Unit 8Chapter 28Arthropods

What is an Arthropod?

Bilaterally symmetrical, segmented coelomates

Segmented body, exoskeleton & jointed appendages

Appendages = body outgrowths

What is an Arthropod? Arthropods must molt (shed

exoskeleton periodically) Arthropods have variety of

respiration types: gills, tracheal tubes & book lungs

Arthropods have complex digestive and excretory systems: Mandibles (jaws) are used to

classify arthropods

What is an Arthropod? Arthropods have well-developed senses: Pheromones = chemical odor signals given

off by animals (detected by others) Compound eyes =

visual structure with many lenses

Simple eye = visual structure with only one lens for detecting light

What is an Arthropod? Arthropods reproduce sexually:

Some are hermaphroditic, most have internal fertilization

A few have parthenogenesis = new individuals develop from unfertilized eggs

Ex: social insects, such as bees, ants & wasps

Diversity of Arthropods

Arachnids Includes spiders,

scorpions, ticks & mites (chiggers)

Two body segments & six pairs of jointed appendages, including 8 legs, 2 chelicerae (fangs) and 2 pedipalps (sensors)

Diversity of Arthropods

Crustceans Includes crabs,

lobsters, shrimp, crayfish, pill bugs & barnacles

Two body segments & 2 pair of antennae, 5 pair of legs, and numerous “jaw feet”

Diversity of Arthropods Millipedes & Centipedes

Many body segments and paired legs

Millipedes are herbivorous, while centipedes are carnivores

Horseshoe Crabs These “living fossils” have

remained unchanged for 200 million years

Diversity of Arthropods Insects…Most successful class in terms of diversity

Includes beetles, butterflies, ants & bees, flies & mosquitoes, and many others

Three body segments, 3 pair of legs, one pair of antennae, and wings

Metamorphosis Series of changes in body shape and form

during life history

Incomplete M:

3 stages including nymph (smaller, immature version of adult)

Complete M: 4 stages including larva (wormlike creature which eats and grows) and pupa (enclosed structure that changes into adult form)