Unit 8 Chapter 28 Arthropods

What is an Arthropod?

 Bilaterally symmetrical, segmented coelomates  Segmented body, exoskeleton & jointed appendages 

Appendages

outgrowths = body

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)