Classification of OrganismsClassification of Organisms

Chapter 14 NotesChapter 14 Notes

14-1 Categories of Biological Classification

A. Taxonomy – The science of classifying living organisms, based on shared characteristics

B. Binomial Nomenclature – two-word system for naming organisms

C. Scientific Names – 1. Each organism is assigned a unique two-

word scientific name. Consists of Genus, species, ex. Homo sapiens

*helps scientists classify newly discovered species

Scientific Names (con’t)

2. These enable scientists to communicate in the same scientific language with each other about organisms, regardless of their own native language

3. There could be confusion when different cultures, societies, or nations, refer to the same organism by different common names.

What Makes Up a Scientific Name?

• Two different types of organisms cannot have the same scientific name, so every species has its own unique scientific name.

• Ex: All red oaks have the same scientific name (Quercus rubra) because they are all the same species, but willow oaks (Quercus phellos) have a different species than red oaks.

Table 1

Classifying Organisms1. There are 8 levels to the

classification hierarchy:a. Domain, kingdom, phylum, class,

order, family, genus, species (in order from least specific to most specific)

b. Phrase to help memorize: Did King Phillip Come Over For Grape Soda?

Grizzly bear Black bear Giant panda

Red fox Abert squirrel

Coral snake Sea star

KINGDOM Animalia

PHYLUM Chordata

CLASS Mammalia

ORDER Carnivora

FAMILY Ursidae

GENUS Ursus

SPECIES Ursus arctos

Classification of Ursus arctos

Example

14-2 How Biologists Classify Organisms

A. Biological species – a group of natural populations that are interbreeding or that could interbreed, and that are reproductively isolated from other groups

Biological Species

1. Hybrids – offspring that result from interbreeding by individuals of different species

a. Example: Wolves and dogsb. Not all species interbreeding

produce fertile offspring (like a horse and a donkey producing a mule)

Evolutionary History

1. Phylogeny – an organism’s evolutionary history

2. Convergent evolution – organisms evolve similar structures independently, usually because they live in similar habitats

a. Example: shark and dolphin

Convergent Evolution/Analogous Structures

Evolutionary History (con’t)

3. Analogous structures – similar features that evolved through convergent evolution.

a. Homologous structures are similar because of common ancestry, but analogous structures are similar because of similar natural selection acting on two different species in similar environments.

Evolutionary History (con’t)

4. Cladistics – using shared characteristics to infer relationships between organisms

a. Cladograms – branching diagrams which show the evolutionary relationships among groups of organisms

Cladogram

Cladistics (con’t)

b. Ancestral character – a characteristic that evolved in a common ancestor of both groups

c. Derived character - a characteristic that evolved in an ancestor of one group but not of the other; they are the characteristics listed on the bottom of a cladogram that separate the two groups above it.

CLASSIFICATION BASED ON VISIBLE

SIMILARITIES

CLADOGRAM

Appendages Conical Shells

Crab Barnacle Limpet Crab Barnacle Limpet

Crustaceans Gastropod

Molted exoskeleton

Segmentation

Tiny free-swimming larva

Traditional Classification Versus Cladogram

Evolutionary History (con’t)

5. Phylogenetic tree – another type of branching diagram that shows evolutionary relationships, it separates organisms also on the basis of how important a character is (like feathers on birds)

Phylogenetic Tree vs. Cladogram