Biological Classification. The Linnean system, first formally proposed by Linneaus in Systema naturae in the 18th century, has two main characteristics.

Biological Classification

• The Linnean system, first formally proposed by Linneaus in Systema naturae in the 18th century, has two main characteristics.

• Each species has a two-part name.

• Species are organized hierarchically into broader and broader groups of organisms.

1. Taxonomy employs a hierarchical

system of classification

• The seven basic taxonomic categories are: Kingdom, Phylum, Class, Order, Family, Genus and Species; kingdom being the broadest category, and species being the most specific.

Taxonomic Categories

Mnemonic aids for remembering the seven taxonomic levels and their

correct order?

• ‘King Philip came over for green soup.’

Table 1Taxonomic Level

Organism #1

Organism #2 Organism #3

Organism #4

Kingdom Animalia

Phylum Chordata Chordata

Class Mammal Amphibia

Order Primate Salienta Primate

Family Hominid Ranidae Pongidaea Pongidaea

Genus Homo Rana Pan Gor

Species sapiens pipiens troglodyte gor

Complete Table 1

Table 1Taxonomic Level

Organism #1

Organism #2 Organism #3

Organism #4

Kingdom Animalia Animalia Animalia Animalia

Phylum Chordata Chordata Chordata Chordata

Class Mammal Amphibia Mammal Mammal

Order Primate Salienta Primate Primate

Family Hominid Ranidae Pongidaea Pongidaea

Genus Homo Rana Pan Gor

Species sapiens pipiens troglodyte gor

How would you convert the information on Table 1 to a dichotomous key?

• Complete the key provided for you.

Taxonomic Level

Kingdom: Animalia

Phylum: Chordate

Class: Amphibia Mammal

Order: Salienta Primate

Family: Ranidae Hominid Pongidae

Genus: Rana Homo Gor Pan

Species: pipiens sapiens gor troglodyte

Table 1Taxonomic Level

Organism #1

Organism #2 Organism #3

Organism #4

Kingdom Animalia Animalia Animalia Animalia

Phylum Chordata Chordata Chordata Chordata

Class Mammal Amphibia Mammal Mammal

Order Primate Salienta Primate Primate

Family Hominid Ranidae Pongidaea Pongidaea

Genus Homo Rana Pan Gor

Species sapiens pipiens troglodyte gor

Organism 1

Kingdom: They eat other organisms (Animalia kingdom)Phylum: They have a backbone and gill slits as an

embryo (Cordata phylum)Class: They produce live young (babies) and nourish their

young with milk from the mother (Mammal class)Order: Their most important sense is their vision; they have a

poorer sense of smell; they have flattened fingers and nails (Primate order) Family: They walk on two legs, have flatter faces, and see in

color(Hominid family) Genus: They have large brains, can speak and have long

childhood(Homo genus)Species: They have a high forehead, their body hair is

reduced and they have a prominent chin (sapiens species)

• The scientific name of the organism above is:________________________

• or its more common name is:________________________

Taxonomic Level

Organism #1

Kingdom Animalia

Phylum Chordata

Class Mammal

Order Primate

Family Hominid

Genus Homo

Species sapiens

Scientific name

The Linnaean binomial system consists essentially of giving a one-word name such as Rhododendron or Pan to a genus and a two-word name such as Rhododendron ponticum or Pan troglodyte to an individual species within the genus.

Rhinecanthus aculeatusHawaii: – Huma Huma Nuka Nuka Apua ’aOther Places - Picasso Triggerfish

Taxonomic Level

Organism #1 Organism #2 Organism #3 Organism #4

Kingdom Animalia

Phylum Arthropoda

Class Hexopoda

Order Lepidoptera

Lepidoptera

Family Tortricidae

Psychidae

Tortricidae

Genus Archips Solenobia Archips Eulia

Species rosana Walshella fervidana

pinatubana

Table 2

Taxonomic Level

Organism #1 Organism #2 Organism #3 Organism #4

Kingdom Animalia Animalia Animalia Animalia

Phylum Arthropoda Arthropoda Arthropoda

Arthropoda

Class Hexopoda Hexopoda Hexopoda Hexopoda

Order Lepidoptera

Lepidoptera

Lepidoptera

Lepidoptera

Family Tortricidae Psychidae Tortricidae

Tortricidae

Genus Archips Solenobia Archips Eulia

Species rosana Walshella fervidana pinatubana

Table 2

• Traditionally, systematists have considered kingdom as the highest taxonomic category.

• As a product of a long tradition, beginning with Linnaeus organisms were divided into only two kingdoms of life - animal or plant.– Bacteria, with rigid cell walls, were placed with

plants.– Even fungi, not photosynthetic and sharing little

with green plants, were considered in the plant kingdom.

– Photosynthetic, mobile microbes were claimed by both botanists and zoologists.

1. The five-kingdom system reflected increased knowledge of life’s diversity

• In 1969, R.H Whittaker argued for a five-kingdom system: Monera, Protista, Plantae, Fungi, and Animalia.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 26.15

• The five-kingdom system recognizes that there are two fundamentally different types of cells: prokaryotic (the kingdom Monera) and eukaryotic (the other four kingdoms).

• Three kingdoms of multicellular eukaryotes were distinguished by nutrition, in part.– Plants are autotrophic, making organic food by

photosynthesis.– Most fungi are decomposers with extracellular

digestion.– Most animals digest food within specialized

cavities.

• In Whittaker’s system, the Protista consisted of all eukaryotes that did not fit the definition of plants, fungi, or animals.– Most protists are unicellular.– However, some multicellular organisms, such as seaweeds,

were included in the Protista because of their relationships to specific unicellular protists.

– The five-kingdom system prevailed in biology for over 30 years.

• During the last three decades, systematists applying cladistic analysis, including the construction of cladograms based on molecular data, have been identifying problems with the five-kingdom system.– One challenge has been evidence that there

are two distinct lineages of prokaryotes.– These data led to the three-domain system:

Bacteria, Archaea, and Eukarya, as superkingdoms or domains.

2. Arranging the diversity of life into the highest taxa is a work in progress

• Many microbiologists have divided the two prokaryotic domains into multiple kingdoms based on cladistic analysis of molecular data.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 26.16

Applications of classificationAmerican Museum of Natural History- New York- Hall of biodiversity

Biodiversity Tools - Biodiversity Information Databases in the Americas

Classification of lacewings by sound