18-2 Modern Evolutionary Classification

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18-2 Modern Evolutionary

Classification

18-2 Modern Evolutionary Classification

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Evolutionary

Classification

Biologists currently group organisms into

categories that represent lines of

evolutionary descent, or phylogeny, not

just physical similarities.


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Evolutionary

Classification

Different Methods of Classification

Appendages Conical Shells Crustaceans Mollusk

Crab Barnacle Limpet Crab Barnacle Limpet

Molted external

skeleton

CLASSIFICATION BASED ON

VISIBLE SIMILARITY CLADOGRAM

Segmentation

Tiny free-

swimming larva

Resources/ActiveArt/cladograms.html


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Evolutionary

Classification

Superficial similarities once led barnacles and limpets

to be grouped together.

Appendages Conical Shells

Crab Barnacle Limpet


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Classification Using

Cladograms

A cladogram shows the evolutionary relationships

between crabs, barnacles, and limpets.

Crustaceans Mollusk

Crab Barnacle Limpet

Tiny free-swimming larva

Molted external skeleton

Segmentation


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Similarities in DNA

and RNA

Similarities in DNA and RNA

The genes of many organisms show

important similarities at the molecular

level.

Similarities in DNA can be used to help

determine classification and evolutionary

relationships.


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Molecular Clocks

Molecular Clock

new mutation

new mutation

2 mutations

A B C

A gene in an

ancestral species

Species Species Species

new mutation

2 mutations

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18-3 Kingdoms and Domains


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The Tree of Life Evolves

Five Kingdoms

Scientists realized there were enough differences

among organisms to make 5 kingdoms:

• Monera

• Protista

• Fungi

• Plantae

• Animalia


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The six-kingdom system of classification

includes:

• Eubacteria

• Archaebacteria

• Protista

• Fungi

• Plantae

• Animalia


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Changing Number of Kingdoms

Introduced Names of Kingdoms

1700’s

Late 1800’s

1950’s

1990’s

Plantae Animalia

Protista Plantae

Monera Protista Fungi Plantae

Eubacteria Archae-

bacteria

Animalia

Animalia

Animalia Protista Fungi Plantae


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The Three-Domain System

The three domains are:

• Eukarya, which is composed of protists, fungi, plants, and animals.

• Bacteria, which corresponds to the kingdom Eubacteria.

• Archaea, which corresponds to the kingdom Archaebacteria.


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Domain Bacteria

The domain Bacteria

corresponds to the

kingdom

Eubacteria.


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Domain Archaea

The domain

Archaea

corresponds to

the kingdom

Archaebacteria.


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Domain Eukarya

Domain Eukarya

The domain Eukarya consists of organisms that have a nucleus.

This domain is organized into four kingdoms:

• Protista

• Fungi

• Plantae

• Animalia


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Domain Eukarya

END OF SECTION

18-2 Modern Evolutionary Classification

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