Cycle 10 - Evolutionary Relationships Flashcards
Explain the taxanomic hierchies
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- Domain (eukaryotes, archaea, bacteria)
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Explain monophyletic and non-monophyletic
Monophyletic: the group must include all descendants of the MRCA (i.e. includes the clade and node)
Non-monophyletic: the group contains species that are not in the clade or does not include the MRCA node
Define paraphyletic taxon
Paraphyletic taxon: includes an ancestor and some, but not all, of its descendants (ex., “dinosaurs”: birds are descendants of one group of terrestrial dinosaurs).
Define node, root, clade, and sister clade/taxa
Node: branching points called nodes (MRCA)
Root: the root of the tree is the LUCA (bottom diverging point)
Clade: each collection of a node and branches is called a clade (a monophyletic grouping)
Sister clade/taxa: two organisms that emerge from the same node
Explain anagenesis and cladogenesis
Anagenesis and cladogenesis are the two main ways speciation occurs.
- During anagenesis, a species slowly accumulates changes until it reaches a point where it’s no longer the same species it was thousands or millions of years ago.
- Ex., Eohippus
- During cladogenesis, one species splits up into two or more groups, with each one evolving on its own path, until the groups are now different species.
- Ex., Darwin’s finches
Define synapomorphy, symplesiomorphy, autapomorphy
Synapomorphy: shared by two or more taxa; derived –> reveal relationships between taxa
Symplesiomorphy: shared by two or more taxa; ancestral
Autapomorphy: unique to a single taxon; derived
Explain homology and convergence
Homology: similarity that results from shared ancestry (i.e. the trait is inherited) (similar in structure but not necessarily in function)
Convergence: the evolution of similar adaptations in distantly related organisms that occupy similar environments (homoplasy or analogous characters)
- Misleading
Explain the advantages and disadvantages of molecular data in constructing a phylogeny
Advantages
- Only minute quantities of DNA are required (ex., from fossil)
- Provides abundant data
- Allows comparisons to distantly related organisms because many genes have been conserved through evolution
Disadvantage
- Biologists still do not understand the significance of molecular differences they discover
- Limited number of character states, homology can be difficult to asses
Explain traditional systematics
Traditional systematics: an approach to systematics that uses phenotypic similarities and differences to infer evolutionary relationships, grouping together species that share both ancestral and derived characters.
Explain whether each of the following is ancestral or derived
- Present in outgroup and ALL of ingroup?
- Present in outgroup and SOME of ingroup?
- Absent in outgroup, present in SOME of ingroup?
- Present in outgroup, but NONE of ingroup?
- Absent in outgroup, present in ALL of ingroup?
- Present in outgroup and ALL of ingroup?
- Ancestral - MRCA of outgroup and ingroup had it
- Present in outgroup and SOME of ingroup?
- Ancestral - MRCA of the whole group had it, but at some lineage in the ingroup the trait disappeared
- Absent in outgroup, present in SOME of ingroup?
- Derived
- Present in outgroup, but NONE of ingroup?
- Equally likely to either; this trait is not useful to us because either ancestral state or derived state could be likely as either follows single evolutionary step (law of parsimony)
- Absent in outgroup, present in ALL of ingroup?
- Same as above
What are molecular clocks?
Molecular clocks: the amount of differences that form at a constant rate after one species diverges from another
Because different molecules exhibit individual rates of evolutionary change, every molecule is an independent clock, ticking at its own rate; these rates are learned
Explain how comparative methods are used to test hypotheses
Accurate phylogenetic trees are essential tools for analyses that biologists describe as the “comparative method.” –> used to study any trait
Example case
- Birds and crocodiles exhibit many of the same parental care behaviour
- By examining the distribution of parental care behaviour on a cladogram of archosaurs, biologists predicted that nonavian dinosaurs probably incubated their eggs and cared for their young
