lecture midterm 2 Flashcards
main characteristics of Phylum Platyhelminthes (7)
- triploblastic
- cephalization
- bilateral symmetry
- acoelomate
- gut with one opening
- unsegmented
- dorsoventrally flattened
— nervous system w cerebral ganglia and two nerve cords
— protonephridia appear
Phylum Platyhelminthes new characteristics:
- nervous system with cerebral ganglia and two nerve cords
- protonephridia appear
what do protonephridia do for Phylum Platyhelminthes ?
help with osmoregulation (maintain salt and water balance)
excretion of ammonia
reproduction: Phylum Platyhelminthes
sexual and asexual
body plan (key notes): Phylum Platyhelminthes
- start of cephalization
- no respiration or circulatory system
— rely on diffusion - cilia for motility
locomotion: Phylum Platyhelminthes
by muscular undulations/cilia/mucous
can crawl and swim
feeding: Phylum Platyhelminthes
pharyngeal glands secrete digestive enzymes — suck up semi-digested soup
some swallow prey whole
intentional hunting
diagnostic characteristics: Phylum Platyhelminthes
new characteristics of Phylum Annelida
- eucoelomate and gut musculature
- gut with 2 openings (linear digestive tract)
- metamerism (repeated body plans)
- blood vascular system (beginning of circulatory system)
- metanephridia
- nervous system
— dorsal brain
— ganglionated ventral nerve cord - chaetae/setae
lost characteristics: Phylum Annelida
flattened body plan
protonephridia
reproduction: Phylum Annelida
asexually and sexually
functions of coelomic compartments
- circulation of nutrients and gases
- hydrostatic skeleton - enables peristaltic burrowing
- role in excretion and osmoregulation (metanephridial systems)
- storage of gametes
difference between protonephridia and metanephridia
protonephridia :
- excretory tube without an internal opening
found in platyhelminthes and rotifers
— helps in osmoregulation with cilia creating pressure to move waste/excess metabolites from the animal
metanephridia :
- open to the body cavity and attached to duct that opens to exterior
found in annelids
— more efficient than protonephridia
— selective reabsorption is performed in the cells lining metanephridium
lost characteristics: Phylum Annelida
flattened body plan
protonephridia
locomotion: Phylum Annelida
peristaltic
Errantia vs Sedentaria
groups of annelids
Errantia : eversible pharynx w jaws
Sedentaria : eversible pharynx never armed w jaws
general
general characteristics of all lophotrochozoans
- true tissues
- bilaterial
- triploblastic
- protostome embryos
- either eucoelomate or pseudocoelomate
- extracellular digestion
Phylum Nemertea ‘Ribbon worms’ diagnostic feature
proboscis apparatus - hydrostatically eversible
characteristics: Phylum Nemertea ‘Ribbon worms’
- eucoelomate
- circulatory system w ciliated lateral blood vessels derived from mesoderm, brain and nervous system
reproduction: Phylum Nemertea ‘Ribbon worms’
- dioecious (2 sexes , not hermaphroditic)
- temporary gonads (transient gonads) — developing only when ova and sperm are ready
- free swimming larva
locomotion: Phylum Nemertea ‘Ribbon worms’
ciliated epidermis
feeding: Phylum Nemertea ‘Ribbon worms’
predatory - w thin proboscis apparatus, some species pierce & inject neurotoxin
lost characteristics: Phylum Nemertea ‘Ribbon worms’
chaetae/setae, metamerism (segmentation)
new characteristics: Phylum Rotifera
- eutly (fixed number of cells)
— develop by cell division until maturity then only cell growth - have lorica (shell-like protective outer covering)
- reinforced with sand grains
- closed at one end
- protonephridia
- colonial
- small cerebral ganglion
distinct characteristics: Phylum Rotifera
- ciliated corona (for suspension feeding)
- mictic reproduction (stressed cycle)
- cryptobiosis
what is cryptobiosis
helps rotifers and other species survive in fresh water
in one of their reproductive stages they can enter into this
essentially like a death state, can dry up completely, metabolism shuts down, can last for years, decades, or even up to a century — can recover in as little as 10 minutes when water is added
this makes them industrially useful - used to feed other organisms
locomotion: Phylum Rotifera
can be sessile or free swimming by movable ‘scales’ - can swim well
feeding: Phylum Rotifera
ciliated corona (suspension feeding)
predatory in some species