Classification and Identification

Spring 2010

Recognition versus Identification

dandelion

• Recognition relies upon previous experience with the organism. You “know” it is this, because you’ve seen it before, and have learned the name from some authority.

• The process of identification relies upon an analytical review of the characters observed, and following a logical order of inclusion and exclusion, to finally arrive at the name. For example, through the use of identification keys.

• Confirmation of the name is done through comparison with a known “standard” (e.g. checking the specimen against previously identified specimens in a reference collection, the herbarium), or consulting with an authority who has much experience with the plant group, or checking a published treatment of the plant diversity of your region (flora) or a photographic atlas or web resource for that group of plants.

Recognition versus Identification

Classification

A systematic arrangement in groups or categories according to established criteria.

Biological classification involves the delimitation, ordering and ranking of taxa.

Classification in Your Life…

• Do you classify things?

• Do you do it deliberately? Unconsciously?

Let’s go home...*• In your room or apartment, think about what

groups of items you automatically classify…

• What characteristics and criteria do you use to do this?

• Is the classification a continuous, ongoing thing, does it happen occasionally, or at very distinct times?

• WHY do you do this?

*Mentally, that is – so just sit down and think…

Some examples:• Kitchen:

- Silverware [knives, forks, spoons], plates, bowls, pots, pans, cooking utensils, trays, etc.

- Refrigerator – meats, vegetables, fruits, eggs, bottles, cans, salad dressings, frozen foods.

• Bedroom: - Closet & dresser [shoes, boots, shirts, slacks,

etc.] - Jewelry

• Living room: - CDs, Video tapes/DVDs, books, magazines

• Study: - Textbooks, pens & pencils, paper, etc.

A basic fact of life:

“Everyone is a Taxonomist”

Artificial taxonomy

• These classifications are based on use or similarity of shape.

• Generally based on one or few “characters”.

• Single character taxonomy may work in these situations, but…

Single character taxonomy is bad taxonomy for biological systems.

Elements of UnderstandingBiological Diversity

Description of Diversity

Classification of Diversity

Naming of Diversity

Elements of UnderstandingBiological Diversity

Description of Diversity

Classification of Diversity

Naming of DiversityNaming of Diversity

Naming of Diversity

Observation & Organization

Convention & Communication

Description

• Provides some basic identifiable set of characteristics to associate with the organism.

• Can be as general or as detailed as practicality dictates.

• Needs to contain enough data to provide adequate discrimination between similar organisms.

• Needs terminology.

• Descriptions are linked with a name when there is consistency in the set of observed characters for a given organism.

Classification

• Classification provides ORDER to the group of entities.

• Relies on observations, many definable and comparable characters, and an ability to discern them.

• Completely effective classifications can be artificial, that is, not necessarily reflecting evolutionary relationships: i.e., trees vs. shrubs vs. herbs.

• But modern classifications are based on evolutionary history (phylogeny) because this provides predictive power.

• Biological classifications are hierarchical.

Naming and Nomenclature

• We need names to communicate about plants with others.

• Organized system of names enables fitting the plant into an accepted scheme.

• Following formal naming rules is nomenclature (International Code of Botanical Nomenclature; ICBN)

• The system must allow for changes as new information (and other species) are discovered.

• Will discuss nomenclature in more detail later in the semester.

Classification

precedes

nomenclature!

What makes a good classification?

- Groups recognized according to overall similarity (as seen by multiple characters) and relatedness (evolutionary history).

- The classification has predictive value – Characteristics of other related organisms can be predicted by the classification because of the evolutionary perspective.

- Classification is practical and useful.

Why is biological classification possible?

Because variation exists in nature.

Four species of the bamboo genus Chusquea

• Must be able to identify discrete “packages” of biological diversity: species. Discontinuity is caused by:

1. evolution and speciation, or2. extinction, or3. a combination of 1. and 2.

Discontinuity of Biological Diversity

Speciation Phylogeny

Evo

luti

onar

y T

ime

Speciation Phylogeny

Effects ofExtinction

Speciation Apparent Phylogeny

• To establish a classification, one must be able to use discontinuities to delimit groups at various hierarchical levels, e.g.:

- How different are populations to warrant calling them distinct species? - How distinct are two groups to be able to recognize them as separate genera? • Establishing ranks can be very subjective – the more objectivity we can impose on the process, the more reliable the classification.

Assessing Biological Discontinuity

Hierarchical (nested) categories and phylogeny

PHYLUM

CLASS

ORDER

FAMILYGENUS

TIM E

Hierarchical (Nested) Categories

KINGDOM

CLASS

CLASS

CLASS

PHYLUM PHYLUM

PHYLUM

ORDER

ORDER

Classification of a bamboo

Kingdom Plantae (Viridiplantae)

Phylum/Division Magnoliophyta (Anthophyta)

Class Liliopsida

Order Poales

Family Poaceae

Genus Chusquea

Species C. antioquensis

Angiosperms(Magnoliophytaor Anthophyta)

Liliopsida

Fig. 9.1 from the text

Liliopsida

Poaceae

Fig. 9.2 from the text

Fig. 9.29 from the text

Fig. 9.36 from the text

…have only RELATIVE meaning, not absolute meaning! …are artificially created to accommodate different hierarchical levels of organization.

…rely on inclusiveness of various shared characteristics that all members of the group should possess.

…are subject to modification as data accrue!

Taxonomic Ranks…

A tale of three families

• Sapindaceae—ca. 140 genera, 1500 species, 1° tropical & subtropical, mostly woody

• Aceraceae—2 genera, ca. 112 species, 1° temperate, woody; the maples

• Hippocastanaceae—2 genera, ca. 16 species, temperate & tropical, woody; the horse chestnuts (buckeyes)

Phylogenetic Analysis

SAP

HIPP

ACER

SAP

SAP

SAP

SAP

SAPChemistryAppendaged petalsCurved embryo w/ seed coat “pocket”8 or fewer stamensEtc. See p. 35 of lab manual for more detail

Phylogenetic Analysis

SAP

HIPP

ACER

SAP

SAP

SAP

SAP

SAPChemistryAppendaged petalsCurved embryo w/ seed coat “pocket”8 or fewer stamensEtc.

One family: Sapindaceae

SAP

HIPP

ACER

SAP

SAP

SAP

SAP

SAPChemistryAppendaged petalsCurved embryo w/ seed coat “pocket”8 or fewer stamensEtc.