Entomology
Entomology is the study of insects. As a subdiscipline of the biological sciences, it focuses on the life, history, morphology, physiology, genetics, reproduction, development and ecology of this most abundant and diverse taxonomic group of terrestrial organisms. The number of species of insects is estimated in the range of 5-10 million; the biology and ecology of most of these species are virtually unknown as only about 1 million species have been described by scientists.
Insects are most abundant and diverse in the tropics. They occupy nearly every conceivable terrestrial habitat and many freshwater ones. In contrast, the marine ecosystems possess only a few species. Due to their small size insects can inhabit a wide variety of microhabitats unavailable to larger animals. Many insects are phytophagous, feeding and living on various parts of plants such as seeds, flowers and stems. Some of these species, such as aphids, may transmit plant diseases by their feeding activities. Other species are soil dwellers, decomposers, pollen and nectar gatherers of flowering plants, symbionts in the dens of vertebrates, or predators of other insects and other small invertebrates. Some species, such as mosquitoes and black flies, cause irritation, blood loss and transmit disease organisms as they feed on the blood of animals. This tremendous diversity in lifestyles and feeding habits makes it quite improbable to find a terrestrial animal or plant that does not interact in some way with an insect.
Various important ecosystem functions are performed by insects. Many insects, such as soil-dwellers, carrion-feeders, and woodborers, aid in the decomposition process and nutrient cycling. Insects are consumed by fish, birds, and other vertebrates and thus serve as an important food source in both aquatic and terrestrial food webs. In some cultures, insects are even an important protein source for humans. Many insects are entomophagous predators, preying on other insects, and hence, are important regulators of population levels of many herbivorous insects. Many flowering plants are dependent upon pollinating bees, flies, and butterflies for their continued survival.
Although most insects perform some vital ecosystem services that indirectly benefit humans, a minority of insect species adversely affect agricultural crops, livestock and poultry production, stored products, wood and lumber materials, and human health. Consequently, most entomologists focus their study on the interactions of these insects with humans and our products and activities. Most crops are damaged to various degrees by plant-feeding insects. Insects may feed or oviposit into stems, leaves, roots, flowers or fruits greatly limiting the crop yield. Thus, agricultural entomologists devise methods to limit insect damage by using a variety of techniques such as pesticides, adjusting crop practices (e.g., crop rotation), and encouraging natural predators and diseases of the pest insects (i.e., biological control). The compatible use of a variety of such pest suppression techniques in an ecological sensitive manner that is economically feasible to agriculture is termed integrated pest management (IPM). This philosophy is a cornerstone principle of entomologists involved in controlling pestiferous insects.
Medical entomologists study insects that directly impact human health, e.g. bloodsucking flies or stinging wasps, and those that serve as vectors for human disease organisms. Mosquitoes, lice, fleas and other blood-sucking insects transmit some of the most prominent infectious diseases in the world such as malaria, yellow fever, dengue fever, plague, and typhus.
Other entomologists investigate the physiology, development, genetics, predators, diseases, and behavior of pest insects to discover new ways of controlling insect populations. For example, investigations of insect development have led to the use of specific chemicals that disrupt the hormones guiding metamorphosis. Also, behavioral studies have discovered the widespread use of insect-produced and plant-produced chemicals orienting insects to mates, food or other habitat needs. Entomologists use these behavior- modifying chemicals to monitor or even suppress pest populations. Many universities and government agencies house and maintain insect museums so entomologists can conduct systematic studies of species and other higher categories of insects.
Insects are also important in environmental studies. For example, aquatic insects are used as key indicators of the effects of pollution in streams and other aquatic systems while other insects, such as butterflies, are used as ecological indicators of changing terrestrial habitats. Other entomologists focus on conservation efforts to protect certain insect species that are endangered of extinction. These biological studies of insects contribute to advances in biology, especially to the subdisciplines of ethology, hormonal physiology, chemical ecology, population ecology, evolution, and genetics. For example, enormous strides in genetics have resulted from the study of the Drosophila fruit fly. Consequently, the field of entomology is interdisciplinary in scope as the study of insects often involves basic and applied sciences within the agricultural, environmental, and biomedical fields.
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