Chapter 5 - Acoelomorpha, Platyzoa and Metazoa Flashcards
Is Platyzoa a phylum or a clade?
A clade
Cephalization is the concentration of ____ in the head region
sense organs
What does the coelomate structure develop from?
The mesoderm
What differentiates the acoelomate structure?
No coelom but have digestive cavity; region between epidermis and digestive cavity filled with parenchyma
Contrast the pseudocoelomate structure with a coelomate
Has an internal body cavity surrounding the gut like the coelomate, but is not completely lined by mesoderm
This phylum has small flat worms less than 5 mm in length
Phylum Acoelomorpha
Where do acoelomorphs typically live?
Typically marine sediments; few pelagic, some in brackish water
True or False: Phylum Acoelomorpha includes the Platyhelminthes
False: Acoelomorpha is a separate phylum containing members that were originally in Class Turbellaria
Acoelomorpha are not part of the same clade as Platyhelminthes and only resemble them superficially
Acoelomorphs are dioecious: True or false.
False, they are monoecious
This reproductive feature may be one of the defining morphological features of acoelomorphs:
* Following fertilization some or all cleavage events produce a ____ pattern of new cells
duet-spiral
What are the protostomes? Differentiate them from the deuterostomes
A clade characterized by the development of the mouth first before the anus in embryonic development, which is reversed in the deuterostomes
Protostome: Mouth first
What structure/s do Lophotrochozoans share?
Either:
* a horse-shoe shaped feeding structure called the lophophore
* or a unique larval form called the trochophore
What does the clade Platyzoa include?
- Clade Platyhelminthes
- Clade Gastrotrichia
- Clade Gnathifera
Mesozoa is thought to be a sister group (actually 2022 cladistics says they’re under Platyzoa and also Gnathifera is a sister group and shouldn’t be included but don’t mind that <3)
What are the four phyla of Gnathifera?
- Gnathostomulida
- Micrognathozoa
- Rotifera
- Acanthocephala
Rotifera and Acanthocephala are under the clade Syndermata
Compare the body of parasitic platyhelminthes to free-living ones. What distinct trait do their bodies have?
An external body covering called a synctial tegument (neodermis)
Free-living species have a cellular ciliated epidermis
This is a genus of terrestrial flatworm
Bipalium
Enumerate the four classes of Platyhelminthes
- Turbellaria
- Trematoda
- Cestoda
- Monogenea
Monogenea, Trematoda, and Cestoda are all parasitic but differ in lifestyle. How?
Monogeans are mostly ectoparasites, while trematodes and cestodes are endoparasites
These rod-shaped structures found in the cells of the epidermis of turbellarians have what function?
Swell and form a protective mucus sheath when discharged with water
What is the function of the dual-gland organs of the epidermis in turbellarians?
Adhesion/adhesive organs
The clade Neodermata includes Trematoda, Monogenea, and Cestoda. How is their neodermis formed?
Several surface layers of epidermis are shed, which allows the cytoplasmic extensions from cells below the basement membrane to reach the surface.
What reason does the syncytial tegument exist?
Gives resistance to a host’s immune system and digestive juices
How do tapeworms (cestodes) digest?
They have no digestive system, instead relying on the host’s digestive tract to absorb digested nutrients as small molecules
Describe the digestive system of turbellarians.
- The pharynx may extend through the ventral mouth
- The intestine has three branches: one anterior and two posterior
- Generally carnivorous, detects food by chemoreceptors
- Food is trapped by mucous secretions from glands and rhabdites
- Extends their proboscis to suck up food
Unlike cestodes which have no digestive system, monogeneans and trematodes do. How and what do they digest? Describe their digestive system.
Graze on host cells, feeding on cellular debris and body fluids
- Mouth opens near the anterior end
- Unlike turbellarians, pharynx is not extensible
- Blind gut branching usually in a Y-shape
True or False: Turbellarians can reproduce asexually and sexually. If true, how do they reproduce asexually?
True. They reproduce asexually through fission
