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BIOL1010/1011 > Evolution: Lecture 6 > Flashcards

Evolution: Lecture 6 Flashcards

1
Q

What is systematics?

A

The study if the diversity of life. Trying to work out all our information about it.

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2
Q

What are the two components of systematics?

A

Taxonomy and Phylogenetics

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3
Q

What is taxonomy?

A

Naming and identification of taxa: species and groups of species. The identification of taxa and categorization of taxa to house species.

  • Family, orders, domains
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4
Q

What is phylogenetics?

A

An estimation of the influence of evolutionary trees (phylogenetic trees or phylogenies)

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5
Q

what are the taxa in increasing specificity?

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

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6
Q

What are taxa?

A

They are groups of similarities between organisms. It is highly based on Linnaean evolution. Each taxa are groups of other (smaller) taxa.

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7
Q

What kind of name do we give spices?

A

Binomial nomenclature. Made up of genus and specific epithet.

Panthera pardus

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8
Q

Why do we use such unique names?

A

We use unique names that mean the same thing to all scientists. They would stay the same regardless of the language.

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9
Q

What supports taxonomy and phylogeny?

A

Hierarchical nested taxonomy is consistent with the tree of life. It is also the part of Linnaean’s ideas that worked well with Darwin’s ideas.

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10
Q

Biologists consider that?

A

Most biologists today consider that taxonomy should reflect phylogeny.

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11
Q

What are phylogenetic trees?

A

A branching tree diagram that communicates relationships between organisms/evolving things.

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12
Q

Tips and Branches and sister taxa?

A
  • Tips are normally representative of living species
  • Branch points or internal nodes represent the common ancestors
  • Sister taxa are species that branch from the same ancestor
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13
Q

Cladogram?

A

A phylogenetic tree where branch lengths have no particular meaning.

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14
Q

Phylogram?

A

Where branch lengths represent inferred amount of evolutionary change or time.

  • Very useful for molecular phylogenies.
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15
Q

Monophyletic group (clade)?

A

An ancestor and all of its descendants.

Example: snipping off a full branch

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16
Q

Paraphyletic group?

A

An ancestor and some, but not all, of its descendants

Example: snipping off a branch and getting rid of a twig on it

17
Q

Polyphyletic group?

A

A group that does not include its own most recent common ancestor (= 2+ branches artificially grouped together)

Example: grabbing a bunch of twigs and holding them together like a branch

18
Q

Many biologists also consider?

A

Taxonomy should reflect phylogeny and taxa should be monophyletic groups when possible.

19
Q

How do we infer phylogenies?

A

Character states (possible homologies)
– Morphological features, etc.
– Identities in DNA / protein sequences

Distribution of character states among organisms reflect evolutionary relationships

20
Q

What do we look at for the distribution of character states?

A

We look at the distribution (among organisms) of a characteristic by observing the different states of it.

Example: Non-retractable vs retractable claws.

21
Q

What are the 2 options for a state of a character?

A
  • There is the original (ancestral) state
  • There was an evolutionary change where the ancestral state changed into a new one (derived state).
22
Q

Shared derived states?

A

Imply relationships. Evidence that they are closer to each other than the ancestral states.

23
Q

Shared ancestral states?

A

do not imply relationships.

24
Q

What is the outgroup comparison?

A

Outgroup comparison (usually) to distinguish ancestral and derived states

25
Q

How do we measure evolutionary change?

A

From ancestral to derived: 0-1
From derived to ancestral: 1-0

Derived = 1
Ancestral = 0

26
Q

What is cladistics?

A

Cladistics is when we examine multiple characters and form a character matrix/table.

27
Q

What is cladistic reasoning?

A

A way of inferring evolutionary relationships from the character states of a series of characters.

28
Q

Why are character state distributions not all consistent with the same tree?

A

This could be due to:
- Convergent evolution. Traits evolve similarly on different parts of the tree. “analogy not homology”
- Reversals (loss of derived state 1-0)

29
Q

What is parsimony?

A
  • Compare many (all) possible trees:
  • Best inference is the tree that implies fewest evolutionary changes total.
30
Q

Molecular sequence data involves?

A
  • Phylogenies of living taxa are usually estimated by comparing molecular sequences (e.g. DNA).
  • A site in a set of aligned DNA sequences is a character: Different bases at site are the states
31
Q

Molecular sequence table?

A

It is similar to the character table. We compare similar gene sequences in organisms. We try to have the same nucleotide sequence being compared.

32
Q

Example with a gap in species Z?

A

There is a nucleotide missing. We can place a gap in the sequence to have the best fit possible. This is under the assumption that there was a possibility that Z had an event where a nucleotide was deleted.

  • Information is inferred by the scientist for the best fit.
33
Q

Morphological character vs. site in DNA sequence?

A

0-1 would be c-t

34
Q

Phylogenetic trees of molecular sequence analyses?

A

Most analyses use models of sequence evolution (rather than parsimony)

Example: Model may reflect the fact that transitions occur more frequently than transversions

Transition substitutions: common
C-T and G-A

Transversion substitutions:
G-T C-A G-C and T-A

35
Q

Sars COV-2 (COVID-19)?

A

Shows us that there is proof that COVID-19 was related or is related to other viruses in bats. Therefore, we have a level of certainty that COVID descended from a bat virus.

36
Q

Phylogenies of trees?

A

Evolution of genes themselves often of interest. Gene’s evolutionary history in genomes.

  • e.g. tracing history of gene duplication or of gene transfer between genomes
  • One of many aspects of the disciplines of molecular evolution and genome evolution
37
Q

Lateral or Horizontal Gene Transfer?

A

Transfer of genes between species
* Quite common in unicellular organisms and plants

38
Q

Where do we see this transfer?

A

Typically it is between distantly related species or those that aren’t related at all.

39
Q

What is the result of the gene transfer?

A

The cell that received the segment will now express new genes. Ones that the ancestor would not have had.

BIOL1010/1011 (22 decks)

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