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The Cambrian Explosion

The Cambrian Explosion. The Phylum Arthropoda. The most successful animal group on earth HOW DO THEY DO THAT?. 1. Hard exoskeleton composed of chiton 2. Segmented body and specialized jointed appendages 3. Complex nervous & sensory system 4. Variety of respiratory organs

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The Cambrian Explosion

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  1. The Cambrian Explosion

  2. The Phylum Arthropoda The most successful animal group on earth HOW DO THEY DO THAT? 1. Hard exoskeleton composed of chiton 2. Segmented body and specialized jointed appendages 3. Complex nervous & sensory system 4. Variety of respiratory organs 5. Complex innate and learned behaviors 6. Complex life cycle with metamorphosis

  3. Segments of Arthropod Body Partitioned into Two or Three Tagmata cephalothorax abdomen cephalothorax head thorax abdomen

  4. Arthropod Muscular System

  5. Arthropod Respiratory Systems

  6. Subphylum Trilobita Once abundant in ancient oceans Extinct for over 200 million years

  7. Subphylum Chelicerata 1. Two tagmata (cephalothorax and abdomen) 2. 6 pairs of appendages: chelicerae, pedipalps, 4 pairs walking legs (no antennae, no mandibles) 3. Respiration via book gills or book lungs

  8. Class Merostomata: Horseshoe Crabs 1. cephalothorax completely covered with a large carapace • Long, spine-like telson • Book gills

  9. Class Pycnogonida: Sea Spiders 1. Four pairs of long, thin walking legs (some males have one pair modified for carrying eggs = ovigers) 2. Proboscis for sucking juices from hydroids 3. Abdomen reduced or absent

  10. Class Arachnida spiders, scorpions, mites, ticks 1. cephalothorax partially or completely covered with a carapace-like shield 2. Abdominal appendages (if present) modified into spinnerets (spiders) or pectines (scorpions)

  11. Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

  12. Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

  13. Brown Recluse Spider

  14. Class Arachnida Order Araneae - Spiders Cephalothorax and abdomen joined by narrow pedicel Chelicera function as fangs and connect to poison glands Breathe using book lungs and/or tracheae Have 8 pairs of simple eyes Have silk glands and spinnerets

  15. Multiple Pairs of Eyes Spinnerets

  16. Class Arachnida Order Scorpionida - Scorpions Modified abdominal appendage (pectine) Order Opiliones - Harvestmen Chelicera modified into pincer-like appendages Order Acari - Ticks and Mites Mouthparts on anterior projection (capitulum) Transmit a wide variety of diseases

  17. Subphylum Myriapoda (millipedes, centipedes) • Uniramous (unbranched) appendages • Paired appendages on most/all segments • Body of two tagmata (head & trunk) • One pair of antennae, mandibles, maxillae • Respiration via tracheae and spiracles

  18. Class Chilopoda: Centipedes • one pair legs per segment • appendages of 1st body segment modified to form poisonous fangs • predatory

  19. Class Diplopoda: Millipedes • two pair legs per segment • hatch with 3 pairs of legs • herbivores or scavengers • unique defensive behavior

  20. Subphylum Crustacea • Mostly marine, some freshwater • Three tagmata (head, thorax, abdomen) • 2 pr antennae, 1 pr mandibles, 2 pr maxillae • Biramous, highly specialized appendages • Respiration via gills

  21. Biramous Specialized Appendages

  22. Stalked Compound Eye

  23. Simple vs. Compound Eye Compound Eye Simple Eye 1. Light enters transparent cuticle Concave Mirror Eye 2. Crystalline cone 3. Light sensitive cells stimulated 4. Nerve impulses fired off to brain Camera Eye Pinhole Eye

  24. Ecdysis Have to molt to grow Under hormonal control 1. Epidermis secretes new cuticle under old cuticle 2. Dissolves and resorbs calcium to weaken the old cuticle 3. Splits old cuticle and discards 4. Absorbs water to swell body 5. Hardens new shell 6. Reestablishes osmotic balance

  25. Crustacean Reproduction • Aquatic larval stages: nauplius and zoea • Molt through many intermediate larval stages • Separate sexes with sexual dimorphism

  26. Oligostraca Ostracoda, Branchiura, Pentastomida bivalve carapace completely encloses body

  27. Pentastomida parasite of carnivorous vertebrates • Four claw-like appendages • Chitinous cuticle • Extensive parasitic modifications make phylogeny difficult

  28. Vericrustacea Branchiopoda, Copepoda, Thecostraca, Malacostraca

  29. Branchiopoda Diplostraca (cladocerans), Anostraca (fairy shrimp), Notostraca (tadpole shrimp) • bivalved carapace or no carapace • no abdominal appendages

  30. Malacostraca isopods, amphipods, euphausids, decapods • All thoracic and most abdominal segments bear specialized appendages • Gills occur along the bases of thoracic appendages

  31. Kiwa hirsuta

  32. Subphylum Hexapoda (entognatha, insects) • Uniramous (unbranched) appendages • Body of three tagmata • One pair of antennae, mandibles, maxillae • Respiration via tracheae and spiracles

  33. Class Insecta: Insects • Body composed of three tagmata (head, thorax, abdomen) • One pair of large compound eyes and multiple ocelli • One pair of antennae • Three pairs of walking legs • Two pairs of wings one may be reduced = halteres

  34. Wingless insects Winged insects • some species lack tracheae • direct development • all have tracheae • metamorphic development

  35. Insect Respiratory System Tracheoles Air sacs Tracheae Spiracles

  36. Insect Excretory System

  37. muscles to raise wings longitudinal muscles muscles to lower wings dorsoventral muscles direct muscle system indirect muscle system Insect Flight

  38. Complete metamorphosis egg  larva  pupa  adult

  39. Modifications of Mouthparts mouthparts modified for chewing plant material mouthparts modified for piercing/sucking mouthparts modified for grabbing mouthparts modified into a long proboscis

  40. Complex Behaviors nocturnal swarming

  41. Social Systems queen worker drone

  42. 1. Subphylum Trilobitomorpha 2. Subphylum Chelicerata a. Class Merostomata - horseshoe crabs b. Class Pycnogonida - sea spiders c. Class Arachnida – spiders, scorpions, ticks, mites 3. Subphylum Crustacea • Class Branchiopoda - cladocerans, brine shrimp • Class Maxillopoda - ostracods, copepods, barnacles • c. Class Malacostraca - isopods, shrimps, crabs, lobsters 4. Uniramia Subphylum Myriopoda a. Class Diplopoda - millipedes b. Class Chilopoda - centipedes 5. Uniramia Subphylum Hexapoda • Class Insecta – insects • Class Entognatha – spring tails, bristletails, proturans

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