Download Ch. 21 Notes

PHYLUM ARTHROPODA
SUBPHYLUM
UNIRAMIA/HEXAPODA
CH. 21
• Outnumber any other species of
animals
• Adapted to all climates/all land
environments
• 200 million insects per every human
being
• 2 classes in subphylum: Insecta and
Entognatha
• Entomology- study of insects
• Extensive group that provides
ecological, medical and
economic significance
BODY PLAN
• Six legs
• Uniramous legs (not biramous)
• Three tagmata (fusion of segments)
• Head, Thorax, and abdomen
• Cuticle is made of Four plates
• Exoskeleton is made of a complex
system of plates
• Sclerites
Exoskeleton is rigid due to
schleroproteins and not due to chiton
• Pair of large compound eyes, three
ocelli
• 1 set of antennae
• Mouthparts: Mandible and Maxillae
• Each section of thorax has a pair of
legs
• Legs are modified for special purposes
• Many variations among beetles
FLIGHT
• Only invertebrates that can fly
• Wings are not homologous to mammal wings and
bird wings
• Homologous? - means from a common ancestor
• Many variations among wing patterns and
development
• EX: some are wingless (silverfish)
• Female ants lose wings after nuptial flight
• Termite workers are wingless
• Wing movement may be direct (attached to wing)
or indirect (not attached to the wing)
• Flight muscle contraction can have two basic types
of neural control:
• 1) synchronous –single nerve impulse & one wing
stroke
• 2) asynchronous –complex action depending upon
energy storage ; not inline with nerve impulses
NUTRITION
• Varies depending on species
• Digestion system includes: foregut, mouth,
esophagus, crop, gizzard, midgut, and hindgut
• Most insects feed on plant tissues and juices
(herbivorous )
• Many are also parasites
Few are saprophagous (feed on dead animals)
Some are truly evil and kill their hosts like many wasps(
in movie)
OTHER SYSTEMS
• Respiratory S.- tracheal tubes ,
spiracles that lead to the outside
• Trachea branch out into smaller tubes
called tracheoles
• Some have air sacs
• Aquatic insects have tracheal gills
OTHER SYSTEMS
• Excretory : Malpighian tubules –
operate with specialized glands in wall
of rectum.
• Nervous System: fusion of ganglia
• Sense Organs: keen sensory
perception: mechanical, hearing,
chemical( odors), and visual
OTHER SYSTEMS
• Vision- two types of eyes: simple and
compound
• Nymphs and Larvae may have simple,
• Most adult insects have compound
eyes
• Reproduction: some can reproduce with just
females (parthenogenesis)
• Majority of insects reproduce sexually
• Demonstrate courtship behaviors:
• EX: Pheromones (chemicals given off to excite the
opposite sex), flashes of light, sounds, colors
• Many eggs are produced (great survivability)
METAMORPHOSIS
• Changing in form from youth to adult stages
• Incomplete metamorphosis: EX: grasshoppers,
cicadas, mantids, dragonflies
Young are called nymphs, increase in size through
molting
Complete metamorphosis: EX: 88% of insects, stages
represent many physical processes from youth to
adult
COMPLETE METAMORPHOSIS
• 1) Larvae- young: ex: caterpillars, maggots, grubs
• 2) Pupa-transitional stage, inactive, can survive
winter
• 3) Adult –
• Hormones regulate metamorphosis
• Insects may also have a period of hibernation or
dormancy
• Some have a longer period called diapause
DEFENSE
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Mimicry- impersonating a poisonous insect
Camouflage- blending in with environment
Repulsive odors (EX: Stinkbug)
Bad taste – Monarch butterfly
• Intensely Social creatures: cooperation among all
• EX: honey bees, ants, termites
• Caste system: Queen, workers, drones, soldiers
BENEFICIAL VS. HARMFUL
• Important for the cross-fertilization of of crops
• Bees pollinate 14$ billion worth of crops every year
• Coevolution with plants
• Other insects destroy harmful ones :
• EX: tiger beetles, praying mantids, ladybugs, ant
lions
HARMFUL
• Destroy crops and forests
• 10% are parasites: lice, bloodsucking flies,
Anopheles mosquito, mosquito (West Nile)
• Destroy food, clothing , and property
• Use of pesticides, bacteria and viruses, and
biocontrol have all been used to rid harmful insects
• Using crop rotation, resistant plant varieties have
also been used as of late