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18-1 Finding Order in Diversity

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1 18-1 Finding Order in Diversity
Photo credit: ©Gary Randall/Visuals Unlimited

2 Finding Order in Diversity
Section 18-1 To study the diversity of life, biologists use a classification system to name organisms and group then in a logical manner. Taxonomists are scientists that classify organisms into groups that have biological significance and assign each organism a universally accepted name. Binomial Nomenclature Developed by a Swedish botanist, Carolus Linnaeus, in the 18th century. Each species is assigned a two-part scientific name that is always written in italics. The first word is capitalized, and the second word is lowercased. The first word is the genus and the second word is unique to each species of the genus. It is usually a Latinized description of some important trait of the organism or an indication of where the organism lives. Examples, Ursus maritimus – polar bear; Ursus arctos, grizzly bear

3 We only know about a fraction of the
organisms that exist or have existed on Earth. Taxonomists give a unique scientific name to each species they know about whether it’s alive today or extinct. The scientific name comes from one of two “dead” languages – Latin or ancient Greek. Why use a dead language?

4 Devil Cat

5 Ghost Cat

6 Mountain Lion

7 Screaming Cat

8 Puma

9 Florida Panther

10 Cougar

11 There are at least 50 common names for
the animal shown on the previous 7 slides. Common names vary according to region. Soooo……why use a scientific name?

12 Flowchart Linnaeus’s System of Classification Kingdom Phylum Class
Section 18-1 Linnaeus’s System of Classification Kingdom Phylum Class Order Family Linnaeus’s classification system is hierarchical; it consists of levels. Each level is called a taxon. Genus Species

13 Figure 18-5 Classification of Ursus arctos
Section 18-1 Grizzly bear Black bear Giant panda Red fox Abert squirrel Coral snake Sea star KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos

14 Humans Domain Eukarya Kingdom Animalia Phylum Chordata Sub Phylum Vertebrata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapien Scientific name: Homo sapien

15 Evolutionary Classification
Section 18-2 Species within a genus are more closely related to each other than to species in another genus because all members of a genus share a recent common ancestor. All genera in a family share a common ancestor that is further in the past than the ancestor of the entire order. The higher the level of the taxon, the further back in time is the common ancestor of all the organisms of the taxon.

16 A phylogenetic tree is a family tree that shows a hypothesis about the evolutionary relationships thought to exist among groups of organisms. It does not show the actual evolutionary history of organisms. Why a hypothesis?

17 Phylogenetic trees are usually based on a combination of these lines of evidence:
    Fossil record     Morphology     Embryological patterns of development     Chromosomes and DNA

18

19 Evolutionary Classification
Section 18-2 Cladistic analysis identifies and considers only those characteristics of organisms that are evolutionary innovations. Derived characteristics are those that appear in recent parts of a lineage but not in its older members. Used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.

20 There are three basic assumptions in cladistics:
Organisms within a group are descended from a common ancestor. There is a bifurcating pattern of cladogenesis. Change in characteristics occurs in lineages over time.

21 CLASSIFICATION BASED ON VISIBLE SIMILARITIES
Traditional Classification Versus Cladogram Section 18-2 Classifying species based on easily observed adult traits can pose problems. Which of these three organisms seem most alike? What additional information might you gather to help inform your decision? Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM

22 CLASSIFICATION BASED ON VISIBLE SIMILARITIES
Traditional Classification Versus Cladogram Section 18-2 Appendages Conical Shells Crustaceans Gastropod Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities. This strategy is called evolutionary classification. Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM

23 The Dichotomous Key A key is a device for easily and quickly identifying an unknown organism. The dichotomous key is the most widely used type in biological sciences. The user is presented with a sequence of choices between two statements, couplets, based on characteristics of the organism. By always making the correct choice, the name of the organism will be revealed.

24                                                             

25 Evolutionary Classification
Section 18-2 In addition to physical characteristics, similarities in DNA and RNA can be used to help determine classification and evolutionary relationships. The genes of many organisms show important similarities at the molecular level. The more similar the DNA sequence of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.

26 The three domains are Eukarya, Bacteria, and Archaea.
Kingdoms and Domains Section 18-3 The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia The three domains are Eukarya, Bacteria, and Archaea. The domain Eukarya includes the kingdoms Protista, Fungi, Plaintae, and Animalia. The domain Bacteria includes the kingdom Eubacteria. The domain Archaea includes the kingdom Archaebacteria.

27 Concept Map Section 18-3 Living Things Eukaryotic cells
Prokaryotic cells are characterized by Important characteristics and differing which place them in Domain Eukarya Cell wall structures such as which is subdivided into which place them in Kingdom Plantae Kingdom Protista Kingdom Fungi Kingdom Animalia Domain Bacteria Domain Archaea which coincides with which coincides with Kingdom Eubacteria Kingdom Archaebacteria

28 Characteristics of Domain Bacteria
Section 18-3 Characteristics of Domain Bacteria Kingdom Eubacteria Unicellular and prokaryotic Thick, rigid cell walls surrounding a cell membrane Cell walls contain peptidoglycan Ecologically diverse, ranging from free-living soil organisms to deadly parasites Some are photosynthetic Some anaerobic

29 Characteristics of Domain Archaea
Section 18-3 Characteristics of Domain Archaea Kingdom Archaebacteria Unicellular and prokaryotic Thick, rigid cell walls surrounding a cell membrane Cell walls lack peptidoglycan Cell membranes contain unusual lipids found only in Archaea Live in some of the most extreme environments (hot springs, brine pools, and black organic mud) Many are anaerobic

30 Characteristics of Domain Eukarya
Domain Bacteria Section 18-3 Characteristics of Domain Eukarya Eukaryotes (organisms with a nucleus) Kingdom Protista - cannot be classified as animals, plants, or fungi - greatest variety - most unicellular; some colonial; some multicellular - cell walls of cellulose in some; some have chloroplasts - some photosynthetic, others are heterotrophic - some share characteristics with plants, others with fungi, and others with animals - animal-like protist include Euglena, Paramecium and Amoeba - other examples include algae, slime molds, and giant kelp

31 Characteristics of Domain Eukarya, continued
Section 18-3 Characteristics of Domain Eukarya, continued Kingdom Fungi - cell walls of chitin - most multicellular (mushrooms); some unicellular (yeasts) - heterotrophic - often found on dead or decaying organic matter; secrete digestive enzymes into their food source; absorb smaller molecules into their bodies

32 Characteristics of Domain Eukarya, continued
Section 18-3 Characteristics of Domain Eukarya, continued Kingdom Plantae - multicellular, photosynthetic autotrophs - nonmotile – cannot move from place to place - cell walls that contain cellulose; have chloroplasts - includes cone-bearing plants, flowering plants, mosses, and ferns Kingdom Animalia - multicellular, heterotrophs - no cell walls - mobile for at least some part of their life cycle - incredible diversity - examples include sponges, worms, insects, fishes, and mammals

33 Classification of Living Things
Figure Key Characteristics of Kingdoms and Domains Section 18-3 Classification of Living Things DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Eukarya Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals

34 Figure 18-13 Cladogram of Six Kingdoms and Three Domains
Section 18-3 DOMAIN ARCHAEA DOMAIN EUKARYA Kingdoms Eubacteria Archaebacteria Protista Plantae Fungi Animalia DOMAIN BACTERIA

35

36 Modern Hominoids

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