Science

• Zygote


  Single cell resulting from an ovum (egg) that is fertilized by a sperm cell
• Gastrulation


  Blastula becomes flattened on one side and folds in on itself
• Germ Layers


  • Outer layer or gastrula: ECTODERM
  • Inner layer of gastrula: ENDODERM
• Digestive tract


  Round central cavity enclosed by endoderm
• Blastopore


  Opening in gastrula
• If blastopore becomes mouth

  Animal is a protostome ("first"-"mouth")
• If blastopore becomes anus

  Animal is a deuterostome ("second" "mouth")
• Modern sponges and cnidarians

  • Have little internal specialization
• As larger and more complex animals have evolved, specialized cells join together to form tissues, organs, and organ systems
• Radial symmetry


  Body parts extend from the center of the body
• Bilateral symmetry


  Mirror-image right and left sides
• The evolution of bilateral symmetry was accompanied by the trend toward cephalization, which is the concentration of sense organs and nerve cells in the front of the body
• Invertebrates with cephalization can respond to the environment in more sophisticated ways than can simpler invertebrates
• Coelom


  A true body cavity lined with tissue derived from mesoderm
• Acoelomates


  Flatworms that don't have a coelom
• Pseudocoelomates


  Roundworms with a coelom only partially lined with mesoderm
• Annelids, mollusks, arthropods, and echinoderms have true coeloms
• Protostomes


  Blastopore develops into a mouth
• Deuterostomes


  Blastopore develops into an anus
• Worms, arthropods, and mollusks are protostomes
• Intracellular digestion


  Digesting food inside cells
• Extracellular digestion


  Breaking down food outside the cells in a digestive cavity or tract
• Complex animals digest food in a tube called the digestive tract
• Respiratory systems


  • Have large surface areas in contact with air or water
  • Respiratory surfaces must be moist
• In terrestrial animals, surfaces are covered with water or mucus to prevent water loss and moisten air
• Open circulatory system


  Blood is only partially contained within blood vessels and moves through vessels into a system of sinuses
• Closed circulatory system


  A heart or heartlike organ forces blood through vessels that extend throughout the body
• Hydrostatic skeleton


  Muscles surround a fluid-filled body cavity that supports the muscles
• Exoskeleton


  An external skeleton
• Endoskeleton


  Structural support located inside the body
• External fertilization


  Eggs are fertilized outside the female's body
• Internal fertilization


  Eggs are fertilized inside the female's body
• Shell


  Made by glands in the mantle that secrete calcium carbonate
• Radula


  Tongue-shaped structure with tiny teeth used by snails and slugs for feeding
• Open circulatory system


  Blood works its way through body tissues in open spaces called sinuses
• Closed circulatory system


  Blood always moves inside vessels
• Nephridia


  Simple tube-shaped organs that remove ammonia and release it to the outside
• Gastropods


  • Have a single piece shell that protects their soft bodies
  • Some have a small shell or lack a shell completely
• Bivalves


  • Have two shells that are hinged together at the back and held together by one or two powerful muscles
• Blood always moves inside the vessels