Eumetazoa can be divided into 2 groups (nb cnidarians
and nematodes)
Protostomes (Proto = first,
stome = mouth)
Blastopore becomes mouth
Cleavage is spiral
Determinate development
Coelom is schizocoelic
Platyhelminths, Annelids, Molluscs and Arthropods
Deuterostomes (deutero
= 2nd, stome = mouth)
Blastopore becomes anus
Cleavage is radial
Development is indeterminate
Mesoderm and coelom arises from outpockets of the
gut
Echinoderms and Chordates Both Protostomes and deutorostomes
are
TRIPLOBLASTIC
ectoderm: epidermis and
nervous tissue
mesoderm: muscle tissue
and circulatory system
endoderm: digestive system
Kingdom Animalia
Branch Eumetazoa
Grade Bilateria
Division Protostomia
Acoelomates
Phylum Platyhelminthes
(plathy = flat, helminthes = worms)
Class Turbellaria
Free living flat worms
Class Monogenea
Ectoparasitic flukes
Class Trematoda
Endoparasitic flukes
Class Cestoda
Tapeworms
Characteristics of the phylum
~ 12000 species
Triploblastic:
mesoderm forms parenchyma tissue
Dorsoventraly flattened
Bilaterally symmetrical
Marine, freshwater and terrestrial
Acoelomate
Free living and parasitic
Scavengers and carnivores
No anus
No circulatory system
No respiratory system (one reason for there flat
architecture)
Have Protonephridia (Proto = first; nephridia = kidney)
Cephalisation
Nervous system
Predominantly monoecious
Nervous system
Central nervous system
Concentration of nervous tissue in anterior end;
"head"
posses nerve chords (usually two of; laterally placed)
Class Turbellaria
Free living
predatory and scavenging
Freshwater, marine and terrestrial
Epidermis is cilliated
Locomotion
Glide on ventral ectoderm using cillia
Muscular contractions to elongate
Digestive system
No anus
Tubular branching gut
Extendable pharynx tears of tissue pieces
Excretory system
Protonephridia
Base units are flame cells
Network of fine tubules
Current of fluid flows along the tubules aided by
the flagella of the flame cells
Exit the body at excretory pores
Highly abundant in freshwater species, nearly absent
in marine
Same purpose as contractile vacuoles
Probably also removes some metabolic wastes
Nervous System
Cephalisation: brain, nerve cords and eyes
Reproductive system
Sexual : monoecious
Asexual: regeneration and budding
Class Trematoda
Parasitic
Dorsal and ventral suckers
Have 2 hosts; mollusc (snail or clam) and vertebrate
May have a 3rd or 4th intermediate host
Reproduction
Adult
Egg
Miracidium
Sporocyst
Redia
Cercaria
Metacaria
Adult
Class Cestoda
~ 3500 sps
1mm to 30 metres
Entirely parasitic
No mouth
No digestive cavity
Scolex
Body divided in repeated segments or proglottids
Reproduction
Hermaphroditic
Adult
Larva
Cysticercus
Adult