1. Chapter 18: Classification

2. 18–1 Finding Order in Diversity
Life on Earth has been changing for thousands of years
1.5 million species named
between 2 and 100 million additional species have yet to be discovered

3. Why Classify?
Organize living things into groups that have logical meaning.
Taxonomy = discipline of classifying organisms and assigning each organism a universally accepted name

4. Assigning Scientific Names
Common names are confusing and vary among languages or even regions
Ex: cougar, mountain lion, panther, puma
different species sometimes share a single common name
In the United Kingdom, a BUZZARD refers to a hawk

5. Scientists have agreed to a single name for each species
In the United States, a BUZZARD refers to a vulture.
Scientists have agreed to a single name for each species
Use Latin & Greek

6. Binomial Nomenclature
Carolus Linnaeus,
a Swedish botanist, 1700s
binomial nomenclature = classification system in which each species is assigned a two-part scientific name
written in italics
first word is capitalized, the second word is lower case

7. Scientific Names grizzly bear is called Ursus arctos
Ursus — is the genus
Genus = group of closely related species
arctos – is the species
unique to each species within the genus
Often a Latinized description of some important trait of the organism or an indication of where the organism lives
Ursus maritimus, the polar bear
maritimus, referring to the sea

8. Linnaeus's System of Classification
Hierarchical - it consists of levels
includes seven levels
from smallest to largest—species, genus, family, order, class, phylum, and kingdom.
Each level is called a taxon or taxonomic category

10. Ursus arctos (Grizzly Bear)
Kingdom – Animalia
Phylum – Chordata
Class – Mammalia
Order – Carnivora
Family –Ursidae
Genus –Ursus
species - arctos

11. Humans Kingdom = Animalia Phylum (Division for plants) = Chordata
Class = Mammalia
Order = Primates
Family = Hominidae
Genus = Homo
species = sapiens

12. Taxonomic groups above the level of species are “invented” by researchers who decide how to distinguish between one genus, family, or phylum, and another.

13. Phylogeny = the study of evolutionary relationships among organisms
Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities.

14. Look at these 3 organisms
BARNACLE
CRAB
LIMPET

15. Judging by
appearances you
would probably put
limpets and barnacles
together in a group
and crabs in a different group.
BUT LOOKS can be deceiving!

16. Look more closely! BARNACLE LIMPET CRAB
Limpet and barnacle larvae are very different.
Barnacles have jointed limbs.
Limpets DON’T !
Barnacles have a segmented body
Barnacles have an exoskeleton that molts.
BARNACLE
LIMPET
CRAB

17. Look more closely! BARNACLE LIMPET CRAB
Crab and barnacle larvae are very similar
Barnacles have jointed limbs.
So do CRABS !
Barnacles have a segmented body
Barnacles have an exoskeleton that molts.
BARNACLE
LIMPET
CRAB

18. evolutionary classification = method of grouping organisms together according to their evolutionary history

19. Cladogram = diagram that shows the evolutionary relationships among a group of organisms

23. The genes of many organisms show important similarities at the molecular level.
Similarities in DNA can be used to help determine classification and relationships.
The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more closely they are related.

24. Dichotomous Key
A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.
Keys consist of a series of choices that lead the user to the correct name of a given item.
"Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.