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Insects (Phylum Arthropoda; Sub-Phylum Uniramia)

Insects (Phylum Arthropoda; Sub-Phylum Uniramia). Evolved over 300 million years ago Most successful group of animals (700,000 to 10 million species). Diversity (species and variety) Numbers (population size) Success due in part to enormous range of variation Structural (morphological)

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Insects (Phylum Arthropoda; Sub-Phylum Uniramia)

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  1. Insects (Phylum Arthropoda; Sub-Phylum Uniramia) • Evolved over 300 million years ago • Most successful group of animals (700,000 to 10 million species)

  2. Diversity (species and variety) • Numbers (population size) • Success due in part to enormous range of variation • Structural (morphological) • Physiological (chemical) • Behavioral

  3. Characteristics and Classification • Body - 3 parts • Head with 1 pair of antennae • Thorax with 3 pair of jointed legs and in many species 1-2 pair of wings • Abdomen with 11 segments (lacks wings and legs)

  4. Success of the • Found virtually everywhere except the deep ocean • Extremely short life span -> rapid adaptation to new environments • Small size -> greater partitioning of habitats while minimizing competition • Flight -> greater dispersal, escape from predation, and movement into environments less accessible to other species

  5. Insects and Human Society • Positive impact • Major pollinator of flowering plants (2/3 of all plants) • Food for fish, birds and mammals (important link in food web) • Help recycle materials (termites) • Useful biproducts (honey and silk)

  6. Negative impact • Agricultural pests • Spread disease

  7. Grasshoppers • 3 main body segments • Head (brain and sense organs) • Antennae • Compound and simple eyes • Complex moth parts

  8. Thorax (legs and wings attached) • Prothorax and mesothorax (each have pair of walking legs) • Metathorax (jumping legs

  9. Abdomen (organs of reproduction, digestion, respiration, and excretion) • 2 pair of wings • Leathery protective forewing (mesothorax) • Hind wing which is used for flight (metathorax)

  10. Digestive System • Specialized mouthparts (liplike labium and labrum, jawlike mandibles and maxillae) • Salivary glands (produce saliva) • Digestive ceca (produces digestive enzymes)

  11. Food -> mouth -> esophagus -> crop (storage) -> gizzard (chitinous plates shred it) -> stomach (mid gut) (mixes with gastric enzymes from ceca and absorbed) -> hind gut (colon and rectum) -> anus

  12. Excretory System • Malpighian tubules in hindgut remove wastes from blood and deposit them in the rectum

  13. Circulatory System • Open circulatory system • Blood -> aorta -> hearts (muscular region of aorta in posterior abdomen) -> anterior coelom (head) -> abdomen (absorbs and disperses nutrients) -> aorta via ostia

  14. Respiratory System • Air -> spiracles (opening in thorax and abdomen) -> tracheae (network of air tubes) -> body tissues • Contraction of abdomen reverses process

  15. Nervous System • Simple brain • Ventral nerve cord • 3 simple eyes (detect light) • 2 compound eyes (composed of hexagonal lenses capable of detecting movement but not sharp images)

  16. Tympanum (detects sounds; located on first abdominal segment) • Antennae (detects touch and smell)

  17. Reproductive System • Sperm deposited into female's seminal receptacle (stored until eggs are released) • Eggs fertilized internally • Ovipositor (pair of pointed organs at tip of abdomen) used to dig a hole in soil and deposit eggs

  18. Development • Metamorphosis - developmental changes -> distinct changes in form and size • Incomplete Metamorphosis • 3 stages (egg, nymph, and adult) • Nymph- smaller immature form; similar to adult but underdeveloped reproductive organs and lack wings • Examples are grasshoppers and termites

  19. Complete Metamorphosis • 4 stages (egg, larva, pupa, and adult) • Examples are butterflies, beetles and most other insects

  20. Hormonal Control • Controlled by sequential expression of genes • Interaction of 3 hormones (brain, molting and juvenile)

  21. Brain hormone stimulates release of molting hormone (effect depends on level of juvenile hormone) • Juvenile hormone level high -> molting hormone -> larva molts • Juvenile hormone level decreases -> molting hormone -> larva develop into pupa • Juvenile hormone absent -> molting hormone -> pupa develops into adult

  22. Importance of Metamorphism • Different developmental stages -> different functions (specializations) • Eliminates energy conflicts between growth and reproduction • Eliminates competition between life stages • Multistage life cycle helps survive harsh weather

  23. Defense • Defensive adaptations (agressive and passive) -> enhanced survival • Camouflage (cryptic coloration) • Warning coloration • Mullerian mimicry- poisonous or dangerous species having similar patterns of coloration

  24. Batesian mimicry- nonpoisonous or nondangerous species having similar pattern or color to a poisonous or dangerous unrelated species

  25. Insect Behavior • Social behavior in honeybees • Behaviors are genetically determined (instinctual or innate) • Division of labor ->complex societies -> interdependence and need for communication

  26. Hive consists of 3 distinct forms • Workers - sterile females; majority of individuals in hive • Queen - fertile female; only function is reproduction • Drones - male bees; only function is

  27. Workers • Average life span approximately 6 weeks • Perform many functions at different times during their lives • 1st stage - feed honey and pollen to queen, drones and larvae (nurse bees); secrete royal jelly (high protein diet) • 2nd stage - Stop producing royal jelly and begin secreting wax -> build and repair hive, guard hive and fan wings to circulate fresh air in hive

  28. 3rd stage - gather nector and pollen; legs modified with special structures to collect pollen; ovipositor modified for defense (stinger)

  29. Queen and Drones • Queen identical to workers except continuously supplied with royal jelly; Queen secretes "queen factor" which prevents other female larvae from becoming sexually mature • Mates only once; sperm stored in seminal receptacle for up to 5 years or more

  30. Drones (haploid (n) males) develop from unfertilized eggs; sole function to deliver sperm to queen; must be feed by workers

  31. Communication • Pheromones - chemicals released by an animal that affects the behavior or development of other animals of the same species • Sounds • Tapping, rubbing, or signaling

  32. Honey Bee communication • Round dance - food source near but no indication of exact location • Waggle dance- food far from hive, dirction of food indicated by the angle of the straight run and the distance indicated by the duration and the number of waggles

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