Phylum Arthropoda General Characteristics Arthropod jointed feet Largest

Phylum Arthropoda

General Characteristics • Arthropod = jointed feet • Largest group of animals – 80% of described species – 30 -50 million species • Most varied

General Characteristics Con’t • Metamerism (body divided into segments) – Head, abdomen, thorax • Paired, jointed appendages • Ecdysis-molting (growth) • Open Circulatory System (means no vessels) • Complete digestion tract

Metamerism (Body Segments) 3 Segments 2 Segments

General Characteristics Con’t • Ventral Nervous System • True exoskeleton • Metamorphosis • 5 Subphylum –Trilobitomorpha, Myriapoda, Chelicerata, Crustacea, Hexapoda

Exoskeleton • Functions of exoskeleton –protection –Gas exchange –Minimize H 2 O loss –Muscle attachment

Exoskeleton Structure • Composed of chitin – a carbohydrate • Epicuticle: outer layer –Water proof • Procuticle: inner layer –Made of chitin

Ecdysis (molting) • 3 step process – 1. Enzymes digest old exoskeleton – 2. New exoskeleton secreted New exoskeleton is soft – 3. Scleratization (hardening)

Ecdysis (molting) • Molting is important for arthropod growth –Can’t grow in a suit of armor • Is also a dangerous time for arthropods –Typically animals about to molt, will go into hiding just before the process begins

Metamorphosis • Changes in body form from larval to adult –Ex. Butterfly, Dragonfly • Reduces competition for food and living space (*)

Subphylum Trilobitomorpha • MOST PRIMITIVE! • All extinct and marine • Body with 3 sections

Subphylum Myriapoda • Myriapoda- “many legs” • Millipedes, centipedes • Paired legs • Terrestrial

Millipedes vs. Centipedes • Millipedes: –Herbivorous –Appear to have 2 legs per segment –Slow –Non-venomous

Centipedes –Carnivorous –Have only 1 pair of legs per segment –Faster –Venomous

Subphylum Chelicerata • Spiders, mites, ticks, scorpions, horseshoe crabs, • Have chelicera - fangs • 2 Segments – Cephalothorax (head-chest) –Abdomen

Feeding • Appendages: st – 1 pair- chelicera: feeding (often fang-like) nd – 2 pair- Pedipalps: feeding, locomotion, reproduction

Subphylum Hexapoda INSECTS

General Characteristics • Hexapoda = “six legs” • Includes the class Insecta – 30 million species – 27 Major orders • We will only learn 8

General Characteristics Con’t • 3 pairs of legs – 6 total • 1 pair of antennae • Most have 2 pairs of wings • Compound eyes (2) and Oscelli (3 in middle) • 3 part body plan –Head, Thorax, Abdomen

Insect Flight • Is a unique trait to the insects • Different insects have wing modifications for specific functions

Economic Importance �Parasites �Ticks, fleas �Are considered agricultural pests. � 1949 -European corn borer caused $349 million in damage to the US corn crop

Economic Importance Con’t • Provide goods –Honey –Beeswax –Yummy (to certain cultures) –Silk –Dyes

Economic Importance Con’t • Also are vectors for many diseases –Bubonic plague (flea) –Malaria (mosquito) –West Nile Virus(mosquito) –African Sleeping Sickness (Tsetse fly)

Subphylum Crustacea

General Characteristics �Includes crabs, lobsters, crayfish, shrimp, and barnacles �Carapace – “shell” that protects organs (like a turtle) �Biramous Appendage: branched Yshaped appendages

General Characteristics Con’t �Habitat � Marine and Freshwater � 2 or 3 body segments � Head, Thorax, and Abdomen � OR � Cephalothorax and Abdomen

Reproduction • Sexual reproduction (most external, some internal) • Few monoecious (hermaphroditic)

Females retain eggs until hatching

Economic Importance • Tasty—people like to consume them

Ecological Importance • Scavengers-eat dead material • Basis of food chain(shrimps, barnacles) • Keystone species