Topics for Experiments in Ecology
Ecology, the study of the relationships between living things and their environments, covers everything from predator-prey dynamics to the biological weathering of rocks by mosses, lichen and plant roots. The science of ecology inspires limitless questions and equally limitless experiments to test those questions. The experiments presented here are just a subset of ways that you can approach ecological investigations.
How Do Plants Affect Erosion?
Erosion is the gradual process of moving soil from one place to another through natural forces, such as the flow of water. The presence of plants, the slope, how densely the soil is packed and how much water falls on the soil can all influence the rate at which soil erodes. Use two test plots to design an experiment to examine the impact of plants on erosion rates. Some questions to get you started: How do you think the plots will differ? What do you know about plants that influences your hypothesis? How will you measure erosion? How will you make sure other variables are constant?
How Does Crowding Impact Population Growth?
Populations grow as long as individuals have enough resources, such as food, water, light and space, to enable them to reproduce. Duckweeds, or lemna, are tiny water plants that can be used to model population growth. Starting with a few lemna, use a large and small container of water to test how crowding affects population growth. Here are some questions to get you started: How do you think the populations will increase initially? At what point do you think the population sizes will begin to vary? How will you count the lemna? How will you make sure other experimental factors are kept constant?
How Does Symbiosis Affect Plant Growth?
Symbiosis is a mutually beneficial relationship between organisms. Many plants have symbiotic relationships with rhizobia bacteria that fix nitrogen from the air for the plant to use. You can buy powder containing these bacteria for garden plants. With a packet of bacteria and a packet of pea seeds from a local greenhouse, design an experiment to test the effects of the symbiotic relationship on the plant. Here are some questions to get you started: What is your hypothesis? How will you make sure the control plants don’t have any bacteria in their soil? How will you measure growth? How will you make sure all plants in your experiment have the same environmental conditions aside from the variable you are testing?
How Has Human Demography Changed Over the Last Century?
Of course, ecology can also be studied using non-experimental investigation. Demography is the study of the structure of a population, including birth and death rates, population growth and the number of individuals in each age group. A great place to study human demography is a cemetery. Using grave markers, examine how human longevity has changed over the life of the cemetery by comparing the ages of the deceased at death with the years they were born. Some questions to get you started: How do you think longevity has changed? What factors might have influenced demography over the life of the cemetery? How do you think the cemetery you selected might differ from other cemeteries?
Based in Wenatchee, Wash., Andrea Becker specializes in biology, ecology and environmental sciences. She has written peer-reviewed articles in the "Journal of Wildlife Management," policy documents,and educational materials. She holds a Master of Science in wildlife management from Iowa State University. She was once charged by a grizzly bear while on the job.