the design of organisms
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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 = 1st 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