A. Organizing the invertebrates into a coherent whole
1. Early schemes emphasized a theme with humans as the most
evolved of all creatures.
2. This concept was called Scala Natura, the scale of nature
3. Classification schemes preceeded evolutionary theory
and represented commonality of external features, eg.,
legs, wings, etc.
4. At least three different approaches to organizational
schemes
a. Evolutionary Phylogenetics
b. Phenetics
c. Cladistics
B. How can we tell how closely related different organism are?
1. External and internal similarities
a. Using homology as a way of determining relationship
b. Related-ness as differentiated from functional
convergence
2. Looking at embryologic relationships
a. Example of the origin of the mouth as a way of
dividing up the multicellular creatures
3. Determining relationships by genetics
a. DNA fingerprinting
b. Ribosomal DNA
C. Evolutionary Phylogeneics
1. Investigator spends many hours studying specimens
2. Determines in mind which characteristics are most
important and also those that are subjected to the
greatest evolutionary changes, eg., in insects, many
body parts are very similar, but the external genitalia
vary amongst all species.
3. Trees are developed that represent relationships amongst
origins of the different groups
4. Personal bias as to what characters are important
D. Phenetics
1. Concept of attributes and character states for attributes
2. Use of a binary approach, where 0 and 1 can represent the
presence of absence of an character state
3. Use of digital computers to calculate coefficients of
similarity. Use of cluster analyse to determine
relationship. When analysis begins, similarities must
be very closely related for different groups to cluster
together. As analysis proceeds, values necessary to
cluster are loosened. Groups begin to show relationship
as process continues.
4. Graphs of relationships often close to those produced by
evolutionary phylogenetics, but there are differences
5. Theoretically removes bias of observer, but in reality,
observer decides which attributes to examine.