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introductory lect-1 ento.ppt

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introductory lect-1 ento.ppt

  1. 1. Introduction to Entomology
  2. 2. What is Entomology? - the branch of zoology that deals with the study of insects. - who study insects are known as Entomologists.
  3. 3. NUMBER AND BIODIVERSITY OF INSECTS the largest, most successful and most diverse form on the planet. more widely distributed over the earth than any other animal phylum live in virtually every habitat on earth research on various insects species reveals that there are about 5 million species of insects. They account for around 75% of total animal species on earth. Every year thousands of new species has been discovered.
  4. 4. INSECT DIVERSITY 25-27% 10-13% 60-65% Long term survival 400 m yrs in Devonian Pd while man is 2-3 m yrs old during Pleistocene Pd. Abundance More no. of species Varied habitats All kind of habitats, from aquatic to desert, cold to hot
  5. 5. Following are some of the reason for cosmopolitan distribution of insects: 1.Many human-loving (anthropophilic) insects eg. Houseflies, cockroaches and silverfish accompany humans everywhere. 2.Many human associated (synanthropic) insects bedbugs, ticks & lice act as ecto or endoparasites on humans and get distributed to different places. 3.Phytophagous (plant feeding) insects are spread where plants are present. 4.Some insects spread due to anthropogeny (aided by humans) for use as biological control. Eg- Coccinella (lady bird beetles) is used to control mustard pests (aphids). 5.Coprophages (dung feeding) insects eg. Dung beetles
  6. 6. WHY INSECTS ARE SO SUCCESSFUL ? Insects are the only animals giving challenge to man for his supremacy.  They occupy more than 2/3 of the known species of animals. They have been upon earth for 400 million years. Insects have great potential for rapid rise in population through a variety of ways. Insects are the most successful forms of life on this planet. They are typically very small. They locomote in a variety of ways, including swimming, jumping, gliding, flying, skating, clinging, floating, crawling, walking, running, and/or drifting.
  7. 7. The insects do have a unique combination of characteristics which, as a whole, have given them an unusual survival advantage. In brief, these attributes include an 1. Exoskeleton: an insect's supporting skeleton is located on the outside of its body. This exoskeleton is a marvelous structure that not only gives shape and support to the body's soft tissues, but also provides protection from attack or injury, minimizes the loss of body fluids in both arid and freshwater environments, and assures mechanical advantage to muscles for strength. As a "suit of armor", the exoskeleton can resist both physical and chemical attack.
  8. 8. 2. Small body size: Another advantage of small size is the minimal resources needed for survival. A crumb is a feast; a dewdrop quenches thirst; a pebble provides shade. In some cases, food requirements are so modest that an insect may live on a single plant or animal for its entire life and never exhaust its food supply.
  9. 9. Finally, small size is a big advantage to insects that must avoid predation. They can hide in the cracks of a rock, beneath the bark of a tree, behind the petal of a flower, or under a blade of grass. Dichomorpha echmepterygis is the world’s smallest insect. Discovered in 1997, this Costa Rican wasp (family Mymaridae) is a parasite of other insects' egg. Adult males may be only 0.139 mm (0.00055 inch) in length -- nearly 1/3 smaller than some single- celled protozoa (e.g., Paramecium caudatum).
  10. 10. 3. The ability to fly: Flight gave these insects a highly effective mode of escape from predators that roamed the prehistoric landscape. It was also an efficient means of transportation, allowing populations to expand more quickly into new habitats and exploit new resources. 4. High reproductive potential: In insect populations, females often produce large number of eggs (high fecundity), most of the eggs hatch (high fertility), and the life cycle is relatively short (often as little as 2-4 weeks). Together, these three characteristics enable insects to produce remarkably large numbers of offspring. A typical female lays 100-500 eggs in her lifetime, but numbers in the thousands are not uncommon.
  11. 11. American dog tick female laying egg mass (1000-2000 eggs!).
  12. 12. 5. Metamorphosis: Most insects undergo significant developmental changes as they grow from immature to adults. These changes, collectively known as metamorphosis, may involve physical, biochemical, and/or behavioral alterations that promote survival, dispersal, and reproduction of the species. Types: Incomplete & complete metamorphosis – In some insects the transformation process is slow and does not include all body tissues (incomplete metamorphosis) the immature and adults share many characteristics -- they often live in similar habitats and feed on similar types of food.
  13. 13. Incomplete INCOMPLETE METAMORPHOUS Insects change shape gradually!
  14. 14. Incomplete meta Incomplete Metamorphosis egg naiads adult This life cycle starts as an egg, but each growth, or nymphal stage looks similar, except it lacks wings and the reproductive capacity that the adult possesses. The "incomplete" metamorphosis which is found among the aquatic insect orders such as mayflies (Ephemeroptera) and dragonflies (Odonata).
  15. 15. Complete Metamorphosis • Egg -Larvae-Pupae-Adult Larvae not look like adult- are wormlike Can live in different environment Eat different food Larvae usually the main pest Lepidoptera (butterflies) & Hymenoptera (bees, ants, wasps)
  16. 16. Complete Metamorphosis Four stages that all look different
  17. 17. Complete Metamorphosis
  18. 18. 6. Adaptability in an ever-changing environment: they were among the first creatures to invade the dry land and exploit green plants as a source of food, they were the first animals to use flight as an escape from predators. As a group, they have endured 400 million years of climatological and geophysical upheaval, including the evaporation of inland seas, formation of mountain ranges, shifts in continental plates, onset of ice ages, and the fallout from cosmic impacts.
  19. 19. Just within the few thousand years since humans began roaming the earth, insects have acquired a taste for new products that would never be a part of their "natural" environment: e.g., glue and wallpaper paste, book bindings, cardboard, paintbrushes, tanned leather products, the corks of wine bottles, mummies, stuffed museum specimens, chocolate, ginger, yeast cakes, tobacco, pepper, and even potent drugs like marijuana and opium.
  20. 20. Perhaps the most remarkable example of insect adaptation in this century has been the speed with which pest populations have developed resistance to a broad range of chemical and biological insecticides. After World War II, public health officials in the United States made a concerted effort to eradicate the house fly (Musca domestica) with DDT. For several years the campaign seemed promising: fly populations decreased. But a few resistant flies managed to survive because they were endowed with an enzyme that could detoxify DDT. These survivors reproduced and passed this resistant trait to their offspring. In time, DDT-resistant flies repopulated their environment and the species now appears to be living happily ever after!
  21. 21. Insects affect man’s interest in many ways: -Because they dominate all terrestrial environments that support human life, insects are usually our most important competitors for food, fiber, and other natural resources. -Some insects act as vectors of some diseases and some also attack wood workings, stationary articles and museum specimens.
  22. 22. • Some other insects affects man’s health. Mosquitoes, housefly and rat flea are some insects transmit diseases to man. For E.g. Bubonic Plague epidemic that wiped out the population of Europe in the 14 century was carried by fleas that infested rodents. • However, many insects are harmless and beneficial to human beings. They are productive insects like honey bees, silk worm and lac insects. • Ecological impact: insects can acts as scavengers (aerate the soil by nest and burrows) and decomposers (enhancing decomposition of manure (beetles).

Editor's Notes

  • Metamorphosis: transformation
  • Coleoptera (beetles)
    Hymenoptera (bees, ants, wasps)
    Diptera (flies) Lepidoptera (butterflies)