Closed ecosystems, as used by scientists for the exploration of self-sustaining communities, can be a good topic for experiments in ecology. One experiment can include placing various biological matter, including soil, plant material and water, into a bottle together with a thermometer. Seal the bottle and place it somewhere with an indirect light source. The class can document the daily changes in the bottle. In other experiments, you can build a small pond in the garden and watch the wildlife it attracts, or produce an closed ecosystem in an aquarium.
Although alternative energy sources are a wide-spread ecological topic, few people know how energy can be extracted from the sun, wind or water. Easy experiments that give a picture on the powers embedded in natural sources can include the building of a water-powered turbine with the help of a milk carton. Punch a hole in each corner of the milk carton, go outside and hang the milk carton on the washing line or a low branch of a tree. Cover each hole with masking tape and fill the carton with water. Remove the masking tape and see how the milk carton transforms into a turning turbine. In another experiment, you can connect a small solar panel to the circuit of a radio and see how much sun is needed to make the radio work, or attach a fan to a hobby motor and create a wind energy generator.
Pollution is a serious ecological issue and checking on pollution in the local area can bring the issue closer to home. Simple experiments can give an easy overview over types of pollution in everyday life. Smear petroleum jelly on index cards, leave them on various locations for 12 to 24 hours and see what got stuck in the jelly. Compare samples from road sides, your garden and a nature area. Other experiments can include collecting water from ponds, puddles or the tap and investigate their pH value with the help of pH paper strips. Test the effect various pH levels have by placing the flowers in pure water, and in acidic and alkaline solutions.
Soil is an easy-to-find ingredient that can be used in a variety of ecological experiments. You can collect soil from various places, including road sides, your garden and an area away from traffic. Place each sample in one pot together with one sunflower seed and label the pots with the locations. Compare the speed of growth of each plant by measuring the individual progress with a tape. Other experiments can include erosion tests where you make mounts with various types of earth matter, including soil, sand, clay and gravel and water it with a hose. Investigate which mounts slide the most, and try out combinations of various matters to find the most, and least erosion-prone dirt.