Presentation on theme: "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."— Presentation transcript:
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
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
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
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