Bilateral Animals Flashcards
General characteristics of phylum platyhelminthes?
Bilateral
Vermiform- “wormlike”
Elongated, bilateral animals reduced appendages-
Large numbers are parasitic
Important pathogens of humans and domestic
animals.
Parasitic forms- Bodies severely modified.
Use non-parasitic members to give general
features (Phylum characteristics)
External features of platyhelminthes?
Vermiform- (wormlike)
Range of sizes (2 mm or less to more than a
meter long- some tapeworms are meters
long)
Flattened, leaf-like, long and ribbon-like
Non-parasitic, free-living form: Auricles (ear
lobes), Ocelli- eye spots, pharynx
Characterisitics of platyhelminthes? (summarized)
Bilaterally symmetrical; Dorsoventrally flattened
Acoelomate structure: No body cavity- parenchyma of
mesodermal origin in space between outer wall and internal
organs -replaces gelatinous mesoglea.
Triploblastic (parenchyma - mesenchyme)
Mouth opens into intestinal sac (no anus)- Mouth the only
opening to digestive tract (if present)
Excretory system- Protonephridia (flame cells) + function in
osmoregulaton
Nervous system- Nerve net + longitudinal cords.
Reproduction: Asexual or hermaprhroditic- Biflagellate sperm
No respiratory or circulatory system - diffusion/intercellular
junctions
25,000 spp.
Includes 4 classes: Both free-living (one class) and parasitic
individuals
general Characteristics of Nematoda phylum?
- Bilaterally symmetrical, cylindrical,
pseudocoelomate.
2. Cuticle covers epidermis (no cilia and flagella)
3. Longitudinal muscles only.
4. Complete gut
5. Excretory system either gland cell, canal system or
both- No flame cells (protonephridia)
6. “Brain”- nerve ring + dorsal and ventral nerve
cords
7. Dioecious- tubular testes or ovaries in
pseudocoelom.
Briefly describe the structure of Turbellaria
Epidermis
cellular epithelium
Ectodermal origin
dorsal – rhabdoid
glands
ventral – mucus
glands; ciliated
Parenchyma
mesodermal origin
storage of glycogen
diffusion of nutrients
and dissolved gases
pleuripotent cells
