Biology 11- 27.1 (Flatworms)

unsegmented worms

worms with bodies that are NOT divided into segments

Phylum which flatworms belong to

Phylum Platyhelminthes

3 layers of flatworms

ectoderm, mesoderm, endoderm

feeding in flatworms

carnivores, detritus feeders, or parasites

digestion in free-living flatworms

-GVC with ONE opening at the end of a muscular tube (pharynx)
-GVC formed an intestine with many branches along the entire length of the worm
-Enzymes break down food in intestinal wall
-Intestine runs along the ENTIRE body so digested food can diffuse into other body tissues
-Undigested food leaves through mouth/anus

digestion in parasitic flatworms

-Feeds on blood, tissue fluids, cells of host
-SIMPLER digestive tract than free living flatworm (no digestive tract)
-Absorb food by hooking themselves onto the intestine with their sucker

How freshwater flatworms respire

-rely on diffusion to transport oxygen and nutrients to their tissues, and getting rid of water and CO2
-They have flame cells that help them get rid of extra water
-OSMOSIS
-Flame cells join together to form a network that empties through tiny pores

Nervous system in flatworms

-Definite head in anterior region
-Simple brain
-Nerve cord runs from the brain down the length of the body on either side.
-Shorter nerve cords run side of body
-One of more pairs of OCELLI (Detects light)

How flatworms feed

-Has cells that are sensitive to chemicals found in food
-Cells tell them which way water is flowing
-sense organs scattered all around body

auricles

sense organs in flatworms

How flatworms move

-Small cilia on epidermal cells help them glide through water
-Muscle cells allow them to twist and turn
-Muscle cells controlled by nervous system

How flatworms reproduce sexually

-Worms join in pairs
-One worm delivers the sperm at the same time that it received sperm from its partner
-They lay eggs

How flatworms reproduce asexually

-Binary fission (divided on its own to produce identical copies of itself)
-Can "fall to pieces"- each piece regenerates into a new worm

Turberllarians

Class: Turbellaria.
-free living flatworms that live in marine or fresh water

Flukes

Class: Trematoda.
-parasitic worms that infect hosts' internal organs or outside parts

phylum which roundworms belong to

phylum nematoda