insects (phylum arthropoda; sub-phylum uniramia) evolved over 300 million years ago most...
Post on 28-Dec-2015
224 Views
Preview:
TRANSCRIPT
Insects (Phylum Arthropoda; Sub-Phylum Uniramia)
Evolved over 300 million years agoMost 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 variationStructural (morphological)Physiological (chemical)Behavioral
Characteristics and Classification
Body - 3 parts Head with 1 pair of antennaeThorax with 3 pair of jointed legs and in many species 1-2 pair of wingsAbdomen with 11 segments (lacks wings and legs)
Success of the
Found virtually everywhere except the deep oceanExtremely short life span -> rapid adaptation to new environmentsSmall size -> greater partitioning of habitats while minimizing competitionFlight -> greater dispersal, escape from predation, and movement into environments less accessible to other species
Insects and Human Society
Positive impactMajor 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)
Negative impactAgricultural pestsSpread disease
Grasshoppers
3 main body segmentsHead (brain and sense organs)AntennaeCompound and simple eyesComplex moth parts
Thorax (legs and wings attached)Prothorax and mesothorax (each have pair of walking legs)Metathorax (jumping legs
Abdomen (organs of reproduction, digestion, respiration, and excretion)2 pair of wingsLeathery protective forewing (mesothorax)Hind wing which is used for flight (metathorax)
Digestive System
Specialized mouthparts (liplike labium and labrum, jawlike mandibles and maxillae)Salivary glands (produce saliva)Digestive ceca (produces digestive enzymes)
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
Excretory System
Malpighian tubules in hindgut remove wastes from blood and deposit them in the rectum
Circulatory System
Open circulatory systemBlood -> aorta -> hearts (muscular region of aorta in posterior abdomen) -> anterior coelom (head) -> abdomen (absorbs and disperses nutrients) -> aorta via ostia
Respiratory System
Air -> spiracles (opening in thorax and abdomen) -> tracheae (network of air tubes) -> body tissuesContraction of abdomen reverses process
Nervous System
Simple brainVentral nerve cord3 simple eyes (detect light)2 compound eyes (composed of hexagonal lenses capable of detecting movement but not sharp images)
Tympanum (detects sounds; located on first abdominal segment)Antennae (detects touch and smell)
Reproductive System
Sperm deposited into female's seminal receptacle (stored until eggs are released)Eggs fertilized internallyOvipositor (pair of pointed organs at tip of abdomen) used to dig a hole in soil and deposit eggs
Development
Metamorphosis - developmental changes -> distinct changes in form and sizeIncomplete Metamorphosis3 stages (egg, nymph, and adult)Nymph- smaller immature form; similar to adult but underdeveloped reproductive organs and lack wingsExamples are grasshoppers and termites
Complete Metamorphosis4 stages (egg, larva, pupa, and adult)Examples are butterflies, beetles and most other insects
Hormonal Control
Controlled by sequential expression of genesInteraction of 3 hormones (brain, molting and juvenile)
Brain hormone stimulates release of molting hormone (effect depends on level of juvenile hormone)Juvenile hormone level high -> molting hormone -> larva moltsJuvenile hormone level decreases -> molting hormone -> larva develop into pupaJuvenile hormone absent -> molting hormone -> pupa develops into adult
Importance of Metamorphism
Different developmental stages -> different functions (specializations)Eliminates energy conflicts between growth and reproductionEliminates competition between life stagesMultistage life cycle helps survive harsh weather
Defense
Defensive adaptations (agressive and passive) -> enhanced survivalCamouflage (cryptic coloration)Warning colorationMullerian mimicry- poisonous or dangerous species having similar patterns of coloration
Batesian mimicry- nonpoisonous or nondangerous species having similar pattern or color to a poisonous or dangerous unrelated species
Insect Behavior
Social behavior in honeybees Behaviors are genetically determined (instinctual or innate)Division of labor ->complex societies -> interdependence and need for communication
Hive consists of 3 distinct formsWorkers - sterile females; majority of individuals in hiveQueen - fertile female; only function is reproductionDrones - male bees; only function is
Workers
Average life span approximately 6 weeksPerform many functions at different times during their lives1st 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
3rd stage - gather nector and pollen; legs modified with special structures to collect pollen; ovipositor modified for defense (stinger)
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 matureMates only once; sperm stored in seminal receptacle for up to 5 years or more
Drones (haploid (n) males) develop from unfertilized eggs; sole function to deliver sperm to queen; must be feed by workers
Communication
Pheromones - chemicals released by an animal that affects the behavior or development of other animals of the same speciesSoundsTapping, rubbing, or signaling
Round dance - food source near but no indication of exact locationWaggle 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
Honey Bee communication
top related