Zoology Test 2c Flashcards
annelids are….
segmented worms
characteristics of annelids body form
- eucolomates
- possess a eucoelom or true body cavity
- lined with peritoneum of mesodermal origin
- peritoneum encloses internal organs
advantages of true body cavity
- allows for segmentation of body
- individual segments can move independently of each other, master burrowers
peristalsis
contraction of muscles for movement of food
mesentary
contains blood vessels, hold things in the right place
what do nematodes and annelids have in common?
- have bilateral symmetry and cephalization (only internal)
- complete mouth to anus digestive tract
- parasitism occurs in both groups, but annelids are mostly ectoparasites
- no developed respiratory system
- require wet or moist environment
nematode muscles
muscular pharynx, but no muscles in intestine, contain longitudinal muscles
annelid muscles
contain both circular and longitudinal muscles in body walls and digestive system
nematode excretory system
use diffusion through excretory canals
annelid excretory system
- more complex
- basic unit is the nephridium
- nephridium covered in chlorogogue cells
homoplasy
similarity probably due to convergent evolution
homology
anatomy similar due to evolutionary derivation from common ancestor
chlorogogue cells in annelids
- cells that cover the peritoneum of the digestive system
- convert waste product of protein metabolism to ammonia and urea
- synthesize glycogen and fat from excess calories
nematode circulatory system
contains no circulatory system
annelid circulatory system
complex, closed circulatory system of arteries, capillaries and veins
- have multiple hearts (aortic arches)
- aortic arches regulate blood pressure
- pumping done by muscular dorsal vessel
- respiratory pigments present
nematode respiratory system
- no specialized structures to increase efficiency of gas exchange
- done via diffusion
annelid respiratory system
- some contain “gills” or structures containing blood
- but most non- marine forms have no specialized structures and breath via diffusion
nematode nervous system
dorsal and ventral nerve cords
annelid nervous system
- have ventral nerve cord connected to dorsally located brain via circumpharyngeal connectives
- each segment has pair of nerves
somite
means segment
annelid classes
- oligochaeta
- polychaeta
- hirudinea
oligochaeta
- mainly earthworms, have few setae
- Lumbricus terrestris
setae
means bristles
polychaeta
- mainly marine annelids, many setae
- Nereis virens
hirudinea
- leeches
characteristics of Lumbricus terrestris
- type of oligochaeta
- soil and freshwater annelid
- with few and small setae
- common earthworm
- complete digestive system (mouth to pharynx to esophagus to crop to gizzard to gut)
- monoecious, but don’t self fertilize
- detrivores, important to recycling nutrients
characteristics of Nereis virens
- type of polychaeta
- marine annelids
- external cephalization
- known as tube worms
- contain parapodia
- many setae
- dioecious, no permanent organs
- indirect development, contains a larvae stage
parapodia
fleshy extensions of each somite
characteristics of leeches
- type of hirudinea
- freshwater predator of invertebrates
- ectoparasite of vertebrates
- segmented but no setae
- anterior and posterior suckers
- monoecious with direct development
- 4 to 12 pairs of testes and pair of ovaries
how do leeches differ from annelids?
- setae are lacking
- no septa are present, but do have external segmentation
- coelom is filled with connective or chlorogogue tissue
- modified circulatory system, closed
- digestive system is modified for fluid feeding
septa
internal segmentation
