ch.19, 20 and 21 - cnusd.k12.ca.us · phylum arthropoda 4 subphyla trilobita-extinct...
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Arthropoda
The most diverse and
numerous of all animal
phyla
Joint-foot
900,000 species
More beetles than all
vertebrates(species)
Evolution of Arthropods
Natural selection
Fewer body segments
Specialized
appendages
Tagmata – head ,
thorax, abdomen
Cephalothorax,
abdomen
Phylum Arthropoda
4 subphyla
Trilobita-extinct
Chelicerata-chelicerae-2 body segments – 4
pairs of walking legs
Crustacea-2 pair antennae-mandibles
Uniramia-jaws-one pair of antennae-
unbranched appendages-3 pairs
Arthropoda
Cambrian period
570 million years ago
Exoskeleton developed
Molting/hormonal control
Hydrostatic skeleton lost – replaced by open
system
Common Characteristics
Cephalization – eyes,
fused ganglia,
antennae(fiirst to form
images)
Metemerism – somites
are very specialized
Paired jointed
appendages
Exoskelton
Complex social
structures
Protective coloration
Characteristics
Bilateral symmetry
Head, thorax, tail
Cephalothorax,
abdomen
Complete digestive
system
Respiration – body
surface, gills, tracheael
tubes or book lungs
Air enters through
spiracles
Paired excretory glands-
malpighian tubules
Versatile Exoskeleton
Cuticle secreted by the epidermis
Made of several layers secreted during
molting
Exocuticle first then endocuticle
Layers made of chitin
Tough resistant nitrogenous polysaccharide
Insoluble in water and weak acids
Protection, coloration, movement
To grow must shed the exoskeleton or molt
Limits body size – no giant arthropods
Segmentation
Each somite – jointed appendages
Often modified
Hollow levers that are moved by internal
muscles
Sensory hairs – modified for sensory
functions, food handling, swift walking and
swimming
Air piped directly to cells
Efficient tracheal system of air tubes
Oxygen delivered directly to tissues and cells
Makes high metabolic rate possible
Limits body size
Some use gills
Complex behavior patterns
Inate controls most activities
Some learning
Complex societies and division of labor
Metamorphosis
Larval state to adult stage
Adapted for different ecological niches
Less competition among the species
Incomplete or Complete
Trilobita
Before Cambrian period
200 million years ago
Abundant during the Cambrian and
Ordovician periods
Trilobed shape of body
Bottom dwelling scavengers
Could roll like pill bugs
Chelicerata
Horseshoe crabs
Spiders
Ticks
Mites
Scorpions and sea spiders
Name for mouth parts called Chelicerae
3 classes
Merostomata
Pycnogonida
Arachnida
Horseshoe crabs
Sea spiders
Scorpions, spiders,
ticks, mites
Characteristics
6 pairs of appendages
1 pair of chelicerae – suck liquid from prey
Pedipalps
4 pairs of walking legs
No mandibles
No antennae
Subphylum Crustacea
5 classes
Lobster
Crab
Shrimp
Pill bug or sow bug - terrestrial
Named after hard outer shell
Uniramia
5 classes
Chilopoda – centipedes
Diplopoda – millipedes
Pauropoda – small soft bodied myriads
Symphyla – small centipede like animals
Insecta – grasshopper to bumble bee to beetle