Transcript Insect Characteristics

Insect Characteristics
Rainier Jr/Sr High School
Advanced Life Science
Mr. Taylor
Insect Characteristics
Insects are the largest single class of
organisms with >700,000 named species
This is > ½ of the total named species of
organisms (including plants and fungi!)
Insects are the only invertebrates to fly …
resulting in a great natural selective
advantage.
Insect Characteristics
4 main orders of Insects (several minor
orders will be ignored)
Diptera: “two-winged” includes flies and
mosquitoes
Lepidoptera: “scale-winged” includes butterflies
and moths
Hymenoptera: “membrane-winged”: includes
bees, wasps, and ants. Many social insects.
Coleoptera: “shield-winged”: beetles. Largest
group of insects.
Insect Characteristics
Body plan: 3 divisions
Head
1st segment have 2 antennae … sensory
2nd segment has mandibles … obtain food
Next segments have other specialized mouthparts.
Insects are extremely specialized in their methods of
obtaining food supplies.
Also have compound eyes.
Insect Characteristics
Body plan: 3 divisions
Thorax
3 fused segments each have a set of walking legs.
2 of the segments also have wings on most insects.
Wings are made of chitin with supporting veins.
Veins are filled with air, not blood or other fluid.
Insect Characteristics
Body plan: 3 divisions
Abdomen
9-11 segments
Contain most of digestive and reproductive organs.
No appendages attached to abdomen.
Insect Characteristics
Digestive system
Specialized mouthparts for specialized feeding
allow for minimal competition.
Insect Characteristics
Digestive system
Food passes through
Mouth; food is ground up
Crop: more grinding, addition of digestive enzymes.
Gizzard; mixing of food, enzymes act on food.
Midgut/stomach; most absorption here.
Anus; indigestible wastes are passed out.
Insect Characteristics
Excretory system:
Malpighian tubules: eliminate nitrogen wastes
as urea: allows for conservation of water.
Insect Characteristics
Respiratory System
Most have spiracles and tracheae.
Insect Characteristics
Nervous System
Ventral nerve cords with ganglia in each
segment.
Brain in anterior segment.
Also have antennae (1 pair): chemo- and touchreceptors. Sensors are extremely sensitive.
Insect Characteristics
Life Cycle
Most undergo complete
metamorphosis
Adult lays egg
Egg hatches to larva
Larva wraps in chrysalis to become
pupa
Pupa emerges as an adult
Most larva feed on different food
than adults: a means of minimizing
competition.
Insect Characteristics
Life Cycle
Some undergo incomplete metamorphosis
Adult lays egg
Egg hatches into a wingless nymph.
Less mature nymph molts to more mature nymph.
Several nymphs later, the adult form appears.
Insect Characteristics
Reproduction
Sexual
Internal and external fertilization
Some females have pouches to store sperm,
often for long periods of time
Eggs often resistant to heat, cold, dryness.
This allows survival of species during long
periods of unfavorable conditions (winter,
drought, etc)
Insect Characteristics
Flight
First animals with wings to appear in fossil
record.
This allowed insects to invade and exploit new
environments.
This allowed insects to escape predators better
Most have 2 sets of wings, some have only 1
(house flies), a few have no wings (fleas).
Usually only one set of wings used for flight.