Most successful group of organisms on the planet NUMBER OF SPECIES

1. THE DOMINANCE OF INSECTS • 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.

2. A single colony of Australian termites can swell to several million individuals within an earthen mound 20-25 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

3. 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)

4. 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.

5. Reasons for Success Marvels of Miniaturization • most species are of insects are between 2 and 200 mmm (0.1 -1.0 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.

6. 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

7. 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

8. 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.