6-4 Notes Classifying Organisms Chapter 6, Lesson 4.

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6-4 Notes Classifying Organisms

Chapter 6, Lesson 4

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Historic Classification Systems• Aristotle, a Greek

philosopher, was one of the first people to put organisms into categories.

• He categorized things as animals, plants, or minerals, and then according to where they lived—air, land, or sea.

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Historic Classification Systems

• In the mid-1700s, Swedish botanist, Linnaeus developed a classification system that grouped organisms by similar physical structures

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Historic Classification Systems• Linnaeus’s

system went from kingdom (most general) to species (most specific).

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Species

Genus

Family

Order

Class

Phylum

Kingdom

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• Members of a species group have the greatest number of traits in common and can breed and produce fertile offspring.

• Only species are subject to natural selection and evolve.

Felis catus

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• Linnaeus also developed a system for naming species that is still used.

• Each species has a two-word scientific name called its species name.

• The first word identifies its genus.

• Human’s species name is Homo sapien.

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• All small cats have Felis as the first word of their species name, because that is their genus.

domestic cat

Felis catus

sand cat

Felis margarita

jungle cat

Felis chaus

wild cat

Felis silvestris

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Historic Classification Systems• Basic features such as cell type, presence

of a cell wall, or single-celled versus multicellular define each of the 6 kingdoms:

1. Eubacteria2. Archaebacteria3. Protists4. Fungi5. Plantae6. Animalia

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Modern Methods of Classification

• The modern study of classification, called systematics, uses DNA and molecular biology to identify related organisms.

• The more shared DNA sequences two species have, the more recent ancestor they probably share.

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• Scientists use haplotypes, samples of 1000 base pairs, to compare DNA sequences among organisms.

• DNA hybridization measures the percentages of DNA that are the same between two organisms.

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• Molecular biology led to a new highest level of classification called “Domain,” which is based on differences in a particular genetic sequence. There are 3 domains:

1. Bacteria

2. Archaea

3. Eukarya

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• As more sophisticated techniques are developed, the classification system will continue to become more refined.

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Modern Methods of ClassificationThe current system of classification (from highest to lowest):

1.Domain

2.Kingdom

3.Phylum

4.Class

5.Order

6.Family

7.Genus

8.Species

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Cladograms

• Scientists create diagrams called cladograms to group organisms based on certain characteristics.

• A cladogram shows common ancestry, and helps scientists to better understand evolution.

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Cladograms

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Cladograms

MYA

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Cladograms

The National Museum of Natural History - Washington, D.C

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What was Linnaeus’ classification system based on?

A whether things were plant, animal, or mineral

B where organisms lived—air, water, or land

C similar DNA sequences

D similar physical structures

6.4 Classifying Organisms

What approach measures the percentage of DNA that is similar between two organisms?

A DNA hybridization

B DNA sequencing

C haplotypes

D systematics

6.4 Classifying Organisms

What is currently the highest level of classification?

A animalia

B domain

C kingdom

D order

Which of the following does not provide independent evidence for the theory of evolution through natural selection?

A fossil record

B comparative anatomy

C systematics

D molecular biology

Which of the following is not a kingdom?

A protista

B fungi

C eukarya

D animalia

SCI 3.

6-4 Notes Classifying Organisms Chapter 6, Lesson 4.

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