Chapter 14: Phylum Platyhelminthes Flashcards
Platyhelmithes are the ________ animals with bilateral symmetry. Their _______ is well defined. They are __________. They are also highly specialized_______.
simplest, mesoderm, triploblastic, parasites
What are the two major evolutionary advances ? (2)
-Cephalization - concentration of sense organs in anterior region
-Primary Bilateral Symmetry
I> body can be divided along only ONE plane of symmetry to yield two mirrored images of each other.
I> active, directed movement most efficient with an elongated body form with anterior, posterior, dorsal and ventral sides.
Platyhelminthes are Acoelomates meaning>
space between the epidermis and digestive cavity?
atypical acoelomates>
- have only one internal space, the digestive cavity
L> between the epidermis and digestive cavity is filled with parenchyma
-no digestive cavity!
Are Platyhelminthes acoelomate Protostomes or deuterostomes ?
Protostomes! their mouth develops first via blastopore !
Some platyhelminthes are _______; others are _____.
The parasitic clades share an external body covering called a ___________. (also called ______)
free-living, parasitic, syncytial tegument, neodermis
What are the four classes of Platyhelminthes?
Turbellaria, Trematoda, Monogena and Cestoda
Class Turbellaria are mostly___________. Habitat wise they are mostly _______ dwellers in ________ or ________.
Freshwater planarians are found in? (3) Terrestrial flatworms are limited to ____________. (2)
All members of monogena and Trematoda and Ceatoda are ______?
- free-living forms, bottom, marine, freshwater
- freshwater planarians are found in streams, pools and hot springs
- terrestrial are limited to moist places
Epidermis and Muscles?
Most have cellular ________ on a basement membrane. Rod shaped ________ that swells and form a protective mucous sheath.
- ciliated epidermis, rhabdites
Most turbellarians have dual-gland adhesive organs.These are?
- viscid gland cells which fasten microvilli of anchor cells to substrate.
- secretions of releasing gland cells provide a quick chemical detachment
Some turbellarians and others in this phylum have a Syncytial epidermis which is ?
-nuclei are not separated by cell membrane !
Those that are not turbellarians lack _______ and have a ______
cilia and have a tegument
Under the basement membrane there are what??(hint muscles) (3)
muscle fibres which run circularly, longitudinally and diagonally
Parenchyma cells fill spaces in the body which are mostly what?
non contractile portions of muscle cells
Nutrition and Digestion??? Cestodes have no _________ system.
Others in this phylum have a ______, _____, and ______.
In planarians the ________ may extend through the ventral mouth.
digestive, mouth, pharynx, intestine, pharynx
The intestine has how many branches?
three! one anterior and two posterior
The gastrovascular cavity is lined with what type of epithelium?
columnar!
Characteristics of the mouth of trematodes and monogeneans? (3)
- opens?
- pharynx?
- intestine?
- opens near the anterior end
- pharynx is not extensible
- intestine ends blindly, varies in branching
Planaria are carnivorous and detect food via ___________.
Food is trapped in ______________ from glands and _______.
They wrap themselves around prey
They extend the ________ to suck up bits of food.
chemoreceptors, mucous secretions, rhabdites, proboscis
Monogeneans and Trematodes?
-Feed on what? (3)
-Proteolytic enzymes from the intestine are secreted for _______.
-Phagocytic cells in gastrodermis complete digestion at ________ level.
-Undigested food is egested out via _______.
Cestodes rely on the host’s ____________. They absorb the _______ nutrients.
- host cells, cellular debris, and body fluids
- extracellular digestion
- intracellular
- pharynx
- digestive tract, digested
Protonephridia?
- flame cell?
- excretory system occurs how?
- osmoregulation?
- osmoregulation
- beating flagella drive fluids down collecting ducts
- wall of the duct beyond the flame cell bears folds or microvilli to reabsorb ions and molecules
- metabolic waste is removed via diffusion across the cell wall
- collecting ducts join and empty at nephridiopores (mostly for osmoregulation…therefore absent in marine turbellarians)
Marine Turbellarians lack Protonephridia b/c they have no need to expel _____?
excess water
Monogeneans have two excretory pores. Location of each?
- open laterally near anterior end
- flame cell protonephridia present also in the parasitic taxa.
Ducts of tematodes open into ___________ that opens to a terminal pore.
excretory bladder
Cestodes have two main excretory canals. Located?
one on each side.
metabolic waste is removed largely by diffusion through the body wall.
Nervous System yo?
- Subepidermal Nerve Plexus?
- longitudinal nerve cords?
- Fresh Water Planarians?
- resembles nerve net of cnidarians, most primitive ns found in flatworms…turbellarians
-one to five pairs of cords lie under the muscle layer…more derived worms have fewer nerve cords.
-one ventral pair of nerve cords forming a ladder type pattern.
I> brain is a bilobed ganglion anterior to the ventral nerve cords
Neurons are organized into?(3)
-sensory, motor and association types…this is an important development in evolution of the NS
Sense organs?
- Ocelli( appear in what classes)
- Tactile and Chemoreceptive cells
- Statocysts
- Rheoreceptors
- sensory nerve endings are found in?
- light sensitive eyespots… present in Turbellarians, Monogeneans and larval trematodes.
- abundant, especially in the ear-shaped auricles
- equilibrium
- sense direction of water currents
- the oral suckers and genital pores of parasitic groups
Reproduction and Regeneration?
- Fission-turbellarians?
- Regeneration - retaining of polarity?
-turbellarians constrict behind the pharynx and separate into two animals ..each half regenerates missing parts….causes rapid pop growth..some do not separate right away making chains of zooids.
-if the head or tail are cut off…each end grows the missing part-retains polarity….
L>extracts of heads added to culture of headless worms prevents regeneration ..
Some asexual reproduction occurs where?
in the intermediate host
Nearly all are ___________ but cross fertilize.
monoecious
Endoleicthal eggs with spiral determinate cleavage are _____ and ____
typical , ancestral
Some turbellarians and all other groups have female gametes with little yolk. The yolk is contributed by the sex organ _____. What brings yolk cells to the zygote for ectolecithal development? A cleavage pattern cannot be distinguished. The zygote and yolk cells surrounded by eggshell move into the ____.
- Vitellaria
- Vitelline ducts
- uterus
Male structures?
- testes connect to
- vas defrens connect to? And run to ?
- what is the copulatory organ?
- one or more testes are connected to vasa efferentia that connect to one vas defrens
- vas defrens run to a seminal vesicle
- A papilla like penis or extensible cirrus is the copulatory organ
Turbellarians develop both _____ and _____ organs opening at a _____ pore. After copulation, ____ and ____ enclose in small cocoon.
-what occurs next?plants, marine forms , embryos resemble?
- male, female , common, yolk cells, eggs
- attach by a stalk to plants
- embryos emerge and resemble little adults
- some marine forms are ciliated, free-swimming larvae
Larval trematodes emerge as _________. Which penetrate a snail or eaten by a host.
Cestodes hatch only after being _______ ?
Trematoda, Monogenea and Cestoda are united into a single clade called?
- ciliated larvae
- consumed by a host
- Neodermata
