In t r o d u c t io n t o B ila t e r iaProtostome BilateriaSubkingdom: Eumetazoa• Tissues, symmetry, digestive tract, muscles and nervesGroup Bilateria Bilateral symmetry, triploblastic, organs and organ system
B ila t e r a l S ym m e tr yB ila t e r ia n - Organisms having BilateralSymmetryAnimals that are similar to the front and back, upsideand downside.An animal is considered to have Bilateral Symmetry ifonly one plane of bisection of the midsagittal ormidplane produces right and left mirror halves.Streamlining is allowed by Bilateral Symmetry.
E n c o u n t e r in g R e s ourc e sMost animals, including Humans, are bilaterallysymmetric. They belong to the group called Bilateria.Bilateral Symmetry is also known as Plane Symmetry.Bilateral Symmetry may have evolved when radialanimals began to move up the surface.The oldest known bilateral animal is theVe r n a n im a lia c u la .
B ila t e r a l A n im a l L in e sMust have evolved in PrecambrianFirst fossils are Cambrian Spiralian (3rd Cleave Division is spiral)
C e p h a liz a t io nThe differentiation of the front/anterior end of anorganism into a definite head is called Cephalization. Itis considered an evolutionary advancement, and isaccompanied by the concentration of nerve tissues aswell as feeding organisms at the head region with thepurpose of integrating actions/movements in thenervous system.
Ta r g e t i n g R e s ourc e sCephalization allows the anterior end of the animal tofirst encounter food, predators and other externalfactors concerning their environment. This is becausethe brain as well as sensory organs can be found onthe anterior end. This helps protect and alarms theorganism 24/7.
M o t ile B a c t e r iaMany, however, not all bacteria is able to displaymotility (ex. self-propelled motion) undercircumstances. There are many different types ofmotility: Flagella (sing. Flagellum) Copious Slime Internal Structure (ex. Axial Filament)
S e s s ile B a c t e r iaBacteria that is not freely able to move about.
M u s c u la t u r eBilaterians have complete digestive tracts along with aseparate mouth and anus. (Except for some red formsof bilaterians.) They have an internal body cavitycalled a Coelome.They are Triploblastic which means they have threetissue layers consisting of the: ectoderm, mesodermand endoderm.
C o m p a r t m e n t a liz a t io nCompartmentalization or Cellular Compartmentscomprise of all the closed parts within the Cytosol ofthe (Eukaryotic) cell of an organism. It has 5 typesnamely the: Nuclear compartments including the nucleus. Intercisternal Space Organelles Cytosol
R e g u la t e d C o mp a rtme ntsEpithelia is maintains the regulated compartmentsCoelenteron or the gut has evolved in cnidarians andhas multiple functions in the taxon.The bilaterian gut is dedicated to digestion. Thereforeother spaces must assume the responsibility for theother functions.Hemal System = new role for the connective tissue.
C o e lo m sA new fluid filled cavityIt is lined by Mesothelium or Middle EpitheliumContains a third regulated compartmentIt is filled with a fluid called Coelomic FluidFunctions as a Hydrostat, Transport, Excretion,ReproductionAnimals with coeloms are called Coelomates
A lt e r n a t iv e C o e lo m icC o n d it io n s
B ila t e r iaMost animals are considered to be Bilaterians. Theyare also known to be the most familiar.They can be found almost anywhere: seas, land,freshwater and even on air.It is important to consider separately the small andlarge Biletarians.
D e v e lo p m e n t : C le a v a g eRadial/Regulative: Cleavage planes are either parallelor perpendicular to the polar axis of the egg.Spiral/Determinate: Cleavage planes are oblique tothe polar axis of the egg.Bilateral/Determinate: Cleavage planes are oblique tothe polar axis of the egg.
C n id a r iaComes from the Greek word “Cnidos” which meansstinging nettleDiverse in formArmed with stinging cells called Nematocysts;inherited from a common ancestorLives in the world’s oceans
H e m a l S ys te mA system of tubes and ducts whichmorphologically parallels that of the watervascular system in echinoderms, but lies justorally to it. Its function is not known, but itseems clear that it does not perform rolestypically associated with a blood-vascular systemin other animals. Possible functions ascribed toit are internal defense and endocrine, but directevidence for either is lacking.
B ila t e r ia B o d y F e a ture sBilateral SymmetryTriploblastyA CoelomeA Through-GutCNS or Central Nervous System