Lecture 10 Flashcards

1
Q

Define taxonomy

A

the theory and practice of classification and naming

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2
Q

define systematics

A

the study of biodiversity and the evolutionary relationships among organisms

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3
Q

Carolus Linnaeus

A

1707-1778
- father of taxonomy
- binomial nomenclature
- hierarchical system of classification

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4
Q

define a taxon

A

a single named taxonomic unit at any level (plural = taxa)

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5
Q

7 taxa

A

kingdom (kingdoms)
phylum (phyla)
class (classes)
order (orders)
family (families)
genus (genera)
species (species)

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6
Q

what is the purpose of a biological classification?

A
  • a name is key to shared information on an organism (eg scientific literature, field guides)
  • therefore has predictive power
  • enables interpretation of origins and evolutionary history
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7
Q

systematics research requires

A

a robust and stable system for classifying organisms (i.e. taxonomy)

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8
Q

describe how phylogenies arise/what they are made up of

A
  1. individual organisms within a population
  2. parents produce offspring
  3. lines of descent persist across generations
  4. a population is an aggregation of the genetic lineages of the individuals they contain
  5. a species is made of many populations, linked by gene flow
  6. individual species split to give rise to multiple species
  7. a phylogeny shows the relationships and evolutionary histories of species
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9
Q

node

A

corresponds to historical lineage splitting events, when one lineage splits into two

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10
Q

branches/ edges

A

correspond to single ancestor-descendant lineages. All branches are connected by nodes

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11
Q

tips/leaves/terminals/OTUs

A

tips do not have represented descendants. can be individuals, species, clades

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12
Q

internal vs external branches

A

external branches (aka terminal branches) connect a tip and a node. internal branches connect two nodes

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13
Q

root

A
  • a node representing earliest time point in the diagram
  • often represented by an unlabelled branch
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14
Q

sister groups/taxa

A

those that are immediate descendants of the same ancestor, eg sister species, sister branches, sister clades

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15
Q

parents and daughters

A

parent branches give rise to daughter branches

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16
Q

ingroup

A

consists of the focal species in a phylogenetic study

17
Q

outgroup

A

a more distant relative of the in-group taxa; can help to root the phylogeny and determine what character states are ancestral

18
Q

MRCA

A

most recent common ancestor; the youngest node that is ancestral to all lineages in a given group of taxa

19
Q

clade

A
  • any piece of a phylogeny that includes a MRCA and all of its descendants
  • i.e. any piece of a phylogeny that exhibits monophyly
20
Q

monophyly

A
  • describes a group made up of an ancestor and all its descendants
  • ie a monophyletic group or clade
21
Q

paraphyly

A
  • describes a group made up of an ancestor and some (but not all) of its descendants
  • ie a paraphyletic group or grade
22
Q

polyphyly

A
  • describes a group that does not contain the most recent common ancestor of all members
  • ie. a polyphyletic group
23
Q

for the species in a clade a trait is ancestral if

A

it was inherited in its present form from the MRCA of the clade

24
Q

for the species in a clade, a trait is derived if

A

it originated within the clade, ie in a descendant of the clade’s MRCA

25
relationship between ancestral and derived clades
the same trait can be ancestral for a clade, but derived within a larger clade
26
define a synapomorphy
a shared, derived trait for a clade. it is a trait that all species in the clade share, and that evolved on the branch leading to the clade (ie its derived within the context of more inclusive clades)
27
homology
when structures observed in different taxa can be traced to a single structure present in a shared evolutionary ancestor
28
homoplasy
when a character or character state arises more than once on a phylogenetic tree (convergence is one kind)
29
why conduct a phylogenetic analysis?
- understand history of life - understand large scale patterns of evolution - understand how many times traits have evolved how fast, under what conditions - practical: where/when did parasites spread? which fly strain is most successful? what are the driver mutations as covid evolves?
30
why is phylogenetic relatedness inferred from homologous traits and not homoplasy?
homoplasy (eg convergent trait evolution) can mislead phylogenetic inference
31
2 principal sources of macroevolutionary insights?
palaeontology - provides a direct record of past evolutionary change - inference is strongest for groups that fossilise well phylogenetics - provides an indirect record of past evolutionary change - inference is strongest for groups that have living representatives
32
mass extinction
extinction of >75% of earth's species in a geologically short period
33
uses of fossil record
- provides only evidence for completely extinct clades - documents long-term patterns of biodiversity - provides evidence for catastrophic extinctions during earth's history
34
diversification rate
speciation rate minus extinction rate
35
what happens after mass extinctions and how do we know?
explosive diversification; phylogenetic provides evidence for this
36
features associated with increased diversification
- herbivory - species with more sexual selection - animal pollination in plants - increased dispersal - increased range size