SOFT BODY, HARD BODY

The image below is a photo of the exhibit panel. Following it is a transcript of the panel.

Photo of the panel from the exhibit.

Insects and crustaceans are closely related to soft-bodied marine worms.

Segmented worms and arthropods (insects, crustaceans, and their relatives) both evolved from a soft-bodied, segmented ancestor.

Segmentation is a simple way to become larger, because each segement is a duplicate of the next. By coordinating the muscle action of independent segments, the animal can move forward.

Annelids ( AN -nel-ids): animals with soft, segmented bodies, including earthworms and extinct, marine Canadia

New feature

    body segmentation increases size and facilitates locomotion and burrowing

When? 600 million years ago to present

Aysheaia (a-she- A -ah): an extinct, segmented marine animal that is thought to be related to the living Peripatus

New features

  • flexible external skeleton helps protect the animal from changes in the environment and provides body support
  • lateral appendages for walking, climbing and catching or manipulating food

When? 530 million years ago to present

Arthropods ( ARTH -ro-pods): segmented animals with jointed "legs", including trilobites, insects, and crustaceans

New feature

    jointed "legs" for walking, feeding, breathing, and sensing (touch, taste, etc.); muscles in both body and "legs" control movement

When? 570 million years ago to present

PICTURE CAPTIONS:

  • annelid
    Canadia (kan-ah- DEE -ah)
  • arthropod relative
    Aysheaia (a-she- A -ah)
  • arthropod
    trilobite ( TRY -lo-bite)
  • Diagram showing common ancestry and evolution of annelids, Aysheaia , and arthropods from organisms with a segmented body. Evolution of Aysheaia and arthropods is where flexible external skeletons and paired lateral appendages branch off.