lec22: phylogenetics and macroevolution

Question 1

taxon

Answer 1

a single named taxonomic unit at any level

plural = taxa

Question 2

taxonomy

Answer 2

the theory and practice of classification and naming (kingdom - species)

Question 3

systematics

Answer 3

the study of biodiversity and the evolutionary relationships among organisms

also plays a role in how we classify organisms

Question 4

1. outgroup taxon, ingroup taxa, terminal nodes, terminal branches, internal nodes, internal branches
2. common ancestor, ancestral characters, derived characters

draw 2 diff diagram for each case of a phylogenetic tree including all and label

Answer 4

.

Question 5

Monophyletic group + draw an example

Answer 5

group that includes the complete set of species derived from a common ancestor

other words: a single ancestor gave rise to all species in that taxon and no species in any other taxon

Question 6

paraphyletic group + draw an example

Answer 6

group that contains some but not all species derived from a common ancestor

other words: a taxon whose members are derives from 2 or more ancestral forms not common to all members (“not including everyone” in that grouping of the main common ancestral)

Question 7

species that share a more recent common ancestor tend to be more similar
- descent with modification

explain based on the lines/tics that lies on the branches of a phylogenic tree

Answer 7

look at slide.

• looking at the species A B and C, there are 3 changes that have happened on this branch, that A and B should share with each other to the exclusion of C
• counting up the number of difference between A and B in terms of eg. these are different phenotypes, they’ve accumulated 2 different changes: B had one change and A had one change thereby a total of 2 differences between them
• but between A and C, 5 differences. so more distantly related species will share fewer derived traits than more similar species. same for B and C
• helps distinct who’s more similar/different from each other

Question 8

look at the slide of “grouping species into higher taxa” and identify if taxon 1 and 2 are either monophyletic or paraphyletic.

based on this, why is monophyletic classifications much preferred?

Answer 8

because they link taxon names to evolutionary history. thereby, paraphyletic is not a true evolutionary history or group of species since it doesn’t include everyone

Question 9

a critical first step in the reconstruction of phylogenic history is the identification and distinction of ____ and ____ traits

Answer 9

of ancestral and derived traits

Question 10

ancestral trait

Answer 10

a trait shared with a common ancestor

Question 11

derived trait

Answer 11

a trait that differs from the ancestral trait in a lineage

Question 12

homology

Answer 12

similarity of traits due to common/ shared ancestry

a trait can evolve and be shared among a group of organisms because a common ancestor had that trait; so that is a sharing of trait because of ancestral history

Question 13

homoplasy

Answer 13

similarity of traits as a result of convergent evolution

get same phenotype, not because of the common ancestor had it, but because of convergent evolution

Question 14

why does homoplasy/ convergent evolution create challenges when trying to reconstruct evolutionary history?

Answer 14

because if we’re using shared derived traits to determine who’s more closely related to whom; it can lead us to astray if there’s a lot of convergent evolution where this trait evolved multiple times independently. so it is important to distinguish these two

Question 15

convergent evolution

Answer 15

the process whereby unrelated organisms share similar traits because they share similar ecological niches

other words: the INDEPENDENT EVOLUTION of structures that RESEMBLE one another and perform SIMILAR FUNCTIONAL ROLES due to SHARED ECOLOY of unrelated organisms

Question 16

how do you tell what is more closely related to what is on a phylogenetic tree?

Answer 16

organisms that have a more recent common ancestor (vertice)

Question 17

to reconstruct the true evolutionary history of species it’s important to have molecular information. why is molecular biology relevant to evolution and phylogeny?

Answer 17

helps us understand trait evolution completely independently from reconstructing evolutionary history because common genetic code is evidence that all life is related through branching descent

evolutionary relationships among species are reflected in their DNA and proteins where learning about protein function in one species can tell us about its function in others eg. mice, rats, flies, worms → humans (studying the function of these genes of those species used as a model for humans due to sharing of common ancestor)

Question 18

inferring species relationships from DNA sequences which gives us a greater resolution of who is more closely related to whom

Answer 18

in slide

Question 19

what are “key innovations” in phylogenetic trees?

Answer 19

also known as an adaptive breakthrough or key adaptation, is a novel phenotypic trait that allows subsequent radiation and success of a taxonomic group

traits that facilitate increased diversification rates and a decrease in extinction rate

Question 20

what is the benefit of key innovations?

Answer 20

carriers of the trait can exploit new resources and sets of habitats

Question 21

what is the most important thing to associate key innovations with?

Answer 21

rapid evolutionary diversification (eg. adaptive radiations)

Question 22

draw a phylogenetic tree including: low diversity clade, high diversity clade, key innovation, ancestor + what does it demonstrate about key innovation

diversification = _____- _____

Answer 22

in slide

diversification = speciation - extinction
- key innovation could increase speciation or decrease extinction to influence net diversification

why so many species on the RS compared to LS? maybe there’s a trait that confers a higher probability of speciation or a lower probability of extinction; so many there some key innovation here for ex, that led to much higher speciation rates on the right hand branch compared to the left. and so we have this species selection; microevolutionary patterns here where because some species have a particular trait = higher rate of speciation or a lower right if extinction

Question 23

based on the “low diversity clade vs high diversity clade” unbalanced phylogenetic tree, why do some groups have more species than others?

Question 24

why do asexual species not survive as long as sexual species?

Answer 24

In an unstable or unpredictable environment, asexually-reproducing species may be at a disadvantage because all the offspring are genetically identical and may not have the genetic variation to survive in new or different conditions

Question 25

ancestral trait

Answer 25

a trait shared with a common ancestor

Question 26

derived trait

Answer 26

a trait that differs from the ancestral trait in a lineage

Question 27

what is a sister group on a phylogenetic tree?

Answer 27

Two descendants that split from the same node

Question 28

what are the 4 other features associated with greater diversification?

Answer 28

1. species with sexual reproduction
   - (asexually extinct as a higher rate due to less able to adapt to changing environment and eliminate harmful mutations because can’t make new combination)
2. outcrossing species
3. animal pollination in plants
4. increased dispersal