arthropods part 1

characteristics

bilateral symm, segmented body, exoskeleton, jointed appendages, coelomates, open circulatory system, separate sexes, nervous systems, molting

subphylas

myriapoda, hexapoda, chelicerata, crustacae

chelicerata classes

arachnida: spiders, scorpions, ticks; merostomata: horseshoe crabs

myriapoda classes

chilopoda: centipedes; diplopoda: millipedes

hexapoda classes

insecta: insects

crustacea classes

branchiopoda: daphnia; malacostraca: crabs, lobsters, crayfish, shrimp

tagmata

segments fused into groups

how many tagmata do hexapods have

3: head, thorax, abdomen

how many tagmata do most crustaceans and chelicerates have

2: head fused to thorax, abdomen

arthropod advantages

joints act as fulcra, exoskeleton protects from water loss and predation, tagmatization

tagmatization

fusing and differentiation of segments

ecdysis

new exoskeleton forms under old, fluid builds breaks old, arthropod inflates new using hemolymph and air, new hardens

compound eyes

1000s ommatidia, lens, 8 retinular cells, light sensitive core=rhabdom