Most successful group of organisms on the planet NUMBER OF SPECIES Every 2 out of 3 living things is an insect Entomologists estimate that over 800,000 insects have been named  Plant Kingdom 400,000 species  Animal Kingdom 250,000 species NUMBER OF INDIVIDUALS Another way to look a the dominance of insects is to consider the distribution and density of individual species of populations. Small size and high reproductive potential = population of epic proportions DISTRIBUTION A third way to assess the dominance of insects is to examine their abundance and diversity in a wide range of ecological habitats Insects are found in virtually every terrestrial and fresh water environment on the face of the earth. THE DOMINANCE OF INSECTS

A single colony of Australian termites can swell to several million individuals within an earthen mound feet tall A swam of migratory locusts may contain up to 10 billion individuals, cover an area of several thousand hectares, and have a total biomass of over 30,000 metric tons Grape leafhoppers reach populations as dense as 30 million hectare in some vineyards

IMPACT OF INSECTS Economic impact Agriculture food and fiber production Health of humans and animals Insects as food Represent an important food source for a wide variety of animal species Many cultures have relied on insects Ecological impact As consumers, scavengers, and decomposers, insects play a vital role in the biogeochemical cycling of nutrients As parasites and predators of other organisms, insects are part of a natural system of checks and balances that strengthens community stability and prevents explosive population growth from overrunning natural resources. Pollinators of angiosperms (flowering plants and trees)

Reasons for Success Exoskeleton – an insects supporting skeleton is located on the outside of the its body Gives shape and support to the body’s soft tissue Provides protection from attack or injury Minimizes the loss of body fluids in both arid and freshwater environments Assures mechanical advantage to muscles for strength and agility in movement Can resist both physical and chemical attack Covered with an impervious layer of wax that prevents desiccation Chitin- a polysaccharide that binds with various protein molecules to from a body wall that may be as flexible and elastic as rubber or as hard and rigid as some metals.

Marvels of Miniaturization most species are of insects are between 2 and 200 mmm ( inch) in length Small size is optimal for exoskeleton Minimal resources are needed for survival and reproduction Ideal for avoiding predation Flight Insects are the only invertebrates that can fly Highly effective mode of escape from predators Efficient means of transportation, allows populations to expand to new habitats and resources Efficient use of energy allows some insects to travel great distances or remain airborne for long periods of time. Reasons for Success

Reproductive Potential Reproductive success is one of the most significant measures of an organisms’ fitness Females often produce large numbers of eggs (high fecundity), most of the eggs hatch (high fertility), and the life cycle is relatively short (as little as 2-4 wks) Since most insects die nfore they ever have the oppurtunity to reproduce, a high reproductive potential is the species’ best chance for survival Females can store the male’s genetic compliment for months or years in the spermatheca, a special region of the reproductive system An unbalanced sex ratio, where females outnumber males and males can supply sperm for a large number of females Many species of insects (aphids, scales, thrips, and midges) can reproduce without males- parthenogenesis Reasons for Success

Metamorphosis most insects undergo significant developmental changes as they grow from immatures to adults Incomplete metamorphosis changes occur gradually as the insect matures allowing immatures and adults to line in similar habitats and feed on similar types of food. Complete metamorphosis a dramatic transformation in form and function between the immature (larval) and adult stages of development – Larva is primarily adapted for feeding and growth. It builds energy reserves that in some cases will sustain the insect for the rest of its life – An adult insect emerges and bears little to no resemblance to its larval form. Its primary function is dispersal and reproduction – In the class Insecta, only 9 out of 28 orders undergo CM, yet those 9 orders represent about 86% if all insects alive today Reasons for Success

Adaptability A combination of large and diverse populations, high reproductive potential, and relatively short life cycles, has equipped most insects with the genetic resources to adapt quickly in the face of a changing environment. Adaptation is an ongoing process. Populations must continually change as new resources appear and old one disappear. Insects record of achievement is impressive. They were among the first creatures to: Invade the arid expanses of dry land and exploit green plants as a source of food The first animals to use flight as an escape from predators First organisms to develop a complex social hierarchy with division of labor and cooperative care of the young. Reasons for Success