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Ch 26 Notes
Terms in this set (33)
classifies organisms and determines their evolutionary relationships. Systematists use fossil, molecular, and genetic data to infer evolutionary relationships.
the ordered division and naming of organisms.
taxonomic groups from broad to narrow
taxonomic unit at any level of hierarchy
depict evolutionary relationships.
represents a hypothesis about evolutionary relationships
represents the divergence of two species
groups that share an immediate common ancestor
a branch to represent the last common ancestor of all taxa in the tree
What We Can and Cannot Learn from Phylogenetic Trees
-do show patterns of descent
-do not indicate when species evolved or how much genetic change occurred in a lineage
-shouldn't be assumed that a taxon evolved from the taxon next to it.
important information about similar characteristics in closely related species.
similarity due to shared ancestry
similarity due to convergent evolution
when similar environmental pressures and natural selection produce similar /analogous adaptations in organisms from different evolutionary lineages.
Analogous structures or molecular sequences that evolved independently
This is an ancestral trait that is found in the common ancestor and two or more unrelated taxa (descendant species).
Shared by two or more species
a shared derived character
Homology can be distinguished from analogy by
comparing fossil evidence and the degree of complexity. The more complex two similar structures are, the more likely it is that they are homologous.
uses DNA and other molecular data to determine evolutionary relationships.
is a group of species that includes an ancestral species and all its descendants
valid clade .
consists of the ancestor species and all its descendants.
consists of an ancestral species and some of the descendants
consists of various species that lack a common ancestor.
shared ancestral character
a character that originated in an ancestor of the taxon
shared derived character
an evolutionary novelty unique to a particular clade.
A character can be both
ancestral and derived, depending on the context.
assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely
given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events.
The best hypotheses for phylogenetic trees
fit the most data: morphological, molecular, and fossil
predicts features of an ancestor from features of its descendents
increases the number of genes in the genome, providing more opportunities for evolutionary changes
found in a single copy in the genome and are homologous between species. They can diverge only after speciation occurs
result from gene duplication, so are found in more than one copy in the genome. They can diverge within the clade that carries them and often evolve new functions.
Horizontal gene transfer
the movement of genes from one genome to another.
Horizontal gene transfer complicates efforts to build a tree of life.
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