Phylum Arthropoda “ joint” “foot” 80% of all animals are arthropods….. 76% of those are insects…..

Major Classes of Arthropods Above:, Class Diplopoda: includes the millipedes Above left: Class Chilipoda: includes the centipedes Lower Right: Class Insecta: includes all 6 legged insects

Above Class Malacostraca: includes the lobsters, crab and shrimp Above Class Arachnida: includes the spiders, mites and scorpions

Features Jointed appendages segmented Coelomate and bilaterally symmetrical Exoskeleton of made of chitin secreted by the epidermis Open circulatory system Respiration by body surface, gills, trachea, or book lungs Sensory organs are well-developed: compound eyes, tympanum (drum-like ear) antenna (touch, smell, chemical reception) Developed nervous system with dorsal brain connected by a ring and double ventral nerve cords Dioecious: fertilization is usually internal

Growth and Development molt- shedding previous exoskeleton for a new one in order to grow metamorphosis- changes that the arthropods undergo as they develop from a larva to an adult grasshoppers undergo incomplete metamorphosis, when they hatch they resemble the adult form Butterflies undergo complete metamorphosis in which the hatched egg looks completely different then the adult butterfly

Obtaining Nutrients carnivores- feed on dead animals and prey on exoskeleton animals ( ex: spiders ) herbivores- some fed on particular plants only others feed on various types of greenery parasites- blood or body fluids of host(ticks) filter feeders- marine arthropods detritus feeders- decayed plants and animals

Feeding Digestive tract with two openings (one-way digestion) Mouthparts of individual species are highly specialized for a particular food type e.g. Australian Bulldog Ant (or bullant) – it’s diet includes small insects, seeds, fruit, and fungi

Respiration Specialized organs for gas exchange Aquatic species have gills Terrestrial species have tracheal systems

Respiration in Aquatic Species Aquatic species have gills formed from the appendages that form mouth and legs, water continuously travels through Some aquatic species (horseshoe crab) have book gills Leaf-like layered tissue that increases the surface area of gas exchange and have blood vessels

Respiration in Terrestrial Species Terrestrial species have tracheal system openings called spiracles lead to a network of tubes called tracheal tubes which run throughout the body the movement of the animal causes the rhythmic pumping that allows air to enter through the spiracles and into the tracheal tubes

Movement Well developed groups of muscles are controlled by the nervous system. Muscle cells are attached to the exoskeleton in order to generate force.

Reproduction Sexual reproduction and all members are separate sexed Terrestrial species have internal fertilization. In some species, males have organs which place the sperm inside the females while others deposit a sperm packet that is picked up by the female. Aquatic species can have either internal or external fertilization where eggs and sperm are broadcast into the surrounding waters.

Class Chilopoda The Centipedes About 30-35pairs of legs Very annelid-like with repeating segments Setae are modified to crude appendages - only specialized in the mouthparts Centipedes are carnivores with venomous mouthparts and feed on earthworms, toads, snakes, and mice

Class Diplopoda The Millipedes Very annelid like but have an exoskeleton No antennae Millipedes are herbivores and may defend themselves by secreting unpleasant or toxic chemicals

Subphylum Crustacea E.g. crabs, shrimps, lobsters, & crayfishes, 2 pairs of antennae (typically) & chewing mouthparts called mandibles 2 or 3 body sections: head, thorax, and abdomen (often the head and thorax are fused into one section called a cephalothorax) – this section is protected by a part of the exoskeleton called the carapace Respiration occurs through structures called gills

Class Arachnidia Includes spiders, scorpions, ticks 2 body sections – cephalothorax & abdomen 4 pairs of walking legs (most) Mouthparts called chelicerae contain fangs – stab & paralyze prey Mouthparts called pedipalps are used to grab prey Lack antennae Spiders all produce silk in organs called spinnerets All are predators or parasties

Class Insecta Compose about 80% of the animal kingdom Have three separate body regions and three pairs of legs Only invertebrate capable of flight Respiration with tracheids, excretion by Malpighian Tubules

Circulation A well developed heart pumps blood through an open circulatory system. The body cavity that contains the blood is called the hemocoel In an open circulatory system, blood is NOT always contained in vessels but will pool in spaces called sinuses to bathe organs in blood.

Excretion Most have specialized structures called Malpighian tubules. These remove metabolic wastes from the blood, concentrate the waste into uric acid, and add them to the feces in the intestine before elimination.

Response All have a brain consisting of 2 ganglia which connects to a nerve cord which runs the length of the body. Well developed sensory organs – many have compound eyes and well developed chemoreceptors (smell/taste) E.g. dragonfly

Why are the insects so successful?? 1. Size: tiny to minute - don’t eat much, can hide 2. Exoskeleton: hard, yet great strength 3. Short life span - don’t eat much 4. Reproduction: all sexual - variation 5. Flight: many advantages 6. Specialized appendages: eat many things 7. Adaption of exoskeleton: camouflage etc 8. Well developed sensory ability 9. Evolved social behavior 10. Very specific niches: minimizes competition

Ecological Roles of Arthropods Pollination Production of honey, wax, and silk Recycle biological materials to aid in producing topsoil Form symbiotic relationships with other organisms (see left) Part of food chain Burrowing shrimp and Goby fish living in Symbiosis shrimp cleans and digs a burrow where they both live (shrimp is blind) When danger approaches, the goby fish touches the shrimp with its tail to warn it and both hide in the burrow

Continued insects help pollinate crops ( example: bees pollinate flowers ) some insects destroy other harmful insects ( Ex: ladybird beetles eat insects which destroy orange and lime crops ) source of food chemicals that are obtained are used by humans ( ex: chitin from crustacean shells is used to dress wounds and to make thread for surgical stitches )

The Largest living Arthropod! is the Japanese Spider Crab with a leg span of 4 meters and a weight of 20kg. This crab has a life expectancy of 100 years.