Students will learn to:
Animal and plant species must adapt to live in different conditions. Some animals and plant life are unable to adapt to certain conditions and are, therefore, unable to sustain life in environments with those conditions. For instance, deserts with their harsh heat and dry conditions are not hospitable to penguins, yet the ice cold, humid conditions of the Polar Regions are ideal for penguins.
There are many ecosystems above ground. A cavern system has its own ecosystem that is different from any above ground environment. Because it is sheltered, outside conditions have very little effect on a cavern’s environment. While above ground ecosystems are affected throughout the year by the seasons, most of the time a cavern is not. Therefore, caverns have a unique, constant environment.
In addition to the lack of environmental changes, there are other aspects that effect the living conditions in a cavern system. Because caverns are between the surface and the water table, they are in the direct path of water that filters from the surface down to the water table. Since the water cannot evaporate out of the cavern, it tends to stay humid.
Probably the most prominent feature of a cavern is the darkness. This plays a very important role in the way animals live in caverns and how they adapt to the environment. A cavern system, if large enough, will have three “zones” based on the level of light it receives. The first is called the “Entrance Zone.” This is the area at the immediate cavern opening. Next is the “Twilight Zone,” the area that starts at the end of the entrance zone and goes until all traces of light are gone. The last zone is the “Dark Zone.” This is the rest of the cavern beyond the twilight zone, where no amount of light ever penetrates. Each cavern will have a different distance for each zone, depending on how large the entrance is and the contours of the cavern. Some caverns may not be big enough to have a dark zone.
Different animals live in different areas of the cavern depending on how well they have adapted to the living conditions. Because the entrance zone is so close to the surface, it is effected by the outside elements. Since it gets direct sunlight and rain, both plants and animals can easily live here. This area of the cavern is used mostly for shelter. The twilight zone, which may not get direct sunlight, is less hospitable. It is close enough to the surface that it is still affected by the outside elements, but provides more shelter and a cooler environment than the entrance zone. Some plant life may still grow here. The animals that live in this zone prefer the cooler, moister conditions. Animals that are found in these two zones are not necessarily cavern inhabitants. They are more like visitors who can also live outside the cavern. However, some may choose to live their whole life in a cavern.
The dark zone is the area of the cavern that requires the greatest degree of special adaptation in order to live there. It gets absolutely no light, is not effected by outside elements and has a constant temperature and fairly constant humidity. Through evolution, the animals that live in this area of the cavern have adapted in order to survive. Due to the lack of sunlight, many of these animals have little or no pigment. Many of them also have no eyes or are blind. To make up for the lack of sight, cavern animals have developed other ways to find their way around and to find food. Some have extra long antennae to feel with; others have acute senses of smell and/or hearing.
All of the Sierra Nevada Recreation Corporation caverns go back or down far enough that they have all three zones. The living conditions are similar in each, yet each cavern has some unique qualities.
Boyden Cavern is a horizontal cavern with a large opening allowing easy access. There is a seasonal stream that flows through it which helps keep the environment cool and moist.
Moaning Cavern is a large vertical chamber with two narrow, vertical entrances that make access to the cavern difficult. Water enters the cavern from surface rain but does not collect inside. However, due to the lack of cross-ventilation that horizontal caverns have, Moaning Cavern stays humid year round.
California Cavern is a horizontal cavern with several small, accessible entrances. It is still close to the water table, so it floods every winter. Even during the driest time of year several chambers remain flooded forming underground lakes. The numerous entrances and water create an ideal environment for cavern life.
Pair off students and blindfold one of each pair. Spend at least 15 minutes doing an activity that involves using one of the four senses listed below, then switch. At the end of the experiment, ask the students questions about what they did to show them how their other senses were heightened during the experiment and explain that this is what happens to animals in the dark zone.
Touch – using different objects (feather, pen, etc) touch the student on the arm and have them describe the sensations and try to identify the object
Hearing – with students located in different areas of the class, have each one take a turn creating a day-to-day sound (closing a drawer, zipping a jacket, etc), then have the blindfolded people indicate where the sound is coming from and what it is.
Taste – have small pieces of fruit, bread, candy, etc for blindfolded people to eat and identify. It should be fed to them so they can’t identify it by touch.
Smell – have containers of strong smelling food that are opened one at a time for blindfolded students to identify.
Using the included “Living Conditions” worksheet, list the environmental conditions that effect the living conditions and how animals adapt to each of the ecosystems listed.
Place bowls side-by-side in an area away from direct sunlight. Fill each with the same amount of water using the measuring cup. Make note of the amount of water used. Mark the waterline on each bowl.
Cover one bowl tightly with plastic wrap then using a straight pin, puncture 4 small holes in the top. This bowl will represent the enclosed nature of a cavern. The second, uncovered bowl will represent water on the surface.
Throughout one week, have students observe the bowls and note any changes on the included “Humidity & Evaporation Worksheet.”
On day 5 pour the water from one bowl into the measuring cup and make note of the amount. For added emphasis, students can use measuring spoons of water to add to the water in the cup until it is back to the original amount used, and record how much water they added.
Repeat process with second bowl.
Explain the process of evaporation and why the covered bowl did not evaporate as much as the uncovered bowl. Compare the covered bowl to a cavern environment and the uncovered bowl to the surface environment.
Study research on different animals that have special abilities and why they have them. Example, bat/echo location, cavern cricket/antennae, etc.