120 likes | 503 Views
Joint-Legged Animals. SBI 3U. Joint-Legged Animals. Phylum: Arthropod a. Ancestors. May have evolved from annelid worms Why?. Phylum Arthropoda. Segmented body Jointed legs Exoskeleton Hemocoel Coelom Gas exchange – gills & trachea. Moulting in Arthropods.
E N D
Joint-Legged Animals SBI 3U
Joint-Legged Animals • Phylum: Arthropoda
Ancestors • May have evolved from annelid worms • Why?
Phylum Arthropoda • Segmented body • Jointed legs • Exoskeleton • Hemocoel • Coelom • Gas exchange – gills & trachea
Moulting in Arthropods • Exoskeleton limits size • Exoskeleton made of chitin protects animal and resists drying • Rigid exoskeletons prevented efficient locomotion why? And what modifications were made to provide for more efficient locomotion?
Rigidity of Exoskeleton • No longer needed coelom for body shape • Coelom shrank
Rigidity of Exoskeleton • Reduced arthropod’s ability for gas exchange • Aquatic arthropods gills • Land arthropods trachae
Rigidity of Exoskeleton • Hindered growth • Moulting
Open Circulatory System • Hemocoel • Ancient annelids developed blood instead of body fluid