Finding Order in Diversity

Classification

Why do we need to classify?

•Imagine a store…..how do you know where

to find the milk or the cereal? Are they in

the same aisle? How is the store

“organized”? Are all stores similar?

•Imagine your computer or mp3

player…..are all of your songs and files in a

single folder or do you have them grouped

in some way?

Evolution overview

All life on earth began about 3.5 billion years ago with organisms that were a single cell

Then one billion years ago organisms that are made of many cells appeared as a result of evolution

During evolution traits that do not help organisms survive disappear while good traits that help with survival remain

Classification

As a result of evolution earth is populated by many different organisms with different traits.

We group these organisms according to their similar characteristics

Classification – grouping and naming of organisms according to their evolutionary relationships and shared characteristics

Taxonomy

Branch of biology that deals with classification of life forms

Taxonomist – use the tools of classification to identify and find relationships among organisms

Taxonomists classify organisms based on their biochemical and genetic information, embryological development, fossil record, and evolutionary relationships, in addition to their body structure

Early Classification and naming systems

Aristotle – Greek philosopher Invented the first classification system He classified organisms into two major groups

plants and animals

Land

WaterShrubsHerbs

Plants Animals

AirTrees

Early Classification and naming systems continued . . .

Carolus Linnaeus – Swedish botanist In the 18th century developed a new classification system He also grouped them into plants and animals He classified animals based on their similar body

structures and not where they lived Example: bats were grouped with mammals not with

birds

Binomial Nomenclature

Linnaeus also gave each organism a two-word, Latin scientific name This is called binomial nomenclature –

still used today Binomial – consisting of two terms Nomenclature – a system of names

Bi-Nominal – two terms, two names

How many names do you use to identify yourself? Example: Karen Wood

But why do we need this? Can we just call her Karen or simply that girl over there?

When you have a lot of information, it is best to

organize and group items so that you can find

them easier or easily see their relationship to

other items

….this is why we CLASSIFY

Even websites

must  organize their

products

Scientists also need a way to

*NAME* organisms•The “common names” used by people 

can sometimes be misleading or confusing

•In order to communicate effectively,

biologists need a CONSISTENT naming

protocol.

*Check out these slides of confusing

names…..

Photo Credits

Sea Lion: Bill Lim

Ant Lion: Amphioxus

Lion: law_keven

Sea Lion?

Ant lion?

Lion?

Which one of these is

NOT actually a bear?

Photo Credits

Panda: Chi King

Koala: Belgianchocolate

Black Bear: SparkyLeigh

Bi-Nominal – two terms, two names: Genus and Species

The first word in binomial nomenclature is called the genus which is a group that has one or more different species classified within it Closely related species that come from a common

ancestor

The second word is species or a group of similar organisms that are capable of producing fertile offspring with each other

Genus and Species Example:

Panthera leo – lion and Panthera tigris – tiger

Both species are classified in the same genus Panthera along with other big cats however they are each a different species because they can’t reproduce with each other

Genus and species names are always italicized.

First letter of the genus is always capitalized and the first letter of the species is always lower case.

Taxonomic Groupings

Taxonomists classify things into seven major groups or taxa

They are: Kingdom – largest group of living things (broadest) Phylum – largest group within a kingdom Class – largest group within a phylum Order – largest group within a class Family – largest group within an order Genus – largest group within a family Species – smallest group of living thing (most specific)

HINT for remembering the order of the levels of classification: King Phillip Came Over For Great Spaghetti King Phillip Cried Out For Great Soup

Grouping

•Kingdom

•Phylum

•Class

•Order

•Family

•Genus

•Species

Each group gets smaller

and more specific – just

think of the way you file

things on your computer

into folders and subfolders

To help you remember the list

KING PHILIP CAME OVER FOR GREAT SOUP

Kingdom, Phylum, Class, Order, Family, Genus, Species

Phylogenetic Taxonomy

Taxonomists use two different approaches to place an organism into the correct taxonomic category: Systematics: a phylogenetic tree or family tree is used to

show the evolutionary relationships between different groups of organisms This process stresses common ancestors and relies on the

amount of differences within a group to construct the tree

Tree is based on evidence from the fossil record, morphology, embryological development, biochemistry and genetic studies

Phylogenetic Taxonomy Continued . . .

Second approach used to place an organism into the correct taxonomic category is called cladistics Scientists construct a diagram based on specific

characteristics of an organism This is called a cladogram and its used to show

evolutionary relationships among the different groups based on traits called shared derived characteristics

Derived characteristics – a trait that evolved only within the specific group under study Example: Feathers in birds

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Primate

Family Hominidae

Genus Homo

Species sapiens

The scientific name is

always the genus +

species

Humans = Homo sapiens

Photo by

atomicshark

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Primate

Family Hominidae

Genus Homo

Species sapiens

The scientific name is

always the genus +

species

Humans = Homo sapiens

Photo by

atomicshark

Lion Tiger Pintail Duck

Kingdom Animalia Animalia Animalia

Phylum Chordata Chordata Chordata

Class Mammalia Mammalia Aves

Order Carnivora Carnivora Anseriformes

Family Felidae Felidae Anatidae

Genus Panthera Panthera Anas

Species Leo Tigris acouta

What are the scientific names of each of

these organisms?

What is a species?

Defined as organisms that can interbreed with one another, and produce fertile offspring

When two organisms of different species interbreed, the offspring is

called a HYBRID

Example:  ligers and mules

Is offspring fertile?

Phylogenetic Taxonomy

Taxonomists use two different approaches to place an organism into the correct taxonomic category: Systematics: a phylogenetic tree or family tree is used to

show the evolutionary relationships between different groups of organisms This process stresses common ancestors and relies on the

amount of differences within a group to construct the tree

Tree is based on evidence from the fossil record, morphology, embryological development, biochemistry and genetic studies

Phylogenetic Taxonomy Continued . . .

Second approach used to place an organism into the correct taxonomic category is called cladistics Scientists construct a diagram based on specific

characteristics of an organism This is called a cladogram and its used to show

evolutionary relationships among the different groups based on traits called shared derived characteristics

Derived characteristics – a trait that evolved only within the specific group under study Example: Feathers in birds

Phylogenetics

A cladogram has CLADES

Clade – a monophylletic group - a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor

Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny — all of the organisms on that pruned branch make up a clade.

The KingdomsThere are currently 6 kingdoms

Classification into a kingdom is

based on certain criteria

- Number of cells (unicellular or multicellular)

- How it obtains energy (heterotroph or autotroph)

- Type of cell (eukaryote or prokaryote)

Kingdom Animalia

•Multicellular

•Heterotrophic

•Most can move

•Examples: birds,

insects, worms,

mammals, reptiles,

humans, anemones

Photo by Eduardo Amorim

Photo by Tambako the

Jaguar

Kingdom Plantae

•Multicellular

•Autotrophic

•Eukaryotic

•Cannot move

(due to cell walls)

Kingdom Fungae

•Multicellular (most)

•Heterotrophic (mainly decomposers)

•Eukaryotic

Photos by

nutmeg66

Kingdom Protista

•Most are unicellular

•Can be heterotrophic or autotrophic

•Eukaryotes (all have nucleus)

•Examples: Ameba, paramecium, euglena,

algae

•Most live in water

Photo of Ameba by PROYECTO

AGUA **/** WATER PROJECT

Kingdom Eubacteria & Kingdom

Archaebacteria

•Unicellular

•Can be autotrophic or heterotrophic

•Prokaryotes (do not have a nucleus)Eubacteria = common bacteria

(E. coli, Salmonella)

Archaebacteria = “ancient

bacteria”, exist in extreme

environments

Three Domain System    

Recently, scientists have added a group above Kingdom.  Three groups, called DOMAINS, contain each of the six kingdoms.

Domain Eukarya - includes organisms composed of eukaryotic cells (plants, animals, fungi, protists – 4 kingdoms)

Domain Bacteria - includes all prokaryotic cells, Kingdom Eubacteria

Domain Archaea - includes only "ancient" bacteria, Archaebacteria (1 kingdom)

Dichotomous Key

Precise method that helps taxonomists classify and identify unknown organisms

Made up of a list of observable, alternative characteristics, that leads, step by step, to the correct identification of an organism

Dichotomous means dividing in two because there are always two choices at each step

At each step the organism will have only one of the traits described and that is the path you follow

Example:

A dichotomous key for a plant would have one step where you chose between spores and seeds as a method of reproduction

Then it might ask for seeds if its cones or flowers

There would also be steps asking about leave structure and the stem

Molecular Phylogenetics

and what it all means......

Chips and Candy vs. Living things

Using only physical characteristics or evolutionary relationships?

Molecular Phylogenetics• Constructing trees based on DNA sequence

comparisons• In certain stretches of DNA mutations occur at

reliable rates - the more mutations the DNA has accumulated, the longer since it split off from its ancestral sequence

• May use RNA (for RNA viruses) or protein sequences

Molecular Phylogenetics• Made possible by the availability of whole

genome sequencing; new technologies make this faster – more organisms genomes sequenced

• Many species genomes have been sequenced• Requires "Bioinformatics" – computer algorithms

that compare sequences from multiple organisms• Comparison – align sequences, determine

similarities, differences, gaps in alignment

Genomes sequenced

What's in a Clade

Clades are nested within one another — they form a nested hierarchy. A clade may include many thousands of species or just a few. A clade may include species that are no longer living (extinct)

How are we related to Chimps?

Adding time to a tree

How do we know the time?

• Life began 3.8 billion years ago, and insects diversified 290 million years ago, but the human and chimpanzee lineages diverged only five million years ago.

• How have scientists figured out the dates of long past evolutionary events?

• Here are some of the methods and evidence that scientists use to put dates on events:

Radiometric dating; stratigraphy; molecular clocks

Molecular Clocks

• Evolutionary changes may occur in a clock-like fashion

• Changes in DNA sequence can build up over the course of million years at a reliable rate

• Example: Alpha-globin gene experiences base changes at a rate of .56 changes per base pair per billion years - IF this rate is reliable, the gene could be used as a molecular clock.

Evolution and Trees beyond Taxonomy

• Phylogenetics can be used to build NEW scientific knowledge:– Identifying the source of new human diseases;– Setting Conservation priorities– Agriculture– Investigating alleged crimes– Use of 'model' organisms in biomedical science

Videohttp://archive.peabody.yale.edu/exhibits/treeoflife/film_study.html

Investigating Alleged crimesDespite overwhelming evidence attesting to their innocence, last month six medical workers were sentenced to death in a Libyan trial.

The crime with which the five Bulgarian nurses and one Palestinian doctor are charged is indeed horrifying. After an outbreak of HIV at the Al-Fateh hospital, the Libyan government accused the defendants of committing an act of bioterrorism by deliberately injecting 426 hospitalized children with HIV-tainted blood.

The HIV strain is particularly virulent and has already contributed to the deaths of more than 50 of the infected children.

Investigating Alleged crimes

The children had been infected and their viruses had begun diverging several years before the medics even arrived on the scene!

'Model' Organisms

• Common ancestor – common morphology, common processes; common development

• Can be used to study human development in the laboratory using 'model' organisms

• Model human processes on studies performed in other organisms

• Some examples:

Use of Model Organisms• Study of common cellular processes – cell division,

glycolysis studied in bakers yeast• Study of common developmental process –

human limb development in chicken• Screen for new drugs – which chemicals activate

or block common/similar cellular pathways altered in human disease (e.g. cancer)

• Toxicology – determine safety of compounds before human use

Think about it!

• The development and safety of all modern medicines, cosmetic products, etc. is based on the Theory of Evolution and Modern Phylogenetics

• The development of new Crops is based on the Theory of Evolution and Modern Phylogenetics

• Conservation Biology is based on the Theory of Evolution and Modern Phylogenetics

Evolution is an inseparable part of ALL Life Science – Medicine -Agriculture

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