SBI 3 U ARTHROPODS JOINT LEGGED ANIMALS ARTHROPODS

SBI 3 U ARTHROPODS – JOINT LEGGED ANIMALS

ARTHROPODS � Diverse: include centipedes, scorpions, crab, lobster � Largest phylum in the Animal Kingdom � Diverse habitats: found in Arctic ice, deserts, the deep ocean, mountains, prairie ponds and the sky!

EVOLUTION OF ARTHROPODS � Segmented ancestor: annelids! � Most have lost their segments or the segments have fused together

DISTINGUISHING CHARACTERISTIC OF ARTHROPODS � Strong external skeleton exoskeleton � Exoskeleton made of chitin a non-living materials � Function of exoskeleton: protects internal muscles and blood vessels

EXOSKELETON, CONTINUED … � Exoskeleton does not grow with arthropod � Arthropod grows new exoskeleton by moulting

NERVOUS SYSTEM � Nervous system some have a primitive nervous system, while others like the crayfish have a more advanced system � A more advanced nervous system allows for an increased ability to sense and respond to changes in their environment more control

CIRCULATORY SYSTEM � “Open” circulatory system blood bathing the tissues in spaces or sinuses � Hemocoel repleaces the coelom as the major body cavity (coelom exists still, but is small). Hemocoel is a cavity through which blood circulates

DIGESTIVE SYSTEM � All arthropods have a digestive system � 3 basic parts: 1) foregut: from mouth to esophagus 2) Midgut: stomach 3) Hindgut: intestine to anus