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Organisms can be classified based on physical similarities.
How would you classify the organisms in your envelope?
• Archaeabacteria - 1
• Bacteria – 2
• Protists – 2
• Fungi – 3
• Plants – 2
• Animals – 6
How to use a Dichotomous Key http://www.youtube.com/watch?v=j0e9GkL3Ow4
http://www.biologycorner.com/worksheets/dichotomous_key_smilies.html
Model of a Dichotomous Key
Di = TwoFollow the steps until you reach the
common name or scientific name.
1. 2. 3. 4. 5. 6. 7. 8. 9.
Taxonomy is the science of naming and classifying organisms. It was started by Carl Linnaeus. A taxon is a group of organisms in a classification system.
White oakQuercus alba
Binomial nomenclature is a two-part scientific naming system using Latin.
Tyto (genus)Alba (species)
Scientific Name
Scientific names help scientists to communicate.
– Some species have very similar common names.– Some species have many common names.
Linnaeus’ classification system has seven levels.
• Each level is included in the level above it.
• Levels get increasingly specific from kingdom to species.
Levels of Classification 2Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species•Only members of the same species can produce fertile offspring.•Scientific Name = Genus and Species
The Linnaean classification system is limited.
Linnaeus taxonomy doesn’t account for DNA evidence.
– The technology didn’t exist during Linneaus’ time.
– Linnaean system based only on physical similarities.
Which is more closely related to a manatee, a seal or an elephant?
Seal or Elephant
• Physical similarities are not always the result of close relationships.
• Genetic similarities more accurately show evolutionary relationships.
The elephant’s DNA is more closely related to the manatee.
Small evolutionary scars: Manatee flipper toe nails
A common method is to make evolutionary trees.
– classification based on common ancestry– species placed in order that they descended from
common ancestor
An evolutionary tree made by showing common ancestors.
– A clade is a group of species that shares a common ancestor.
– Each species in a clade shares some traits with the ancestor.
– Each species in a clade has traits that have changed.
• Molecular data may confirm classification based on physical similarities.
• Molecular data may lead scientists to propose a new classification.
Molecular evidence reveals species’ relatedness.
• DNA is usually given the last word by scientists.
Molecular clocks use mutations to estimate evolutionary time.
• Mutations are thought to add up at a constant rate in related species.– As more time passes, there will be more mutations.
DNA sequence from ahypothetical ancestor
The DNA sequences from twodescendant species show mutationsthat have accumulated (black).
The mutation rate of thissequence equals one mutationper ten million years.
Mutations add up at a fairlyconstant rate in the DNA of species that evolved from a common ancestor.
Ten million years later—one mutation in each lineage
Another ten million years later—one more mutation in each lineage
The current tree of life has three domains.
Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,Animalia and Plantae Animalia
Plantae
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,Animalia and Plantae
– 1866: all single-celled organisms moved to kingdom Protista
Animalia
Protista
Plantae
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,Animalia and Plantae
– 1938: prokaryotes moved to kingdom Monera
– 1866: all single-celled organisms moved to kingdom Protista
AnimaliaProtista
Plantae
Monera
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
– Until 1866: only two kingdoms,Animalia and Plantae
– 1938: prokaryotes moved to kingdom Monera
– 1866: all single-celled organisms moved to kingdom Protista
Monera– 1959: fungi moved to
own kingdom Fungi
Protista
Plantae
Animalia
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.– Until 1866: only two kingdoms,
Animalia and Plantae
– 1938: prokaryotes moved to kingdom Monera
– 1866: all single-celled organisms moved to kingdom Protista
– 1959: fungi moved to own kingdom
– 1977: kingdom Monerasplit into kingdoms Bacteria and Archaea
AnimaliaProtista
Fungi
Plantae
Archea
Bacteria
The three domains in the tree of life are Bacteria, Archaea, and Eukarya.
Three Big Questions
1. Does it’s cell have a nucleus? Do carry – Eukaryote
There’s No – Prokaryote
2. How many cells?One – UnicellularMany – Multi-cellular
3. How does it obtain sugar? Take it in – Heterotroph Make it – Autotroph
How do we know which kingdom organisms belong to? We ask three simple questions:
Domain Bacteria includes prokaryotes
– one of largest groups on Earth
– classified by shape, need for oxygen, and diseases caused
– known for living in extreme environments
Domain Archaea includes prokaryotes
– cell walls chemically different from bacteria
– differences discovered by studying RNA
Bacteria and archaea can be difficult to classify.
– transfer genes among themselves outside of reproduction blurs the linebetween “species”
– more researchneeded tounderstand prokaryotes
bridge to transfer DNA
Domain Eukarya includes all eukaryotes.
Kingdom Protista
- “pond scum” of the earth - lots of variations
– kingdom Protista– kingdom Plantae
Multicellular
producers
Domain Eukarya includes all eukaryotes.
– kingdom Protista
– kingdom Plantae
– kingdom Fungi
Decompose
through
absorption
Domain Eukarya includes all eukaryotes.
– kingdom Protista– kingdom Plantae– kingdom Fungi– kingdom Animalia
Multicellular consumers
Domain Eukarya includes all eukaryotes.
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