The Geography of Evolution

Question 1

What is one important feature of evolution and why?

Answer 1

How evolution progresses through geological time is crucial to our understanding of this biology
It is the temporal dynamics of evolution

Question 2

Darwin came up with the idea of evolution in his book - On the Origin of Species
What were his ideas

Answer 2

Through his tree of life, Darwin implied a gentle pattern of descent with modification - ‘phyletic gradualism’

Question 3

What was Darwins reason for if we see a substantial difference within the fossil record

Answer 3

Most rocks (and hence fossils) are missing
This implication: evolution change happens in gaps - there there is a jumpy rock band, there is also going to be a jumpy fossil record
Hence, although it is not reflected in the fossil record, because of incompleteness, the change in evolution is still gradual

Question 4

Wha is ‘hiatus’ and ‘angular unconformities’ in terms of incompleteness of the geological record

Answer 4

Hiatus: long periods of non-deposition
Angular unconformities: Erosion surfaces

Question 5

Niles Eldredge and Stephen J. Gould came up with a rebuttal for Darwins gradual evolution theory
What was it?

Answer 5

They said: it’s not just because the geology is incomplete - why is there so littoe change in long periods of time which we have see in real life
Instead, Punctuated Equilibrium was propsed, suggesting, that evolution does nothing for long periods the suddenly jumps

Question 6

What are some key features of Punctuated Equilibrium

Answer 6

• Speciation occurs rapidly and then a species experiences stasis
• Transitional links will not necessarily be found
• A sub-population of the ancestral species becomes a new species

Question 7

What are some key features of phyletic gradualism

Answer 7

• Speciation occurs gradually and stasis is apparent rather than real
• Transitional links should be found
• An ancestral species can be transformed into a new species

Question 8

In the theory of Punctuated Equilibrium: why do we see the sudden appearance and disappearance of species

Answer 8

Geographic isolation: a chance dispersal event
Which is then followed by geographical isolation, which leads to little/no sibsequent gene flow as there is reproductive isolation
Different evolutionary pressures within the different geographic environments will lead to evolution and the generation of new species

Question 9

How can geography relate to incomplete fossil records

Answer 9

Locations like the Andes may expecience a lot of this
A species may have a large geographical range and hence depositional site so occurs in the fossil record, however a species on the other side of a mountain may have a really small population and geographical range so isn’t found in the fossil record
The species on the otherside of the moutain could cross the moutain and invade, wiping out the previoua more dominant - hence a new species is suddenly found in the fossil record

Question 10

What geographical change brings species into contact, which originally wouldn’t

Answer 10

• Competition
• Habitat alteration
• Predation
• Diseases/Parasites
• All can lead to extinction, replacement and turnover of a new species
• Hence stasis would indicate a pubctuated equilibrium theory

Question 11

Why would natural geographical invasions occur

Answer 11

Climate change - allowing a species to increase their range
Erosion of moutain tops - increasing ranges and species who were unable can now cross
Tectonic plate collision - breaking sea barriers

Question 12

Stasis is very common in evolution but there is also evidence for heavy evolutionary change
Where has evolution recently run amok

Answer 12

Most famously on remote oceanic islands, moutain tops and some lakes
Environmental types can create differences in the rates of evolution

Question 13

Today, which geological hotspot has the highest speciation

Answer 13

Isolation gives high rates of speciation - in particular oceanic islands

Question 14

Rates of fossilisation can also differ between environment
Name a place where rates of fossiliation may be higher

Answer 14

• Fossiliation mainly happens in sedimentary basins
• They are regions of the Earth’s crust dominated by subsidence allowing sediments to accumulate
• This is because where fast moving water hits flat land, there is rapid deposition e.g. in costal Laggons
• Hence this could explain the reasons for gaps in the fossil record

Question 15

Oceanic islands and Sporadic lakes have high levels of speciation, however why is this not always demostrated within the fossil record

Answer 15

• High ground erodes, or collapses which can ‘erase’ highland taxa and any fossil deposits
• Volcanic islands appear breifly, then erode away and become subducted
• So evolution’s major hotspots do not survive

Question 16

• Why is it then, the fossil record shows mostly stasis

Answer 16

• The record receives taxa produced in hotspots if taxa spread to large and persistent ‘sediment sinks’ that produce rocks
• HOWEVER little change seems to happen in such places
• Therefore taxa which exists in areas by sinks will have little evolutionary change

Question 17

On the other hand, there are hotspots of change in the fossil record, but we have to think temporally rather than spatially
Why was there very little evolution until the Cretacous-Paleogene boundary

Answer 17

There were so many new niches opened up due to the large mass extinction

Question 18

How does evolution link to extinction events

Answer 18

Rates of diversification across multiple taxa consistently differ from background rates
* Basically something about the aftermath of a mass extinction event seems to promote accelerated diversification of life
* There is nothing about the environment that differs consistently before and after extinction events except the absence of species