Leaf Pigment Chromatography

Leaf pigment chromatography is a classic paper chromatography experiment that allows students to separate and observe the different pigments found in plant leaves. In this leaf pigment chromatography lab, students use chromatography paper and a solvent to see how pigments such as chlorophyll and carotenoids move at different rates, creating distinct bands of color. This chromatography experiment provides a visual and hands-on way for students to connect molecular properties to key biological concepts, including photosynthesis and plant structure.

This paper chromatography lab is especially effective in high school biology classes because it reinforces both content knowledge and essential lab skills. As students analyze the separation of leaf pigments, they practice careful observation, data analysis, and experimental design while gaining a deeper understanding of how plants capture and use light energy. Leaf pigment chromatography is a low-prep, high-impact lab that fits naturally into units on photosynthesis, plant biology, and scientific investigation. 

Check out this blog post on Paper Chromatography for additional photos and information.

Leaf Pigment Chromatography Experiment

Here are photos that I took as my students were working on their lab.

Spinach leaves are placed in a mortar and pestle along with a little acetone.  Students grind the leaves until the acetone turns a dark green.  A small piece of capillary tubing is used to transfer drops of the pigment extract to a piece of chromatography paper.

When enough drops have been placed on the chromatography paper to make a dark green circle on the paper, it is ready to be placed into a large 25x200 test tube.

Leaf Pigment Chromatography Diagram

The large test tube has about 1/2 inch of petroleum ether in the bottom of the tube.  The pigments will immediately begin to separate.

Here is the finished chromatogram:

Pigment Chromatography FAQ's:

What pigments can be seen in leaf chromatography?
Plants contain multiple pigments such as chlorophyll, carotenoids, and sometimes anthocyanins. These pigments separate based on their chemical properties when the solvent moves up the paper. 

Why do pigments appear in different bands?
Pigments travel different distances during chromatography due to differences in solubility and how strongly they bind to the chromatography paper. 

Can this experiment predict fall leaf colors?
Leaf chromatography can reveal hidden pigments, which often correspond to colors visible during autumn. 

Here is the lab that I use with my students:

Click image to view in my TpT store.

AP Biology Exam: Teacher In Panic, Students Oblivious

<-------- The teacher feels 

      like this.....

.....and the students feel 

like this!  ----->

Sound familiar?

It is the time of the year when the AP Biology teacher (me) begins to panic.  There are only "x" number of teaching days left, and there is still "y" amount of material that must be covered!  PANIC!

Actually, my students are great.  But it is getting on toward spring time in my part of the country.  The students are tired....very tired!  They have worked hard all year, participated in a ton of extracurricular activities, and they are just worn out!!

It is a difficult time of the year to be sure.  I must continue to teach hard everyday to get all of the material covered.  At the same time, I need to get my students motivated for reviewing for the exam.  It is a fine line to balance.  Push them hard, but don't overload them.

I am fortunate to have a 70 minute class period. (Don't kill me....I realize how lucky I am!!)  Starting this week, we are going to spend the first 15 to 20 minutes of each class period reviewing.  I have written a set of review PowerPoints to use just for this purpose.  These are not teaching PowerPoints.  They are simply slide after slide of questions and answers.  I generally let the students get into groups and make a game out of it.  The group getting the most questions correct wins a prize.  Little Debbie Snake Cakes are a particular favorite award for my students.

Freebie:  Here is the link to one of my review PowerPoints that I have in my TpT store.  It is on organic compounds.  You can easily delete some of my slides and add more slides of your own.

Click picture to download.

If you like the free PowerPoint, you might be interested in my entire set of 25 different review PowerPoints.

Best of luck to you and your students on the AP exam!!  :)

Daphnia, Daphnia, How do I Love Thee?

Let Me Count The Ways (of Measuring Your Heart Rate!)

Valentine's Day does not have to go unnoticed in our high school biology classes!  We might not discuss the emotional affairs of the heart, but we can definitely discuss the physiology of the heart!

Each year, during the week of Valentine's Day, I take my biology students to the lab to measure the heart rate in the crustacean, Daphnia.  Since Daphnia is an ectotherm, its heart rate will vary with changes in its body temperature.  (I also pass out a few Dove chocolate hearts along with the lab supplies!)

First we place the Daphnia into a small, water-filled chamber like the one seen in this photo.  A few strands of cotton fibers placed in the chamber helps to restrain the Daphnia while viewing!

A Petri dish is filled with ice water, and the Daphnia viewing chamber is placed on top of this ice water to cool the internal body temperature of the Daphnia.  After a minute or two, the Daphnia is placed under a dissecting microscope, and the fun begins!

Some students have difficulty at first, finding the heart.  Since the exoskeleton of Daphnia is clear, the heart is easily seen.  Once the students find the heart, they are ready to start counting the number of heart beats per minute.

After repeating three trials at the ice water temperature, students fill the Petri dish with water that is at room temperature and repeat.  Finally the students fill the Petri dish with warm water to finish the experiment.  The data from the experiment is fairly consistent from year to year, and students can quickly conclude that the heart rate of Daphnia speeds up as the temperature increases.

My favorite part of the experiment comes on the next day!  On day 2 of this lab, I have my students design their own experiment.   They are asked to design an experiment to test the effect of caffeine and alcohol 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.

For my honors level and AP Biology students, I have them complete this worksheet to determine the Q10 Temperature Coefficient.

This lab, along with all of the worksheets and a teacher guide, has recently been added to my TpT store.  You can view it here:

Measuring the Heart Rate in Daphnia

Biology Careers Mini Posters - A Freebie!

What can you do as a career if you love Biology?

The answer is "Lots and lots of things!!"  Career week is a really big event at my high school.  I was asked to put together a display illustrating some of the many careers that are possible in the field of biology, so I  made a set of 26 mini-posters.  Each poster highlights one career.  There is a picture of a person "doing the career" as well as a very brief description of the career.

I am sharing these as a free download in my TpT store.  

Click on this link ---> Biology Career Posters <--- to download these for free.

These will make a great display in your classroom!

Give the Kids a Brain-Break!

<-----  What I DON"T want to see in my class!

Over the years of teaching I have come to realize that some topics are very difficult for my students.  I find that the students learn and perform much better if I teach in spurts.  I teach a new concept for 15-20 minutes, and then I give my students a "brain-break".  What is a "brain- break"?  I am glad you asked!!

A "brain-break" is a 2 or 3 minute break away from the topic currently being taught.  It is a couple of minutes where the student can relax, and it relieves the tension of a very complex lesson.  I am still a teacher who wants every minute to count.  So during a "brain-break" I usually throw out a bit of science trivia.  These are just fun and interesting facts that teach the student about the amazing natural world we live in.  Over the last few months my "brain-breaks" have consisted of the Mother Nature Awards for Planet Earth.

Here is an example:

These are PowerPoint slides.  I insert one of these slides into a PowerPoint on cellular respiration or photosynthesis or enzyme-catalyzed reactions.  My students have come to expect these little surprises and they get so excited when one of these pops up into my otherwise overly technical lecture.  This is fun, it teaches a bit about the wonders of nature, and best of all, it gives the student just a minute to relax and get focused again before I launch back into the real topic of the day.

After a slide has been viewed, I print it, laminate it, and place it on the wall in my classroom.  I have been very pleasantly surprised at how often students stop by the wall to look at the Mother Nature Awards.

I have put together a group of 20 of these awards and placed them in my store on TeachersPayTeachers.com.  There are two product listings, one for Grades 2-5 and a separate listing for grades 6-12.

The listing for grades 2-5 comes with a set of activity worksheets (42 pages) for the students to complete as the PowerPoint slide is being viewed.  The finished worksheets can be put together to make a great Mother Nature Award book.

The listing for grades 6-12 comes with a worksheet for students to conduct their own research to develop a PowerPoint slide for a Mother Nature Award of their own choosing.  This makes a nice homework assignment for a grade, or for a great extra credit opportunity.

Don't forget that Earth Day is coming up soon.  The Mother Nature Awards are a perfect Earth Day activity.

Have fun teaching!

My Favorite New Toy!

I have a confession to make......

......when I use a PowerPoint presentation in my classroom, I love to use a lot of animations.....

Okay, I have said it!

I recently got a feedback from one of my buyers suggesting that I remove all of the animations from my PowerPoint presentations.  He wanted all the items on a slide to be visible at one time.  But I couldn't disagree more!  I only want my students to see what I want them to see at any given point in my lesson.  I do not include a lot of moving parts (as you see here), but I do limit the amount of information the student can see.  As I am teaching, I want the student to focus ONLY on what I am currently teaching.  When it is time to move one, then a few clicks gets the students to the next point in my lesson.  This prevents the student from simply copying from the PowerPoint without listening to the explanation.  If the student can only see one sentence at a time, then that is all they can copy!  I get to determine when they should write more information in their notes.

So, now I am getting to the point of this blog post.  I, too, was a prisoner to my computer.  I like to walk around and pace while I am teaching.  This is hard to do if you have to constantly click from your computer keyboard to get to the next PowerPoint slide.

The solution?  Buy a clicker!  I recently bought the  

"Kensington 33374 Wireless Presenter with Laser Pointer" to use with my computer.  It has changed my life!  I cannot say enough good things about this product!  It is so simple to use.  Simply insert the receiver into a USB port on your computer and you are ready to go.  Not only can you click through your PowerPoint with ease, but it also has a laser pointer that can be used to direct your student's attention to a particular part of a slide.  The receiver is inserted at the base of the unit for easy storage.

The cost was around $40, but it may be the best money I have ever spent.

Can I Make Protists More Interesting For My Students?

When a biology teacher says to the class, "Today we are going to start our unit on the algae, followed by a unit on the protozoa,"  the collective groan from the class can be deafening.  Nothing can be worse to a high school kid than studying algae!  Well..... maybe studying the fungi is worse, but not by much!  

My solution?  Excitement!!  I must be a real science nerd, but I really, really like teaching this topic.  And when I get excited, my students (mostly) get excited, too.

The Protista Kingdom contains all organisms that cannot be classified as fungi, true plants or animals.  The range and variety of organisms in this kingdom is huge!  Some protists  are more closely related to plants, fungi, or animals than they are to other protists.  Biologists cannot agree on how to classify these organisms, and some scientists have now split the Protista Kingdom into as many as 20 different kingdoms.  The term "protist" is still used as a convenient way to refer to eukaryotes that are neither plants, animals, or fungi.

This school year, I wanted to give my unit on protists a little extra punch.  I wanted to make it as visual as possible, so I put together a brand new PowerPoint presentation that covers both the algae and the protozoans.  Wow!  It ended up being 99 slides long with handouts for my students of 19 pages.  I did break this up into two units of study, though.  I first covered the algae and gave a unit test on just algae, followed by a unit on protozoans.  

I packed the PowerPoint with color and as many cool photographs as possible.  

Once taught, this is material that needs reinforcement if I expect my students to remember it on test day.  I made a second PowerPoint that is just slide after slide of review questions.  My high school students like review games, so I put them into small groups and made a contest of it.  I would project a question and each group would take a turn at the answer until the question had been answered correctly.  I kept score and awarded a box of Little Debbie Santa Claus Brownies to the winning group.

And finally, we finished it all up with a lab on the living protists.  My students love to watch anything that moves under a microscope.  I purchased a culture of Paramecium, Euglena, Amoeba, Diatoms, Spirogyra, Volvox, and Stentor (my personal favorite!) Oddly enough, my students really enjoyed a mixed culture of 6 algae that came with a dichotomous key.  They had to find the 6 different algae in the culture and name them using dichotomous classification key.

All in all, the unit on Protists was not as bad as it seemed at first.  Most students escaped unharmed.

Kingdom Protista PowerPoint With Notes for Teacher and Student

Kingdom Protista Review PowerPoint

Lab:  The Living Protists