|March 4-11, 2002|
Ten years ago there were approximately 750,000 named insect species. Today, that number is over 1,000,000. And according to a recent article in Scientific American, entomologists estimate that there are likely over eight million different species of insects on Earth. When you compare that to 4,650 named and 4,809 estimated mammal species or the 72,000 named and 1,500,000 estimated fungi, it is easy to see that insects "out-populate" any other living taxonomic group on Earth.
Insects can be found in every environment on our planet. While a select few insects, such as the Arctic wooly bear, are able to inhabit the harsh Arctic climate, the majority of insects are found in the warm and moist tropics. Insects have adapted to a broad range of habitats, successfully finding their own niche, because they will consume almost any substance that has nutritional value.
Insects perform a vast number of important functions in our ecosystem. They aerate the soil, pollinate blossoms, and control insect and plant pests; they also decompose dead materials, thereby reintroducing nutrients into the soil. Burrowing bugs such as ants and beetles dig tunnels that provide channels for water, benefiting plants. Bees play a major role in pollinating fruit trees and flower blossoms. Gardeners love the big-eyed bug and praying mantis because they control the size of certain insect populations, such as aphids and caterpillars, which feed on new plant growth. Finally, all insects fertilize the soil with the nutrients from their droppings.
Learn About the Problem
In his book The Diversity of Life, renowned entomologist Edward O. Wilson discusses the importance of insects and land-dwelling arthropods in the ecosystem, saying that "if [they] all were to disappear, humanity probably could not last more than a few months." Most other life forms, like amphibians, reptiles, birds, and mammals would also become extinct because of the domino effect that would occur in the food chain.
Many insects are herbivores, or plant-eaters, which makes them primary consumers. This abundance of primary consumers provides protein and energy for secondary consumers, known as carnivores. There are many secondary consumers, such as spiders, snakes, and toads that could not survive without feeding on insects. Tertiary consumers eat other carnivores; for example, bears and chimpanzees eat insects as well as other animals.
Students can learn about the relationships between organisms in the ecosystem by completing various activities in Exploring Populations, from Riverdeep's High School Science Gateways. (These activities require Logal Express and a Riverdeep.net subscription. Get a free trial subscription today.)
Think About the Problem
Having completed some of the above activities, students will be better equipped to consider the delicate balance between species in the ecosystem. Insect population management, in particular, makes for an interesting context for students to apply their knowledge of food chains and the interactions between species.
Insects have been imported and exported around the world for the benefits they provide. For example, vedalia ladybird beetles were shipped from Australia to California in the late 1800s to reduce the number of the cotton-cushion scale insects that were destroying orange and citrus fruit harvests. (You can find out more at the O. Orkin Insect Zoo Web site.) Australians have also found importing insects to be a useful practice. When cattle ranchers were running out of suitable land to feed their cattle because of the overgrowth of a particular cactus, a South American moth, Cactoblastis cactorum, was brought in to curb the out-of-control growth of the cactus. Often, manipulating insect populations in this way seems the most effective solution for problems that occur in agriculture.
Extending the Problem
Students can also read the Riverdeep Current article, "To Bee or Not to Bee," which takes an in-depth look at nature's most active pollinator.
It's estimated that at any time, there are some 10 quintillion insects alive on Earth. Students can learn more about insect numbers from the Smithsonian Institution's Buginfo pages. The site has excellent resources for students.
Population management: Students can read how fungi were used to control locust populations in Australia in "Biological Control Conquers Biblical Plague," an article from the Environmental News Network.
If you would like to explore animal population management further, look at "Too Many Deer?", a recent Teaching the News article about using hunting to control deer populations.
Endangered species: Many species of insects are being identified as endangered. Numerous factors are causing populations to dwindle, such as urban sprawl, use of pesticides, and increasing pollution levels. Students can research the status of endangered or threatened insects and investigate what effect the loss of some insect populations may have in the ecosystem:
Students who are interested in learning about other endangered or threatened species can read past Riverdeep Current articles:
Disease-carrying insects: Insects are known to carry diseases. Students can do research to find out which insects pass on diseases, and what strategies have been devised to protect people from infection. A well-known example is the West Nile virus:
by Zora Warren of the Harvard Graduate School in Education's "Technology in Education" program