Arthropods are the most successful phylum, with over 750,000 species. They have segmented bodies, jointed appendages, and a tough exoskeleton. There are three main groups of arthropods: crustaceans, which are primarily aquatic and have two pairs of antennae; spiders and their relatives, which lack antennae and have fangs and pedipalps; and insects, which undergo incomplete or complete metamorphosis and have three body sections.

1. Crustaceans, Spiders and Insects

2.  Arthropods are the most
successful phylum on the
planet!
 750,000 species
 Arthropods have
 Segmented body
 Tough exoskeleton
 Jointed appendages

3.  Feeding – complex mouthparts to eat a wide range of food
 Respiration
 Land – air enters through spiracles – holes in the side of the body.
 Water – gills or book gills
 Circulation – open circulatory system – open sinuses
 Excretion – Malpighian tubules – saclike organ that
combines urine and waste together
 Response – have a brain! Sophisticated eyes and taste
receptors
 Movement – have muscles…can flex and extend
 Reproduction – internal or external reproduction
depending on the species

4. 1. Crustaceans – primarily aquatic
Examples: crabs, shrimps,
crayfishes and pillbugs.
Characteristics:
 Two pairs of antennae
 2 or 3 body sections –
Cephalothorax/Abdomen
 Chewing mouthparts called mandibles

5.  Molting – when arthropods
outgrow their exoskeleton
Steps to molting
1. skin glands digest inner
part of exoskeleton
2. other glands create a new
exoskeleton
3. animal pulls itself out of
old skeleton
4. While new skeleton is soft
– animal fills it with air to
allow for growth

6.  2. Spiders and their relatives
 Characteristics
 No antennae
 Cephalothorax and abdomen
 2 pairs of mouthpart appendages
 Chelicerae – fangs to stab and paralyze prey
 Pedipalps – grab prey
 Spiders are in the class Arachnida
 Spiders have no jaws so they liquify their prey
 Scorpions are found in warm climates.
The abdomen has a stinger that can kill
and paralyze prey.

7.  3. Insects –
 There are 3 classes of Insects
 1. Chilopoda – centipedes
 2. Diplopoda – millipedes
 3. Insecta – the insects
1. Centipedes –
• each body segment has one pair
of legs
 carnivores
 live beneath rocks or in the soil
2. Millipedes – each body segment
has two pairs of legs
Dragon Millipede – produces
cyanide when threatened.

8.  Insects have a body divided into
three parts
 Head – antennae and eyes
 Thorax - three pairs of legs, wings
 Abdomen – stinger or poison gland

9.  Insects undergo metamorphosis – a process of
changing shape and form.
1. Incomplete Metamorphosis – Young (called
nymphs) look very much like the adults.
Examples: Grasshoppers

10. 2. Complete metamorphosis – dramatic change in body
form. Eggs—Larvae—Pupa—Adult
 Examples: bees, moths, beetles, butterflies, flies