Insects….Insectos

Vacaciones en C 695

Insects (from Latin insectum, a calque of Greek ἔντομον [éntomon], “cut into sections”) are a class of invertebrates within the arthropod phylum that have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. They are among the most diverse groups of animals on the planet, including more than a million described species and representing more than half of all known living organisms. The number of extant species is estimated at between six and ten million, and potentially represent over 90% of the differing animal life forms on Earth. Insects may be found in nearly all environments, although only a small number of species reside in the oceans, a habitat dominated by another arthropod group, crustaceans.
The life cycles of insects vary but most insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton and development involves a series of molts. The immature stages can differ from the adults in structure, habit and habitat, and can include a passive pupal stage in those groups that undergo complete metamorphosis. Insects that undergo incomplete metamorphosis lack a pupal stage and adults develop through a series of nymphal stages. The higher level relationship of the hexapoda is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonflies with wingspans of 55 to 70 cm (22–28 in). The most diverse insect groups appear to have coevolved with flowering plants.
Adult insects typically move about by walking, flying, or sometimes swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles. Insects are the only invertebrates to have evolved flight. Many insects spend at least part of their lives under water, with larval adaptations that include gills, and some adult insects are aquatic and have adaptations for swimming. Some species, such as water striders, are capable of walking on the surface of water. Insects are mostly solitary, but some, such as certain bees, ants and termites, are social and live in large, well-organized colonies. Some insects, such as earwigs, show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyridae in the beetle order Coleoptera communicate with light.
Humans regard certain insects as pests, and attempt to control them using insecticides and a host of other techniques. Some insects damage crops by feeding on sap, leaves or fruits. A few parasitic species are pathogenic. Some insects perform complex ecological roles; blow-flies, for example, help consume carrion but also spread diseases. lnsect pollinators are essential to the life-cycle of many flowering plant species on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere (including humans) would be devastated.[8] Many other insects are considered ecologically beneficial as predators and a few provide direct economic benefit. Silkworms and bees have been used extensively by humans for the production of silk and honey, respectively. In some cultures, the larvae or adults of certain insects are a food-source for humans.
http://en.wikipedia.org/wiki/Insect

Los insectos (Clase: Insecta) son artrópodos (Phylum: Arthropoda) que poseen extremidades especializadas y cuerpo segmentado (Insecto quiere decir cortado en medio) con cubierta esclerotizada (exoesqueleto) pero no desarrollan un verdadero caparazón. Tienen un par de antenas, tres pares de patas y dos pares de alas. En su mayoría son pequeños (entre 0.5 a 3 cm de longitud). Los de mayor tamaño pertenecen al grupo de los escarabajos y de las chinches.
El grupo de los insectos no sólo es diverso sino increíblemente abundante, pues se calcula que por cada ser humano en la Tierra, existen 200 millones de insectos. Pueden ser herbívoros, carnívoros, carroñeros o incluso establecen eficientes relaciones de comensalismo y parasitismo (Brusca y Brusca, 2002).
Los insectos juegan un gran papel en las funciones del ambiente. Son los principales depredadores de otros invertebrados y por lo tanto controladores de plagas. Descomponen y eliminan un porcentaje importante de la materia orgánica y son los principales polinizadores de plantas de importancia ecológica y económica. Sin embargo, y en ocasiones derivado de su abundancia elevada, se les ha considerado como un grupo dañino, pues consumen cerca de un tercio de las cosechas a nivel mundial y son los principales vectores de enfermedades humanas (Brusca y Brusca, 2002).
Los insectos son el grupo más diverso del planeta. Hasta la fecha se desconoce el número de especies de insectos descritos en el mundo, pero hay estimaciones que varían desde 890,000 hasta más de un millón de especies. Actualmente se incluyen catálogos (CAT) de siete grupos de insectos, entre ellos los más diversos como los escarabajos (Orden: Coleoptera) y las mariposas y polillas (Orden: Lepidoptera).
http://www.biodiversidad.gob.mx/especies/gran_familia/animales/insectos/insectos.html

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