Classification of Living Things 1 Ch. 20 Outline - Classification

Classification of Living Things 2Taxonomy Branch of biology concerned with identifying, naming, and classifying organisms Began with the ancient Greeks and Romans   Aristotle classified organisms into groups such as horses, birds, and oaks John Ray (1627–1705)   Believed that each organism should have a set name. Names were given in Latin.   Otherwise, “men…cannot see and record accurately.”

3 Classifying Organisms How would you name & classify these organisms?

Classification of Living Things 4 Taxonomy: Binomial System Mid-eighteenth century, Linnaeus developed the binomial system of nomenclature   First word is genus name   Second word is specific epithet ­ ­Refers to one species (of potentially many) within its genus   A species is referred to by the full binomial name (Genus species)   Genus name can be used alone to refer to a group of related species

Classification of Living Things 5 Taxonomy: Binomial System Why do organisms need scientific names?   Common names vary from countries because of different languages   Even in one language area, common names can differ ­ ­Cougar, mountain lion, puma are all same animal ­ ­Robin in England is different bird than in U.S.   When scientists around the world use the Latin binomial name, they know they are discussing the same organism.

6 Carolus Linnaeus Lilium buibiferum Lilium canadense Lynx rufus Lynx canadensis

Classification of Living Things 7 Taxonomy: Distinguishing Species Several ways of distinguishing species: 1. Structural definition rests on distinctive structural characteristics not shared by members of a similar species. ­ ­ In birds: Shape, size, color, feet, beak, wings - Members of same species can also vary from each other

8 Members of a Species - Sexual Dimorphism Mallards Male Female Male

9 Members of a Species - Sexual Dimorphism Male Female Female Terrapin larger Elephant seals - large male Male Female Rhinoceros beetles Male & Female

Classification of Living Things 10 Taxonomy: Distinguishing Species Several ways of distinguishing species: 2. Biological definition rests on recognition that distinctive characteristics are passed from parents to offspring. Based on interbreeding & sharing the same gene pool. - Attempts to demonstrate reproductive isolation is problematic because: ● Some species hybridize, and ● Reproductive isolation is difficult to observe

11 Hybridization between species Zebroids

Classification of Living Things 12 Classification Categories Modern taxonomists use the following classification: (from smallest to largest groups)   Species   Genus – one or more species   Family – one or more genera   Order – one or more families   Class – one or more orders   Phylum – one or more classes   Kingdom – one or more phyla   Domain – one or more kingdoms

Classification of Living Things 13 Classification Categories Classification of Humans:   Domain -- Eukarya   Kingdom – Animalia   Phylum – Chordata SubPhylum - Vertebrata   Class – Mammalia   Order – Primates   Family – Hominidae   Genus – Homo   Species – Homo sapiens

14 Hierarchy of Taxa for Parthenocissus quinquefolia

Classification of Living Things 15 Classification Categories The higher the category, the more inclusive Organisms in the same domain have general characteristics in common In most cases, classification categories can be subdivided into additional categories   Superorder   Order   Suborder   Infraorder

Classification of Living Things 16 Phylogenetic Trees Systematics - the diversity of organisms at all levels One goal of systematics is to determine phylogeny (evolutionary history) of a group Phylogeny often represented as a phylogenetic tree   A diagram indicating lines of descent   Each branching point: ­ ­Is a divergence from a common ancestor ­ ­Represents an organism that gives rise to two new groups

17 Classification and Phylogeny

Classification of Living Things 18 Phylogenetic Trees Classification categories list the unique characters of each taxon and is intended to reflect phylogeny   Ancestral characteristics: ­ ­Present in all members of a group, and ­ ­Present in the common ancestor   Derived characters: ­ ­Own individual characteristics ­ ­Present in some members of a group, but ­ ­Absent in the common ancestor

19 Classification and Phylogeny Derived characters Common ancestor (Ancestral characters)

Classification of Living Things 20 Tracing Phylogeny Fossil Record   It is often difficult to determine the phylogeny of a fossil Are turtles & crocodiles closely related? Molecular data says yes Or are turtles ancestors of crocodiles? Fossil record is incomplete since soft parts have less of a chance of becoming fossils.

21 Ancestral Angiosperm?

Classification of Living Things 22 Tracing Phylogeny Homology   Is character similarity that stems from having a common ancestor   Homologous structures are related to each other through common descent   Examples: Vertebrate forelimbs have same bones as in a common ancestor

Classification of Living Things 23 Tracing Phylogeny Convergent Evolution   The acquisition of same or similar features in distantly related lines of descent   The feature is not present in a common ancestor   Such similarities are termed an analogy.   Analogous structures have same function in different groups of organisms but don’t have a common ancestor Examples: wings of birds and insects American cacti and African spurges

24 North AmericaAfrica Convergent Evolution

Classification of Living Things 25 Tracing Phylogeny Parallel Evolution   The acquisition of a same or similar feature in two or more related lineages   The feature is not present in a common ancestor   Sometimes difficult to tell parallel evolution from convergent evolution.

Classification of Living Things 26 Molecular Data Protein Comparisons   Amino acid sequencing ­ ­Cytochrome c is found in all aerobic organisms ­ ­Compare a.a. sequence in different species to infer relationships: 3 differences between chickens & ducks 13 differences between chickens & humans - Thus chickens & ducks are more closely related than chickens & humans.

Classification of Living Things 27 Molecular Data RNA and DNA Comparisons   All cells have ribosomes   Genes that code for rRNA have changed very slowly during evolution   This can provide a reliable indicator of similarities between organisms.   rRNA information led to the division of life into three domains.

Classification of Living Things 28 Molecular Data DNA-DNA hybridization - Separate DNA into single strands & then combine with different species. - The better the strands stick together the more closely related the organisms. - This has been used to resolve ancestry of giant pandas. Are giant pandas more closely related to bears or raccoons? DNA hybridization says “bears”.

29 Ancestry of Giant Pandas Have raccoon features Feeds on bamboo but lacks false thumb Eat bamboo with help of false thumb but look more like a bear DNA of raccoons & red pandas more similar DNA of giant pandas & bears more similar

30 Molecular Data

Classification of Living Things 31 Classification Systems Until the middle of the twentieth century, biologists recognized only two kingdoms   Plantae (plants)   Animalia (animals) Protista (protists) were proposed as an additional third kingdom in the 1880s but wasn’t accepted until 1950s. Whittaker expanded to five kingdoms in 1969 by adding Fungi and Monera

Classification of Living Things 32 Three-Domain System The Bacteria and Archaea are so different they have been assigned to separate domains Similar in that both are asexually reproducing unicellular prokaryotes Distinguishable by:   Difference in rRNA base sequences   Plasma membrane chemistry   Cell wall chemistry

Classification of Living Things 33 Three-Domain System Characteristics Of Domain BacteriaArchaeaEukaryaUnicellularityYes Some, most multicellular Membranelipids Phospholipids unbranched Varied branched lipids Phospholipids unbranched Cell Wall Yes (has Peptidoglycan) Yes (no Peptidoglycan) Yes; some (no Peptidoglycan) Nuclear envelope No Yes Membrane- bound organelles No Yes Ribosomes IntronsNoSomeYes

Classification of Living Things 34 Three-Domain System Domain Bacteria Unicellular asexually reproducing organisms Very diversified and plentiful group. Found everywhere on Earth. Most are heterotrophic; some photosynthetic Domain Archaea Unicellular asexually reproducing organisms Most live under extreme conditions Cell membrane & wall chemistry is different

Classification of Living Things 35 Three-Domain System Domain Eukarya Unicellular and multicellular organisms Cells with a membrane-bounded nucleus   Sexual reproduction common   Contains four kingdoms ­ ­Kingdom Protista ­ ­Kingdom Fungi ­ ­Kingdom Plantae ­ ­Kingdom Animalia

36 The Three-Domain System of Classification 1.Ancestor of ALL life split into the two Domains of Bacteria & Archaea 2.Archaea split to produce Eukarya 3.First Eukarya were Protists 4.Protists split in three directions to produce: - Plants - Fungi - Animals

37 The Three Domains of Life

Classification of Living Things 38 Eukarya Kingdoms Protists Diverse group of eukaryotes Mainly unicellular Lack true tissues Some heterotrophic; some autotrophic Some texts put protists into several kingdoms Examples: Green algae, paramecia, slime molds

Classification of Living Things 39 Eukarya Kingdoms Fungi Eukaryotes that form spores Have cell walls containing chitin Most multicellular Heterotrophic by absorption – secrete digestive enzymes onto food and then absorb nutrients Examples: Mushrooms, molds, yeast

Classification of Living Things 40 Eukarya Kingdoms Plants Eukaryotes that are multicellular Have cell walls containing cellulose Nonmotile (don’t move on own) Autotrophic via photosynthesis Have true tissues and organs Examples: Trees, cacti, flowers, ferns

Classification of Living Things 41 Eukarya Kingdoms Animals Eukaryotes that are multicellular Motile (do move on own) Heterotrophic by ingestion (eat food) Have true tissues and organs Examples: Birds, fish, reptiles, amphibians, mammals, worms, snails, etc.