Jointed-legged invertebrates Arthropods Jointed-legged invertebrates

Arthropod Characteristics Metamerism with tagmatization Chitinous exoskeleton Paired-jointed appendages Growth with ecdysis (molting) Ventral nervous system Open circulatory system Complete digestive tract Malpighian tubules for excretion

Evolutionary Significance Protostomes Schizocoelous development Paired ventral nerve cord Loss of internal metamerism Increased tagmatization (specialization of segments)

Terrestrial Dominance Minimize water loss Exoskeleton Respiratory system development Advanced excretory system Greater ability for movement Exoskeleton attaches strong muscles Support

Exoskeleton Major reason for success of this group! Provides Support Protection Prevention of dehydration Sites for muscle attachment

Exoskeleton Structure Epicuticle (outer layer) Water tight Barrier Procuticle (inner layer) Made of chitin Allows for protection Forms joints

Ecdysis Shedding or molting of exoskeleton New exoskeleton is soft Tanning (sclerotization) must take place to make outer layer of procuticle hard

Metamorphosis Change in body form from immature (larval) stages to adult forms Reduces competition between stages for Food Living space Larval forms often occupy different habitats than the adults do

Taxonomy of Arthropods 4 subphyla Trilobitomorpha (all extinct) Chelicerata Crustacea Uniramia

Trilobitomorpha Trilobites All extinct All marine 3 sections

Chelicerata Class Merostomata Class Arachnida Horseshoe crabs Water scorpions (eurypterids) Class Arachnida Spiders Mites Ticks Scorpions Class Pycnogonida (sea spiders)

Chelicerate Characteristics Two-part body Opisthosoma Chelicerae (1st pair of appendages – forms feeding palps or fangs) Pedipalps (2nd pair of appendages) Cephalothorax (prosoma) Book lungs or book gills

Crustacea Class Malacostraca Class Branchiopoda Shrimp, lobsters, crayfish Isopods (wood lice – roly poly) Amphipods Class Branchiopoda Fairy shrimp, brine shrimp Water fleas

Class Copepoda Class Cirripedia Cyclops (freshwater) Barnacles Sacculina – parasite of crabs

Crustacean Characteristics 2 pairs of antennae Biramous appendages (Y-shaped) Segments are serially homologous

Uniramia Class Diplopoda (millipedes) Class Chilopoda (centipedes) Class Pauropoda Class Symphyla Class Hexapoda (insects)

Insect Locomotion Flight Walking (3+ legs on ground at all times) Running (Can run on 2 legs) Swimming (legs modified as paddles) Jumping (saltatory locomotion)

Insect Respiration & Circulation Tracheae & spiracle system Circulation Modified open circulatory system Some vessels Primitive Heart

Nervous System Johnston’s organs (hearing - on antennae) Tympanic organs (hearing – on legs or body) Compound eyes (facets – ommatidia – fused) Simple eyes (ocelli)

Metamorphosis Type Appearance Young called Ametabolous larvae look like adults, just smaller instars Paurometabolous Specific number of molts Nymphs (land) Naiads (water) Holometabolous Young very different from adults Larvae

Economic Impact of Arthropods Name one effect each major group has on mankind (good or bad). For insects, list 4 good things that they do and 4 bad things that they are responsible for.