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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