Lecture 3: The Major Events Flashcards
the major effects:
1) The evolution of flight
2) the evolution of wing-folding
3) the evolution of holometabolism
how many times did flight evolve?
once, was a single event
evidence telling us flight was a single event:
-structure of veins is highly conserved across all insects
how did the evolution of flight occur?
wings were not wings, but had another function
what structure(s) could have given rise to wings
- 2 hypothesis
- -Pleural hypothesis
- -Paranotal hypothesis
Pleural hypothesis:
Gills gave rise to wings
–problem with this gills on abdomen not thorax
Paranotal hypothesis:
-thorax outgrowths gave rise to wings
evolution of flight: What function could result in rapid directional selection?
- Courtship
- Thermoregulation
- aerodynamics
- respiration
Evidence to supports pleural hypothesis:
- Molecular genetics
- Neuro anatomy (key inter-neurones arise in the abdomen - NOT in the thorax)
- fossil? as is useless
- –> So far pleural hypothesis is correct
if the pleural is correct how did insects transit from water to air?
James martin gives explanation of how gill to transfer into wing - stone fly:
-‘wind surfing’ to airborne flying as individuals went from primitive to more advanced (also wing vein became more rigid and solid as became more advanced)
2 living orders of insects which don’t have wing folding mechanisms
mayflies & dragonflies
— Paleoptera
-ALL OTHER INSECTS DO –> NEOPTERA
2 major ontogenic paths of insects (juvenile to adult)
- hemimetabolous
- holometabolous
hemimetabolous:
- exoterygote
- external wings
- infant looks like adult
holometabolous:
- pupil stage in the middle
- i.e. butterfly
- larval, pupil, adult
- larval looks nothing like adult
most successful insects on the planet
BEETLES
