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Phylum Arthropoda Introduction

Phylum Arthropoda Introduction

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Phylum Arthropoda Introduction

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  1. Phylum ArthropodaIntroduction

  2. ArthropodaGeneral Characteristics • Largest phylum of animals • Over 900,000 species described • includes: • spiders, scorpions, mites, ticks • insects, millipedes, centipedes • crabs, shrimp, lobsters, crayfishes • very adaptive - found in virtually every habitat

  3. ArthropodaGeneral Characteristics • When compared to annelids • both are metameric • primitively have single pair of appendages/segment • nervous system along the same plan • similar embryonic development

  4. ArthropodaGeneral Characteristics • metameric body plan • divided into tagmata (i.e., tagmatization) • somites fused into functional units • head • thorax • abdomen • or • cephalothorax • abdomen

  5. Appendageslots of specialization • locomotion • swimmerets • walking legs • reproduction • gonopods Appendages: primitively with one pair per segment

  6. Exoskeleton • made of protein, lipids, chitin, calcium carbonate • advantages: • protection • fights water loss; most successful terrestrial invertebrate group • allows for effective movement on land • disadvantages • heavy and bulky • needs to be periodically replaced (i.e., molting) • vulnerable during molting

  7. Selected System Summaries • Complex muscular system that is segmentally arranged • Reduce coelom; mostly a hemocoel filled with blood • Complete digestive tract with mouthparts as modified appendages • Open circulatory system with dorsal contractile heart

  8. Respiratory System • Respiration by: • body surfaces - primitive forms • gills - crustaceans • trachea - insects • book lungs - chelicerates

  9. Excretion • Most with with paired glands • coxal, antennal or maxillary • insects and others • malpighian tubules

  10. Nervous System • similar to that in annelids • dorsal brain (cerebral ganglia) around esophagus • double ventral nerve cords • well developed sensory organs

  11. Reproduction • usually dioecious • usually internal fertilization • oviparous or ovoviviparous • often with metamorphosis • some have parthenogenesis

  12. WHY ARTHROPODS ARE SO SUCCESSFUL? • versatile exoskeleton • segmentation and appendages for efficient locomotion • air piped to cells directly (insects) • highly developed sensory organs • complex behavior patterns • reduced competition through metamorphosis