Evolution - Ch 25 - Phylogenies and the History of Life

Question 1

What is the difference between microevolution and macroevolution?

Answer 1

One happens at the population level, and the other happens at the species level

Question 2

What are sister groups?

Answer 2

2+ lineages that share a recent common ancestor (at the node where their branches meet)

Question 3

What is an outgroup?

Answer 3

A taxon that diverged prior to the taxa that are the focus of the study, which helps root the tree (i.e., reference group)

Question 4

What is a polytomy?

Answer 4

A node that shows an ancestral branch dividing into 3+ descendent branches (either lack of data or adaptive radiation occurred)

Question 5

What is a character?

Answer 5

any genetic, morphological, physiological, developmental, or behavioural trait

Question 6

What is an ancestral trait? What is a derived trait?

Answer 6

• ancestral trait: a trait that any ancestor had
• derived trait: a modified form of an ancestral trait found in a descendant

they are relative to what you are comparing

Question 7

What is the cladistic approach?

Answer 7

where relationships between species can be reconstructed by identifying common derived traits, i.e., synapomorphies

Question 8

What is a monophyletic group/clade/lineage?

Answer 8

an evolutionary unit that includes an ancestral population and all its descendants

Question 9

What is the logical principle, in which the simplest explanation of a phenomenon is often the most likely?

Answer 9

parsimony or Occam’s Razor

Question 10

Homology vs. homoplasy

Answer 10

homology is the similarity of organisms due to common ancestry, whereas homoplasy is the similarity of organisms for reasons other than common ancestry (ex. convergent evolution)

Question 11

What is a polyphyletic group? Paraphyletic group?

Answer 11

• An unnatural group that does not include a recent common ancestor
• A group that includes an ancestral population and some, but not all descendants

Question 12

Do cladograms (a phylogenetic tree using the cladistic approach) care about branch length?

Answer 12

no

Question 13

What is convergent evolution?

Answer 13

a common cause of homoplasy, it is the independent evolution of similar traits in distantly related organisms because of an adaptation to similar environment or lifestyles

Question 14

What is an artiodactyl? What is the Whippo Hypothesis?

Answer 14

An artiodactyl has an even number of toes and an astragalus (ankle boneshape)
-Whales are closely related to hippos (and lost the astragalus) – supported by morphological data, sequencing data, and SINES

Question 15

What are 5 types of fossils?

Answer 15

• intact (ex. pollen)
• compression (ex. leaf)
• cast (ex. ammonite shell)
• permineralized (ex. petrified wood)
• trace (ex. footprints, tracks, feces, feeding marks)

Question 16

What is an intact fossil?

Answer 16

forms when no decomposition and organic remains are intact

Question 17

What is a compression fossil?

Answer 17

forms when sediment accumulates atop the organism and then turns in to rocks which compresses the organic material

Question 18

What is a cast fossil?

Answer 18

forms when the organism decomposes after burial, and the remaining hole contains dissolved minerals that can create an accurate “mold” or cast

Question 19

What is a permineralized fossil?

Answer 19

forms when organisms decay very slowly, and dissolved minerals gradually infiltrate inside the cells and turn to stone

Question 20

What is a trace fossil?

Answer 20

forms when sedimentation and mineralization preserve indirect evidence of a past organism

Question 21

What are limitations of the fossil records, i.e. potential biases that one must be cautious of?

Answer 21

habitat bias
taxonomic and tissue bias
temporal bias
abundance bias

Question 22

What is habitat bias (for fossils)?

Answer 22

organisms that live in areas with active sediment deposits more likely to fossilize

Question 23

What is temporal bias (for fossils)?

Answer 23

newer organisms more likely to be found (older organisms are deeper in layers)

Question 24

What is abundance bias (for fossils)?

Answer 24

more abundant, widespread species are more likely to fossilize

Question 25

What is tissue/taxonomic bias (for fossils)?

Answer 25

harder body parts are more likely to fossilize

Question 26

Precambrian (4.6 bya to 541 mya), what living things dominated this eon, and what were atmospheric conditions like?

Answer 26

• life was only unicellular

- O2 was virtually absent from oceans and the atmosphere until photosynthetic bacteria came along

Question 27

What were the 3 eras of the Phanerozoic Eon? List some major evolutionary events or dominant species of each era.

Answer 27

1. Paleozoic:
   Origin and adaptive radiation of many animals, land plants, and fungi.
   Ended with End-Permian extinction event
2. Mesozoic:
   Gymnosperms were dominant land plants; dinosaurs were largest invertebrates
   Ended with Cretaceous/Paleogene extinction event: all non-avian dinosaurs wiped out
3. Cenozoic
   Angiosperms are dominant land plants; mammals experienced an adaptive radiation (and are largest invertebrates)

Question 28

What is an adaptive radiation?

Answer 28

when a single lineage produces many descendent species with a wide range of adaptive forms

Question 29

What are the 3 hallmarks of adaptive radiation?

Answer 29

1. They are a monophyletic group
2. They speciated rapidly!
3. The descendants diversified into many niches

Question 30

What two general mechanisms cause adaptive radiations?

Answer 30

• factors intrinsic to organisms (ex. evolution of key traits)
• factors extrinsic to organisms (ex. favourable new conditions in environment)

Question 31

What is ecological opportunity?

Answer 31

the availability of new types of resources – it is an extrinsic factor that can cause adaptive radiations

Question 32

What was the Cambrian explosion (541 mya)?

Answer 32

the adaptive radiation of Animalia

Question 33

What are four hypotheses for why the Cambrian explosion happened?

Answer 33

• higher O2 levels
• evolution of predation
• new niches brought about more niches
• new genes, new bodies

Question 34

Mass extinction vs. background extinction

Answer 34

• mass extinction: the RAPID dying off of a great number of lineages scattered throughout the tree of life (due to exceptionally harsh short-term conditions)
• background extinction: the lesser, average rate of extinction when mass extinction not happening – (with normal environmental change, emerging diseases, predation pressure, competition, etc.)

Question 35

What are the “big five” historic mass extinctions?

Answer 35

End-Ordovician
Late Devonian
End-Permian *
Late Triassic
End-Cretaceous

Question 36

What happened in the End-Permian Extinction that caused 1/10 species left???

Answer 36

it’s still a mystery, but:

• flood basalts, intense global warming
• high levels of SO2 -> severe acid rain
• coal fires, and toxic ash with mercury in air
• oceans lacked O2
• sea levels dropped dramatically
• land animals possibly restricted to small patches of low-elevation for habitat

Question 37

What is the leading hypothesis on the K-Pg extinction event?

Answer 37

the impact hypothesis: a meteorite hit Earth ~66 mya, and obliterated 60-80% of multicellular species

Question 38

Which dinosaurs made it out alive of K-Pg

Answer 38

the non-avian ones!

Question 39

What is the evidence for the Impact Hypothesis?

Answer 39

• high amounts of iridium
• spike in shocked quartz
• spike of microtektites