Flatworms and related phyla Flashcards
benefits of bilateral symmetry
- forward, directed movement
- cephalization (formation of a head region)
bilateria are _____ organisms
triploblastic which means they have 3 germs layers (gut, endoderm, mesoderm, ectoderm)
advantages of more germ layers
- give rise to specific tissues and organs; tissue level of organization
- more complex
- diverse
ex of ectoderm, mesoderm, endoderm in mammals
- ectoderm; skin, hair, nails, mouth lining, tooth enamel
- mesoderm; kidneys, gonads, circulatory system, muscles, notochords, body cavity
- endoderm; lining of GI tract, respiratory tubes, liver, pancreas
3 clades of bilateria that we look at
- lophotrochozoa
- ecdysozoa
- deuterostomia
what 4 lophotrochozoa do we consider
- platyhelminthes (flat worms)
- mollusca
- annelida
- acanthocephala
lophotrochozoans are also called
protostomes
do platyhelminthes have a body cavity
no
platyhelminthes (flatworms) are _______ which means they have no body cavity
aceolomate
platyherlminthes (flatworms) can be
predatory and free living, or parasitic or commensals
do platyhelminthes (flatworms) have a circulatory system
no
describe platyhelminthes (flatworm) gut
- simple gut, no anus
- gut (gastrovascular cavity) branches in large forms and ramifies through body
- gaseous exchange across surface
are platyhelminthes (flatworms) motile
yes all motile, although some parasites secondarily sessile
platyhelminthes (flatworms) reproduction
sexual/ asexual
- parasitic species use asexual reproduction because of constraints of life cycle
4 major groups of platyhelminthes
- class turbellaria; free living; marine, fresh water, moist terrestrial
- class monogenea; ectoparasites of fish
- class trematoda; endoparasites (flukes) vet importance
- class cestoda; endoparasitic tapeworms vet importance
turberllaria (class of platyhelminthes)
- mostly free living
- marine, fresh water, moist terrestrial
- some commensal
- some parasitic
- ciliated epidermis for locomotion
- no body cavity; acoelomate
turbellaria excretory system (class of platyhelminthes)
protonephridial; simple system, drains directly from body across wall in excretory vessel
metanephridial excretory system
filtrate is filtered from blood is special filtration sites such as kidney
important model of turbellaria (plathelminthes ie flatworms)
the planarian (dugesia tigrina)
- used to study regeneration and stem cell biology
- can cut worm into many pieces and regenerate entire worm
- generative cell is neoblast; pluripotent cell (can develop into many tissue types)
- models of aging; planarian potentially immortal (has to do w telomeres; caps on the end of chromosomes)
turbellaria vs other classes (monogenea, trematoda, cestoda)
*all platyhelminthes
- turbellaria: mostly free living predatory, epidermis is cellular and ciliated
- other 3 classes; always parasitic/ commensal
- epidermis in larva is ciliated and partly cellular
- epidermis in adults in syncytial (one cell entity but many nuclei) look at pic on slide 23