Body Shape and Position Direct Water Current

Biological Strategy

Black flies

AskNature Team

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Capture, Absorb, or Filter Organisms

Many living systems must secure organisms for food. But just as one living system must capture its prey to survive, its prey must escape to survive. This results in capture and avoidance strategies that include trickery, speed, poisons, constructed traps, and more. For example, a carnivorous plant called the pitcher plant has leaves formed into a tube that collect water. Long, slippery hairs within the tube face downward. When insects enter the tube seeking nectar, they lose their footing and slide inside, unable to climb out and escape being eaten and digested by the plant.

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Distribute Gases

Gases of particular importance to living systems are oxygen, carbon dioxide, and nitrogen. Oxygen and carbon dioxide are involved in respiration, so distributing these gases efficiently and effectively is important for a living system’s survival. However, gases are difficult to contain because they disperse easily. To accommodate this, living systems have strategies for confining gases and using gases’ properties to their advantage. For example, prairie dogs and mound-building termites build systems of tunnels and mounds that take advantage of wind to ventilate their underground homes.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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The larvae of black flies direct water currents to create conditions favorable to gathering and filtering food by adjusting the shape and position of their body and foldable, food-trapping mouth fans.

“Some black-fly larvae that live in shallow, rapid streams have an interesting variation on the device. They are attached at their posteriors and have a pair of food-trapping fans on their anterior ends. A larva twists lengthwise so one fan is uppermost and feeds from material suspended well out in the velocity gradient (fig. 6.12a). The other fan is then lower and a bit downstream; it feeds on material resuspended in the vortices rising behind the body. Upward flow of water in the vortices is further ecouraged by a downstream tilt of the body as a whole. Groups of larvae, positioned as they are in nature, don’t compete for food but instead enhance each other’s feeding efficiency (Chance and Craig 1986).” (Vogel 2003:135)

Vogel S. Comparative Biomechanics: Life’s Physical World. Princeton: Princeton University Press; 2003. 580 p.

Last Updated August 18, 2016

References

Book

Comparative Biomechanics: Life's Physical World, Second Edition

17/06/2013 | Steven Vogel

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Reference

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