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Chapter 8

BIOL 2030 Chapter Notes - Chapter 8: Microstructure, Parthenogenesis, Limnognathia

Course Code
BIOL 2030
German Reyes

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CHAPTER 8 acoelomorpha, platyzoa, mesozoa
- Are worms and (most) have bilateral symmetry and are triploblastic animals
- Have acoelomate bodies (lack coelom) and have mesoderm
- Have only one internal space (digestive cavity)
- Parenchyma is the region between the epidermis and the digestive cavity lining.
- a pseudocoelomate has an internal cavity (pseudocoelom), surrounding the gut, but the cavity
is not lined with mesoderm (unlike coelomate animal)
Phylum Acoelomorpha
- have a distinct anteroposterior axis
- lack “true” brain
Clade Platyzoa: are a part of lophotrochozoan protosome phyla. Contains Platyhelminthes,
Gastrotricha, and phyla in Gnathifera
Phylum Platyhelminthes
- there are four classes: Turbellaria (nonparasitic), Trematoda, Monogenea, and Cestoda (all
- turbellarians have ciliated body ( cellular epidermis with rhabdites) while the parasitic classes
have nonciliatd bodies (called syncytial tegument). The parasitic class have a body has a
- body acoelomate
- have a mouth, pharynx, and intestine (intracellular digestion)
- excretory system comprises two lateral canals with braches bearing flame cells
- have auricles (earlike lobes), statocysts (balancing organ), rheoreceptors (sensing water current)
and ocelli (light sensitive eyespot)
Class Turbellaria:
- some don’t have a larva stage and some have a ciliated larva stage
- locomotion: quickly attach and detach from surfaces (epidermis has dual-gland adhesive
organs) and have cilia
- eg. Dugesia
Class Trematoda
- have a well-developed gut tube but the mouth is on the anterior end
- Similar reproductive, excretory and nervous system as turbellaria. Sense organs are poorly
- subclass Digenea:
o life cycle: first host (intermediate host) is a mollusc and the final hose (definitive host)
is a vertebrate. In the defentive host the parasite reproduces sexually
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