24.1 Arthropod Diversity
Bell Ringer:
• Think about Arthropods that you encounter through out
your life…..
• 1-What arthropods can you hear in the summer????
• 2-What arthropods can you order off a menu at a seafood
restaurant????
• 3-What arthropods have you been bitten by???
24.1 Arthropod Diversity
KEY CONCEPT
Arthropods are the most diverse of all animals.
24.1 Arthropod Diversity
Arthropod features are highly adapted.
• Arthropods are invertebrates that share several features.
– exoskeleton (cuticle) made of chitin & proteins
– jointed appendages: varies in number use & shape
– segmented body parts
24.1 Arthropod Diversity
Larges Arthropod=
Macrocheira
kaempferi
(Japanese spider
crab)
24.1 Arthropod Diversity
Heaviest Arthropod=
Homarus americanus
(American lobster)
up to 40 lbs
24.1 Arthropod Diversity
Smallest known Arthropod= Demodex
(parasitic mite that lives in hair follicles)
0.0004 in or 0.1mm in length
24.1 Arthropod Diversity
• Arthropods are classified into five groups.
– Trilobites—extinct, bottom feeders
24.1 Arthropod Diversity
– Crustaceans—live in
oceans, freshwater streams,
and on land
– Very diverse group
Ex. King crab, copepods,
barnacles, pill bugs.
24.1 Arthropod Diversity
24.1 Arthropod Diversity
24.1 Arthropod Diversity
24.1 Arthropod Diversity
– Chelicerates—specialized daggerlike mouthparts
Ex. Scorpions, horseshoe crab, spiders, ticks, mites
24.1 Arthropod Diversity
24.1 Arthropod Diversity
24.1 Arthropod Diversity
Bed bug
24.1 Arthropod Diversity
Head Louse
24.1 Arthropod Diversity
24.1 Arthropod Diversity
24.1 Arthropod Diversity
24.1 Arthropod Diversity
– Insects—most live on land, have six legs
– Very diverse
– Account for 80% of all animals
24.1 Arthropod Diversity
– Myriapods—long bodies and many pairs of legs
Ex. Centipede & millipedes
– Generally live in humid environments
– One pair of legs bear fangs for prey capture
24.1 Arthropod Diversity
“How did the evolution of jointed appendages lead to the
wide variety of arthropods we see today?”
24.1 Arthropod Diversity
Arthropod exoskeletons serve a variety of functions.
• Joints are made of stiff and
flexible cuticle to allow
movement.
• The exoskeleton is made of
many layers of chitin.
– hard material that
protects the body
– must be shed (molt) in
order to grow
24.1 Arthropod Diversity
• Arthropods have an open circulatory system.
– Tubelike heart & body cavity
– Body movements keep blood circulating
24.1 Arthropod Diversity
• Sensory organs such as antennae are made of modified
cuticle.
• Most arthropods have compound eyes.
– Thousands of tiny individual lenses that interpret
images
24.1 Arthropod Diversity
Bell Ringer:
• look on pg 736 at the figure 24.8. Sketch a crustacean
and label the parts:
• -abdomen, cephalothorax, carpace, antennae,
swimmerets, walking legs, cheliped, mandible
24.1 Arthropod Diversity
“How does the exoskeleton make functions such as
movement & growth difficult?”
24.1 Arthropod Diversity
Arthropod diversity evolved over millions of years.
• The oldest fossils are of trilobites that date back 540
million years.
• Cambrian Period
24.1 Arthropod Diversity
• The evolutionary relationship between arthropods and
other invertebrates remains under question.
– body segmentation similar to annelids
– molecular evidence suggests segmentation is
analogous development
• Velvet worms and water bears are considered the
closest relatives of arthropods.
24.1 Arthropod Diversity
“Explain how ancient fossils can be used to determine
relationships between modern arthropods?”