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biol 108 > Topic 4 > Flashcards

Topic 4 Flashcards

1
Q

What is Systematics?

A
  • the theory and practice of classifying organisms based on evolutionary history (phylogeny)
  • systematics attempt to construct evolutionary informative classifications.
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2
Q

What is a phylogeny ?

A
  • depicted as a phylogenetic tree
  • evolutionary history of a species, or group of related species.
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3
Q

What do phylogenetic trees show?

A
  • show hypotheses for the evolutionary decent of different organisms, or genes from common ancestors.
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4
Q

Phylogenies are inferred from…

A
  1. Morphological data - the size, shape, and presence of different anatomical features.
  2. Molecular data - molecular systematics uses DNA, RNA, and protein structures to infer phylogenies.
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5
Q

A phylogenetic tree is…

A

a hypotheses about evolutionary relationships among a set of organisms called taxa.

  • each branch point (node) represents the divergence of two species (speciation).
  • each node represents the last common ancestor.
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6
Q

What is sister taxa?

A

Two descendants that split from the same node.

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7
Q

What does it mean when a phylogenetic tree is rooted?

A

One branch that corresponds to the common ancestor of all taxa on the tree.

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8
Q

What is polytomy?

A

a branch in a phylogenetic tree from which more than two groups emerge.

  • typically represent unresolved patterns of divergence.
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9
Q

What is a basal taxon?

A

diverges early in a phylogenetic tree, and in the history of the group. Originates near the common ancestor.

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10
Q

What is a clade?

A

A piece of a phylogeny that includes an ancestor and all descendants (living and extinct) of that ancestor.

  • a piece of a larger tree that can be cut away from the root with a single cut.
  • clades form a nested hierarchy.
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11
Q

Can a single external branch be a clade?

A

Yes.

Because tips of external branches (descendent taxa) may represent a group group of taxa.

  • it includes all descendants of a single ancestor.
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12
Q

What is a cladogram?

A
  • 1 of 2 types of phylogenetic trees
  • depict evolutionary relationships where only the pattern of branching (the topology) is important.
  • branch length and the position of the descendant taxa convey no information.
  • does not convey the passage of time.
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13
Q

What are phylograms?

A
  • 1 of 2 types of phylogenetic trees
  • also depict evolutionary patterns, but branch lengths are proportional to evolutionary change.
  • phylogram branch length can represent chronological time, and may also reflect the number of character changes that took place between taxa in that lineage.
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14
Q

What do phylograms show?

A
  • evolutionary relationships, not evolutionary progress.
  • taxa that share a more recent common ancestor are more closely related.
  • the number of nodes between a taxa does not indicate the relatedness of the taxa.
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15
Q

What do phylogenetic polytomies indicate?

A
  1. Lack of knowledge - polytomy indicates there is insufficient data to resolve patterns of divergence (do not make conclusions about lineages)
  2. Rapid speciation - multiple speciation events possibly happened at the same time. (ex: when a species rapidly expands its geographic range).
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16
Q

What is the conceptual difference between taxonomy and systematics criteria?

A
  • taxonomy uses similarity and difference to define taxonomic ranks.
  • systematics uses branching order (phylogeny) to define clades.
17
Q

What are the two reasons that traits can be similar between different groups?

A
  1. the trait is similar because of decent from a common ancestor (shared ancestry) (homologous)
  2. the trait is similar due to independent adaptation (convergent evolution) (analogous)
18
Q

What is homology?

A
  • it is similarly due to shared ancestry.
  • shared evolutionary origin
19
Q

What is analogy?

A
  • it is due to convergent evolution
  • convergent evolution = the independent evolution of similar traits in different lineages.
  • convergent evolution does not provide information about shared evolutionary history.
20
Q

What is convergent evolution?

A

When similar environmental conditions and natural selection produce similar adaptations in organisms from different evolutionary lineages.

(anologous)

21
Q

What is homoplasy?

A
  • interchangeable with analogous
  • analogous structures or molecular sequences that evolved independently
  • a trait that is shared by a set of taxa, but the trait is not present in their common ancestor.
22
Q

When building phylogenetic trees…

A
  • only homologous traits should be used to build phylogenetic trees.
  • only homologous traits reflect evolutionary history.
23
Q

What is the ingroup in a phylogenetic tree?

A

the group of taxa whose evolutionary relationships you are interested in determining.

24
Q

What is the outgroup of a phylogenetic tree?

A

one or more taxa that are related to the ingroup, but have diverged from the ingroup at an earlier time.

25
Q

What is a character in a phylogenetic tree?

A
  • anatomical, physiological, or molecular features of organisms.
  • character state is the observed manifestation of that character.
26
Q

What is cladistics?

A

a method of inferring phylogeny from homologous characters.

  • groups organisms by common decent
27
Q

What is a monophyletic group?

A
  • a group is monophyletic if it consists of an ancestor taxon, all of its descendants, and no unrelated taxa.
  • monophyletic group = clade
28
Q

What is a paraphyletic group?

A
  • consists of an ancestral taxon, but not all of the descendants
  • often arise when highly divergent taxa are removed from their original clade
  • includes distantly related taxa but does not include the common ancestor of all group members.
29
Q

What is a shared, derived character?

A
  • characteristics shared by two or more taxa and their most recent common ancestor
  • is not found in the ancestor that precedes the clade

(synapomorphy)

30
Q

What is a shared, ancestral character?

A
  • an ancestral character shared by two or more taxa, including taxa in an earlier clade.

(symplesiomorphy)

31
Q

What is synapomorphy?

A

a derived character (apomorphy) shared by two or more groups which originated in their last common ancestor.

32
Q

What is symplesiomorphy?

A

an ancestral character (plesiomorphy) shared by several groups, but inherited from ancestors older than the last common ancestor.

biol 108 (13 decks)

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