1. CHAPTER 17
THE TREE of LIFE

2. KEY CONCEPT Organisms can be classified based on physical similarities.

3. Linnaeus developed the scientific naming system still used today.
Taxonomy is the science of naming and classifying organisms.
Standard way to refer to species and organize the diversity of living things
Classified based on their physical and structural similarities
Taxon: a group of organisms in a classification system
Defines a species as a group of organisms that can breed and produce fertile offspring

4. White oak would be a common name Quercus alba is the scientific name
White oak: Quercus alba

5. Binomial nomenclature is a two-part scientific naming system.
uses Latin words (or words following Latin rules)
scientific names always written in italics or underlined
two parts are the genus name and species descriptor

6. A genus includes one or more physically similar species.
Species in the same genus are thought to be closely related.
Genus name is always capitalized.
A species descriptor is the second part of a scientific name.
always lowercase
always follows genus name; never written alone
Tyto alba

7. Scientific names help scientists to communicate.
Some species have very similar common names.
Some species have many common names.
Scientific names are universal
Lessens confusion

8. Linnaeus’ classification system has seven levels.
Each level is included in the level above it.
Levels get increasingly specific from kingdom to species.

9. Seven Levels of Classification
Kingdom: group of similar phyla (most inclusive)
Phylum: group of similar classes
Class: group of similar orders
Order: group of similar families
Family: group of Genera with similar properties
Genera: group of species with similar properties
Species: group of organisms that can breed and produce fertile offspring (least inclusive)
Note: Phylum called division for bacteria, fungi, and plants

10. Biological Species Concept
Species, John Ray
: A group of individuals that can breed and produce fertile offspring
: puts all dogs in one species, all pigeons in one species, etc.
: horse and donkey cannot produce a fertile offspring therefore not same species
Biological Species Concept
: A group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
: Hybrids- offspring of individuals of different species

11. The Linnaean classification system has limitations.
Linnaeus taxonomy doesn’t account for molecular evidence.
The technology didn’t exist during Linneaus’ time.
Linnaean system based only on physical similarities.
Physical similarities are not always the result of close relationships
Does not account for traits that are similar in unrelated organisms
Genetic similarities more accurately show evolutionary relationships

12. Giant Panda and raccoon have similar ears and snouts (placed in the same family by Linnaean system)
Giant Panda is more closely related to the bear family
Red Panda is more closely related to the raccoon than the Giant Panda
Ursidae
Procyonidae

13. KEY CONCEPT Modern classification is based on evolutionary relationships.

14. Cladistics is classification based on common ancestry.
Phylogeny is the evolutionary history for a group of species.
evidence from living species, fossil record, and molecular data
shown with branching tree diagrams

15. Cladistics is a common method to make evolutionary trees.
classification based on common ancestry
species placed in order that they descended from common ancestor

16. A cladogram is an evolutionary tree made using cladistics.
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.

17. basis of arranging species in cladogram
Derived characters are traits shared in different degrees by clade members.
FOUR LIMBS WITH DIGITS
Tetrapoda clade 1
Amniota clade 2
Reptilia clade 3
Diapsida clade 4
Archosauria clade 5
EMBRYO PROTECTED BY AMNIOTIC FLUID
OPENING IN THE SIDE OF THE SKULL
SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW
FEATHERS & TOOTHLESS BEAKS.
SKULL OPENINGS BEHIND THE EYE
DERIVED CHARACTER
basis of arranging species in cladogram
more closely related species share more derived characters
represented on cladogram as hash marks
Outgroup: shares no derived characters with the other groups being studied

18. Nodes represent the most recent common ancestor of a clade.
FOUR LIMBS WITH DIGITS
CLADE
Tetrapoda clade 1
Amniota clade 2
Reptilia clade 3
Diapsida clade 4
Archosauria clade 5
Clades can be identified by snipping a branch under a node.
FEATHERS AND TOOTHLESS BEAKS.
SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW
OPENING IN THE SIDE OF THE SKULL
SKULL OPENINGS BEHIND THE EYE
EMBRYO PROTECTED BY AMNIOTIC FLUID
DERIVED CHARACTER
NODE

19. Molecular evidence reveals species’ relatedness.
Evolutionary trees are a work in progress
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.

20. KEY CONCEPT Molecular clocks provide clues to evolutionary history.

21. Molecular clocks use mutations to estimate evolutionary time.
In 1960s Linus Pauling and Emile Zuckerkandl proposed a new way to measure evolutionary time
Compared amino acid sequences of hemoglobin from a wide range of species
Showed that the more distantly related two species are, the more amino acid differences there are in their hemoglobin
Using this data, they calculated a mutation rate

22. Mutations add up at a constant rate in related species.
Molecular clock: models that use mutation rates to measure evolutionary time
Mutations add up at a constant rate in related species.
This rate is the ticking of the molecular clock.
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.
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.
DNA sequence from a
hypothetical ancestor

23. Scientists estimate mutation rates by linking molecular data and real time.
an event known to separate species (usually a geologic event known to have separated the two species)
the first appearance of a species in fossil record

24. Mitochondrial DNA and ribosomal RNA provide two types of molecular clocks.
Different molecules have different mutation rates.
higher rate, better for studying closely related species
lower rate, better for studying distantly related species

25. Mitochondrial DNA is used to study closely related species.
mutation rate ten times faster than nuclear DNA
passed down unshuffled from mother to offspring
grandparents
parents
child
Nuclear DNA is inherited from both
parents, making it more difficult to
trace back through generations.
Mitochondrial DNA is
passed down only from
the mother of each generation,so it is not subject to recombination.
mitochondrial
DNA
nuclear DNA

26. Ribosomal RNA is used to study distantly related species.
Studying species that are in different kingdoms or phyla
many conservative regions
lower mutation rate than most DNA
Carl Woese first used rRNA to establish that archaea diverged from the common ancestor they share with bacteria almost 4 billion years ago

27. KEY CONCEPT The current tree of life has three domains.

28. Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
1753: only two kingdoms, Animalia and Plantae
Animalia
Plantae

29. Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
1753: only two kingdoms, Animalia and Plantae
Plantae
Animalia
1866: all single-celled organisms moved to kingdom Protista
Protista

30. Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
1753: only two kingdoms, Animalia and Plantae
Animalia
Protista
Plantae
1866: all single-celled organisms moved to kingdom Protista
1938: prokaryotes moved to kingdom Monera
Monera

31. Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
1753: only two kingdoms, Animalia and Plantae
Protista
Plantae
Animalia
1866: all single-celled organisms moved to kingdom Protista
1938: prokaryotes moved to kingdom Monera
Fungi
1959: fungi moved to own kingdom (based on how they fed)
Monera

32. Classification is always a work in progress.
The tree of life shows our most current understanding.
New discoveries can lead to changes in classification.
1753: only two kingdoms, Animalia and Plantae
Animalia
Protista
Fungi
Plantae
1866: all single-celled organisms moved to kingdom Protista
1938: prokaryotes moved to kingdom Monera
Archea
Bacteria
1959: fungi moved to own kingdom
1977: kingdom Monera split into kingdoms Bacteria and Archaea (rRNA research)

33. The three domains in the tree of life are Bacteria, Archaea, and Eukarya.
Domains are above the kingdom level.
proposed by Carl Woese based on rRNA studies of prokaryotes
domain model more clearly shows prokaryotic diversity

34. Domain Bacteria includes prokaryotes in the kingdom Bacteria.
one of largest groups on Earth
classified by shape, need for oxygen, and diseases caused

35. Domain Archaea includes prokaryotes in the kingdom Archaea.
cell walls chemically different from bacteria
differences discovered by studying RNA
known for living in extreme environments

36. Domain Eukarya includes all eukaryotes.
kingdom Protista

37. Domain Eukarya includes all eukaryotes.
kingdom Protista
kingdom Plantae

38. Domain Eukarya includes all eukaryotes.
kingdom Protista
kingdom Plantae
kingdom Fungi

39. Domain Eukarya includes all eukaryotes.
kingdom Protista
kingdom Plantae
kingdom Fungi
kingdom Animalia

40. 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