The Design of Organisms What Patterns do you see?

Body Plans The great diversity of plant and animal forms arises from a surprisingly small number of patterns. Although some organisms have complex shapes, we will begin looking at simple systems

Spheres, Tubes, and Fans A surprisingly large number of biological structures can be described in terms of spheres, tubes, and fans (surfaces).

Phylum Annelida: The Segmented Worms

Annelid Evolution Earliest fossils are about 520 to 550 million years old… right at the beginning of the Cambrian period.

Annelid Characteristics 1. Bilaterally symmetrical and vermiform (worm- shaped)

2. Triploblastic 3 cell layers

3. Coelom (Body Cavity)

More Characteristics 4. Through Gut: Mouth & Anus 5. No true respiratory system (no respiratory organs)

6. Simple Nervous System Ganglia are bundles of nerves that act somewhat like brains. The head contains several “cerebral ganglia” Along the ventral nerve cord (yellow) there are “segmental ganglia”

7. Closed Circulatory System with “Hearts” Annelid worms have blood and 5 pairs of “hearts” to keep it circulating. This is a new characteristic, not seen in simple organisms.

8. Body possesses 3 separate sections, a prostomium, a trunk and a pygidium. Prostomium = 1 st segment, some w/ sensory organs Trunk = body segments Pygidium = end segments, contain anus.

9. Reproduction: Freaky Worms Some annelid worms are gonochoristic. Gonochoristic organisms, like you, have a distinct sex. Usually, there are 2 varieties, i.e. male and female. Most however, are simultaneous hermaphrodites, meaning that individuals have both testes and ovaries. During mating, they may act as a male or female.

Clitellum Fertilized eggs will be wrapped in a mucus- covered coccoon made by the clitellum, which contains the worm eggs

Label ‘er up! Label up your diagram! Skip “C” B = “ganglia” not brain