1. Ch 24 A Closer Look at Arthropods 24.1 Arthropod Diversity
Arthropods characteristics
invertebrates
exoskeleton (cuticle) made of chitin
jointed appendages (paired)
segmented body parts

2. Arthropod Groups Trilobites Crustaceans Chelicerates Insects Myriapods
extinct, bottom feeders
Crustaceans
live in oceans, freshwater streams, and on land
Chelicerates
specialized daggerlike mouthparts
Insects
most live on land, have six legs
Myriapods
long bodies and many pairs of legs

3. The exoskeleton is made of many layers of chitin.
Movement
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 in order to grow
Molting
Secrete new layer cuticle under exoskeleton
Enzyme weakens old exoskeleton, crawl out of it
New exoskeleton filled with fluid/larger than before, will harden

4. Internal/External Functions
Arthropods have an open circulatory system.
Sensory organs such as antennae are made of modified cuticle.
Most arthropods have compound eyes.

5. body segmentation similar to annelids
Arthropod Diversity
The oldest fossils are of trilobites that date back 540 million years.
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.

6. 24.2 Crustaceans Crustaceans evolved as marine arthropods
Crustaceans share several common features.
two distinct body sections, cephalothorax and abdomen
one pair of appendages per segment
two pairs of antennae
exoskeleton
carapace

7. Crustacean appendages are used for a variety of functions.
Appendages include claws, antennae, walking legs, swimmerets, and mandibles.
Crustacean appendages are used for a variety of functions.
collecting and manipulating food
attracting females
protection

8. Crustaceans vary in both anatomy and structure.
Decapods such as lobsters and crabs have ten legs.
Barnacles are sessile filter feeders wrapped in a hard shell.
Isopods such as pill bugs have flattened bodies and seven pairs of legs.
Tongue worms are parasites found in a host’s lungs or nasal passages.

9. 24.3 Arachnids Arachnids are spiders and their relatives
Arachnids are the largest group of chelicerates
Lack antennae
Have 6 paired appendages
4 pairs of walking legs
Fanglike mouthparts chelicerae
Appendages pedipalps grasp prey
2 body sections: cephalothorax and abdomen

10. There are three major groups of chelicerates.
horseshoe crabs
sea spiders
Arachnids

11. Arachnids are a group of chelicerates that live on land.
eight legs
fanglike pincers that inject venom
silk glands
Arachnids have four different adaptations that reduce water loss.
waterproof cuticle
book lungs
Malpighian tubules
spiracles
poison gland
spinnerets
fangs

12. Diversity of Archanids:
All spiders make silk and produce venom.
Spiders make up half of the more than 60,000 known arachnid species.
Arachnids also include mites, ticks, chiggers, and scorpions

13. 24.4 Insect Adaptations Insects are in nearly every ecological niche.
Insects have a body with three parts.
head
thorax
Abdomen

14. Some insects live independently, others live in social colonies
In incomplete metamorphosis, insects look like miniature adults when they hatch.
There are three life stages of incomplete metamorphosis.
larva
nymph
adult

15. There are three life stages of complete metamorphosis.
egg
larva
pupa
adult

16. Evolution to life on land
The evolution of flight occurred in insects 400 million years ago.
An insect’s mouth parts are adaptations related to its specialized diet.
sucking mouth parts
chewing mouthparts

17. 24.5 Arthropods and Humans Arthropods interact with humans.
Many arthropods are herbivores that eat plants humans also depend on.
Arthropods cause millions of dollars of crop damage.
Insecticides have unwanted side effects.

18. Scientists have developed safer insecticide alternatives.
arthropod-specific insecticides
integrated pest management (IPM)
genetically modified crops

19. Vectors are organisms that carry disease from one host to another.
Disease spread by arthropods have serious effects on human populations.
Bubonic plague is caused by a bacterium carried by fleas.
Yellow fever is caused by a virus carried by mosquitoes.
Malaria is caused by a protozoan parasite carried by mosquitoes.
West Nile virus is caused by a virus carried by mosquitoes.