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Stack #4713189
| Question | Answer |
|---|---|
| Why can common names be problematic when identifying organisms? | Common names can refer to more than one species or misrepresent what type of organism something actually is. |
| What naming system do scientists use to identify organisms? | Binomial nomenclature using Latin scientific names. |
| What is binomial nomenclature? | The system scientists use to identify organisms using a two-part scientific name. |
| What scientific name is given for the twospined angelfish in the slides? | Centropyge bispinosa. |
| What is a taxon? | A named taxonomic unit at any level of classification. |
| What is a phylogenetic tree? | A hypothesis about evolutionary relationships among organisms. |
| What does a branch point on a phylogenetic tree represent? | The divergence of two evolutionary lineages from a common ancestor. |
| What is an evolutionary lineage? | A sequence of ancestral organisms leading to a particular descendant taxon. |
| What is a character? | An observable heritable feature that may vary among individuals. |
| What are the main parts of a phylogenetic tree shown in the slides? | Root nodes branches and tips. |
| What does the root of a phylogenetic tree represent? | The ancestral lineage from which the organisms on the tree descended. |
| What is a node on a phylogenetic tree? | A branch point representing the divergence of evolutionary lineages from a common ancestor. |
| What is a branch on a phylogenetic tree? | A line representing an evolutionary lineage. |
| What is a tip on a phylogenetic tree? | The end of a branch representing a particular taxon. |
| Can phylogenetic trees be drawn in different orientations? | Yes; the same relationships can be represented with vertical horizontal or diagonal trees. |
| Does rotating branches around a node change the evolutionary relationships shown by a phylogenetic tree? | No; rotating around a node changes the appearance of the tree but not the evolutionary relationships. |
| Should you determine relatedness by which organisms are physically next to each other on a phylogenetic tree? | No; relatedness is determined by common ancestry and branch points rather than physical position on the page. |
| What is a clade? | A group of species that includes an ancestral species and all of its descendants. |
| What is a monophyletic group? | A group consisting of a common ancestor and all of its descendants. |
| What is the relationship between a monophyletic group and a clade? | A monophyletic group is equivalent to a clade. |
| What is a paraphyletic group? | A group consisting of a common ancestor and some but not all of its descendants. |
| What is a polyphyletic group? | A group containing distantly related organisms that does not include their most recent common ancestor. |
| What is the key difference between monophyletic and paraphyletic groups? | A monophyletic group contains a common ancestor and all descendants while a paraphyletic group leaves out one or more descendants. |
| What is the key difference between monophyletic and polyphyletic groups? | A monophyletic group includes the common ancestor and all descendants while a polyphyletic group contains distantly related organisms but excludes their most recent common ancestor. |
| What is a character matrix? | A table showing which characters are present or absent in different taxa. |
| How can a character matrix be used to construct a phylogenetic tree? | Shared characters among taxa can be mapped onto a tree to estimate their evolutionary relationships. |
| What do the values in a character matrix represent? | Whether particular characters are present or absent in each taxon. |
| What taxa are used in the character-mapping example in the slides? | Lancelet lamprey bass frog turtle and leopard. |
| What organism is used as the outgroup in the vertebrate character example? | The lancelet. |
| What character is shared by lamprey bass frog turtle and leopard but not the lancelet? | Vertebral column or backbone. |
| What character is shared by bass frog turtle and leopard but not lamprey or lancelet? | Hinged jaws. |
| What character is shared by frog turtle and leopard in the character matrix? | Four limbs. |
| What character is shared by turtle and leopard in the character matrix? | Amnion. |
| What character is unique to the leopard in the character matrix? | Hair. |
| What can be used to infer phylogenetic trees? | Morphological and molecular data. |
| What is morphological data in phylogenetic analysis? | Information about observable physical characters of organisms. |
| What is molecular data in phylogenetic analysis? | Information such as DNA sequence data used to estimate evolutionary relationships. |
| Are phylogenetic trees considered absolute facts? | No; every phylogenetic tree is a hypothesis. |
| Why can a phylogenetic tree change over time? | New data can become available and change our understanding of evolutionary relationships. |
| What is maximum parsimony? | The principle that when considering multiple explanations one should first investigate the simplest explanation consistent with the facts. |
| How is maximum parsimony used to choose among phylogenetic trees? | The tree requiring the fewest character state changes is considered the most parsimonious and therefore the most supported. |
| What is a character state change? | An evolutionary change in a character that is mapped onto a phylogenetic tree. |
| If three phylogenetic hypotheses require 7 6 and 8 character state changes which is most parsimonious? | The hypothesis requiring 6 character state changes. |
| Why is a tree requiring 6 character state changes preferred over trees requiring 7 or 8? | It requires the fewest evolutionary character state changes and is therefore the most parsimonious. |
| What is a molecular clock? | A method for estimating the time required for a given amount of evolutionary change based on the observation that some genome regions evolve at constant rates. |
| What assumption allows molecular clocks to estimate evolutionary time? | Some regions of genomes evolve at relatively constant rates. |
| What relationship is shown between mutations and divergence time in the molecular clock graph? | The number of mutations increases as divergence time increases. |
| How can DNA sequence differences help estimate when two lineages diverged? | If mutations accumulate at a relatively constant rate the number of sequence differences can be used to estimate divergence time. |
| Why do phylogenies continue to improve? | New information especially DNA sequence data improves our understanding of evolution and can change how life is mapped into phylogenies. |
| What is a polytomy? | A branch point from which more than two descendant taxa emerge. |
| What does a polytomy indicate? | The evolutionary relationships among the descendant taxa are not yet clear. |
| Does a polytomy necessarily mean that several lineages evolved at exactly the same time? | The slides use a polytomy to indicate that the evolutionary relationships among those descendant taxa are not yet clear. |
| What is horizontal gene transfer? | The transfer of genes from one genome to another. |
| What mechanisms can cause horizontal gene transfer? | Transposable elements plasmid exchange viral activity and perhaps fusion of different organisms. |
| Why can horizontal gene transfer complicate phylogenies? | Genes can move between different genomes rather than being inherited only through direct ancestry. |
| What is an outgroup? | A taxon used for comparison that has fewer shared traits with the taxa being studied. |
| How is the outgroup identified in the character-matrix activity? | The taxon with the fewest shared traits is usually treated as the outgroup. |
| What possible characters are used in the antelope-like phylogeny activity? | Black upper legs spotted rump black tail horns and masked face. |
| Which taxon is identified as the outgroup in the antelope-like character matrix? | Taxon D. |
| Why is Taxon D treated as the outgroup in the activity? | It has the fewest shared traits with the other taxa. |
| What is the first step in creating a phylogeny from observable organisms in the activity? | Identify possible characters that vary among the taxa. |
| What is the next step after identifying characters for a phylogeny? | Create a character matrix showing which taxa possess each character. |
| What do you do after creating a character matrix? | Compare possible trees and determine which requires the fewest character state changes. |
| What should be done after selecting the most parsimonious phylogeny? | Map the character state changes onto the tree. |
| What are the three major tasks in the phylogeny activity? | Complete the character matrix create the most parsimonious phylogeny and map character state changes onto the tree. |
| What characters are considered in the first insect-alien phylogeny activity? | Six legs wings stinger claws antennae loss of arms and long legs. |
| What additional characters appear in the second insect-alien activity? | Eyestalks and star belly. |
| What does it mean when two taxa share a recently occurring character on a phylogeny? | That shared character can provide evidence supporting a closer evolutionary relationship between those taxa. |
| How do you determine which two taxa are most closely related on a phylogenetic tree? | Find the two taxa that share the most recent common ancestor. |
| What is a common ancestor on a phylogenetic tree? | An ancestral organism or lineage from which two or more descendant lineages diverged. |
| What does a more recent common ancestor generally indicate? | A closer evolutionary relationship between the taxa. |
| What does mapping characters onto a phylogeny help show? | Where evolutionary character changes are hypothesized to have occurred along the lineages. |
| What is the main purpose of phylogenetics? | To estimate and represent evolutionary relationships among organisms. |
Created by:
808kadynt