Diversity of Life

-Arthropoda -

(insects, crustaceans, spiders, mites)

Arthropoda - insects, crustaceans, spiders, mites,

Arthropoda - abundance

Arthropoda – Where did they come from?

Peripatus

What about the Onychophora (“velvet worms” )?

Annelid Arthropod Characteristics Characteristics

Peripatus -worm-like body -segmented legs

(during embryogenesis)

-paired nephridia -open circulatory system - hemocoel - trachea - oral appendages

Arthropoda - What makes them all arthropods?

Arthropods are • segmented coelomates • exoskeleton • jointed appendages

Arthropoda - two significant improvements in ��� body architecture

1.  EXOSKELETON 2.  JOINTED APPENDAGES

Arthropoda - Exoskeleton

exoskeleton

heart

digestive cavity

ventral nerve cord

Arthropoda - Exoskeleton The arthropod exoskeleton is made of chitin (also found in the cell walls of fungi)

N-acetyl - glucosamine

Benzene rings

Chains of sugars - cross-linked with benzene

Arthropoda - Exoskeleton

=

Laid down in overlapping layers (like plywood)

Arthropoda - Exoskeleton

Advantages: 1.  Protection from drying - allowed invasion of land 2.  Protection from predators -

Arthropoda - Exoskeleton

Advantages: 1.  Protection from drying - allowed invasion of land 2.  Protection from predators -

Disadvantages: 1.  Doesn’t permit growth - have to moult 2.  Doesn’t bend - need to insert breaks (joints) in it to

permit movement

Arthropoda - Body Sections

Head - sensory and feeding

Thorax - locomotory

Abdomen - digestion and reproduction

Arthropoda - Classification

THE MAIN GROUPS OF ARTHROPODS

1.  CHELICERIFORMES - spiders, mites, ticks, scorpions

2.  MYRIAPODA - centipedes and millipeds

3.  UNIRAMIA - insects

4.  CRUSTACEA - crabs, lobsters, shrimp

Arthropoda - Cheliceriformes

Horseshoe crab Spider

Scorpion

Arthropoda - Cheliceriformes Characteristics

1. Chelicerae - feeding appendages

2. Head and thorax are fused - cephalothorax

3. Eight legs

Arthropoda - Myriapoda - millipedes and centipedes

Characteristic - several pairs of legs

Arthropoda - Uniramia - the insects Most common kind of animal - greatest number of species

Protozoa Meso/Placozoa Porifera Cnidaria Platyhelminthes Pseudocoelomates Annelida Minor inverts Insecta

Other arthropods Mollusca Lophophorates Echinodermata Hemi/Urochordata Vertebrates

Arthropoda - Uniramia - the insects Most common kind of animal - greatest number of species

Arthropoda - Uniramia - the insects

Most common kind of animal - greatest number of species

Characteristics - 1.  Six legs

2. Distinct head, thorax and abdomen

Arthropoda - Uniramia - the insects

Characteristics 3. Wings

Insects are the only invertebrates to have mastered flight

Arthropoda - Uniramia - the insects

Characteristics -

3. Two kinds of life cycles

Complete (or holometabolous)

Egg larva pupa adult

Egg larva adult

Incomplete (or hemimetabolous)

Arthropoda - Crustacea - lobsters, crabs, barnacles

Arthropoda - Crustacea - lobsters, crabs, barnacles

Characteristics -

1. Head and thorax are fused - cephalothorax

Arthropoda - Crustacea - lobsters, crabs, barnacles

Characteristics -

2. 10 primary locomotory appendages

Arthropoda - Summary of characteristics

Group Cheliceriformes Uniramia Myriapoda Crustacea

Cephalothorax Yes No No Yes

Number of legs 8 6 20+ 10

Flight No Yes No No

Jointed appendages

Yes Yes Yes Yes