BIOL 215 Radiations

Question 1

What are adaptive radiations ?

Answer 1

The evolution of diverse members of a single phylogenic lineage into a variety of different adaptive forms over a relatively short interval of time (short branches instead of long branches)

Question 2

What is the Cambrian and when did it happen ?

Answer 2

545 mya, the Cambrian explosion occured during the Cambrian era. We saw a rise in the number and variety of organisms during that time.

Question 3

What is the Sillurian and when did it happen ?

Answer 3

443 mya, plants and invertebrates evolved to become land indicviduals.

Question 4

What is the Devonian and when did it happen ?

Answer 4

417 mya, there were the rise of fishes and vertebrates started to evolve on land.

Question 5

What is the Carboniferous and when did it happen ?

Answer 5

354 mya, there is a rise of reptiles and insects and amphibians developed.

Question 6

What is the Mesozoic (Jurassic) and when did it happen ?

Answer 6

206 mya, there is a rise of dinosaurs and first birds appeared (archeopteryx)

Question 7

What is the Cretaceous and when did it happen ?

Answer 7

142 mya, extinction of dinosaurs and flowering time (angiosperms helped by insects)

Question 8

What is the Tertiary (Paleocene) and when did it happen ?

Answer 8

65 mya, radiation of mammals.

Question 9

Why do we see adaptive radiations [3] ?

Answer 9

Filling previously unavailable niches
Competitive release (less competition)
Competitive adavantage (competition favour one particular individual)

Question 10

Why do we refer to the Cambrian explosion as the Big Bang of evolution?

Answer 10

It is referred as the “Big Bang of Evolution” because we see a large variety of fossils, a lot of metazoan lineages, dated from that era with characteristics that we are able to link to actual life. The main problem is that they are hard to identify.

Question 11

What are the two main site currently studied for their fossils dated from the Cambrian ?

Answer 11

The Ediacaran in South Australia + NFL (Mistaken Point)

The Burgess Shale of Yoho National Park BC

Question 12

What do we mainly find in the Ediacaran sites? (also name the 2 fossils we see on the powerpoint)

Answer 12

Fossilized flat soft bodies.
Dickinsonia (looks like a jellyfish)
Spriggina (looks like a leaf but is an animal)

Question 13

What are the problems observed with the Ediacaran biota ?

Answer 13

It is an enigmatic series of fossils looking like animals but missing important features such as mouths, anuses, intestinal tracts or locomotory appendages and the site Mistaken Point in NFL show Ediacaran fossils dated from 565mya which does not correalate with the Cambrian explosion period.

Question 14

What can we mainly find in the Burgess Shale sites ? (+ species)

Answer 14

Animals that share common characteristics with current living animals defining their phyla.
Hallucigenia sparsa (picspics)
Anomalocaris (espèce de double trompe, fossile ressemble à celui d’un poisson)
Opabinia (homard avec des ailes)
Wiwaxia (artichaut)
Pikaia (larve)

Question 15

What are the two main controversies evolving around Burgess Shale ?

Answer 15

There is an interpretation controversy and a time controversy.

Question 16

Explain the interpretation controversy (Burgess Shale).

Answer 16

Gould : if we would rewind the tape of life, a totally different thing would happen.
Morris: If we would start it back again, it would be exactly the same. Morris theory is more accepted because of the molecular clock theory.

Question 17

Explain the time controversy (Burgess Shale)

Answer 17

The molecular clock show a lot of divergence in time. According to the molecular clock, nucleotides substitutions in a gene follow a linear pattern. If we follow the calculations of gene changes on organisms to become as those we saw during Burgess Shale, the fossils should be dated a 600mya to 1bya.

Question 18

What is the main cause of Cambrian explosion ?

Answer 18

Given that it is the period where we see the biggest number of species arise, and it never happened back again, they define the cause of the Cambrian Explosion to be adaptive radiations. According to the molecular clock, key traits probably appeared at the same time. According to fossils, the environmental conditions were favourable : right amount of O2, CaCO3 and there were diversity.

Question 19

What are the causes of Cambrian radiations ?

Answer 19

Geological Conditions
Rising Oxygen Levels (follow exosqueleton appearance)
Predator-Prey Relationships

Question 20

On 1,2by of evolution, since how much time humans are here ?

Answer 20

200 000years

Question 21

What are called the series of genes that are highly conserved in animals and what are their function ?

Answer 21

The homeobox genes, pax6 gene and engrailed that regulate development : if there will be wings or legs at that spot on the thorax, eyes development, segment polarity, etc. The way they are express depends on the timing.

Question 22

According to Jacob, what is evolution ?

Answer 22

Evolution is a bricolage, thinking that it is working on currently existing genes.