Home >> Science & Nature >> Science

How Does a Carbon Cycle Occur Inside a Clear Jar?

Carbon travels through ecosystems in a circular path; this path is called the carbon cycle. You can witness this series of events for yourself by building a miniature ecosystem inside a glass jar or other clear container and thinking about what happens. These kinds of containers are called terrariums if they contain plants only or a vivarium if they also contain animals.

Conditions
- It's important that the jar be clear or transparent, because plants need light to photosynthesize. Without light, they can't fix the carbon in the first place. At the same time, however, the jar should not receive direct sunlight, because this will cause it to heat up, which could kill your plants. (See References 2) It's also important that the soil you add to the jar be moist and have the nutrients they need to grow. Once the plants in your jar are big enough, you could introduce a herbivore like a snail to illustrate the complete carbon cycle.
Cycle
- Once you have the plants and a hungry herbivore in there, a simple cycle occurs inside your jar. The plants take carbon dioxide from the atmosphere and using energy from sunlight turn it into organic compounds like sugars. The snail, meanwhile, eats the plants and thereby obtains both the carbon and the energy it needs to fulfill its own needs. The carbon dioxide from the air inside your jar is following a cyclic path through your miniature ecosystem.
Priestley Experiment
- This kind of experiment may seem very simple, but it was actually central to one of the great discoveries of early science. In 1773, English chemist Joseph Priestley tried burning a candle in a sealed jar to see how it changed the air inside. A mouse placed in the jar afterwards quickly suffocated. A plant placed in the jar, however, lived. When he placed a mouse in the jar with the plant in it, the mouse did not suffocate. He deduced that the burning candle had exhausted the air in the jar in some way, while the plant had somehow "refreshed" it. These experiments later led to the discovery of oxygen and the carbon cycle.
Earth
- Priestley wondered whether plants around the world "refreshed" the air breathed by animals in the same way they did inside his jar. Today, scientists know his guess was correct. The Earth is a little like the plants and the herbivore inside your terrarium; it receives energy from the sun, which the plants use to fix CO2 before they in turn are consumed by the herbivores. In the process, they also release oxygen, the gas that animals like you need to breathe. Your terrarium is a miniature version of the larger cycle taking place all over your planet.

Science