Lecture—01 October 2003

Movement on to land took place in the Devonian

Exoskeleton of arthropods is useful with respect to preventing water loss

Preadaptation

Locomotion—exoskeleton again is a preadaptation

New niches allow for a rapid spurt of adaptive radiation amongst the arthropods

Arachnids

Spiders

Ticks

Mites

scorpions

Insects

Winged and non-winged insects

Millipedes and centipedes

Onychophorans—Peripatus

New topics

Deuterostomes—echinoderms and chordates

Echinoderms—

Endoskeleton

Radial symmetry—usually of fives

water-vascular system—derived from one set of coelomic pouches

dermo-branchiae

Connection between chordates and echinoderms is through larval stages, not adults