Transcript 1866: all single-celled organisms moved to kingdom Protista

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=j0e9
GkL3Ow4
Model of a Dichotomous Key
http://www.biologycorner.com/workshe
ets/dichotomous_key_smilies.html
Di = Two
Follow the steps until you reach the
common name or scientific name.
1.
2.
3.
4.
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6.
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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 oak
Quercus alba
Scientific Name
Binomial nomenclature is a two-part
scientific naming system using Latin.
Tyto (genus)
Alba (species)
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
2
Domain
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 evidence reveals species’
relatedness.
• Molecular data may confirm classification based on
physical similarities.
• Molecular data may lead scientists to propose a new
classification.
• 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.
Mutations add up at a fairly
constant rate in the DNA of
species that evolved from a
common ancestor.
DNA sequence from a
hypothetical ancestor
Ten million years later—
one mutation in each lineage
Another ten million years later—
one more mutation in each lineage
The DNA sequences from two
descendant species show mutations
that have accumulated (black).
The mutation rate of this
sequence equals one mutation
per ten million years.
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, Plantae
Animalia and 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
– 1866: all singlecelled organisms
moved to kingdom
Protista
Plantae
Animalia
Protista
The tree of life shows our most current
understanding.
New discoveries can lead to changes in
classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all singleProtista
celled organisms
moved to kingdom
Protista
– 1938: prokaryotes
moved to kingdom
Monera
Monera
The tree of life shows our most current
understanding.
New discoveries can lead to changes in
classification.
– Until 1866: only two kingdoms,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
organisms moved to
kingdom Protista
– 1938: prokaryotes moved to
kingdom Monera
– 1959: fungi moved to
Fungi
own kingdom
Protista
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
Plantae
– 1866: all single-celled
Animalia
organisms moved to
Protista
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
– 1977: kingdom Monera
split into kingdoms
Bacteria and Archaea
Archea
Fungi
Bacteria
The three domains in the tree of life are
Bacteria, Archaea, and Eukarya.
Three Big Questions
How do we know which kingdom organisms
belong to? We ask three simple questions:
1. Does it’s cell have a nucleus?
Do carry – Eukaryote
There’s No – Prokaryote
2. How many cells?
One – Unicellular
Many – Multi-cellular
3. How does it obtain sugar?
Take it in – Heterotroph
Make it – Autotroph
Domain Bacteria includes
prokaryotes
– one of largest
groups on
Earth
– classified by
shape, need
for oxygen,
and diseases
caused
Domain Archaea includes
prokaryotes
– cell walls
chemically
different from
bacteria
– differences
discovered by
studying RNA
– known for living
in extreme
environments
Bacteria and archaea can be
difficult to classify.
– transfer genes
among
themselves
outside of
reproduction blurs
the line
between “species”
– more research
needed to
understand
prokaryotes
bridge to transfer DNA
Domain Eukarya includes all
eukaryotes.
Kingdom Protista
- “pond scum” of the earth - lots of variations
Domain
Eukarya
includes all
–eukaryotes.
kingdom Protista
– kingdom Plantae
Multicellular
producers
Domain
Eukarya
includes all
– kingdom
Protista
eukaryotes.
– kingdom Plantae
– kingdom Fungi
Decompose
through
absorption
Domain
Eukarya
includes all
eukaryotes.
– kingdom Protista
– kingdom Plantae
– kingdom Fungi
– kingdom Animalia
Multicellular
consumers