Clade Bilateria Flashcards
Phylum acoelomorpha?
Distinct anteroposterior axis but no brain
Radial nerve arrangement
Mostly in marine sediment
Clade bilateria?
All members exhibit primary bilateral symmetry
Also have cephalization
More active lifestyle requires a different form->form is related to function
All are triploblastic
Phylum Platyhelminthes?
Typically flattened bodies
4 classes
1 free living, the rest are parasitic
Platyhelminthes tegument and muscles?
Free living class have ciliated epidermis
Contain rhabdites-form protective mucous sheath
Also dual gland adhesive organs for locomotion via attachment and disattachment
Parasitic class have tegument with no cilia
Layers of muscle fibres grow diagonally, longitudinally and circularly
Parenchyma fills in between spaces
Platyhelminthes nerve system and sense organs?
Cephalization but vary in complexity
Most simple is sub epidermal nerve net plexus
Others have longitudinal nerve cords
“Brain” mass of ganglion cells->differentiation of neurons into types
Abundant tactile and chemoreceptive cells
Form organs (auricles) in Platyhelminthes
Statocysts for equilibrium
Eye spots (ocelli) in some
Nutrition and digestion in Platyhelminthes?
Mouth, intestine and pharynx
Extra cellular digestion via intestinal secretions
Infra cellular digestion after intestinal cells undergo phagocytosis
Undigested food expelled via pharynx (blind gut).
Excretion for Platyhelminthes
Canals with tubules ending in flame cells
Flagella beat to create negative pressure that will draw fluid in
Collecting ducts open to outside via pores
Metabolic waste excreted by diffusion through body wall
Reproduction for Platyhelminthes?
Many via asexual and sexual means
Asexual reproduction via regeneration
Parent constricts in middle
Each half generates missing end
Parasitic flukes reproduce asexually in mollusc intermediate host
Also sexual reproduction via cross fertilization (even though monoecious)
Clade Turbellaria
Mostly free living flat worms
Fresh water predator of smaller animals
Contain planarians
Form a paraphyletic group
Clade Trematoda?
All parasites
Various structural adaptations depending on environment
3 subclasses: Digenea, Monogenea, Cestoda
Subclass Digenea?
Many with complex life cycles
Alternating sexual and asexual stages
Intermediate and final hosts
(Parasitic castration)
Schistosoma?
Very good defences to evade immune system
Mimic host surface proteins
Release molecules to manipulate immune system
Live in veins of bladder, liver..etc
Bird schistosomes?
Swimmers itch
Class Monogenea?
Mostly external parasites of fish
Clamp on using hooked attachment organ (opisthaptor)
Simple life cycle
Widespread and common
Class Cestoda?
All internal parasites
Long flat bodies of repeating segments (proglottids) with a scolex for attaching to host
Over 4000 species!
No gut and absorb nutrients across body surface
Phylum Mesozoa?
Tiny, ciliated
2 cell layers not homologous to germ layers
No gastrulation during development
Highly specialized parasites or symbionts
Phylum Nemertea?
Thread ribbon worms Long muscular proboscis Ciliated epidermis with gland cells Flame cells for excretion Almost all marine
Nemertea locomotion?
Circular and longitudinal muscles
Usually glide over slime track
Nemertea digestion?
Seize prey with proboscis contained within rhyncocoel
Cavity entirely within mesoderm- true coelomate
Eversion exposes sharp barbs (stylets) that stab and inject neurotoxins
Esophagus thrust through mouth to engulf prey
Digestion system complete
Cilia help move food through intestine
Nemertea circulation?
Have true circulatory system with blood
Vessels contract to keep up flow
Flame bulb protonephrenia are associated
True excretion vs osmoregulation
Nemertea sensory?
Pair of nerve ganglia
Nerve cords connected by transverse nerves
Nemertea reproduction?
Some asexually by fragmentation or regeneration
Others sexually~dioecious
Clade Turbellaria
Mostly free living flat worms
Fresh water predator of smaller animals
Contain planarians
Form a paraphyletic group
Clade Trematoda?
All parasites
Various structural adaptations depending on environment
3 subclasses: Digenea, Monogenea, Cestoda
