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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