1. Classification
biological classification: the systematic grouping of organisms into categories on the basis of defined criteria
Classification is simply the grouping together or sorting of items into various categories based on some set of criteria.
Biological classification: the systematic grouping of organisms into categories on the basis of defined criteria
ex: classifying organisms according to their role in ecosystems (producers, herbivores, carnivores, & scavengers)

2. Developing a Classification System
taxonomy: the science of classifying all organisms (living and fossils!)
With millions of species living on Earth, and countless extinct species, taxonomy is a challenging science!

3. Early Classification Systems
in the 18th century Carolus Linnaeus came up with the Linnean System of Classification
today, scientists use a number of characteristics to determine how organisms are related:
biochemical similarities (similar chemical compounds - similar proteins, enzymes)
genetic similarities (similar chromosomes and genes)
structural similarities
people have been classifying organisms for thousands of years
but early names and classifications systems were very variable
Carl Linnaeus (the “father” of taxonomy) introduced a consistent way of grouping species according to their physical similarities

4. Early Classification Systems Cont’d…
Linnaeus assigned each organism a scientific name using his system of binomial nomenclature
‘Binomial’ refers to the fact that each unique type of organism is classified using two names
The first is called the genus and describes a larger groups of related organisms
The second is called the species and describes a specific and unique group of related organisms
people have been classifying organisms for thousands of years
but early names and classifications systems were very variable
Carl Linnaeus (the “father” of taxonomy) introduced a consistent way of grouping species according to their physical similarities

5. Early Classification Systems Cont’d…
ex. the scientific name for the briar rose is Rosa canina
Rules of Binomial Nomencalature:
always capitalize the genus name
never capitalize the species name
scientific names should be either italicized or underlined
Genera: a taxonomic group consisting a group of similar species

6. Early Classification Systems Cont’d
this system was expanded to grouping organisms into levels called taxa
the 7 taxonomic leves are:
similar species were grouped into genera, similar genera into families etc.
Kingdom
Phylum
Class
Order
Family
Genus
Species

7. Early Classification Systems Cont’d…
each taxonomic level consists of species that that have similar features
ex. all members in the class Mammalia are warm-blooded and feed milk to their young

8. Early Classification Systems Cont’d…
knowing the names of two species, such as Ursus americanus (black bear) and Ursus maritimus (polar bear), tells you that these species likely share many characteristics
whereas, a species of a different genus, Phascolarctos cinereus (Kola), likely does not have as many features in common
The Kola “bear” is a marsupial with a dramatically different anatomy and is more closely related to kangaroos than bears

9. Dichotomous Keys
dichotonmous key: a series of two-part statements used to identify which organism
A large set of items is broken down into smaller subsets, ultimately leading to the smallest available classification unit
At each step in the identification process, the user must choose between 2 defining statements
Each alternative leads to a result or another choice
Eventuall the key ends with the organism into a given taxonomic level

10. Lab Activity: Using & Constructing a Dichotomous Key
use dichotomous key to classify fish belonging to the taxonomic class Chondrichthyes and construct a dichotomous key for insects

11. Homework
answer 1.2 questions # 2, 5, 7 & 8