Lecture 10 - Insect Origins & Flight Flashcards
Midterm II
What are the 2 proposed insect ancestors?
Crustacea and Myriapods
Describe Crustacea anatomy
- have 2 more leg pairs than insects
- have 2 primary body parts: head & the rest
- most primitive have more body segments
What groups evolved from a crustacean-like ancestor?
Non-insect hexapods and true insects
Describe non-insect hexapods
- tiny, soft-bodied animals
- mouthparts internalized in head
- oldest fossil approx. 400 mya
What is needed to fossilize insects?
- fine textured mud or fine volcanic ash
- anaerobic conditions
- encasement in sap (amber) or tar
4 fossil types
- impression fossils
- mineral replacement
- amber
- asphalt
Amber fossils
attempts to extract and sequence DNA from insects in amber
none have been duplicated despite numerous attempts
Continental Drift
had profound impact on insect adaptations and distributions
Devonian
400-350 mya
Evidence of damage on fossil plant material
conditions poor for fossilization
Carboniferous
350-285 mya
extensive evidence of insect radiation
insects large bodied
few fossils from this period
Permian
245-285 mya
first major climatic drying and drought
Triassic
210-245 mya
all continential masses united in to Pangea
first diptera & hymenoptera fossils
dinosaurs much more diverse
Jurassic
145-210 mya
age of dinosaurs
first earwigs
first mammals appeared
Cretaceous
65-145 mya
pangea breaks into two: laurasia & gondwanaland
caused by huge asteriod strike
first social insects
Tertiary
1.6-65 mya
first parasitic orders: fleas, strepsiptera, lice
diversification within birds, specifically flightless birds
Wing Development
- Apterygota - w/o wings (feed primarily on decaying segments, trace of legs on abdominal segrments)
- Paleoptera - primitive wings (most primitive, can’t fold wings, lack 3rd wing muscle
- Neoptera - folded wings (folded over back, winglessness also common)
Evolution of Wings - 4 Theories
- Flying Fish
- Flying Squirrel
- Thermoregulation
- Mating Display
Flying Fish Theory
moveable thoracic gills, climbed out of water to feed & escape enemies, used gills to glide with flapping motion, gill plates enlarged serving as wings
Advantages: dont have to create new muscles & articulations, easy to shift positions
Disadvantages: reasons to leave water unconvincing
Flying Squirrel Theory
developed expansions on thorax for gliding, developed hinges and muscles for flapping
Advantages: expansions of thoracic dorsal plates
Disadvantages: developing new muscle attachments & wing articulations, requires moving muscle attachments from elsewhere
Thermoregulation Theory
Wing precursors were used to capture heat
Advantage: heat leads to aid in developing wing articulation & muscles
Disadvantage: ?
Mating Display Theory
wings evolved as display structures to attract mates
Not clear how you go from display to flight