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Arthropods
Arthropod evolution•Modern arthropods have fewer body segments
and more specialized appendages.
Fossil of a Trilobite, extinct class of Arthropod
Fossil of Leanchoilia, Phylum Arthopoda
www.burgess-shale.bc.ca/ gallery/gallery.htm
Arthropod characteristics•Segmented
bodies•___________________________________•Tough exoskeleton made
of chitin•Multiple shapes and textures• Jointed appendages:
______________________
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Feeding• Herbivores, carnivores, omnivores, parasites, blood
suckers, filter feeders, and detritovores• Variety of mouthparts:
pincers, fangs, sickle-shaped jaws, feeding tubes
stag beetle pincers
Respiration•Most arthropods (usually terrestrial)
• Tracheal tubes:
•Some arthropods • Book lungs:
• Book gills:
• Feathery gills:
Circulation•Open circulatory system: heart pumps blood to
tissues, sinuses, and cavities but
______________________________________________________
Excretion• Malpighian tubules: saclike organs that extract
metabolic wastes from blood and then add them to feces to move
through the gut• Some terrestrial ones have extra small excretory
glands at the legs• Some aquatic ones usually have a green gland
near antennae
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Chrysina quetzalcoatli is freed in Cusuco National Park, leaving
a fecal trail
National Geographic
ResponseSensitive sensory organs (sight, smell, touch)Compound
eyesantennae
Well-developed nervous system BrainVentral nerve cordGanglia:
groups of nerve cells
Flexor muscles Extensor muscles Muscle pulling against
exoskeleton enables movement
Movement
Reproduction•Terrestrial arthropods: internal fertilization
•Male places sperm in female•Sperm sac that female picks up
•Aquatic arthropods: internal or external fertilization
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Growth and development•Molting: period of shedding exoskeleton
when outgrown
• Glands secrete digestive enzymes to break down exoskeleton.•
Glands secrete new exoskeleton.• Vulnerable stage
Insect molting case left on tree bark
Insect life cycle•________________________: process of changing
shape and form from juvenile to adult stage
•________________: juvenile stage (nymphs) appear like adults,
just smaller•__________________: juvenile stage (larvae) becomes
pupa, final stage before becoming an adult
Section 28-3
IncompleteMetamorphosis
CompleteMetamorphosis
EggsLarva
Pupa
Adult
Nymph
Nymph
Nymph
Adult
Eggs
Larva
Adult
AdultImmature
Metamorphosis
Figure 28–18
Arthropod subphylums
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Crustacea characteristicsTwo pairs of antennaeTwo or three body
sectionsMandibles: chewing mouthpartsBody plan: celphalothorax,
abdomen, carapaceBarnacles have “lost” appendages.Decapods have
chelipeds and swimmerets.Ex: shrimp, lobster, crayfish
Section 28-2
Abdomen Cephalothorax
Walking legs
Tail
SwimmeretsCarapace
Cheliped
Mandible Second antennaFirst antenna
The Anatomy of a Crayfish
Subphylum Crustacea – hermit crab Subphylum Crustacea –crab
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Subphylum Crustacea – fire shrimp
Chelicerata characteristics•Classes: Merostomata (horseshoe
crabs) and Arachnida (spiders, scorpions)•Four pairs of walking
legs•Chelicerae mouthparts: fangs that sting and pedipalps that
grab prey•Two body sections: cephalothorax and abdomen•Spiders have
__________________, silk glands.
Section 28-2AbdomenCephalothorax
Book Lung
EyesBrain
Pumpingstomach Heart IntestineOvary
Malpighiantubules
AnusSpinnerets
Silk glandsSpiracle
Bases ofwalking legsFanglikechelicera
PedipalpPoisongland
Airflow
The Anatomy of a Spider
Figure 28–9 Subphylum Arachnida – black widow spider
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Scorpion
Happy face spider Uniramia characteristics•Groups: centipedes,
millipedes, insects• Jaws•One pair of antennae•Unbranched
appendages
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Why insects are evolutionarily successful Insect
characteristics• Compound eyes• Some with wings• Three part body
plan• Three pairs of legs• Sensitive taste and smell receptors•
Three appendages for mouth, including pair of mandibles
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Section 28-1
Ventral View
AntennaeCompound eye Brain Digestivetract Malpighian tubules
HeartReproductive organs
AnusSpiraclesTrachealtubesNervecord
Ganglia
Salivaryglands
Mouth
Tracheal tubesSpiracles
Legs
The Anatomy of a Grasshopper
Figure 28–4
Insects and humans•Although they can be a nuisance or pest,
insects are significant to agriculture.•They facilitate flower
pollination.
Insect communication and societies•Chemical cues:
________________•Visual cues: light, flight patterns•Some insects
form societies where __________, groups of individuals, perform
specific tasks.
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Subphylum Insecta – bee moth
Trilobita Characteristics• Oldest subphylum• Inhabited the sea•
All extinct
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Importance of Arthropods• Ecologically:
• Commercially:
Importance con’t.Medically:
Technologically:
Agriculturally:
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Bug Hunt ActivityDue Tonightby 11:59pm