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Classification of Classification of Living ThingsLiving Things 1
Ch. 20 Outline - ClassificationCh. 20 Outline - Classification
Classification of Classification of Living ThingsLiving Things 2
TaxonomyTaxonomy
Branch of biology concerned with identifying, naming, and classifying organisms
Began with the ancient Greeks and RomansAristotle 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.”
Classification of Classification of Living ThingsLiving Things 4Taxonomy:Taxonomy:
Binomial SystemBinomial 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 Classification of Living ThingsLiving Things 5Taxonomy:Taxonomy:
Binomial SystemBinomial 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.
Classification of Classification of Living ThingsLiving Things 7Taxonomy:Taxonomy:
Distinguishing SpeciesDistinguishing 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
9Members of a Species - Sexual Dimorphism
MaleFemale
Female Terrapin larger
Elephant seals - large male Male
Female
Rhinoceros beetles
Male
& Female
Classification of Classification of Living ThingsLiving Things 10Taxonomy:Taxonomy:
Distinguishing SpeciesDistinguishing 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
Classification of Classification of Living ThingsLiving Things 12
Classification CategoriesClassification Categories
Modern taxonomists use the following classification: (from smallest to largest groups)SpeciesGenus – one or more speciesFamily – one or more generaOrder – one or more familiesClass – one or more ordersPhylum – one or more classesKingdom – one or more phylaDomain – one or more kingdoms
Classification of Classification of Living ThingsLiving Things 13
Classification CategoriesClassification Categories
Classification of Humans:
Domain -- Eukarya
Kingdom – Animalia
Phylum – Chordata SubPhylum - Vertebrata
Class – Mammalia
Order – Primates
Family – Hominidae
Genus – Homo
Species – Homo sapiens
Classification of Classification of Living ThingsLiving Things 15
Classification CategoriesClassification 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 Classification of Living ThingsLiving Things 16
Phylogenetic TreesPhylogenetic 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 treeA diagram indicating lines of descentEach branching point:
Is a divergence from a common ancestor
Represents an organism that gives rise to two new groups
Classification of Classification of Living ThingsLiving Things 18
Phylogenetic TreesPhylogenetic 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
19Classification and Phylogeny
Derived characters Derived characters
Common ancestor(Ancestral characters)
Classification of Classification of Living ThingsLiving Things 20
Tracing PhylogenyTracing 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.
Classification of Classification of Living ThingsLiving Things 22
Tracing PhylogenyTracing 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 Classification of Living ThingsLiving Things 23
Tracing PhylogenyTracing PhylogenyConvergent Evolution
The acquisition of same or similar features in distantly related lines of descent
The feature is not present in a common ancestorSuch 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
Classification of Classification of Living ThingsLiving Things 25
Tracing PhylogenyTracing 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 Classification of Living ThingsLiving Things 26
Molecular DataMolecular Data
Protein ComparisonsAmino 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 Classification of Living ThingsLiving Things 27
Molecular DataMolecular 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 Classification of Living ThingsLiving Things 28
Molecular DataMolecular 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”.
29Ancestry of Giant Pandas
Have raccoon featuresFeeds on bamboo but
lacks false thumb
Eat bamboo with help of false thumb
but look morelike a bear
DNA of raccoons & red pandasmore similar
DNA of giant pandas & bears more similar
Classification of Classification of Living ThingsLiving Things 31
Classification SystemsClassification 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 Classification of Living ThingsLiving Things 32
Three-Domain SystemThree-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 Classification of Living ThingsLiving Things 33
Three-Domain SystemThree-Domain System
CharacteristicsCharacteristicsOf DomainOf Domain
Bacteria Archaea Eukarya
UnicellularityUnicellularity Yes Yes Some, mostmulticellular
MembraneMembranelipidslipids
Phospholipidsunbranched
Varied branched lipids
Phospholipidsunbranched
Cell WallCell Wall Yes (hasPeptidoglycan)
Yes (no Peptidoglycan)
Yes; some (no Peptidoglycan)
Nuclear Nuclear envelopeenvelope
No No Yes
Membrane-Membrane-bound bound
organellesorganelles
No No Yes
RibosomesRibosomes Yes Yes Yes
IntronsIntrons No Some Yes
Classification of Classification of Living ThingsLiving Things 34
Three-Domain SystemThree-Domain System
Domain BacteriaUnicellular asexually reproducing organismsVery diversified and plentiful group.Found everywhere on Earth. Most are heterotrophic; some photosynthetic
Domain Archaea Unicellular asexually reproducing organismsMost live under extreme conditionsCell membrane & wall chemistry is different
Classification of Classification of Living ThingsLiving Things 35
Three-Domain SystemThree-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
36The Three-DomainSystem of
Classification1. 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
Classification of Classification of Living ThingsLiving Things 38
Eukarya KingdomsEukarya 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 Classification of Living ThingsLiving Things 39
Eukarya KingdomsEukarya 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 Classification of Living ThingsLiving Things 40
Eukarya KingdomsEukarya 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 Classification of Living ThingsLiving Things 41
Eukarya KingdomsEukarya 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.