Arthropods!

Do Now:

1. Turn in Earthworm dissection

Phylum Arthropoda• Biggest phylum of animals

currently alive and extinct.• Several MILLION different

species• Exist in every environment, in

almost every ecosystem on Earth.

• By any measure, the most “successful” animal phylum. ¾ of all known species of animal are arthropods.

What Makes an Arthropod?

• Exoskeleton:– Hard, protective

outer “shell.”– Used for movement– Made with chitin, a

polysaccharide.

Exoskeleton for Muscle Attachment• Your muscles are attached to an endoskeleton.• An exoskeleton serves the same purpose

What Else Makes an Arthropod?

• Bilateral symmetry

Segmented body plan• Each segment has at least 1 pair of appendages.– Legs, antenae, flipers, claws, etc. are all appendages.– Some segments may be fused together.

3 Main Body Sections • Called tagmata: Some may be fused

Jointed Appendages (and lots of ‘em)

Recap: Arthropod Characteristics

• EXOSKELETON• Bilateral symmetry• Segmented body plan (3 main sections: head,

thorax, abdomen)• Jointed appendages (many pairs). Note: arthropod

means “jointed foot.”

Arthropod Circulatory System

• Open circulatory system with heart.

Arthropod Respiration• Gills/book lungs: oxygen diffuses into blood• Trachea: air moves into insect directly

Types of Arthropods

• Domain: Eukyra• Kingdom: Animalia• Phylum: Arthropoda

• Classes: Crustacea, Insecta, Arachnida (+ Myriapoda

The Family Tree

Class Crustacea: The Crustaceans

• Only arthropod class with 2 pairs of antennae.

• Includes crabs, lobsters, shrimp, as well as pillbugs.

Class Crustacea: The Crustaceans

Crustacean Orders

• “True” Crustaceans = Order Decapoda– 5 pairs of thorasic legs– 2 tagmata• Cephalothorax• Abdomen

• “Pillbugs” = Order Isopoda– 7 pairs of thorasic legs– 3 tagmata

Class Insecta• 1 pair of

antennae

• 3 pairs of legs

• 3 tagmata

• Wings or wingless

Insect Diversity

• Biggest order of animal on Earth

• Over 900,000 documented species.

• Highest estimates suggest up to 30,000,000 species may exist.

Class Arachnida: Spiders, Ticks, Scorpions, Mites, etc.

• No antennae

• 4 pairs of legs

ArachnidsTrilobites =

Extinct Arachnids

Centipedes And Millipedes: Class Myriapoda

• One pair of antennae.• Two tagmata: head and trunk

2 pairs of legs per segmentMillipedesubclass diplopoda

1 pair of legs per segmentcentipedesubclass chilopoda

Recap: Arthropod Family TreePhylum Arthropoda

Class Crustacea

Class Insecta

Class Arachnida

Class Myriapoda

Deca-poda

Iso-poda

many orders many orders, including extinct trilobites

Chilopoda

diplopoda