Contraction of circular, radial or transverse muscle fibers will decrease the diameter, thereby increasing the pressure, and because no significant change in volume can occur, this decrease in diameter must result in an increase in length. Following elongation, shortening can be caused by contraction of the longitudinal muscle fibers, re-expanding the diameter and thus re-elongating the circular, radial or transverse muscle fibers.
Invasive Species Compendium. Maggots scrape dead tissue with mouth hooks then spew a stew of enzymes to liquefy, swallow, and digest it. Fungi create a strong but lightweight material by producing a random network of tiny threads.
Three muscle fiber patterns inside trunks work together to provide the strength, support, and resistance needed to bend and twist with extreme agility. The shell of a tortoise withstands pressure through interlocking scutes of various shapes consisting of both rigid and flexible layers. A combination of mineral crystals and collagen fibers protects bone from major fractures by sacrificing small structural elements.
We use cookies to give you the best browsing experience. By clicking the Accept button you agree to the terms of our privacy policy. Functions Performed More from this Living System. See More of this Function. Distribute Gases Gases of particular importance to living systems are oxygen, carbon dioxide, and nitrogen. Manage Compression When a living system is under compression, there is a force pushing on it, like a chair with a person sitting on it.
Prevent Buckling When a living system undergoes compression to the extent that it causes structural damage, it results in buckling.
See More of this Living System. The Strategy The soft, flexible body of the earthworm is divided into segments, which allows it to easily move through the soil to find food. The Potential An earthworm has a special ability to crawl through tight spaces. This strategy was contributed by Sue White and edited by Natalie Chen.
Kier embedly preview toggle icon Reference toggle icon. CABI embedly preview toggle icon Reference toggle icon. They can be separated into three major ecological groups based on their feeding and burrowing habits. All three groups are common and important to soil structure. These species live in or near surface plant litter. They are typically small and are adapted to the highly variable moisture and temperature conditions at the soil surface. The worms found in compost piles are epigeic and are unlikely to survive in the low organic matter environment of soil.
Some species move and live in the upper soil strata and feed primarily on soil and associated organic matter geophages. They do not have permanent burrows, and their temporary channels become filled with cast material as they move through the soil, progressively passing it through their intestines.
They feed mainly on surface litter that they pull into their burrows. They may leave plugs, organic matter, or cast excreted soil and mineral particles blocking the mouth of their burrows. It is easy to determine whether you have an adequate population of earthworms in your soil. Look for their casts in the forms of little piles of soil, mineral particles, or organic matter at the soil surface. They can be seen moving over the soil surface or even breeding, particularly on warm, damp nights.
Dump a spadeful of moist soil into a bucket or onto a sheet of plastic, and sort through for earthworms. Can you identify different species? To find the deep burrowing species, pour a dilute mustard solution onto the soil. Many will quickly come to the soil surface in response to this irritant. The majority of temperate and many tropical soils support significant earthworm populations. A square yard of cropland in the United States can contain from earthworms, or even larger populations in highly organic soils.
A similar area of grassland or temperate woodlands will have from earthworms. Based on their total biomass, earthworms are the predominant group of soil invertebrates in most soils. The family of earthworms that is most important in enhancing agricultural soil is Lumbricidae, which includes the genuses Lumbricus, Aporrectodea , and several others. Lumbricids originated in Europe and have been transported by human activities to many parts of the world.
The United States has only one or two known native species of lumbricids. Others were brought to this country by settlers probably in potted plants from Europe , and were distributed down the waterways. Worms have tiny bristles, made of a hard substance called chitin, that help them to move and to cling on to the sides of the burrow. To survive freezing cold temperatures, worms must burrow to an area below the frost line wherever they live.
Night crawlers, for example, can burrow to depths of six feet or more. When they burrow down below the frost line, they nest in small chambers at the bottom of the tunnels they dig. They are also efficient at replicating, and sometimes can produce worm babies starting with only one worm acting as both male and female. The only thing that does stop them is dry soil. Earthworms need a moist environment to survive. In any good story, there's some drama.
Nonnative plants, animals and insects have a tendency to create an ecosystem upset, and the litter dweller earthworms are no exception. In the Chippewa forests of Minnesota, these machine-like composters are depleting important forest-floor litter and worming their way into tree root systems. In the Smokey Mountains, the Asian jumper earthworm is gorging on the forest floor. As a result, the native species of beetles and insects at the lowest end of the food chain have limited food supplies, creating an imbalance in the entire food web.
There are ways everyone can chip in to turn the page on the bad earthworms. Commonly used as fishing bait, earthworms find a path to forest floors through rivers.
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