BIOL 112 Lecture 28

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Ecdysozoa: Nematoda

Reproduction

• Dioecious (male/female) or
• Hermaphroditic
  • Internal Fertilization (c.f. cross fertilization in annelids)
• C. elegans is androdioecious—hermaphroditic, but make a few males
  • Hermaphrodites can use sperm from a male, but won't mate until self-sperm (~300 ct.) are depleted

Model Organism

C. elegans is a genetically-tractable model organism

• simple anatomy (~300 neurons per worm)
• easy to grow (cheap!) in lab
• ~40% of C. elegans genes have clearly human orthologs

3 Nobel prizes for work in C. elegans

Ecdysozoa: Arthropoda

4 subphyla:

• Cheliceriforms
• Hexopods
• Myriapods
• Crustaceans

Arthropods comprise 75% of all animals; success from

• hard chitonous cuticle
• jointed appendages
• segmented bodies
• well-developed sensory organs
  • concentration of neurons in head = cephalization
  • large compound eyes
  • ocelli for navigation (detect polarization of light)
  • antennae for touch sensors
• some appendages used as mouth parts
• hexapoda: wings