Teaching in Action: AP Bio with Mr. Markham


Xavier is proud of our world-class faculty and the rigorous curriculum they provide our students. Throughout this year we’ll be highlighting some of the insightful work from our leaders in the classroom.

At Xavier, we place a premium on teaching and learning.

Here is a quick glance at a recent lab from Mr. Markham’s AP Bio class on diffusion and osmosis. You may be wondering what sets Xavier High School apart from other schools when it comes to science education. The answer is simple: our commitment to hands-on learning.

On this rainy afternoon in room SJ3, students created model "cells" out of dialysis tubing and filled them with sugar, salt, or protein solutions. Dialysis tubing is made of material that allows water to pass through but prevents larger molecules from doing the same.

Their models were then submerged in different solutions of sugar, salt, or protein, and they calculated how much mass their model cells gained or lost due to osmosis - the flow of water from where it is to where it is not. Real cells don't like to gain or lose too much water, so this reinforces the idea that the cells within us must work to remain in the "Goldilocks zone."

If you guessed that the Goldilocks zone has something to do with the famous children’s story, you’re on the right track. The Goldilocks zone, or habitable zone, is the range of environmental tolerance in which a cell can survive. No cell wants to be too hot or too cold, nor do they want to take on too much or too little water.

As another experience during the lab, the students also viewed thin sections of an onion under a microscope before and after the addition of salt water.

Before, the onion cells appeared healthy, but after exposure to salt, the cells appeared plasmolyzed or shrunken because of water loss from osmosis. This reinforces the idea that water generally flows toward salt, so it left the onion cells causing them to shrink.

Mr. Markham's teaching philosophy, like many members of the Xavier faculty, is all about challenging and provoking students to think critically and creatively. He believes that true learning happens when students are actively engaged in the material, rather than just passively absorbing information. This is why his classes, and all of our science classes, are full of hands-on experiments and exercises that allow students to explore scientific concepts in a tangible way.

Watching the students work was truly a sight to behold. They were all fully engaged in the process, carefully measuring and recording their observations, and excitedly discussing their findings with each other. Mr. Markham circulated around the room, offering guidance and encouragement, but letting the students take the lead in their own learning.

Xavier, We’re Something More!