<span>The geologic time scale is divided into periods, which are then divided into epochs, which are further divided into ages. For example, the time of the dinosaurs lasted 3 periods (Triassic, Jurassic, Cretaceous), each period had 3 epochs (late, early, middle), and each age fit into one of those. Many epochs have more than 1 age associated with them.
As for the basis for differentiating the eras, I'm not so sure. The only one I can say for sure is the end of the Cretaceous, which is when the dinosaurs suddenly became extinct due to a meteor impact. I think the divisions are based on significant, global-scale events that changed the world.
Sorry its so long but that the answer i think >:) ur welcome
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Body fluids are drawn into the valved ostia
Answer:
depends on the day of the week really.. on Wednesdays not so much because Wednesdays just hit different but on any other day yea..
The complete statement is this: CNIDARIA exhibit two radial body forms, the polyp and the medusa, and use stinging cells to capture prey.
Cnidaria is categorized under the Animalia kingdom. It is made up of more that eleven thousand species, which all live in aquatic habitats; either fresh or salt water environments. There are four basic classes of cnidarians, these are: Anthozoa, Cubozoa, Scyphozoan and Hydrozoa. Their common feature is the cnidocytes, which are specialized cells that they use to capture their preys.
Cnidaria have two radial body types, which are called polyp and medusa. They used cnidocytes (stinging cells) to capture the foods they feed on.
Answer:
The endoderm gives rise to the nervous system.
Explanation:
Gastrulation is the process that occurs during the third week of embryonic development and includes transformation of embryonic disc with epiblast and hypoblast into a three layered embryonic disc made up of ectoderm, mesoderm and endoderm. These are the three primary germ layers and give rise to various tissues and body organs.
Endoderm of the embryo give rise to epithelial lining of gastrointestinal tract (except the buccal cavity), respiratory tracts and other organs such as gallbladder, liver,etc. Mesoderm forms connective tissues such as bones as well as muscles and peritoneum. All the tissues of nervous system and epidermis of skin are derived from ectoderm.
