Classification of Living Things 1 Ch. 20 Outline - Classification.

Classification of Classification of Living ThingsLiving Things 1

Ch. 20 Outline - ClassificationCh. 20 Outline - Classification


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.”

3Classifying Organisms

How would you name & classify

these organisms?

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


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.

6Carolus Linnaeus

Lilium buibiferum

Lilium canadense

Lynx rufus

Lynx canadensis


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

8Members of a Species - Sexual Dimorphism

Mallards

MaleFemale

Male

9Members of a Species - Sexual Dimorphism

MaleFemale

Female Terrapin larger

Elephant seals - large male Male

Female

Rhinoceros beetles

Male

& Female


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

11Hybridization between species

Zebroids


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 Humans:

Domain -- Eukarya

Kingdom – Animalia

Phylum – Chordata SubPhylum - Vertebrata

Class – Mammalia

Order – Primates

Family – Hominidae

Genus – Homo

Species – Homo sapiens

14Hierarchy of Taxa forParthenocissus quinquefolia



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


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

17Classification and Phylogeny


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)


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.

21Ancestral Angiosperm?



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


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

24

North America AfricaConvergent Evolution



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.


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.



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.



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

30Molecular Data


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


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



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



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



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

37The Three Domains of Life


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



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



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



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.

Classification of Living Things 1 Ch. 20 Outline - Classification.

Documents

species zebroids slide

outline classification

genus species genus

species family

similar species

ways of distinguishing

following classification

largest groups species