1/32
Chapter 14
Name | Mastery | Learn | Test | Matching | Spaced |
---|
No study sessions yet.
Phylogeny
the evolutionary history of a group
Phylogenetic tree
A diagrammatic reconstruction of that history showing relationships among species.
Phylogenies
representations of evolutionary relationships among groups of organisms.
Taxonomy
hierarchical way of categorizing species
Binomial nomenclature
Gives every species a unique name consisting of two parts: the genus and the species. Ex. Homo sapiens
Carl Linnaeus
The Swedish botanist who created the system of binomial nomenclature, classifying organisms into hierarchical categories.
A phylogenetic tree may portray the evolutionary history of:
All life forms
Major groupings of taxa
Populations
Individuals
Small groups of closely related species
Genes and proteins
Root
represents the ancestral lineage
Nodes (branch points)
represent speciation events
Sister taxa
Two taxa that are each other’s closest relatives (two branches off a single node)
Sister clades
any two clades that are each other’s closest relatives
Monophyletic group
A group of organisms that includes a common ancestor and all of its descendants, forming a complete branch on the tree of life.
Paraphyletic group
A group that includes a common ancestor but not all of its descendants, resulting in an incomplete branch on the tree of life.
Polyphyletic group
A group that does not include its common ancestor and contains members from different lineages.
Parsimony
fewest character changes is our best hypothesis
Synapomorphies
shared, derived characters used to establish evolutionary relationships.
Ancestral characters
Found in common ancestor of two or more species/groups.
Outgroup(s)
A reference group, should be closely related but without shared derived characters that unite the ingroup.
Convergent evolution
Superficially similar traits may evolve independently in different lineages.
Evolutionary reversal
A character reverts from a derived state back to an ancestral state
Homoplasy
the similarity in traits or structures between different species or lineages that evolved independently, not from a shared ancestor.
Morphological strengths
Allow inclusion of extinct species, determine ancestral states and date divergences
Morphological weaknesses
Some taxa show few differences, difficult to compare distantly related species, variation is caused by the environment
Developmental strengths
Clarifies deep relationships where significant divergence in form occurs in adults; we learn about mechanisms of diversification in form
Developmental weaknesses
are “reused” for different functions
Molecules strengths
Making for LOTS of characters, rates of change vary among loci in genome
Molecules weaknesses
Only 4 traits states per character and homoplasies are common.
Behavior strengths
Often as heritable as morphology (E,x. Fixed action patterns)
Behavior weaknesses
Trait expression is often plastic, precise measurements of comparable behavior may be difficult
Gonochoristic
Either male or female from birth to death.
Protogynous hermaphrodites
Female first, larger individuals change to male
Simultaneous hermaphrodites
Produce male and female gametes at the same time, mating partners may take turns fertilizing each other’s eggs.
Molecular clock
The average rate at which a given gene or protein accumulates changes to gauge the time of divergence.