Phylum Arthropoda

Arthropods

Make up about 80% of the known animal species Insects are by far the most common species of arthropods

Arthropod means joint-footed Range from the deep sea to mountain peaks

Bilateral symmetry Growth requires molting

General Arthropod CharacteristicsArthropods have:

1. Exoskeleton - Most prominent characteristic is their outside skeleton, or exoskeleton.

- Exoskeleton provides support, protection and attachment site for muscles. Made of protein and chitin Chitin is a strong, flexible, polysaccharide

- All arthropods molt, or shed their exoskeletons periodically. After it molts, it grows before the new skeleton hardens.

- Skin glands digest the inner part of the exoskeleton and other glands secrete the new one.

http://www.youtube.com/watch?v=ffo37DlH5DM

General Arthropod Characteristics

Arthropods have:

2. Segmented Bodies - Have segmented bodies that show various patterns of segment fusion (tagmosis) to form integrated unit like the head, abdomen, ...

General Arthropod CharacteristicsArthropods have:

3. Jointed Appendages

- Have joints between body sections (includes legs and antennae)

- Have jointed appendages (a structure such as a leg that grows out from the main part of the body)

Arthropod Characteristics

Cephalization is more prominent than in annelids (brain and complex sense organs in the head region)

Special organs sense touch, vibration, and chemicals. The eyes of many arthropods are particularly specialized.

Open circulatory system. The dorsal heart pumps blood from the posterior end of the animal to the anterior end. - Blood moves through the hemocoel (major body cavity)

Phylum Arthropoda – 2 Subphylum

Subphylum Chelicerates Class Arachnida

Spiders, scorpions, mites, ticks Subphylum Mandibulates (4 major classes) Class Crustacea

Crayfish, Crab, Lobster Class Chilopoda

Centipedes Class Diplopoda

Millipedes Class Insecta

Insects, Grasshoppers

Subphyla Chelicera

Chelicera are pointed appendages (modest pinchers) used for feeding and manipulating food (in lieu of chewing mandibles)

The body of chelicerates has two major parts: 1. The cephalothorax is a fused section composed of the head and any body segments that have legs attached.

2. The abdomen consists of posterior segments that contain most of the internal organs.

Lack antennae Nearly all have 4 legs

http://www.youtube.com/watch?v=Cha-lmuPdek

Subphlya Chelicera:Class Arachnida

Subphyla Mandibulata

Unlike chelicerates, mandibulates have - mandibles, or jaws, for chewing food.

All mandibulates have antennae - segmented sense organs on the head

Three distinct body regions - head, thorax, abdomen

They have three or more pairs of walking legs

Subphyla Mandibulata: 1. Class Crustacea

Crustaceans typically have: - two pairs of antennae - two or three body sections

Cephalothorax – head fused with the thorax

- chewing mouthparts called mandibles.-5 or more pairs of legs

• Primarily aquatic, few terrestrial

Ex: Crustacean

Subphyla Mandibulata:2. Class Chilopoda (centipedes) & 3. Class Diplopoda (millipedes)

Subphyla Mandibulata: Class Insecta

Insects typically have: The three distinct segments (head, thorax, abdomen)

Three pairs of legs attached to the thorax

Mandibles One pair of antennae One pair of compound eyes Two pairs of wings on the thorax Tracheal tubes for respiration

Tracheal tubes open to the outside through small holes called spiracles