Quiz
Phylogenetic Trees
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1[blank_start]Phylogenetic[blank_end] trees = allow us to recognise similar traits in organisms that are due to [blank_start]common[blank_end] ancestors and the differences that are the result of historical separations or [blank_start]speciation[blank_end] events
- [blank_start]phylogenetics[blank_end] = the study of evolutionary relationships between species or wider taxonomic groups, a genus or something narrower- Aphylogenetics
- BPhylogenetic
- Ccommon
- Dspeciation
2Species at the terminals (end of branches) on phylogenetic trees are [blank_start]extant[blank_end] (still living) species
- Aextant
3What is a [blank_start]phylogeny[blank_end]?
- [blank_start]history[blank_end] or a species (or population, gene sequence or another taxonomic group) and its relationships to other species, described as a tree
- its a hypothesis describing history of descent of a group of organisms from their [blank_start]common[blank_end] ancestor
greek, phyl = [blank_start]tribe[blank_end]
gen = origin or descent- Aphylogeny
- Bhistory
- Ccommon
- Dtribe
4In a [blank_start]phylogenetic[blank_end] tree
- a lineage is represented as a branching tree
- each split (called a [blank_start]node[blank_end]) represents a [blank_start]speciation[blank_end] event
[blank_start]lineage[blank_end] = line of small changes over time- Alineage
- Bphylogenetic
- Cspeciation
- Dnode
5The only image in [blank_start]Darwin[blank_end]'s origin of species is of a phylogenetic tree
- ADarwin
6Components of a phylogenetic tree
- a [blank_start]species[blank_end], population or gene at one point of time becomes a [blank_start]lineage[blank_end] as we follow the descendants through [blank_start]time[blank_end]
- a [blank_start]node[blank_end] = where a lineage splits
- a split occurs when the ancestral lineage divides into [blank_start]two[blank_end] descendant lineages
- each of the descendent lineages continues to evolve [blank_start]independently[blank_end] as different traits (represented by dots) arise
- the lineages continue to split and a phylogenetic [blank_start]tree[blank_end] emerges- Aspecies
- Blineage
- Ctime
- Dnode
- Etwo
- Findependently
- Gtree
7in a phylogenetic tree
- [blank_start]x[blank_end] axis has meaning, represents time
- [blank_start]y[blank_end] has no meaning
Not all trees have a time axis, some are just a hypothesis of the sequential order these are referred to as cladograms- Ax
- By
8[blank_start]clade[blank_end] = all evolutionary descendants of a common ancestor
- node = split, speciation event that signifies an [blank_start]extinct[blank_end] species
OTU = [blank_start]operational[blank_end] taxonomic unit = extant species found at the terminals- Aclade
- Bextinct
- Coperational
9Branches in a phylogenetic tree can be rotated around any node without changing the meaning of a tree
- ARichtig
- BFalsch
10relatedness is about descent not [blank_start]similarity[blank_end]
- species are closer in relatedness if they share a more recent [blank_start]common[blank_end] ancestor
- if two species shared a more recent common ancestor that with other species then the more [blank_start]shared[blank_end] characters they will have- Asimilarity
- Bcommon
- Cshared
11[blank_start]Ancestral[blank_end] traits
- a trait present in the [blank_start]ancestor[blank_end] of a group
- traits inherited from a [blank_start]common[blank_end] ancestor in the past, shared by its descendant species
- if the ancestral trait appeared longer ago [blank_start]more[blank_end] species will have it
- shorter ago = fewer species will have it
Also known as a [blank_start]plesiomorphie[blank_end]- AAncestral
- Bancestor
- Ccommon
- Dmore
- Eplesiomorphie
12[blank_start]Derived[blank_end] trait
- [blank_start]not[blank_end] found in the ancestors of the group
- traits that first appeared in the most recent ancestor which gave rise to the split
also known as a [blank_start]apomorphie[blank_end]- Aapomorphie
- BDerived
- Cnot
13Whether a trait is derived or ancestral depends on what the group of interest is
- if looking a longer teeth is purely rodents this is an [blank_start]ancestral[blank_end] trait
- if looking at the phylogeny of mammals = this is a [blank_start]derived[blank_end] trait unique to the rodents- Aancestral
- Bderived
14[blank_start]Homologous[blank_end] traits
- a feature shared by species that are descended from a [blank_start]common[blank_end] ancestor
- e.g. the vertebral column is homologous is all [blank_start]vertebrates[blank_end]
feature shared by [blank_start]all[blank_end] descendants of a common ancestor- AHomologous
- Ball
- Ccommon
- Dvertebrates
15[blank_start]synapomorphie[blank_end]
- [blank_start]derived[blank_end] traits shared among a group
- evidence of [blank_start]common[blank_end] ancestry
- almost the same thing as [blank_start]homologous[blank_end] traits but people tend to use this term more as [blank_start]evidence[blank_end] for a common ancestor
- its a shared derived trait that distinguishes a clade from other organisms, whereas a [blank_start]homologous[blank_end] trait is only a shared trait not used to distinguish- Asynapomorphie
- Bcommon
- Cderived
- Dhomologous
- Eevidence
- Fhomologous
16[blank_start]Homoplasies[blank_end] / homoplastic traits
- a very [blank_start]similar[blank_end] morphological trait as a result of convergent evolution or evolutionary [blank_start]reversal[blank_end]
e.g. orcas and penguins have fins for swimming but they are not closely related, so fins are a [blank_start]homoplastic[blank_end] trait- Ahomoplastic
- BHomoplasies
- Csimilar
- Dreversal
17define: [blank_start]convergent[blank_end] evolution = evolution of similar traits arise independently in different lineages
- Aconvergent
18So homoplasies/[blank_start]homoplastic[blank_end] traits are [blank_start]derived[blank_end] traits that seem similar but are similar for some other reason other than [blank_start]inheritance[blank_end] from a common ancestor
- species may appear similar however it might just be because they are adapted to a similar [blank_start]habitat[blank_end]- Ahomoplastic
- Bderived
- Cinheritance
- Dhabitat
19Two processes can confuse phylogenetic trees through morphological similarity
1. convergent/[blank_start]parallel[blank_end] evolution = independently evolved features subjected to similar selection [blank_start]pressures[blank_end] become superficially similar
2. [blank_start]evolutionary[blank_end] reversal = a characteristic reverts from a derived state back to an [blank_start]ancestral[blank_end] state- Aparallel
- Bpressures
- Cevolutionary
- Dancestral
20Example of evolutionary [blank_start]reversal[blank_end]
- a characteristic reverts from a [blank_start]derived[blank_end] state back to an ancestral state
- e.g. a [blank_start]frog[blank_end] genus, Amphignathodon, has re-evolved [blank_start]teeth[blank_end] in lower jaw
evolution can go in any direction e.g. number of [blank_start]ribs[blank_end] in trilobites- Areversal
- Bderived
- Cfrog
- Dteeth
- Eribs
21Parallel/[blank_start]convergent[blank_end] evolution in [blank_start]Littorina[blank_end] saxatalis
- divergent selection for [blank_start]shell[blank_end] morphology
- populations in England, Spain and [blank_start]Sweden[blank_end]
Divergent selection has made 2 ecotypes on shell morphology
- [blank_start]high[blank_end] shore = small, thin shell with [blank_start]wide[blank_end] aperture to tolerate desiccation and wave action
- mid-shore ecotype = larger, [blank_start]thick[blank_end] shell with small aperture adapted to resist predation by [blank_start]crabs[blank_end]
The Spanish and Swedish species have similar adaptations but are adapted to very different [blank_start]selection[blank_end] pressures- Aconvergent
- BLittorina
- Cshell
- DSweden
- Ehigh
- Fwide
- Gthick
- Hcrabs
- Iselection
22Constructing Phylogenies
- [blank_start]outgroup[blank_end] = lineage closely related to an ingroup (the lineage of interest) but branched off earlier on the [blank_start]tree[blank_end] than the ingroup
- [blank_start]ancestral[blank_end] trait = if present in ingroup and outgroup
- [blank_start]derived[blank_end] trait = if present in the ingroup and not in the outgroup
so outgroup is not in the lineage- Aoutgroup
- Btree
- Cancestral
- Dderived
23Early [blank_start]developmental[blank_end] stages of many organisms reveal similarities to other organisms but these similarities may be lost in adulthood
- e.g. the [blank_start]notochord[blank_end] of larval sea [blank_start]squirts[blank_end] and vertebrates is a shared characteristic
Can't just look at morphology: the presence of a notochord in [blank_start]tunicates[blank_end] makes them closely related to humans but only present in the [blank_start]larvae[blank_end], once attached to a rock tunicates eat their own [blank_start]brain[blank_end]- Adevelopmental
- Bnotochord
- Csquirts
- Dtunicates
- Elarvae
- Fbrain
24distinguishing [blank_start]derived[blank_end] traits from ancestral traits may be difficult because traits often become very [blank_start]different[blank_end] (may be ancestral but look quite different)
- Aderived
- Bdifferent
25Reconstructing Phylogeny
- construct all possible trees using a [blank_start]computer[blank_end]
- then decide which [blank_start]tree[blank_end] reflects the data best satisfying a logical and agreed upon criterion
- uses the [blank_start]parsimony[blank_end] principle = simplest, the one that has the fewest changes along the whole tree
- the parsimony principle provides the [blank_start]simplest[blank_end] explanation for phylogenetic data- Acomputer
- Btree
- Cparsimony
- Dsimplest
26[blank_start]parsimony[blank_end] principle = widely used, states that the [blank_start]simplest[blank_end] hypothesis that explains the observed data is preferred
- minimises the number of evolutionary changes that need to be assumed over all characters in all groups of the tree
- the best hypothesis is the one that requires the fewest [blank_start]homoplasies[blank_end] (homoplastic traits; similar traits that arise in [blank_start]different[blank_end] lineages)- Ahomoplasies
- Bparsimony
- Csimplest
- Ddifferent
27The [blank_start]parsimony[blank_end] principle is not the only method for constructing a [blank_start]tree[blank_end], there are many other methods like 'distance' (cm, miles) method
- maximum likelihood methods > these use explicit [blank_start]mathematical[blank_end] methods, probability of the observed data on a specified tree, given a model of evolution
- the advantage of maximum likelihood methods is they can be statistically [blank_start]tested[blank_end]- Aparsimony
- Btree
- Cmathematical
- Dtested
Informationen
- Beschreibung
- Evolution Quiz am Phylogenetic Trees, erstellt von sophie waddington am 28/04/2018.
- Autor
- sophie waddington
- Sprache
- English
- Aufrufe
- 7
- Verlauf
- Erstellt am 28 Apr 2018 · aktualisiert am 30 Apr 2018
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