flatworms, roundworms, & rotifers
DESCRIPTION
Flatworms, Roundworms, & Rotifers. Chapter 34. Phylum Platyhelminthes. Section 34.1. General Structure:. 3 germ layers – ectoderm, mesoderm, and endoderm acoelomates Bilateral symmetry Anterior and posterior ends Dorsal and ventral surfaces only Flat body plan Flatworms!. - PowerPoint PPT PresentationTRANSCRIPT
FLATWORMS, ROUNDWORMS, & ROTIFERS
Chapter 34
PHYLUM PLATYHELMINTHES
Section 34.1
General Structure:
3 germ layers – ectoderm, mesoderm, and endoderm acoelomates
Bilateral symmetry Anterior and posterior ends
Dorsal and ventral surfaces only Flat body plan Flatworms!
General Functions:
Exchange oxygen and carbon dioxide directly with the environment to cells by diffusion No circulatory system or respiratory system
needed Only one opening where food and wastes
pass through! Cephalization
Classification:
Four Classes:1. Turbellaria - non-parasitic
2. Trematoda- parasitic3. Monogenea - parasitic
4. Cestoda –parasitic
1. Class Turbellaria: 4,500 species Mostly marine Swim in wavelike
motion Glide over solid
surfaces on layer of mucus
Example: Planarian Dugesia freshwater
Video
Planarian Body Plan:
Planarian Organ Systems:Digestive System: Scavengers & predators
Decaying plants & animal matter Prey on smaller organism
Pharynx – throat that extends to the middle of body video
Planarian Organ Systems:Excretory System: Flame Cells – enclosed tufts of cilia that draw
excess water together and excretes it through pores video
Planarian Organ Systems:Nervous System: Cerebral ganglia: two
clusters of nerve cells at anterior “Brain” Can learn
Eyespots: sense direction and intensity of light
Other senses: touch, water currents, chemicals
Planarian Organ Systems:Reproductive System: Sexual:
Hermaphrodites Eggs laid in protective capsule
Hatch in 2-3 weeks Asexual:
Regeneration video
Video