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What does Platyhelminthes mean

flat worm

What is the level of organization

organ system

What kind of body cavity do they have


What are the three classes of platyhelminthes?

Turbellaria, trematoda and cestoda

what are turbellaria

Planaria, free living worms

what are trematoda

flukes, mostly parasitic

what are cestoda

tapeworms, all parasitic

how big are planaria?

microscopic to 60 cm (2 feet)

what is planarias habitat

mostly freshwater

charecteristics about planaria

bottom dwellers, nocturnal, carnivourous/scavengers

why do planaria have a triangle head

to be aerodynamic

what are eyespots

contain black pigment and sensory cells to detect light, no lens

what are auricles

sensory areas for touch, contain chemical receptors for food

what is on the ventral surface

covered with cilia (traction) and mucas cells (traction/capture prey)

where is its mouth

1/2 way down, pharynx extends from it

where is its genital pore

2/3 way down, exchange sperm/lay eggs

What are the parts of the nervous system

ganglia,longitudinal nerves, transverse nerves, peripheral nerves

what is the ganglia

brain, cluster of sensory cells that sorts stimuli

what are longitudinal nerves

run anterior to posterior

what are transverse nerves

connect longitudinal nerves

what are peripheral nerves

extend outwards from longitudinal nerves

what are the parts of the muscular system

longitudinal muscles, circular muscles, diagonal muscles and parenchymal muscles

what do longitudinal muscles do


what do circular muscles do


what do diagonal muscles do

bend side to side

what do parenchymal muscles do

run dorsal to ventral, push animal downward

describethe excretory system

runs through mesoderm, many tubes, run from anterior to posterior, from these pores open to dorsal surface, smaller tubules branch off and end with a "flame cell"

what is a flame cell

contain cilia which beat to pull fluid from mesoderm into tubes and out pores

what are the steps of ingestion

capturing prey, break prey into smaller pieces, pharynx sucks bits of food into intestine

how do they capture prey

slime cells on ventral surface secrete mucas which gets sprayed onto prey to immobilize them

how do they break prey into smaller pieces

gland cells inside intestine secrete digestive enzymes which get sprayed onto prey (partially digests it)

Describe intestine structure

3 branches, 1 anterior 2 posterior, these further branch into smaller tubes which increase surface area for digestion and absorbtion of food

how does digestion work

gland cells in the intestine secrete digestive enzymes, nutritive cells have flagella which mix the food/enzymes, nutritive cells then engulf food and finish digestion inside vacules, food then difuses to all parts of the planaria

what are the nutritive cells similar to in cnidarians

epitheliodigestive cells

how does elimination work

pharynx extends, animal sucks in water to fill the intestine, once filled the muscles contract to force contents back out of pharynx

what kinds of reproduction is there

sexual and asexual

how does asexual reproduction work

regeneration- worm constricts into middle and pulls apart, each piece will develop new halves

how does sexual reproduction work

1- exchange sperm through the genital pore
2- sperm goes to the copulatory sac to mature
3- once mature, the sperm traves through oviducts towards eggs
4- zygote then travels back towards genital chamber, along the way yolk (food) and capsule is added
5- encapsulated zygote released into water to eventually hatch in 2-3 weeks

what are the barriers parasites have to overcome

1- reaching and penetrating new hosts
2-surviving against defenses of host (white blood cells)

what adaptations have parasites used to overcome

1- structures for attachment (flukes have suckers, tapeworms have suckers, hooks and teeth)
2-resistant outer body coverings (tapeworms have cuticles)
3- complex reproductive systems (tapeworms have reproductive organs in each of their body segments, can self fertilize)
4- intricate reproductive cycles (flukes usea variety of intermediate hosts to reach primary host, snail to fish to human, hard to get rid of)

what are cuticles

tough,secreted coverings which resist WBC, chemicals, ect

what traits have parasites lost

1- mouth/digestive cavities(food difuses through the skin, food is already digested for them)
2- muscles/cilia/mucas (host provides everything, dont need to go anywhere)
3- nerves/brain (no need to locate mates, food, home, ect)

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