ch 20: Natural Selection Flashcards
Linnaeus
- a botanist who collected and classified objects.
- produced today’s more specific system of classification for plants and animals (taxa).
classification
a way of grouping/organizing organisms.
Taxonomy
major categories into which organisms are grouped
taxon
unit at any level of hierarchy
Binomial nomenclature
Linnaeus’s system for naming species
Each species has a Latinized name composed of two words (Bi-nomial) written in italics or underlined.
genus
First word is written with a capital initial letter
species
2nd word is a lowercase
all taxonomies
Kingdom Phylum Class Order Family Genus Species
Katie poured coffee on frank’s green shirt
Phylogeny
The evolutionary history of a species or a group of related species
- Use fossils, morphological and molecular evidence
- Constructed by using evidence from systematics - a discipline that focuses on classifying organisms and their evolutionary relationships.
phylogenetic trees
Systematists depict evolutionary relationships in branching, A branching diagram, that depicts hypotheses about evolutionary relationships. Depicts common descent of species or higher taxa
A phylogenetic tree represents a hypothesis about evolutionary relationships
Homology
character similarities that result from a common ancestry (evolution)
differ from Lin and phy
Linnaean classification(resemblances) and phylogeny can differ from each other
PhyloCode
which recognizes only groups that include a common ancestor and all its descendants
branch point
represents the divergence of two species
sister taxa
are groups that share an immediate common ancestor
rooted tree
includes a branch to represent the last common ancestor of all taxa in the tree
basal taxon
diverges early in the history of a group and originates near the common ancestor of the group
polytomy
a branch from which more than two groups emerge
What We Can and Cannot Learn from Phylogenetic Trees(3)
- Phylogenetic trees show patterns of descent, not phenotypic similarity
- Phylogenetic trees do not indicate when species evolved or how much change occurred in a lineage
- It should not be assumed that a taxon evolved from the taxon next to it
Cladistics
groups organisms by common descent
Cladogram
depicts patterns of shared characteristics among taxa and forms the basis of a phylogenetic tree
clade
is a group of species that includes an ancestral species and all its descendants
Clades can be nested in larger clades, but not all groupings of organisms qualify as clades
monophyletic clade
signifies it consists of the ancestor species and all its descendant’s
paraphyletic clade
contains some but all descendants
polyphyletic
grouping consists of various taxa with different ancestors
shared ancestral character
is a character that originated in an ancestor of the taxon
shared derived character
is an evolutionary novelty unique to a particular clade
A character can be both ancestral and derived, depending on the context
Inferring Phylogenies Using Derived Characters
When inferring evolutionary relationships, it is useful to know in which clade a shared derived character first appeared
outgroup
is a species or group of species that is closely related to the ingroup,
An outgroup is a group that has diverged before the ingroup
ingroup
the various species being studied
extra in and out-group
Systematists compare each ingroup species with the outgroup to differentiate between shared derived and shared ancestral characteristics
Characters shared by the outgroup and ingroup are ancestral characters that predate the divergence of both groups from a common ancestor
Maximum Parsimony
assumes that the most likely tree is the one that requires the fewest evolutionary events (appearances of shared derived characters)
- Systematists can never be sure of finding the best tree in a large data set
- They narrow possibilities by applying the principle of maximum parsimony
- In phylogenies based on DNA, the most parsimonious tree has the fewest base changes
- Computer programs are used to search for trees that are parsimonious
Evolutionary history Documented in an organism’s genome(4)
- The rate of evolution of DNA sequence varies from one part of the genome to another.
- Comparing these different sequences helps us to investigate relationships between groups of organisms that diverged a long time ago.
- DNA that codes from Ribosomal RNA Changes relatively slowly – useful for investigating relationships between taxa that diverged hundreds of million years ago.
- DNA that codes for mitochondrial DNA evolves rapidly and can be used to explore recent evolutionary events
mol clock
Methods used to measure the absolute time of evolutionary change based on the observation that some genes and other regions of the genome appear to evolve at contestant rates.
molecular clock
uses the constant rate of evolution observed in some genes to estimate the absolute time of evolutionary change
The number of nucleotide substitutions in related genes is assumed to be _____ to the time since they last shared a common ancestor
proportional
- Molecular clocks are calibrated by plotting the number of genetic changes against the dates of branch points known from the fossil record
- Average rates of genetic change can be used to estimate dates of events not discernable from the fossil record
Taxonomy
Used to be two kingdoms Then 5 Now 3 domains
Used to be two
Plant, Animals
Then 5
Monera, Protista, Plantae, Fungi and Animalia
Now 3 domains
Bacteria, Archaea, Eukarya
- Bacteria- Normal bacteria**
- Archaea- Hot spring bacteria
-
Eukarya- Everything else’
- Both of these are prokaryotes
