Introduction: Breathing Through Their Skin/ Amphibians As Pollution Indicators
Have you ever wonder why amphibians like frogs and salamanders are so slimy? They need that slime to help them get oxygen! Amphibians not only breathe in oxygen using lungs, like we do, but they also “breathe” through their skin!
Cutaneous Respiration: form of respiration in which gas exchange occurs across the skin rather than gills or lungs
Diffusion: the net movement of something from a region of higher concentration to a region of lower concentration
Permeable: having pores or openings that permit liquids or gases to pass through
Vertebrate: Any animal that has a backbone or spinal column. Some vertebrates include mammals, birds, reptiles, amphibians, and fishes.
Carefully, and with adult supervision, you will poke holes in a water bottle with a thumb tack or similar item. Also, we are using pepper so avoid inhaling and sneezing!
· Two containers for water (we use foil roasting pans)
· Two "prepared" plastic water bottles that have tiny holes poked all around the bottle with a push pin tack
· Black, ground pepper
Step 1: Fill Each Container With Water
Place about two inches of clean water in both of the foil pans. Make sure one of the pans of water remains clean. In the other pan shake 1 teaspoon of pepper over the surface of the water and stir.
Step 2: Dip a Prepared Bottle Into Each Pan.
Dip one prepared water bottle in the clean water and hold for about 30 seconds. Dip the second prepared water bottle in the pepper “polluted” water and hold for about 30 seconds.
Step 3: Examine the Bottle That Was in the Clean Water.
Take the water bottle out of the clean water. Observe how the water seeped in through the tiny holes. This is similar to what happens with amphibians through their skin. They are actually exchanging oxygen for carbon dioxide through the skin by diffusion.
Step 4: Examine the Bottle From the Peppered (polluted) Water.
Take the water bottle out of the peppered “polluted” water. Observe. Both the water and pepper have diffused into the bottle through the tiny holes. This is similar to when water has been polluted. The pollutants are also small enough to enter the amphibians’ permeable skin.
Step 5: Connection to the Science
Amphibians have unique skin compared to that of many other vertebrate animals. An amphibian’s skin is thinner, which allows for higher levels of oxygen exchange with the blood vessels that are close to the surface of the skin. This permeable skin distinguishes them from birds, mammals and reptiles – and it is one of the characteristics that has contributed to their declining populations and extinctions.
Many amphibians also use their permeable skin to help them breathe. Oxygen is a small molecule that can easily pass through the skin of an amphibian. The oxygen first dissolves into the liquid on the surface of the animal’s skin, then it is picked up by blood that is in vessels close to the surface of the skin.
Questions to think about:
1. What layer of covering do humans have that would compare to an amphibians skin?
ANSWER- The epithelial lining in human lungs forms alveoli that carry out respiration by diffusing oxygen and carbon dioxide for humans. This respiration is done only with gases, NEVER fluids.
2. Why are amphibians sometimes referred to as an "indicator species"
ANSWER- As you observed in the experiment amphibians absorb many substances from the environment through any contact with their skin. This easy absorption makes them very susceptible to pollution that once in their bodies makes them sick. If a scientist observes that many amphibians are sick or absent, it "indicates" that the environment is not healthy for organisms.
3. To help an amphibians carry out better respiration would you place them in high or low oxygen concentrated water?
ANSWER- Diffusion works as a concentration gradient. Which means, it spreads out from an area of high concentration to an area of low concentration. By placing an amphibian in water with a higher oxygen concentration it would allow them to "breath" easier.