how to calculate the Q10 temperature coefficient.

And this is what we do to celebrate Valentine's Day in my biology classroom.  Happy Valentine's Day everyone!

In my TpT Store: "Measuring the Heart Rate of Daphnia" contains handouts for all parts of this experiment, including the student designed experiment and the Q10 worksheet.  Teacher Guide included. 

How to Teach Your Students to Design an Experiment

It is time-consuming and exhausting, but well worth the effort!

The bottom line here is that students must learn to write and carry out an experiment of their own design. Major problem: A truly well designed experiment takes time. It takes time for the teacher to teach the student "HOW" to design the experiment, it takes a lot of time for the student to actually design the experiment, and then it takes more time for the student to carry out the experiment.

I think this is an important skill and well worth the effort.  But if you decide to go this route with your students, be prepared for the fact that it will take much preparation and teaching on your part.

Okay, so where do you start?  The first step is to make sure that the student is well-grounded in the scientific method.  This means the student has to be able to do more than write down the steps to the scientific method.  They have to be able to APPLY the scientific method to a problem or a question.

I can help with that. I have a PowerPoint, complete with notes for the teacher and the student, that teaches the application of the scientific method. Click this link:  Scientific Method PowerPoint and Notes.

The next step is to have the students practice writing a lab procedure. I love this activity:  Give the students some building materials. They can be old legos, tinker toys, paper clips, styrofoam peanuts. Any type of items will do. Each student takes their building materials and builds some sort of structure or device. They then have to describe, in writing, how to build their device. The students swap written descriptions and try to build their lab partners device from the written description.  Click this link: Can You Write A Lab Procedure.

Now it is time for the student to design their own experiment from beginning to end.  Start with something simple....something VERY simple. For our first effort, I had my students design an experiment to test the effect of different quantities of water on the germination of radish seeds. Simple , right?  It turned out to be such a great idea!  There are limited options for the students and no advanced knowledge about the topic was needed. 

Radishes were a great choice!  They germinated within 24 hours, and I allowed my students to observe their germination rate every day for three days.  I had my students complete a lab report in which they had to design and complete the following:

• State a hypothesis that is testable.
• Write out detailed steps to their procedure.
• Determine the independent and the dependent variables.
• Include a description of their control and how it served as a control.
• Include a description of their experimental groups.
• Identify factors that must remain constant throughout the experiment.
• Design a data table.
• Graph their germination rates.
• Form a conclusion based on the data gathered.

Below are a few pictures that I took during the lab activity:

Our science students need to develop this skill.  Take the time in your class to teach experimental design.  It is well worth the effort!

Here are the links to the radish seed experiment as well as a few other labs I do in which the student must design their own experiment.

The Student Designed Lab

Measuring the Heart Rate in Daphnia: A Student Designed Lab

Making Coacervates: A Student Designed Lab

Our First Experience With the Student-Designed Lab

Did you read my blog post from two days ago? In case you did not, here is a quick update:  I am trying to change the focus of my high school biology classes by incorporating more student-designed lab activities.  The previous post was about getting my students ready for their first attempt.

Well, today we have completed our first lab in which the student designed the lab from top to bottom.  I am happy to report that I am quite pleased with the results!!

For our first attempt, I gave the students a very, very, very simple idea to work with.  After all, the point of this lab is to learn how to design and carry out an experiment.  I asked my students to design an experiment that would test the effectiveness of different quantities of water on the germination of seeds.  Simple , right?  It turned out to be such a great idea!  There are limited options for the students and no advanced knowledge about the topic was needed.  The students only had these materials to work with:  Petri dishes, filter paper, radish seeds and a graduated cylinder.  Initially I did not include the filter paper, but we quickly realized that a small quantity of water would "pool " together in the plastic Petri dish, and we needed the water to spread out across the entire surface.  Students were instructed that if they lined the dish with a piece of filter paper, the water would evenly spread across the surface.

Radishes were a great choice!  They germinated within 24 hours, and I allowed my students to observe their germination rate every day for three days.  I had my students complete a lab report in which they had to design and complete the following:

• State a hypothesis that is testable.
• Write out detailed steps to their procedure.
• Determine the independent and the dependent variables.
• Include a description of their control and how it served as a control.
• Include a description of their experimental groups.
• Identify factors that must remain constant throughout the experiment.
• Design a data table.
• Graph their germination rates.
• Form a conclusion based on the data gathered.

Below are a few pictures that I took during the lab activity:

The first dish on the left served as a control since these seeds received no water.  The other three dishes received varying amounts of water.

Some students elected to keep their dishes in front of the window....

.....while others elected to keep their dishes under a plant growth light that remained on 24 hours a day.  Other students placed their dishes in complete darkness.  

Light level was not a variable being tested.  Whichever light level the student picked, had to remain constant throughout the experiment.  The variable being tested was the amount of water placed in each dish.  

The only problem with this experiment was that some students had difficult reaching a conclusion.  They found that there was not that much difference between germination rates of radish seeds when given varying quantities of water.  

All in all, our first attempt at the "student-designed lab" when extremely well.  Most of the anxiety I have about allowing students to design the experiment is now gone, and I am very much looking forward to our next attempt!

Have fun teaching~

Science Skills Lab:  Let the Student Design the Experiment

Let the Student Design their Own Experiment

Can we teach our science students how to be successful conducting open-ended labs?

As teachers, we can teach the steps of the scientific method until we are blue in the face.  Many times, all we succeed in doing is having the students memorize the 6 steps to the scientific method and then repeat them on a test.  Too often science teachers conduct laboratory activities in which students follow a list of steps and record an observation at the end.  I need to be one of the first in line to say "Guilty!".  

Today's science educators are pressured to have successful end of course scores.  Sadly, a student can often perform well on these standardized tests without every doing any "real" laboratory work.  One of my goals this year is to change the focus of my class.  I am going to devote the time it takes to allow my students to write and carry out open ended lab experiments.

I have been back in school with my students for one week now.  I have covered the scientific method and gone into great detail on how to design an experiment.  We have mastered (I think!) how to define the experimental group and the control group.  My students can identify the independent and dependent variables.  They understand that only one variable can be changed at a time, and that all other variables must remain constant.  They can write a hypothesis and a conclusion.  We are just about ready to put all we have learned into practice.

I have written a PowerPoint that my students responded to extremely well.  It covers the scientific method with slides that are bright and colorful and visually attractive.  You can download this from my store, Amy Brown Science,  on TeachersPayTeachers.com.  It comes with a set of notes for the teacher and a notes outline for the student.  The student fills in the notes as the lesson is being taught.  I feel that this PowerPoint goes beyond just listing the steps to the scientific method.  Students are given practice problems in which they have to apply what they have learned.  Here is the link to my PowerPoint and notes:  Scientific Method PowerPoint with Notes for Teacher and Student.

You might also want to consider:
Scientific Method Homework
Applying the Scientific Method and Scientific Writing

Coming up this week.... I am taking my students to the lab to conduct their first open ended experiment.  It is going to involve the germination of seeds.  It will be a simple idea and will use only simple supplies.  Perhaps it may end up being more of a "guided" inquiry, but we have to start somewhere, right?  Later this week, I will post about how this goes and have some pictures as well.

Have fun teaching!

Measuring Heart Rate in Daphnia

Watch Their Hearts Beat: A Daphnia Lab That Brings Biology to Life

An Unexpected Star in the Biology Lab:  Need a classroom lab that’s easy to set up, exciting to run, and packed with teachable moments? Meet Daphnia—a tiny aquatic crustacean with a see-through body and a heart you can actually see beating under a microscope. It’s weird. It’s wonderful. And it’s the perfect hook for teaching circulatory systems, environmental effects on physiology, and graphing real data.

This Daphnia heart rate lab checks all the boxes for a super-engaging, low-prep biology investigation. Students get hands-on experience with live organisms, observe real-time physiological changes, and collect data that sparks discussion and curiosity. This lab encourages deeper thinking, reinforces graphing skills, teaches the scientific method and experimental design, and turns abstract textbook concepts into visual, measurable experiences.

What Students Discover: When Daphnia are placed in environments of varying temperatures, their heart rates respond—dramatically. Students watch as these tiny creatures go from chilled-out to heart-racing, helping them understand the link between metabolism and temperature in ectothermic animals. 

Even better? Students can extend the lab activity by designing their own experiment to test a different variable —testing how caffeine, pollutants, or pH levels influence heart rate. Honors and AP students can take it further by calculating Q₁₀ temperature coefficients, analyzing their results like real researchers.

Please note: Teach students to respect all living organisms. No harm should come to the Daphnia in this experiment.

This isn’t just a fluff activity. The Daphnia heart rate lab builds core science skills:

• Graphing and analyzing data
• Comparing variables and controls
• Designing and running investigations
• Problem solving and critical thinking

It also supports NGSS and AP Biology objectives, from cellular processes to environmental impacts on organisms.

The biggest problem with this lab is helping students find the heart. The digestive system of Daphnia is quite active, and the students often think that the moving digestive system is the heart. The heart is located just behind the head on the dorsal surface of the body.  It will appear as a very small, clear and transparent, beating sack.

Classroom-Ready, Teacher-Approved: Looking for something that won’t eat up your prep time? This Daphnia heart rate resource comes with the following.

• Clear student worksheets
• Ready-to-go graphing templates
• Background reading for context
• Optional extensions for advanced learners
• A teacher guide to make implementation a breeze

Ready to Try It?

This lab isn't just about watching hearts beat—it’s about getting your students excited to learn. Whether you're teaching standard biology, honors, or AP, this investigation delivers science that sticks.

👉  Click here: Measuring the Heart Rate in Daphnia

The benefits of this lab? 

• Labs keep the student excited and interested in science.  
• If the student views your class as "fun", they are more likely to perform well in the parts of the class that are less fun.....think lecture days.
• Working with living organisms is a fundamental part of a biology class and should be included at every opportunity.
• Students gain an appreciation for the living world when they get to view organisms that they are unlikely to see or notice in nature.

What do you do with the Daphnia when the lab is over?  Well, our Daphnia will spend the remainder of their days in my Elodea tank!

Science Skills: Applying the Scientific Method

Teaching the “skills of science” is of the utmost importance.   I cannot stress this enough!  Yes, the "content of science" is important, but the content cannot be taught to our students until the skills are taught to our students. Scientific method, metric measurement, scientific notation, prefixes and suffixes, significant figures, compare/contrast, problem solving, critical thinking, dimensional analysis, proper use of lab equipment, scientific writing ... these are the skills I am referring to.  If the skills are taught properly at the beginning of the school year, your students will be equipped with the tools they need to be successful for the rest of the year.  Science is more than the memorization of a long list of facts.  Science is problem solving, analyzing, predicting and experimenting.  Make the teaching of basic science skills a priority in your class.

In a previous article, I talked about the importance of graphing skills.  Today, I want to talk about the importance of being able to apply the scientific method.  The key word here is...... apply.  You may be thinking, "I teach the scientific method every year during the first week of school."  Many teachers have their students write down the 5 or 6 steps to scientific method, define some keywords such as hypothesis, variable, and theory, re-state the 6 steps on a test, and .... DONE!  Time to move on to the next topic.  

We can do better than that.  Teaching our students how to apply the steps of the scientific method is not easy, and it takes up quite a bit of valuable class time.  We have to create lessons that teach the application of the scientific method, not lessons that teach the memorization of the scientific method.  

At the beginning of the school year we should give assignments that:

• Reinforce graphing skills.
• Teach students to interpret and analyze graphs.
• Provide writing prompts to teach students how to design a controlled experiment.
• Teach students to identify the independent and dependent variables in an experiment.
• Teach students how to apply the scientific method to a particular scenario.
• Give students practice in scientific writing.

Please get away from using only multiple choice, true and false, and matching questions.  I try as much as possible to have my students WRITE.  It is very time consuming to grade, but when students are asked "to design an experiment to show..." , you are teaching so many of the above skills.  And you are not just teaching the scientific method.  You are reinforcing critical thinking, problem solving, and best of all, good writing skills.

If you are just beginning to develop lessons on the scientific method, try my Scientific Method PowerPoint.  This is a 26 slide PowerPoint presentation on the nature of science and the scientific method.  The slides are colorful and visually appealing.  Steps of the scientific method are covered, but more importantly, the lesson provides examples and practice problems illustrating the application of the scientific method.  Analysis questions and answers are included.  The download also includes 4 pages of notes for the teacher and a 5 page outline of the notes for the student.  

Now take your students to the lab and see how well they can apply what they have learned about the scientific method.  My "Can Your Students Write a Clear and Concise Procedure" is a great introduction into scientific writing. It's a fun activity that reveals to students the importance of accuracy and details when writing in science.  

Now you are ready to teaching students how to design and carry out a controlled experiment.  Start with this classroom activity (Applying the Scientific Method and Scientific Writing) involving hypothetical situations.  

Forge ahead with a student-designed lab activity:  The Scientific Method Lab. Students will plan and carryout the entire process from start to finish.  Full disclosure ... This takes time and quite a bit of patience, but it is worth it.  Your students will hone their problem solving and critical thinking skills as they complete these activities.