Definition: Body segments with similar structure and function often heal to form different body regions

Body area: head, chest, abdomen

Head: Sensation and feeding

Chest: Movement and Support

Abdomen: Reproduction and Metabolism

Significance: It ensures the coordination of various physiological functions of the animal body and is conducive to the animal's adaptation to the environment.

Bilimb type body segments: original limb, outer limb segment, inner limb segment

The single-limbed arthropod evolved from the bilimbed type, and its outer limbs have completely degenerated.

The appendages are arranged in rhythm, forming various forms of mouthparts, tentacles, feet for various movements, and assistance in respiration and reproduction, or they have degenerated and disappeared.

Differences from wartfoot: It has joints and has higher mobility and flexibility

Importance: Arthropods are the only invertebrate animals with segmented appendages

Body wall: composed of epidermis, epithelium and basement membrane

epidermal action

Epidermal classification

limit

The muscles of platyhelminthes, nematodes, and annelids are mainly oblique muscles.

Arthropod striated muscles: contract quickly and powerfully

Meaning: The cyst wall of the mesodermal sac disintegrates and is a mixture of the true coelom and the protocoelom. Therefore, the cavity between the body wall and the digestive tract is formed by the true coelom and the blastocoel cavity.

Three divided blood sinuses: dorsal blood sinus, perivisceral sinus, and abdominal blood sinus

Heart: a tubular or sac-like structure located at the back of the digestive tract with multiple pairs of heart holes

Blood circulation: starts from the heart, flows into the blood chambers or sinusoids through the arteries, and directly infiltrates various tissues and organs. The blood in the blood chambers returns to the heart through the cardiac holes.

Arthropod blood transports only nutrients and metabolic waste products

Blood is colorless

respiratory organs

excretory organs

Performance: Enhanced hunting ability

Mouthparts: feeding, broken food structure

Grind stomach or gizzard

Midgut: Secretes digestive enzymes and is the main site for food digestion and absorption.

Hindgut: completes ion and water reabsorption

Chain-shaped like annelids

The brain is further concentrated in the anterior segment

Brain (formed by the union of three pairs of ganglia), subesophageal ganglion, abdominal nerve chain

Classification: Tactile receptors, chemoreceptors and visual receptors

Tactile organ: Tactile hairs, which can sense the stimulation of changes in contact, air flow, water flow, etc.

Chemoreceptors: olfactory receptors (antennae), taste receptors (in the mouth and on the mouthparts), visual receptors (monocular and compound eyes)

Most dioecious

Aquatic: Multiple IVF

Terrestrial: internal fertilization

Summary: Reproductive forms are diverse, mostly oviparous, ovoviviparous, parthenogenetic, larval and polyembryonic.

Protective coloration: Use body color and shape similar to their environment to hide themselves from natural enemies.

Mimicry: Imitation of other organisms to protect oneself or capture food

Warning colors: bright colors and patterns that make enemies easy to identify and prevent them from being attacked

The most primitive group of arthropods

Flat body

Representative animal: Macrobrachium

Limestomata

Arachnida

The body is divided into cephalothorax and abdomen

Body divided into head and trunk

tracheal breathing

Malpighian duct excretion

All are terrestrials

Representative animal: migratory locust