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?
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
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
(1)biochemical and genetic information (DNA,
proteins),(2) embryological development, (3)fossil
record – (1)+(2)+(3)=evolutionary relationships,
(4) 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
Plants
Animals
Land
Trees
Water
Shrubs
Herbs
Air
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?
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
To help you remember the list
KING PHILIP CAME OVER FOR GREAT SOUP
Kingdom, Phylum, Class, Order, Family, Genus, Species
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
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
Is offspring
fertile?
Example: ligers and mules
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
Tree of Life
Shared characteristics or evolutionary relationships?
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.
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?
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
What characteristics did you use to classify the chips
and candy?
Did all the teams use the same
characteristics?
Could you use different ones?
Molecular Phylogenetics
and what it all means......
Chips and Candy vs. Living things
Using only physical characteristics or evolutionary relationships?
How would you group these?
How would you group these?
• They are both Mammals – have a common
ancestor
BUT
• Have markedly different physical
characteristics
Fossil Records and DNA comparison
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
(1)similarities, (2)differences, (3)gaps in
alignment
Allignment
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
Video
http://archive.peabody.yale.edu/exhibits/treeoflife/film_study.html
Investigating Alleged crimes
Despite 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
The Kingdoms
There 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
Photo by Tambako the
Jaguar
•Multicellular
•Heterotrophic
•Most can move
•Examples: birds,
insects, worms,
mammals, reptiles,
humans, anemones
Photo by Eduardo Amorim
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)