Phylum Arthropoda

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 H2O 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:–1st pair- chelicera: feeding

(often fang-like)–2nd pair- Pedipalps: feeding,

locomotion, reproduction

Subphylum HexapodaINSECTS

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 Y-shaped appendages

General Characteristics Con’t

HabitatMarine and Freshwater

2 or 3 body segmentsHead, Thorax, and Abdomen

ORCephalothorax 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