Arthropods

What are ARTHROPODS? Coelomate – definition? Segmented – definition? Bilateral Symmetry – definition? Exoskeleton – made of protein and chitin Jointed appendages – any structure (leg or antennae) that grows out of the body

What are Arthropods? Earliest invertebrates to exhibit jointed appendages Jointed appendages are an advantage because they allow more flexibility for animals with hard, rigid exoskeletons Joints allow powerful movements and allow appendages to be used in many ways

What are Arthropods? Appendages Jointed Appendages

Phylum Arthropoda: crustaceans, spiders, insects -Hard exoskeleton, segmented bodies, jointed appendages -Arthropods are the most successful of all animal phyla based on diversity, distribution, and numbers.  -Nearly one million species identified so far, mostly insects. -The exoskeleton, or cuticle, is composed of protein and chitin. -Molting of the cuticle is called ecdysis. -Extensive cephalization.  -Open circulatory systems in which a heart pumps hemolymph through short arteries and into open spaces (sinuses). -Aquatic members- gills for gas exchange; terrestrial members- tracheal system of branched tubes leading from surface throughout body.

Exoskeletons Provide Protection Made up of protein and CHITIN Continuous - covering over most of body OR Plates - that are held together by hinges Continuous Hinged

Exoskeleton Advantages Protects, supports internal tissues Provides place for muscle attachment Aquatic arthropods have exoskeleton reinforced with calcium carbonate

Exoskeleton Disadvantages Heavy the larger the animal, the thicker and heavier the exoskeleton Exoskeletons don’t grow animals must molt when they get too large for exoskeleton

Molting Animal contracts muscles and takes in air or water Body swells and causes exoskeleton to split open, usually along the back Most arthropods will molt 4-7 times before becoming an adult.

Before the new exoskeleton hardens... Increased circulation to all parts of the body cause the animal to puff up and new exoskeleton hardens leaving some “growing room” Animal can’t protect itself, can’t move What is another term for molting? Ecdysis

Segmentation 3 segments Abdomen Thorax Head

Segmentation Sometimes these segments can be fused together some have head and fused thorax and abdomen some have abdomen and fused head and thorax (cephalothorax)

Respiration Efficient respiratory systems to meet large O2 demands Large oxygen demand needed to sustain high metabolism for fast movements 3 types of respiratory structures gills (aquatic arthropods) tracheal tubes (terrestrial arthropods) book lungs (terrestrial arthropods)

Respiration Gills water moves over gills O2 from water diffuses into gills and into bloodstream CO2 from body diffuses out through gills into surrounding water

Respiration Tracheal tubes branching network of hollow air passages that take air throughout the body Muscle movement brings air in/out through SPIRACLES (openings in abdomen and thorax)

Respiration Book lungs spiders and relatives air filled chambers with leaf-like plates stacked plates are arranged like pages of a book