Classifications

Question 1

Define classification

Answer 1

Systematic arrangement into groups according to established criteria (this is essential for efficient processing of information)

Question 2

What is the basic Linnaean hierarchy for classification

Answer 2

Kingdom
Phylum/Division
Class
Order
Family
Genus
Species

(Remember Mattichuk’s abbreviation except without Domain)

Question 3

Biological classification may combine what two functions

Answer 3

1. show relationships
2. assist identification

Question 4

The dual aims of biological classification are historically grounded in “systems” versus “methods” - what does this mean and how might you equate classification based on phyloggenetic hypothesis and identification keys

Answer 4

• Systems were supposed to represent the true plan of creation, while methods were quick, easy and relatively accurate means to identify specimens.
• Today we might equate classifications based on phylogenetic hypotheses with a natural system, and identification keys with methods, recognized as artificial, but still useful for telling which red flower, for example, you are holding in your hand

Question 5

What are the 4 philosophical approaches to classification

Answer 5

1. Evolutionary (Synthetic) classifications
2. Phylogenetic (Cladistic) classifications (nested or sequenced)
3. Unranked classifications
   (partial unranked classification, phylocode)
4. Classifying fossils

Question 6

What are the 2 types of Phylogenetic (Cladistic) classifications used

Answer 6

1. Nested
2. Sequenced

Question 7

What are the 2 types of unranked classifications used

Answer 7

1. Partial unranked classifications
2. Phylocode

Question 8

Synthetic classification was produced by what kind of taxonomists

Answer 8

Evolutionary taxonomists

Question 9

Describe Synthetic classification

Answer 9

• Both clades and paraphyletic groups are used
• Polyphyletic groups are not allowed
• The criteria for allowing a paraphyletic group:
  –> “important differences”
  –> evolution to another major “adaptive zone” from the excluded part of the clade

Question 10

What are the criticisms of synthetic classifications

Answer 10

1. It is arbitrary: when is it different enough
2. They phylogeny cannot be reconstructed from the classification
3. Human perception of differences is a worse predictor of underling differences than a phylogeny is

Question 11

Describe cladistic classifications

Answer 11

• only “natural groups,” that is monophyletic clades rather than paraphyletic groups, are given formal names
• The cladogram can (and must) be perfectly reconstructable from the classification
• it is still necessary for the taxonomist to decide on ranks, unless an unranked classification is the goal
• Thy phylogeny is assumed to be strictly dichotomous unless there is insufficient evidence
• There are different approaches (conventions) to cladistics classifications: nested vs sequenced (now used more)

Question 12

Describe nested cladistic classifications

Answer 12

• ALL Clades are named
• it must be possible to perfectly reconstruct the cladogram from the classification

Question 13

What are the problems with nested cladistics classifications

Answer 13

• proliferation of names and ranks in diverse groups
• classification must be changed as phylogenetic ideas change

Question 14

What does monotypic mean

Answer 14

• that the subfamily or genus for example only have one species

Question 15

Describe sequenced cladistic classifications

Answer 15

• not all clades are named
• the cladogram still can (and must) be perfectly reconstructed from the classification
• but it must be stated when sequencing is used or else polytomies will be inferred when not intended
• this system is now the most commonly used

Question 16

What is the most commonly used cladistic classification

Answer 16

sequenced cladistic classifications

Question 17

What are the problems with common cladistic approaches

Answer 17

• problem 1: proliferation of names and ranks
• problem 2: instability of classification when phylogenetic ideas change

Question 18

describe unranked classifications

Answer 18

this is an umbrella expression that describes different attempts at solving the 2 problems with common cladistic approaches (proliferation of names and ranks, instability of classification when phylogenetic ideas change)

Question 19

What are the 2 approaches to unranked classifications

Answer 19

1. intersperse formally ranked (Linnean) taxa with informal ranks (e.g. “genus group”) or no ranks
2. disposing of ranks entirely (ex. using phylocode)

Question 20

Describe PhyloCode and its three main objectives

Answer 20

• an approach of disposing ranks entirely in unranked classification method
• its main objectives are stability, uniqueness, and phylogenetic context (only clades are named)
• so their are no ranks, including no genus ranks
• clades have single word names (uniomial)
• species can be uninomial or binomial (but the two parts remain fixed and so are functionally uninomial)

Question 21

Overall compare the two types of unranked classification methods

Answer 21

• partial unranked –> increasingly common in cladistic classifications
• phylocode –> experimental, controversial, no yet widely favoured

Question 22

Overall compare synthetic (evolutionary) classification and cladistic classification

Answer 22

• synthetic –> older, traditional, paraphyly allowed, no longer favoured
• cladistic –> more modern, clades only. basic principle: bidirectional information flow

Question 23

What is the problem with including fossils in classifications

Answer 23

• fossils are often incomplete
• including fossils can exacerbate the problems related to cladistic classifications (more taxa –> more names and ranks needed, uncertain position of fossil –> instability)

Question 24

What does incertae sedis mean

Answer 24

of uncertain position (can write this beside genus’s if they are polytomies in sequenced cladistic classifications)

Question 25

What are the potential advantages of including fossils in phylogenetic analyses

Answer 25

• fossils are a major source of data about new species
• fossils can be a source of novel phylogenetic information (can display primitive traits, have important impact on phylogenies, can help with the problem of long branch attraction, are the only independent source of information on ages)

Question 26

Overall describe using fossils for classification

Answer 26

• often unranked
• use dagger symbol
• can be important for phylogenetic analysis or dating divergences