Entomology mainly signifies to the study of insects and all that surround them. The fact is that nowadays human population is a drift in a sea of insects. When we look at numbers alone, the anticipated ratio of insects to humans is 200 million to 1, and there are around 40 million insects for each acre of land.
All along with humans, insects live in nearly each and every habitable place on the earth, apart from the depths of ocean. A few distinguished entomologists assert that insects own the land. They are mainly consumers of plants; they are the main predators of plant eaters; they play a main role in decay of organic matter and they serve up as food for other types of animals.
General features of Insects:
1) Insects similar to other mandibulates encompass one pair of pre-oral antenniform appendages
2) The insect body is generally categorized into three parts: head, thorax and abdomen
3) The insect head comprise of six segments, a pair of mandibles (segment 2), (segment 5) and a pair of 2nd maxillae (segment 6).
4) Compound eyes are present.
5) The thorax comprises of three segments and three pairs of walking legs ventrally and two pairs of wings dorsally.
6) The abdomen comprises of eleven segments generally and stands no ambulatory appendages.
7) Insects respire through trachea that opens through segmental-arranged spiracles.
8) Excretion in insects is through means of Malpighian tubules.
9) Insects experience metamorphosis.
Success of Insects:
The class Insecta builds up into one of the dominant life forms on earth. They suitably have been termed 'conquerors of the land' but what reasons can be advanced for their huge success? What features account for their tremendous variety and numbers?
Primary, is arthropod body architecture that emphasizes an integument which is light and strong, making a shell to protect inner tissues and attachment to muscles. Furthermore, this shell that generally comprises an outermost wax layer assists to prevent water loss from evaporation, a critical problem for small animals living on the land. Arthropod body architecture as well comprises jointed appendages that, in insects, have been abundantly adapted into legs for locomotion, mouth parts for feeding, structures of reproduction and other utilizations.
Second, insects are as well animals of relatively small size. Most differ from around 1/16 inch (around 2mm) to 1 inch (around 3cm). Some might be smaller, though, and a few such as much as 6-inch (around 15cm). The small size of most insects allows dispersal, lets them to escape from birds and other predators and facilitates them to use food present just in small amounts.
Third, is the capability to fly that makes insects distinct from the other arthropods and invertebrates. The capability to fly is one of the most significant reasons for the success of the whole class. This capability to fly assists insects in escaping predators and possibly more significantly, it enables extensive dispersal of species. This dispersal encourages colonization of latest habitats, which in turn encourages the evolution of latest species.
Insects as well show great reproductive capacity and some special features of their growth and growth have improved their capability to persist even in unfavorable environments. The capability to lay big numbers of resistant eggs which can be carried by air, water currents, animals and so on joined by a relatively short generation time, generates a high amount of genetic variability which can be tested against the environment. The outcome is quick adaptation of population to changing ecological conditions and formation of new species.
At last in their adaptability, such main characteristics collectively unique to insects are joined by great changes in the physical conditions and habitat on the land.
Beneficial Effects of Insects:
1) Insects pollinate flowers therefore, fruit formation based on them.
2) Insects make a source of food for man example: termites, honey and caterpillar.
3) Helpful materials like bee wax, silk and so on are obtained from the insects.
4) Insects are significant in food chains, example: Aquatic insects prepare food for the fishes.
5) Insects are significant as scavengers - (decomposition comprising cycling of materials).
6) Insects are significant tools, example: Drosophila is employed for research in the physiology, genetics and so on.
7) A few insects are employed to control others that are pests (that is, Biological Control)
8) Insects have aesthetic value (example: Butterflies are gathered for their beauty).
Detrimental Effects of Insects:
1) A few insects are parasites of plants and animals example: Lice and stem boring caterpillars.
2) A few insects example: mosquitoes and tsetse flies are vectors of the parasitic diseases.
3) A few insects example: bean weevils destroy crops and stored food.
4) A few insects example: termites demolish wooden structures.
5) A few insects example: house fly and mosquito is frequently nuisance to man. The advantageous consequences of insects, though, far outweigh their adverse consequences.
Evolution of Insects:
Insects are the most successful class of animals reported to have existed much longer than human beings for more than 350 million years! Insects are the first small animals to live in the land having complete success, having evolved from creatures which probably looked similar to our present day earthworms. The primary insects have multiplied and expanded and over 800 species have been reported.
The land had been colonized by low-growing plants, a few 100 million years before insects became famous and had witnessed a succession of vegetative changes which eventually resulted in an immense coastal forest.
It was throughout this time, the carboniferous period, (around 350 million years ago), if amphibians and reptiles flourished, that, insects gained a firm foothold on the land. Throughout this early phase, changes in insect form and the degree of species diversity accelerated quickly. A few insects then resembled big dragonfly's gigantic forms by wingspans as broad as 29 inches (that is, 75 cm).
Of the one million or so acknowledged species of animals, above 850,000 or 76% are insects. Thousands of species remain to be exposed.
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