Chapter 2: Tree of Life Flashcards
Futuyma, 4th Edition
evolutionary change of features within a single lineage (species)
anagenesis
branching of a lineage into two or more descendant lineages.
cladogenesis
when individuals in one species, or closely related species, acquire enough variations in their traits that it leads to two distinct new species
divergent evolution
when two unrelated species develop similar traits because they live in similar environments.
convergent evolution
the history of the events by which species or other taxa have successively arisen from common ancestors
phylogeny
a diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor.`
phylogenetic tree
occur when two lineages merge or form a hybrid descendant so that the tree has a netlike structure.
reticulation
the study of relationships among different groups of organisms and their evolutionary development.
phylogeny
analysis of DNA and protein structure is used to determine genetic relationships among different organisms.
molecular phylogeny
a schematic diagram used as a visual illustration of proposed evolutionary relationships among taxa.
phylogenetic tree or cladogram
a classification system that categorizes organisms based on shared traits, or synapomorphies, as determined by genetic, anatomical, and molecular analysis
cladistics
- These are points on a phylogenetic tree where branching occurs.
- represents the end of the ancestral taxon and the point where a new species splits from its predecessor.
nodes
- These are the lines on a phylogenetic tree that represent ancestral and/or descendant lineages.
- arising from nodes represent descendant species that split from a common ancestor.
branches
This group is a single branch on a phylogenetic tree that represents a group of organisms that are descended from a most recent common ancestor.
Monophyletic Group (Clade)
specific groupings or categories of living organisms.
taxon (pl. taxa)
Each segment in the tree is a __, or __, which may split at an internal branch point or __, representing the formation of two descendant lineages by __ from their common ancestor.
- lineage, branch
- node
- speciation
All the descendants of any one ancestor form a __ (also called a __)
- clade
- monophyletic group
__ do not indicate time or the amount of difference between groups, whereas __ often indicate time spans between branching points.
- Cladograms
- phylogenetic trees
illustrates hypothetical relationships between species based on traits
cladogram
do not describe the process of evolution, and they don’t reflect the amount of difference between groups
cladograms
the branch lengths represent __—these are technically called __
- time
- phylograms
the term that describes two lineages that come from the same branch point, or node.
sister taxa
represents the divergence of two species, and the two species’ most recent common ancestor.
branch point
shows the common ancestor of all species in the tree
rooted phylogenetic tree
a lineage that does not branch again after it branches from the root
basal taxon
- a branch of more than two species.
- appear when we don’t have enough information to determine branch placement.
polytomy
The lineage leading to the __ (MRCA) of all the species in the phylogeny is called the __ of the tree.
- most recent common ancestor
- root
Even though certain aspects of similarity may be used as data to determine the relationships among species, a phylogeny portrays relationship (__), not similarity.
common ancestry
A phylogenetic tree may be drawn in any of several equivalent ways. The junctions may be __ or __.
angular or rectangular
Our estimate of how taxa are related to one another is based on characteristics that are __ among the taxa
homologous
the group of taxa that is investigated for determining evolutionary relationships. They are closely related taxa or sister taxa.
ingroup
- a reference group that is outside the group of interest.
- distantly related to the group of taxa investigated.
outgroup
__ principle is basic to all science and tells us to choose the simplest scientific explanation that fits the evidence. In terms of tree-building, that means that all other things being equal, the best hypothesis is the one that requires the fewest evolutionary changes.
parsimony
A branching tree that portrays the history of DNA sequences of a gene (__) is often called a __ or a __
- haplotypes
- gene tree
- gene genealogy
genes that originate from an ancestral gene duplication
paralogous
genes that diverge from a common ancestral gene by phylogenetic splitting at the organismal level (i.e., homologous in the usual sense).
orthologous
Two segments of DNA can have shared ancestry because of either a speciation event (__) or a duplication event (__).
- orthologs
- paralogs
Sequence regions that are homologous are also called __
conserved
are genes in different species that originated by vertical descent from a single gene of the last common ancestor
orthologs or orthologous genes
As long as the increase is linear with time, the difference in sequence can serve as a __.
molecular clock
often belong to the same species, but this is not necessary
paralogs or paralogous genes
the same or similar function, but sometimes do not
paralogs or paralogous
Patterns of evolution
- Most features of organisms have been modified from pre-existing features
- Rates of character evolution differ
- Evolution is often gradual
- Homoplasy is common
- Phylogenies describe patterns of diversification
The most common criteria for hypothesizing homology of anatomical characters are:
- correspondence of position relative to other parts of the body
- correspondence of structure (the parts of which a complex feature is composed).
not a useful criterion for homology
Correspondence of shape or of function
retained with little or no change over long periods among the many descendants of an ancestor.
conservative characters
Evolution of different characters at different rates within a lineage is called __
mosaic evolution
Darwin argued that evolution proceeds by small successive changes (__) rather than by large “leaps” (__).
- gradualism
- saltations
the independent evolution of a character or character state in different
homoplasy
a term that has been used to describe cases in which independent evolution of a character state is thought to have similar genetic and developmental bases, especially in closely related species
parallel evolution
constitute a return from a derived character state to a more ancestral state.
evolutionary reversals
It was long assumed that complex characters, once lost, are unlikely to be regained, a principle known as __.
Dollo’s law
often adaptations by different lineages to similar environmental conditions.
convergent features
If the time of each branching point in a phylogeny has been estimated by a calibrated __, the phylogeny may suggest whether new lineages arose steadily over a long period, or episodically, in one or more bursts of diversification.
molecular clock
Divergent evolution of numerous related lineages within a relatively short time is called __
evolutionary radiation/ adaptive radiation
probably the most common pattern of long-term evolution.
directional evolutionary trends
Evidence for evolution
- The hierarchical organization of life.
- Homology
- Embryological similarities
- Vestigial characters
- Convergence
- Suboptimal design
- Geographic distributions
- Intermediate forms
Darwin listed a dozen vestigial features in the human body
- the appendix
- the coccyx (four fused tail vertebrae)
- posterior molars, or wisdom teeth, that fail to erupt, or do so aberrantly, in many people.
sequences that retain some similarity to the functional genes from which they have been derived.
pseudogenes
the origination of a lineage through the partial merging of two ancestor lineages, leading to relationships better described by a phylogenetic network than a bifurcating tree.
Reticulate evolution
