Biology Cycle 9 - Phylogenetic Trees Flashcards
What is taxonomy?
the science of that identifies, names, and classifies new species and their natural relationships
What is binomial nomenclature? Who invented it?
naming species with a two-part scientific name
–> first: genus
–> second: species
Carolus Linnaeus
What is genus?
Taxonomic category ranking below a family and above a species
What is a specific epithet?
the species name in a binomial
Which species concept did Linnaeus use to name new species?
morphological species concept – shared anatomical characteristics
What is a classification?
an arrangement of organisms into hierarchical groups that reflect their relatedness
How is the taxonomic hierarchy arranged?
domain, kingdom, phylum, class, order, family, genus, species, and subspecies
What is a taxon?
organisms included within any category of the taxonomic hierarchy
How do taxon show genetic relatedness?
species in the same taxon near the bottom of the hierarchy have more similar characteristics that a taxon near the top
does the taxonomic hierarchy relate to ancestry?
organisms in the same genus share a fairly recent common ancestor while organisms in the same class have a more distant ancestor
What is phylogeny?
the evolutionary history of a group of organisms
What are phylogenetic trees?
a branching diagram depicting the evolutionary relationships of groups of organisms
What is a ROOT on a phylogenetic tree?
the common ancestor of all species included in the tree
What is a NODE on a phylogenetic tree?
represent a (hypothetical) common ancestor that may be unknown
What is a anagenesis?
Gradual evolutionary change that transforms one species into another as its characteristics shift over time
How is anagenesis shown in an phylogenetic tree?
Straight line
WHAT IS CLADOGENESIS?
Ancestral species undergoes speciation producing two descendants that are both distinct form their common ancestor
How is cladogenesis represented on a phylogenetic tree?
Branching - CLADE
Does cladogenesis or anagenesis create biodiversity?
Cladogenesis
What is a polyphyletic taxon?
Group of organisms that belong to different evolutionary lineages and do not share recent common ancestry
Ex. Bats and birds
What is a paraphyletic taxon
A group of organisms that includes an ancestral species and some but not all of its descendants
Ex. Dinosauria includes birds and non flying relatives
What is a character state?
One or more forms of a character used in a phylogenetic analysis
What is the ANCESTRAL CHARACTER STATE?
A trait that was present in the most recent common ancestor
Aka plesiomorphy
What is a DERIVED CHARACTER STATE?
evolved after the most recent common ancestor of the group
Aka apomorphy
What are shared and derived traits?
synapomorphy – trait shared by at least two organisms in the group
– this is important for determining evolutionary relationships
What are Why are synapomorphies important for phylogenetic trees?
they are markers for monophyletic lineages (common ancestry)
What is outgroup comparison?
identify ancestral and derived characters by comparing the group under study to a more distantly related species that are not otherwise included in the analysis
How does outgroup comparison determine if a character is ancestral or derived?
if the outgroup has the trait then it is ancestral
What is the principle of parsimony?
The simplest tree, with the least evolutionary changes, is the most likely
What are the two statistical approaches of phylogenetic tree determination?
Maximum likelihood - compares the alternative tree with specific models of evolutionary change
Genetic distance - calculates the overall proportion of nucleotide bases that differ among species
Are animals at the top of the tree of life?
no – all species have evolved and gained complexity for the same amount of time
What are the species at the tips or leaves of a tree?
species that exist in the present = extant
How can you determine if a trait is homologous or due to convergence?
- structural or developmental similarity is more informative than superficial similarity
- use traits that are known to be homologous
- use molecular data
