Basic terms and philosophies

Question 1

Define taxonomy

Answer 1

The theory and practice of describing the diversity of organisms.

Question 2

Define systematics

Answer 2

The theory and practice of studying organismic diversity so as to discover the phylogenetic interrelationships among organisms.

Question 3

Define classification

Answer 3

A representation of a particular arrangement of organisms according to some principle to their interrelationships.

Question 4

Define phylogenetic systems (cladistics)

Answer 4

The approach to systematics that attempts to discover the genealogical relationships among organisms by taking shared derived characteristics (synapomorphies) as primary data. The resulting classification should reflect the genealogical (evolutionary) relationships as closely as possible. Trees are chosen based upon the principle of parsimony – the simplest explanation that fits the facts is most likely correct. This means that the preferred tree(s) is (are) the shortest one(s). GROUPS TAXA BY SYNAPOMORPHIES.

Question 5

Define evolutionary systematics, the traditional approach

Answer 5

The approach to systematics that believes that classifications should reflect more (?) than genealogy. Characterized by its acceptance of grades as real taxa- eg. Reptiles, because of clear morphological gaps and/or adaptations that make members distinct from other “related” taxa irrespective of evolutionary decent. Proponents (of which there are not many left) consider it unnecessary for a classification to reflect the same information as a phylogeny.

Question 6

Define numerical taxonomy (phenetics)

Answer 6

The approach to systematics that believes that a classification should reflect some measure of overall similarity among organisms and need not reflect genealogy.

OVERALL SIMILARITY, SYMPLESIOMORPHIES ARE JUST AS IMPORTANT AS SYNAPOMORPHIES.

Question 7

Define maximum likelihood and Bayesian analysis

Answer 7

These are complex model-based approaches to constructing evolutionary trees. They have supplanted cladistics as the preferred approach in some circles, especially those where the data are DNA sequences. Often the results of one of these methods are presented along with those of cladistics (which is called Maximum Parsimony, MP under such circumstances). While these methods have some interesting properties, they are too complex and time consuming for most of the issues we will be dealing with in this course, though they would be required understanding on a course that was devoted to systematics.