Bioluminescence refers to the ability some living organisms, such as protists, bacteria and fireflies, have to emit light. Some species of protists dinoflagelates, such as Pyrocystis fusiformis, are popular in bioluminescent experiments and are commercially available. Grow the dinoflagelates in a clear water container, in an environment with periods of light and darkness. Observe the water container during light and darkness periods and compare the emission of light according to the luminosity of the room. You can also shake the water container to generate pressure on the dinoflagelate's cells and see if this changes their light emission.
Nerve stimulation is closely linked to muscle contraction and movement. You can observe the relation between a nervous stimulus and the contraction of the muscle by gently hitting your knee with your knuckles or a rubber hammer. Cross your leg or sit in a high chair, allowing your leg to hang lose. Gently hit the area around your knee. When you reach the nerve, this is visible through the involuntary movement of your leg upward, as if kicking. This movement is the result of the nervous stimulus you created.
Osmosis refers to the balance of water between the interior of cells and the extracellular environments by diffusion. Although it may sound complicated, it is easy to observe the effects of osmosis in plants. Plant beans or other seeds in three separate pots or buy two small plants to perform your experiment. Prepare a solution with 20 oz. of water and 3 tablespoons of salt to water only one plant. Water the second plant using a solution of 20 oz. of water and 1 tablespoons of salt, and only use water in the third plant. Observe the leaves after a week.
Plants respond to light and gravitational stimuli; these phenomena are called phototropism and geotropism, respectively. Put a plant or seedling in a box, close it and make a small hole on the lid, near a corner. Water regularly and observe the plant growing towards the light source. To observe geotropism, put a seedling in a small pot with big holes underneath. Keep the pot on its side, watering regularly. When growing through the holes, the roots tend to bend downward, due to the attraction of gravity.