|We looked at the air bubbles coming out of this egg when it was placed in vinegar and talked about why the shell is porous. This lets the growing embryo get oxygen. We then talked about how since it is porous it can let things through — like acid (vinegar), acid rain and pollutants. We talked about DDT (how eagles nearly became extinct)– and how poisons, pesticides and so forth can harm the animal populations. We soaked this egg in vinegar for an entire day/night. It was interesting how much the shell changed. In the pictures below you’ll see how much of the brown coloring came off.