Worms. Flashcards
Triploblastic
3 tissue layers
Platyhelmenthes
Flatworm “body flattened”
What type of symmetry do playthelmenthes have?
Bilateral symmetry
Level of development for platyhelmenthes
Organ system
Acoelomate
Flatworms have no body cavity other than gut
How does the lack of body cavities help respiration in Platyhelmenthes?
Allows them to be as flat as they can so that they can respire by diffusion. No cell is too far from the outside, flat shape necessary
Parenchyma
Form of mesodermal tissue containing cells and tissue
Planaria Characteristics
- negatively phototaxic
- chemoreception
- similar to u gut
Rhabodites
Cells in planarians that form a protective mucus sheath around body
Muscles in planarians
Run circularly, longitudely, and diagonally
Digestion in Planarians
Mouth >> pharynx >> intestine ~ no anus ~ gut branched so it can deliver food to all parts of body ~ digestion completed intracellularly ~ waste out the pharynx
Intestines in planarians
Secrete enzymes that break down food
Flame cells
Collect water and waste and transport them into the cavity
Cilia
Moves waste down extratory ducts
Extrectory pores
Waste goes out
Metabolic waste
Removed by diffusion through body wall
Neurons in planarians
Sensory, motor, and association
Sub epidermal nerve plexus
Very simple. Similar to a nerve net
Reproduction in Planarians
Reproduce by fission (separate into two organisms, regenerate lost parts)
Monoecious but do not fertilize themselves, mate
Class Turbellaria
Free living
Protrusible probasics
Class Trematoda
Parasitic flukes, leaflike
Structural adaptation for prasitism
Poorly developed sense organs (Dont need them)
2 hosts in Trematoda life cycle
Difinitive (snails) & intermediate (cows)
Life cycle of trematoda
Cyst like eggs, need water Larval trematodes enter snails & burrow Burst through snail, kiling it Swim upwards & incyst Wait for host to eat it Grows in next host (difinitive)
Class Monogenes
External parasite
Enter gills & surface of fish
Simple lifestyle- single host
Economic impact
