The night sky throbs with sound as the alien spaceship settles onto a landing pad near the summit of Devil's Tower. Blinking lights and musical tones forge a communication link between two civilizations, and then, in a brilliant glare of halogen light, mankind makes first contact with an alien lifeform. This memorable scene from the movie "Close Encounters of the Third Kind" is only science fiction, but it makes us wonder how living organisms begin to develop the complex interrelationships that characterize life on Earth.
Our planet is teeming with living organisms that survive only because they have a "close encounter" with some other species. This special type of association is called symbiosis. It occurs among many groups of plants and animals, but it is especially common in the insect world. The symbiosis may occur between two different species of insects, or it may include an insect and another lifeform such as a plant, a fungus, or a microorganism. Sometimes this "close encounter" is beneficial to both species (mutualism), and in other cases only one species benefits (commensalism). But either way, the symbiosis is a complex and intricate relationship that is shaped over many generations of natural selection and adaptation.
Symbiotic relationships may provide a number of different survival advantages. Some insects harbor intestinal microorganisms that assist in the digestion of food, while others rely on a symbiont for shelter, defense, or transportation from one place to another. Insect pollination of flowering plants is one of the most interesting examples of symbiosis. The plants have a variety of attractant stimuli and trap mechanisms to lure specific insect pollinators. In return, the insects collect floral "rewards" from the plants (nectar or pollen). These products are used for food or as raw materials in nest construction. Neither species could survive without the other.
- Look for intestinal symbionts in the digestive system of a termite or a cockroach.
- Take a field trip to hunt for plant galls and the insects that inhabit them.
- Observe different types of flowers and find out which insects visit them.
Examples of Symbiotic Relationships in Insects