poriferan

• phylum Porifera (sponges) have no body plan symmetry
• This radial symmetry enables sea creatures to symmetry enables sea creatures to become become sedentary or only capable of slow movement or floating slow, to experience the environment equally from all directions.
• Bilaterians have a “head ” and ”tail” (anterior vs. posterior)
• dorsal vs. front and back (dorsal vs. ventral)
• This right and left sides. This promotes cephalization , wherein themouth, sense organs, mouth, and nerve ganglia become concentrated at the front end of an animal, resulting in a concentrated at the front end of an animal, resulting in a head region
• Echinoderms (such as sea stars, sand dollars, and sea urchins) display radial symmetry as adults, but their larval stages exhibit bilateral symmetry
• Echinoderms (such as sea stars, sand dollars, and sea urchins) display radial symmetry as adults, but their larval stages exhibit bilateral symmetry. This is termed secondary radial symmetry.
• During embryonic development, the majority of animal species experience a separation of tissues into germ layers. The specialized tissues and specialized tissues and organs of the animal are formed from these germ layers during gastrulation
• Radially-symmetrical animals are DIPLOBLASTS, developing two germ layers: an inner layer (endoderm) and an outer layer (ectoderm).
• Diploblasts have a non-living layer (mesoglea) that function as a hydrostatic skeleton.
• Bilaterally-symmetrical animals are TRIPLOBLASTS, developing three tissue layers: an inner layer (endoderm), an outer layer (ectoderm), and a middle layer (mesoderm).
• Protostomes - "mouth first", the first opening in the embryo becomes the mouth
• Deuterostomes - "mouth second", the first opening in the embryo becomes the anus, and the mouth develops later.
• Acoelomate - Do not develop an internal body cavity (coelom). Their mesoderm region is completely filled with tissue. (e.g., flatworms).

  
• eucoelomate- With true coelom. True coelom arises within the mesoderm germ layer (e.g., annelids, mollusks, arthropods, echinoderms, chordates)
• Pseudocoelomate - With "false coeloms" because the coelom is derived partly from mesoderm and partly from endoderm (e.g., nematodes)

  
• 9 MAJOR ANIMAL PHYLA 9 MAJOR ANIMAL PHYLA

  Porifera

  Cnidaria

  Platyhelminthes

  Nematoda

  Mollusca

  Annelida

  Arthropoda

  Echinodermata

  Chordata
• PHYLUM PORIFERA

  Mostly marine; All aquatic. Multicellular; Body an aggregation of several types of cells differentiated for various functions. No organs or true tissues; digestion intracellular; excretion and respiration by diffusion Radial or asymmetrical body Body with pores (ostia), canals, and chambers that form a unique system of water currents on which sponges depend for food and oxygen.

  
• Segmented features are characterized by the presence of distinct, repeating units along the body axis
• Unsegmented features, on the other hand, refer to body structures that lack distinct segmental divisions along the body axis. Animals with unsegmented features typically have bodies that are not visibly divided into repeating units.
• Sponge larvae are flagellated and motile, while adults are sessile
• Class Calcarea have calcium carbonate, needle shaped, 3 or 4-rayed spicules.

  
• Class Hexactinellida have silica, six-rayed spicules.

  
• Class Demospongia have needled-shaped or four rayed siliceous spicules, or spongin, or both.