CHAPTER 18 CLASSIFICATION

SECTION 1 FINDING ORDER IN DIVERSITY

KEY CONCEPT QUESTIONS: How are living things organized for study? What is binomial nomenclature? What is Linnaeus’s system of classification?

How are living things organized for study? To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner

Taxonomy is the science of naming and classifying organisms. White oak: Quercus alba A taxon is a group of organisms in a classification system.

Classification System to organize all living creatures plants animals microbes etc.

Why not use common names? Misleading starfish dragonfly Confusing blue jay, blue coat, corn thief dog, perro, chien I swim, but I’m still a bird!

Why not use common names? But they all have only one scientific name! Pisaster ochraceus Pyrrhosoma nymphula Cyanocitta cristata

Some species have very similar common names. Scientific names help scientists to communicate. Some species have very similar common names. Some species have many common names.

A more universal way of scientifically classifying came about Binomial nomenclature is a two-part scientific naming system. uses Latin words scientific names always written in italics two parts are the genus name and species descriptor

Carolus Linnaeus The Linnean system proposed in 1700s each species has a 2 part name genus species Homo sapiens

A genus includes one or more physically similar species. Species in the same genus are thought to be closely related. Genus name is always capitalized. A species descriptor is the second part of a scientific name. always lowercase always follows genus name; never written alone Tyto alba

The grizzly bear is called Ursus arctos. The first part of the scientific name—in this case, Ursus—is the genus to which the organism belongs The second part of a scientific name—in this case, arctos—is unique to each species within the genus (this is usually a Latin name)

Genus groupings Leopard Panthera pardus African lion Panthera leo Tiger Panthera tigris

Linnaeus’ classification system has seven levels. Each level is included in the level above it. Levels get increasingly specific from kingdom to species.

Classification Kings Kingdom Play Phylum Chess Class Order On Family Funny Green Squares Kingdom Phylum Class Order Family Genus species

Orders & families

The Linnaean classification system has limitations. Linnaeus taxonomy doesn’t account for molecular evidence. The technology didn’t exist during Linneaus’ time. Linnaean system based only on physical similarities.

KEY CONCEPT QUESTIONS: How are living things organized for study? Taxonomic categories What is binomial nomenclature? 2-part universal naming system What is Linnaeus’s system of classification? each species has a 2 part name genus species

SECTION 2 MODERN EVOLUTIONARY CLASSIFICATION

KEY CONCEPT QUESTIONS: How are evolutionary relationships important in classification? How can DNA and RNA help scientists determine evolutionary relationships?

Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships. The red panda has given scientists taxonomic fits. It has been classified as a relative of the giant panda, and also of the raccoon, with which it shares a ringed tail. Currently, red pandas are considered members of their own unique family—the Ailuridae.

With the help of newer technology scientists have found more accurate ways of classifying organisms Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities. In other words, species placed within the same genus should be more closely related to one another than to species of any other genus

EVOLUTIONARY CLASSIFICATION method of grouping organisms together according to their evolutionary history To refine the process of evolutionary classification, many biologists now prefer a method called cladistic analysis

Cladistics is classification based on common ancestry. Phylogeny is the evolutionary history for a group of species. evidence from living species, fossil record, and molecular data shown with branching tree diagrams

Cladistics is a common method to make evolutionary trees. classification based on common ancestry species placed in order that they descended from common ancestor

A cladogram is an evolutionary tree made using cladistics. A clade is a group of species that shares a common ancestor. Each species in a clade shares some traits with the ancestor. Each species in a clade has traits that have changed.

basis of arranging species in cladogram Derived characters are traits shared in different degrees by clade members. basis of arranging species in cladogram more closely related species share more derived characters represented on cladogram as hash marks FOUR LIMBS WITH DIGITS Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE DERIVED CHARACTER

Molecular evidence reveals species’ relatedness. Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. DNA is usually given the last word by scientists.

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 Comparisons of DNA can also be used to mark the passage of evolutionary time.

Molecular clocks use mutations to estimate evolutionary time. Mutations add up at a constant rate in related species. This rate is the ticking of the molecular clock. As more time passes, there will be more mutations. DNA sequence from a hypothetical ancestor The DNA sequences from two descendant species show mutations that have accumulated (black). The mutation rate of this sequence equals one mutation per ten million years. Mutations add up at a fairly constant rate in the DNA of species that evolved from a common ancestor. Ten million years later— one mutation in each lineage Another ten million years later— one more mutation in each lineage

Scientists estimate mutation rates by linking molecular data and real time. an event known to separate species the first appearance of a species in fossil record

Modern Systematics Shaking up some trees! Crocodiles are now thought to be closer to birds than other reptiles

KEY CONCEPT QUESTIONS: How are evolutionary relationships important in classification? evolutionary history of a species based on common ancestries inferred from fossil record morphological & biochemical resemblances molecular evidence How can DNA and RNA help scientists determine 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

SECTION 3 KINGDOMS AND DOMAINS

KEY CONCEPT QUESTIONS: What are the six kingdoms of life as they are now identified?  What is the three-domain system of classification?

Classification is always a work in progress. The tree of life shows our most current understanding. New discoveries can lead to changes in classification. 1866: all single-celled organisms moved to kingdom Protista Until 1866: only two kingdoms, Animalia and Plantae 1938: prokaryotes moved to kingdom Monera 1959: fungi moved to own kingdom 1977: kingdom Monera split into kingdoms Bacteria and Archaea Animalia Protista Fungi Plantae Archea Bacteria

The three domains in the tree of life are Bacteria, Archaea, and Eukarya. Domains are above the kingdom level. proposed by Carl Woese based on rRNA studies of prokaryotes domain model more clearly shows prokaryotic diversity

KEY CONCEPT QUESTIONS: What are the six kingdoms of life as they are now identified?  bacteria, archea, protista, fungi, plantae, and animalia What is the three-domain system of classification? Bacteria Archea Eukarya