lecture 9 Flashcards
Features uniting bilateria
- bilateral symmetry
- cephalization
- mesodermally derived tissues (triploblastic)
bilaterally symmetrical organisms have
anterior end,
posterior end, dorsal side, ventral side, and left and
right sides
Types of sections in a bilaterally
symmetrical organism
transverse: Cross-section and x section
sagittal: longitudinal and frontal
cephalization
concentration of sense organs & nervous
system at anterior end
mesodermally derived tissues
true’ muscles derived
common features of bilaterians
- coelom
- complete through-gut with a mouth
and an anal opening - excretory organs
coelom
-a fluid transport system
-fluid-filled cavities that are fully enclosed with fluid under control of organism
2 fluid-filled systems in many bilateria
1) eucoelom
-completely lined by mesodermally derived
epithelium
2) blood-vascular system
-channels or tubes in connective tissue
why do larger body sizes and extensive
mesoderm require some kind of excretory
system
because not all cells are directly in contact
with the surrounding medium
excretion
discarding of metabolic
wastes, especially nitrogenous wastes
egestion
discarding of undigested materials
3 steps of system of excretion
1) ultrafiltration (typically across the basal lamina)
2) resorption of ions & valuable biomolecules
3) transport (to move wastes out of body)
2 forms of excretory systems
protonephridia
metanephridia
protonephridia excretory systems
-small animals lacking coelom
or blood-vascular system.
-filtration, resorption & transport
all occur in one structure
-ultrafiltration by diffusion and pressure gradients
metanephridia excretory systems
-typically in large animals with a blood-
vascular system;
-filtration occurs in a structure separate from resorption and transport
-pressure differences for ultrafiltration
Phylum Xenacoelomorpha
whatdo they lack
-lack complete guts (no anus) and also lack
circulatory and excretory systems
-marine worms
Acoela
how many spp
how do they move
what about their gutcavity
-400 spp
-taxa of Xenacoelomorpha
-move via cilia
-complete lack of a gut cavity
-mouth leads instead to solid endodermal mass
Xenoturbellida
taxa of Xenacoelomorpha
-only 6 named spp
worm
general term for an animal with bilateral
symmetry that lacks well-developed appendages
Acoela what do they feed on
protists, capable of preying on
invertebrates
how does aceola eat small items
extrudes its solid
gut mass through the mouth
food items then enclosed withing temporary cavities in gut mass(vacuoles) where they are digested
unlike protists, vacuoles in aloela are not
intracellular
undigestible parts of the food items acoela
are egested
through the mouth
do acoels have endosymbiotic relationships?
yes, endosymbiotic algae whose
photosynthetic production of carbohydrates is
rewarded by nitrogen from the acoel
cephalization in acoels
-circular array of
nerves that act as a
very simple brain
-presence of
statocyst:tells mf which way down
acoel nervous
system lacks what?
lacks cross-
connectivity
Xenoturbellida
phylum w acoela and nemertodermatida
Xenoturbellida similarities w aceola
-have statocysts, a mid-ventral mouth, mesodermally
derived musculature
-move w cilia
-lack a complete gut and excretory structures
-hermaphrodites
-direct development
Xenoturbellida differences w aceola
statocyst
midventral mouth
meodermally derived muscle
-nerves concentrated along body furrows
-having a small sac- like gut
-lack penis, sperm and egg shed through mouth for external fertilization
aleola ecological aspects
cover coral and interfere w shit
