1. Classification

2. Finding Order in Diversity
Biologists have…
identified and named 1.5 million different species
estimate million additional species have yet to be discovered

3. Why Classify?
To study the diversity of life, scientists must name each organism
Scientists use a classification system to name organisms and group them in a logical manner
Taxonomy is the study of naming organisms
Names are universally accepted
Names have biological significance
Categories go from larger groups to smaller groups.
Ex) teacher= larger, biology teacher = smaller

4. Assigning Scientific Names
Calling things by their common name can be confusing
Names change by region
Ex) puma, mountain lion, panther & cougar are all regional names for Felis concolor
In the 18th century scientists used Latin & Greek to assign scientific names, because these languages were common to all.

5. Early Naming
In the beginning, scientific names were often detailed physical descriptions
Often names were 20+ words long
There was difficulty in standardizing names because different scientists described organisms differently
Ex) the blue-winged/red breasted/
white stomached bird

6. Binomial Nomenclature
Carolus Linnaeus developed a two word naming system called binomial nomenclature
Each species is give a two part scientific name:
The name is written in italics
The first word is capitalized and the second is written in lowercase
The first word is the genus
(closely related species)
The second word is the species
(name usually describes an important trait)

7. Linnaeus’s System of Classification
Hierarchal system, with seven levels
Each level is referred to as a taxon
From largest to smallest:
Kingdom
Phylum
Class
Order
Family
Genus
Species
“King Philip Cried Out For Good Soup”

8. Which similarities are most important?
Organisms that look very similar may not share a common ancestor.
Their similar appearance may be the result of convergent evolution.
Darwin’s idea of descent with modification gave rise to the study of phylogeny, or evolutionary relationships among organisms.

9. Evolutionary Classification
Biologists now group organisms into categories that represent lines of descent, or phylogeny, not just physical similarities.
Species within a genus are more closely related to each other than to those in another genus because they share a recent common ancestor.
The higher the level of the first taxon in common between two organisms, the farther back in time the common ancestor.

10. Classification Using Cladograms
Cladistic analysis: identification and consideration of only those characteristics of organisms that are evolutionary innovations (new characteristics that arise as lineages evolve over time)
Characteristics that appear in recent parts of lineage but not older members are called derived characteristics
These characteristics can be used to construct a cladogram to show the evolutionary relationships between organisms
Cladograms are useful tools for scientists to understand how one lineage branched from another in the course of evolution.

11. Similarities in DNA & 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
The more similar the DNA sequence of two species, the more recently they shared a common ancestor and the more closely related they are in evolutionary terms.

12. Molecular Clocks
Comparisons of DNA can also be used to mark the passage of evolutionary time.
A molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.
A molecular clock relies on mutations to mark time.
The degree of dissimilarity in the DNA of two species indicates how long ago the two species shared a common ancestor.