Some Basic Ideas in Ecology

A.  The Concept of Heirarchies in Ecology
     1.  The heirarchies
          a.  Ecosystems
          b.  Communities
          c.  Populations
          d.  Individuals
          e.  Systems
          f.  Organs
          g.  Tissues
          h.  Cells
          i.  Organelles
          j.  Macromolecules
          k.  Elements
     2.  Categories a-d are the applicable to ecology
B. Evolution and Ecology
     1.  Tenents of Natural Selection
          a.  Some traits adapt an organism other don't
          b.  Traits are passed between parents and adults
          c.  Too many organism are born for the resources 
               available
          d.  Some must die, others will survive.  Ones that
               survive have the suite of characteristics most
               favored by the environment.
          e.  Thus change takes place by the differential survival
               progeny.
     2.  Types of selection
          a.  Selection for the mean--typical of most populations
               where environment isn't changing.  Normal 
               distribution of characters causes continued selection
               for the mean.  If  environment doesn't change for
               long periods, then dispersion is decreased.  Mean
               stays the same, but distances of min and max decrease
               Longterm effects would be less variation amongst the      
               members of the population.
          b.  One way selection against the mean--selection for one 
               of the end points and against the mean and the other      
               end point.  
          c.  Selection against the mean--Population separates into
               two distinct entities
C.  Speciation
     1.  Definitions of species
          a.  Morphospecies--Creatures that possess a common set
               of morphological features
          b.  Biological species-a population of creatures that 
               possess a similar set of features that under natural
               conditions only breed with each other and not with
               similar species.
     2.  Single population through time typically by differential 
          selection could change through time.  Constant observer
          would see no species change, but paleontologist looking
          at end points would declare them as two species.
     3.  Most thoughts on speciation imply two types of isolation
          a.  geographic
          b.  genetic
     4.  In this case a population gets separated into two 
          components.  Some barrier, typically geographic, separates
          the two groups.  If time is long enough and if both groups
          are subjected to different environmental pressures,
          the two groups will differentiate genetically.  If brought
          back together, the groups are now different enough so
          that cross breeding is no-longer possible.
     5.  Rates of speciation through time
          a.  In most instances, particularly when environment
               stays constant, few species should be formed
          b.  Higher rates of speciation take place when 
               environments change rapidly.  Examples of such 
               changes take place at the ends of geologic periods,
               such as, at the end of the Ordovician, Permian, 
               Cretaceous, etc.
          c.  Name given to such a phenomenon is "punctuated
               equilibria".  Proposed by S.J. Gould and others
D.  Some interesting examples
     1.  Clutch size in birds
          a.  Why don't birds have larger clutches
          b.  Because there are costs and benefits associated with
               the number of offspring produced.
          c.  As environment changes, costs and benefits change