1 Chapter 18: Classification

2 18–1 Finding Order in Diversity  Life on Earth has been changing for more than 3.5 billion 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 biological meaning  Taxonomy = discipline of classifying organisms and assigning each organism a universally accepted name

What is classification?  Classification is the arrangement of organisms into orderly groups based on their similarities  Classification is also known as taxonomy  Taxonomists are scientists that identify & name organisms

Benefits of Classifying  Accurately & uniformly names organisms  Prevents misnomers such as starfish & jellyfish that aren't really fish  Uses same language (Latin or some Greek) for all names Sea”horse”??

Early Taxonomists  2000 years ago, Aristotle was the first taxonomist  Aristotle divided organisms into plants & animals  He subdivided them by their habitat --- land, sea, or air dwellers

Early Taxonomists  18th century taxonomist  Classified organisms by their structure  Developed naming system still used today

8 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 (Genus), the second word is lower case (species)

9 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  Ex: buzzard: hawk? Vulture?  Scientists have agreed to a single name for each species  Use Latin & Greek

10 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

Which TWO are more closely related?

12 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

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

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

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

17  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.

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

19  The higher the level of the taxon, the farther back in time is the common ancestor of all the organisms in the taxon.

20  Cladogram = diagram that shows the evolutionary relationships among a group of organisms

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24  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 sequences of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.

25 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.

Dichotomous Keying  Used to identify organisms  Characteristics given in pairs  Read both characteristics and either go to another set of characteristics OR identify the organism

Example of a Dichotomous Key 1a Tentacles present – Go to 2 1b Tentacles absent – Go to 3 2a Eight Tentacles – Octopus 2b More than 8 tentacles – 3 3a Tentacles hang down – go to 4 3b Tentacles upright–Sea Anemone 4a Balloon-shaped body–Jellyfish 4b Body NOT balloon-shaped - 5

28 18–3 Kingdoms and Domains  There are now 6 Kingdoms – listed below.

29  Domain = most inclusive taxonomic category; larger than a kingdom

30 Eubacteria  Unicellular  Prokaryotic  Autotroph or heterotroph  Cell walls with peptidoglycan  Examples: E. coli, Streptococcus, Staph

31 Archaebacteria  unicellular  prokaryotic  extreme environments –volcanic hot springs, brine pools, and black organic mud totally devoid of oxygen  Auto or heterotroph  cell walls lack peptidoglycan peptidoglycan

32 Protista  eukaryotic  greatest variety  Most single-celled, some multi  photosynthetic or heterotrophic  Ex: kelp, amebas, slime mold, paramecium, euglena

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34 Fungi  heterotrophs –feed on dead or decaying organic matter organic matter  Eukaryotic  Most multicellular, some uni  Cell walls of chitin  EX: mushroom, yeast

35 Plantae  multicellular  photosynthetic autotrophs  Eukaryotic  Cells walls of cellulose

36 Animalia  multicellular  heterotrophic  Eukaryotic  No cell walls