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Animal diversity (Specialized cell structure (Neurons, Muscle cells,…

- - - - A blastopore is an indentation in the embryo
  - - - During the process of gastrulation, the blastula begins invaginating, forming a blastopore
        
        The indentation forms all the way through, creating a "tube" called the gastrula
        
        In radially symmetrical organisms, the gastrulation ceases as an indent, which is why they have a shared mouth and anus
- - - - Animals have a top and bottom, but no front, back, left or right
        
        Sessile
        
        Attached to a substrate (example: sea anemone)
        
        Planktonic
        
        Drifting or weakly swimming (example: jellies)
      - Animals with radial symmetry share a mouth and anus
    - - Two axis; dorsal and ventral; anterior and posterior
      - Can move from place to place
      - Evolved with cephalization
        
        Cephalization is essentially the evolution of the head
- - - - Innermost layer; gives rise to lining of digestive tracts and organs such as the liver and lungs
      - "Inner skin"
    - - Middle layer; present in all bilaterally symmetrical animals; forms muscles, most organs between the digestive tract, and outer covering
    - - Outermost layer; gives rise to central nervous system
      - "Outer skin"
    - - Animals that have only two of these three layers (endoderm and ectoderm)
      - Includes cnidarians (corals and jellies)
    - - Animals that contain all three of these layers
      - All bilaterally symmetrical animals are triploblastic
      - Most triploblastic animals have a coelom
        
        A coelom is a fluid or air filled space between the digestive tract and the outer body wall
        
        Animals with a coelom are called coelomates
        
        Coeloms cushion suspended organs and enables internal organs to grow independently of body surface
        
        Without a coelom, each heartbeat would distort the body's surface
        
        Can act as a skeleton against which muscles work (in soft-bodied coelomates)