1 Announcements Web pages up (see my home page) Today’s reading (mostly on reserve) – Anderson: pages on lecture topic handout •pp. 289-299 only for the big picture! – Text: pp 178-183, 202-21 Phylum Onychophora and Tardigrada Phylum Onychophora and Tardigrada • Like arthropods, both groups have – Reduced coelom (body cavity) – Open circulatory system – Outer covering (cuticle) • Onycophorans sister group to arthropods • Tardigrades can live in extreme environments
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1
Announcements
Web pages up (see my home page)Today’s reading (mostly on reserve)
– Anderson: pages on lecture topichandout•pp. 289-299 only for the big picture!
– Text: pp 178-183, 202-21
Phylum Onychophora andTardigrada
Phylum Onychophora andTardigrada
• Like arthropods, both groups have– Reduced coelom (body cavity)– Open circulatory system– Outer covering (cuticle)
• Onycophorans sister group to arthropods• Tardigrades can live in extreme
environments
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Introduction to PhylumArthropoda
Introduction to PhylumArthropoda
• Very old group of animals (>500 MYBP)• Oldest fossils in ocean• Highly diverse in water and on land.• Four major living groups, others extinct
Arthropod Features
• Body plan
– bilateral symmetry– metamerism
– paired jointed appendages– tagmata (tagma)
– exoskeleton
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Arthropod Features
• Jointed appendages•sensory structures•feeding appendages•locomotion•reproductive structure
Uniramous or Biramous
Arthropod Features
• Eyes
Simple CompoundOne lens, records daylength many lenses, detects movement
Arthropod Features
• Physiology•body cavity: hemocoel•circulatory system: open with dorsalheart, not used for gas exchange
•nervous system: paired ventral nervecords
•respiratory systems: gills ortracheal system
•excretory systems: Diverse.Malpighian tubules found in mostterrestrial forms
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Arthropod Features– Growth through molting
Arthropod Features• Reproduction
– internal fertilization
Adaptations toTerrestrial Life
• Internal fertilization
• Tracheal system
• Excretory system
• Waxy cuticle (Hexapoda)
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Living Groups of Arthropods• Superclasses
– Crustacea
– Chelicerata– Myriapoda– Hexapoda
Superclass Crustacea
Crustacean Features
– Diverse body plans with differentpatterns of segment fusion
– 2 pair antennae– Mandibles– biramous appendages– exoskeleton is chitin and calcium– gills
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Biramous appendages
Terrestrial Crustaceans• Sowbugs, pillbugs
Superclass Chelicerata
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Chelicerate Features I
– variable morphology based on commonbody plan• cephalothorax
– Anterior prosoma: bears limbs– Posterior opithosoma
– six pairs of appendages• chelicerae• pedipalps• walking legs
– Appendage morphology• most appendages uniramous• a few marine forms show biramous appendages
Chelicerate Features II– NO antennae
– book gills or book lungs– Possess chelicerae for feeding– juveniles look like adults
– generally predaceous, someparasites
Chelicerate Groups• Pycnogonida
• Merostomata
• Arachnida
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Pycnogonida
• Ancient group, reduced abdomen
MerostomataAlso ancient, compound eyes
Arachnida
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Arachnida• Diverse on land• Waxy cuticle• Vary in size of abdomen vs throax• Predaceous or parasitic
Superclass Myriapoda
Myriapod Features
– little tagmatization– many segments- growth throughaddition
– uniramous– numerous pairs of legs– juveniles look like adults– jointed mandibles
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Myriapod Groups
Diplopoda: Millipedes
Chilopoda: Centipedes
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