Arthropod phylogeny&

Insect Evolution

Objectives:

Identify characteristics of the Arthropoda

Discuss Arthropod Phylogeny

Characteristics of major taxa

Discuss Insect Evolution

Arthropoda

Arthro- Refers to Joints

Poda- Refers to feet

Arthropoda

Characteristics• Paired, jointed

appendages• Segmented body plan• Land forms have tracheae or book lungs, • Aquatic forms have gills

Arthropoda

Characteristics• Compound eyes• Open circulatory system• Digestive system is a

tube• Nervous system with

brain, paired ventral nerve cords

Arthropoda

• Exoskeleton is molted

Arthropoda

Arthropoda

• Evolved from Annelida

Ecdysozoans

Arthropoda Phylogeny

• Many hypotheses exist

• Molecular data suggest:

Arthropoda Classification

ChelicerataMandibulata

Hexapoda = antennae

• Chelicerae = feeding appendages

Arthropoda Classification

= fangs in spiders

Arthropoda Classification

1. ChelicerataClasses:

Merostomata - horseshoe crabsArachnida - spiders, scorpions, ticks, mites

Arthropoda Classification

Chelicerata• Mainly terrestrial• Body Divisions - Cephalothorax,

abdomen• No antennae• No chewing mandibles

Arthropoda Classification

Chelicerata• First and second pair of appendages -

chelicerae, pedipalps used for manipulation of food, locomotion,

defense, copulation• Next four pair of

appendages - walking

Arthropoda Classification

Crustacea• Aquatic• Body divisions - cephalothorax and

abdomen• Gills • 2 pairs antennae - touch and taste• Biramous appendages - two jointed

branches arising from their base

- biramous appendages

Arthropoda Classification

Crustacea• Mandibles and maxillae used for feeding• Chelipeds on lobsters and crayfish -

pinching claws• Larval stage• Green glands

Arthropoda ClassificationHexapodaClass:

Insecta - insects

Arthropoda Classification

Insecta characteristicsTerrestrial and some aquaticBody plan - Head, thorax, abdomenUniramous1 pair antennae3 pairs legs on thoraxMalpighian tubules

Insect Evolution

• Four stages of insect evolution:1. Development of insect body form

2. Development of wings

3. Development of wing flexion

4. Development of complete metamorphosis

Orders:

Ephemeroptera = ?

Odonata = ?

Plecoptera

Megaloptera

Coleoptera

Lepidoptera

Diptera

Hemiptera