Lecture 9: Vertebrate Origins

September 22, 2016

I. What is Life?

     A. An elaborate system of carbon-based (organic) molecules

         dispersed in an aqueous medium, bounded by a Cell

          Membrane.  All organisms are made of cells.

     B. Life forms metabolize.  Metabolism is the transformation of

        energy from an outside source to produce organic molecules,

        cell membranes, tissues, bones, etc.

          1. Energy for metabolism comes directly from the Sun, or via

              other organisms that can convert the Sun's energy.

          2. The base of the food chain is formed by organisms that can

              directly convert the Sun's energy (Plants, Algae, etc.).

              Secondary and tertiary levels in the chain are formed by

              organisms that eat the organisms at lower levels of the

              chain.

          3. Metabolism maintains organisms and all their tissues.

             When Metabolism ceases, life ceases.

     C. Life forms Reproduce:

          1. Phylogeny (Genealogy) is the simple consequence of

              Reproduction.

          2. Reproduction is moderated by DNA, organized into

              Genes, which are located on Chromosomes.

            3. Non-sexual organisms are clones of each other (genetically

              identical, or nearly so, with each other). Only rare

              mutations cause differences.

          4. Sexually reproducing organisms mix their chromosomes, so

              each organism is different.

          5. The origin of Sexual Reproduction created enormous

              variability among organisms, and enabled very rapid

              evolution of new, different life forms.

II. Synapomorphies of Vertebrata

     A. A Skeleton, made of bone and cartilage, and consisting of the

        following:

          1. Skull - houses the highly specialied organs of the head.  All

              vertebrates are highly encephalized (i.e. They all have

              skulls organized to house a huge brain and its special

              sense organs).

          2. Branchial Arches - support the mouth and gills, and used

              in feeding and respiration; eventually transform to form

              jaws, bones of the ear, skeleton of the tongue.

          3. Specialized hard mouth parts: teeth or tooth-like

             structures.

          4. Vertebral Column - the "backbone," which supports the

              body, and enables fast, powerful locomotion.

     B. A very sophisticated Nervous System consisting of the

         following:

          1. Huge Brain that integrates information from special sense

             organs.

          2. Olfactory system - analyzes chemistry of environment;

              located at front of skull (i.e. nose or something like a

              nose).

          3. Optic system - analyzes visual information about

              environment; located in middle of skull (i.e. eyes, 2 or 3).

          4. Otic system - analyzes mechanical vibrations in

              environment; balance; also involved in coordination;

              located toward back of skull (i.e. ears and associated

              structures).

          5. Lateral Line System - analyzes electrical signals from

              environment; located in skin over skull and body.

     C. Improved Circulatory/Respiratory systems:

          1. Well-developed, large heart - can pump more blood

              faster.

          2. Gills - specialized structures for rapid gas exchange.

          3. Red blood cells - specialized to carry lots of oxygen, which

             fuels metabolism.

          4. Well-Developed, Extensive Muscle System - initially

              designed to move vertebral column through water by

              throwing it into S-shaped waves, from side to side.

          5. Elevated Metabolic Rate - vertebrate metabolic "engines"

              run at higher speed; they can move faster, for greater

              distances.

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