Create your biodome in a plastic container. Layer the bottom with pebbles until they are about half an inch deep. Pour an inch of topsoil on the pebbles and smooth out the surface. Move your finger from one side of the container to the other to make a trench. Plant seeds along the line and cover them with the topsoil. Pour water into the biodome until it begins to show on the pebbles. Place a sealing gallon-sized bag or sheet of plastic wrap on top of the plastic container. The container will run through the water cycle and become self-sustaining. Examine the progress of the seeds through a month's time and record their growth with a ruler.
Experiment with conditions by creating separate biodomes and exposing them to different climates while benefiting the planet by recycling. Cut three empty soda bottles in half. Layer the bottom with pebbles until they can lie flat. Add topsoil and seeds to the pebbles. Pour water into the bottles until the pebbles become saturated. Cover the tops of the bottles with plastic wrap and leave them in three different place. Place one bottle in constant shade, one under a constantly running sunlamp and another in a mixture of the two. Track the progress of the seeds as they grow.
Design a way for humans to live on the moon by creating a biodome that will sustain human life indefinitely. You must account for a food and water source, a way to heat the biodome at night and living quarters for every person on Earth. Draw out your design on graphing paper first. Design living quarters, recreational rooms, growing areas and an infirmary. Once you are finished designing, write up an explanation of what each room's function is and why it has been placed in a certain location. Build a model of your lunar biodome from wood and plastic and bring it into the science fair as a demonstration.
A terrarium is one type of biodome that typically does not support human life but can sustain animals. Create a small biodome in a glass container. Place a layer of stones on the bottom of your glass container before filling it with topsoil. To add a water feature, such as a pond, cut up a soda bottle and place it on the pebbles before surrounding it with topsoil. Plant your seeds in the topsoil and allow them to grow by sealing the container with plastic wrap. Once the science fair is over, add a lizard or turtle to the terrarium and seal the top with wire mesh.