Lecture 6 Flashcards
What is phylogeny a study of?
- study of the evolutionary history of related groups of organisms
what is taxonomy
naming and classifying
What is a phylogenetic tree
- an illustration of a hypothesis about the relationships among “taxa” (taxonomic categories: species, genera, families, etc.) based on currently available information (open to change)
How are organisms grouped into phylogenetic taxa?
- based on unique shared traits that result from common ancestry (homologies)
what are synapomorphies?
- a trait found in 2 or more taxa that are present in their most recent common ancestor but is missing in more distant ancestors
- unique to this group
- What does classic taxonomy lack?
- useful for creating and organizing groups, but provides limited information about evolutionary relationships within and between groups
What is modern tree-building based on?
- modern tree-building is based on CLADISTICS, a series of principles that define a CLADE, a group of organisms that meet the requirements of sharing evolutionary relationships: a common ancestor and all known descendants
- An evolutionary tree is technically called a CLADOGRAm
What are sister groups on the tree?
- share a recent common ancestor at the node where their branches meet
what is a branch
- a line representing a population through time`
What is the root
the most ancestral branch in the tree
What is the tip (terminal node)?
endpoint of a branch
- represents a living or extinct group of genes, species, families, phyla, or other taxa
What is an endpoint?
a taxon that diverged prior to the taxa that are the focus of the study
- helps to root the tree
What is the node (fork)?
a point within the tree where a branch splits into 2 or more branches
- the node represents that most recent common ancestor of the descendant groups
what is polytomy?
- a node that depicts an ancestral branch dividing into 3 or more (rather than 2) descendant branches
- usually indicates that insufficient data were available to resolve which taxa are more closley related
What is a character or trait
- any genetic, morphological, physiological, development, or behavioural characterisitc to be studied
what is an ancestral trait
a character that existed in an ancestor
what is a derived trait
one that is a modified form of the ancestral triat, found in descendant
What is the cladistic approach based on?
- based on the principle that relationships among species can be reconstructed by identifying shared derived traits, called synapomorphies
What is a monophyletic group?
- an evolutionary unit that includes an ancestral population and all of its descendants, but no others
What is homology?
- similarity in organisms due to common ancestor
- traits inherited from a common ancestor, even though they may appear different (after descent with modification)
What is homoplasy?
- similarity in organisms due to reasons other than common ancestry
- traits (analogous in function) may appear similar but are not inherited from a common ancestor
- this is the result of convergent or parallel evolution
- not helpful for tree-building
What is a polyphyletic group?
- an unnatural group that does not include the most recent common ancestor
What is a paraphyletic group?
- a group that includes an ancestral population and some of its descendants, but not all
- loss of trait
What is a convergent evolution
- the independent evolution of similar traits in distantly related organisms due to adaptation to similar environments and lifestyles
What are the 3 tools for creating a phylogeny and studying history?
- fossils are evidence for history of life on earth, extinction, and evolution
- comparative anatomy and embryology provide evidence of ancestor/descendant relationships
- DNA sequences are currently the most widely used evidence in creating phylogenies
review flower homology in angiosperms
although flowers are very diverse in shape, color, and other traits, they:
- have structural similarity; petals and sepals are modified leaves
- Share a genetic similarity for flower development and overall genomics
- evidence. unites them as true monophyletic clade, derived ultimately from a common ancestor