Theme 5A and 5B Flashcards
(21 cards)
What is a phylogeny?
History of descent with branching
What is a phylogenetic tree?
A branching diagram that shows the relationships between species (often according to a common ancestor). Provides a hypothesis of evolutionary relationship, and builds a tree based on data
What are nodes on a phylogenetic tree?
The branching point where the population diverges. Nodes can also be rotated without changing evolutionary relationships (important)
What is the root in a phylogenetic tree?
The common ancestor
What are sister groups?
Two species that share a common ancestor not shared by any other group
What is a phylogram?
A phylogenetic tree where the branch lengths represent the amount of change/time. (branching + time)
What is a cladogram?
A phylogenetic tree where all branches are of equal length (just branching, time is not factored in)
What is a monophyletic group?
Includes a common ancestor and all of its descendants
What is a paraphyletic group?
Includes a common ancestor and some (but not all) of its descendants
What is a polyphyletic group?
Does not include a common ancestor
How are phylogenies inferred?
Using characteristics that are shared between species. The characteristics should vary among but not within species and have a genetic basis (morphological, chromosomal, molecular)
What are homologous characters?
Shared because of common ancestry (shared derived characters)
What are analogous characters?
Shared because of convergent evolution. Exhibit homoplasy, where basically there is similarity in appearance but no in origin
How are homologies recognized?
- Structural similarity
- Relations between parts
- Embryonic development
What is the strongest hypothesis for evolutionary relationships?
The tree with the fewest number of changes required (the simplest tree is often favoured, but does not always mean it is correct in reality). The most parsimonious
What is macroevolution?
Evolution above the species level, it assesses the diversity of an entire clade. Includes adaptive radiation, anagenesis, and cladogenesis
What is adaptive radiation?
The rapid evolution of new species occupying new ecological niches
What is anagenesis?
Speciation where the ancestor species is wholly replaces by a new species (evolution within the lineage)
What is cladogenesis?
Parent species splits into two species
What is punctuated change?
Rare and rapid events of branching speciation (on a geological time scale), it results in more cladogenesis
What is graduated change?
Slow and steady evolution, results in more anagenesis
