Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 15 Lecture Slides

15.1 The Invention of the Linnaean System To talk about and to study organisms, it is necessary to give them names  biologists use a kind of multilevel grouping of individuals called classification  the earliest classification scheme grouped animals and plants into basic units called genera (singular, genus) early biologists added a series of non-standardized descriptions to the genus name this created a string of subjective names called a polynomial

15.1 The Invention of the Linnaean System A much simpler system than the polynomial for the naming of organisms was developed by Carolus Linnaeus  Linnaeus assigned organisms a two-part name called a binomial  he also grouped similar organisms into higher-level categories based on similar characteristics

Figure 15.1 Carolus Linnaeus

Figure 15.1 How Linnaeus named two species of oaks

15.2 Species Names Taxon (plural, taxa) is a group of organisms at a particular level in a classification system  the branch of biology that identifies and names such groups is called taxonomy  no two kinds of organisms can have the same name and all names are given in Latin

15.2 Species Names The scientific name for an organism is comprised of the two-part binomial  the first part is the genus, which is always capitalized  the second part is the specific epithet, referring to the particular species, and is not capitalized  the two words together are written in italics or are underlined

15.3 Higher Categories The binomial has been expanded into a Linnaean system of classification  genera with similar properties are grouped together into a family  families that share similar characteristics are put into the same order  orders with common properties are placed into the same class  classes with similar characteristics are placed into the same phylum  phyla are assigned to one of several gigantic groups called kingdoms  kingdoms are sometimes assigned to an additional level of classification, called domains

Figure 15.4 The hierarchical system used to classify a gray squirrel

15.4 What Is a Species? The basic biological unit is the species John Ray (1627–1705) proposed one of the first definitions of a species:  all the individuals that belong to it can breed with one another and produce fertile offspring The Biological Species Concept defines species as groups that are reproductively isolated  the biological species concept definition works well for animals, but not as well for organisms in which asexual reproduction is more common

15.4 What Is a Species? The biological species concept is not always employed for plants and other organisms Molecular data are causing a reevaluation of traditional classification systems Since the time of Linnaeus, about 1.5 million species have been named  the actual number of species is much greater

15.5 How to Build a Family Tree Phylogeny is the evolutionary history of an organism and its relationship to other species  scientists use different approaches to construct phylogenetic trees

15.5 How to Build a Family Tree Cladistics is an approach that infers phylogeny according to similarities derived from a common ancestor  derived characters are characters that are present in a group of organisms that arose from a common ancestor that lacked the character  a clade is a group of organisms, related by descent, that share a derived character  by examining the distribution of derived traits among related organisms, it is possible to construct a cladogram, a branching diagram that represents the phylogeny

Figure 15.6 A cladogram of vertebrate animals

15.5 How to Build a Family Tree Cladograms convey comparative information about relative relationships  organisms that are closer together on a cladogram simply share a more recent common ancestor than those that are farther apart  each cladogram must have an outgroup, a rather different organism to serve as a basis for comparisons among the other organisms being evaluated, called the ingroup  sometimes cladograms are adjusted to “weight” characters that have a particular importance

15.5 How to Build a Family Tree An alternative approach to constructing phylogenies is traditional taxonomy  a great deal of information about the morphology and biology an of organism is used this wealth of information often permits a knowledgeable weighting of certain characters, but this weighting can be subjective

Figure 15.7 Two ways to classify terrestrial vertebrates

15.6 The Kingdoms of Life Most biologists use a six-kingdom classification system first proposed by Carl Woese  four kingdoms consist of eukaryotes Animalia, Plantae, Fungi, and Protista  two kingdoms consist of prokaryotes Archaea and Bacteria Recognizing that there are further differences among the prokaryotes, the domain level above kingdom was created  Domain Archaea contains the Kingdom Archaea  Domain Bacteria contains the Kingdom Bacteria  Domain Eukarya contains the eukaryotic kingdoms

Figure 15.9 Different approaches to classifying living organisms

15.7 Domain: A Higher Level of Classification Bacteria are the most abundant organisms on earth  there are many different types of bacteria and the evolutionary links between them are not well understood  many species of bacteria play critical roles throughout the biosphere Although archaea are also prokaryotic like bacteria, the archaea are more closely related to eukaryotes

15.7 Domain: A Higher Level of Classification The Archaea branched off from a line of prokaryotic ancestors that led to the evolution of eukaryotes Archaea, although a diverse group, share certain key characteristics they possess unique cell walls, lipids, and rRNA sequences some genes in the archaea have introns Archaea are often found in extreme environments but are not restricted to them

Figure A tree of life

15.7 Domain: A Higher Level of Classification Eukaryotes appeared about 1.5 billion years ago  there are three largely multicellular kingdoms (fungi, plants, and animals)  the remaining eukaryotic kingdom, Protista, is a diverse array of mostly unicellular forms that basically don’t fit into the other kingdoms

15.7 Domain: A Higher Level of Classification Mitochondria and chloroplasts are both believed to have been derived from bacteria that entered early eukaryotic cells by endosymbiosis Figure Endosymbiosis: (a) how an organelle could have arisen by endosymbiosis; (b) endosymbionts (golden-brown protists called zooxanthellae) within the tentacles of a coral animal

Animation: Horizontal Gene Transfer

Inquiry & Analysis Three great innovations in the jaw and tail occur during the history of the bony fishes, producing the superorders represented by sturgeons, then gars, then teleost fishes. In what period did each innovation occur? What Causes New Forms to Arise?