Maori Mystery

Question 1

Laurasia contained which modern landmasses

Answer 1

Eurasia and N.America

Question 2

Where was there really a strong divide between N. and S.Hemisphere continents

Answer 2

80Mya
After the breakup of Laurasia

Question 3

Gondwana was the Southern part of the Supercontient Pangea, Laurasia was the northern
Gondwana, however split ip but the Cretaceous, forming which modern landmasses

Answer 3

• S.America
• Africa
• Madagascar
• Antarctica
• Australia
• New Zealand

Question 4

What is the Nothofagus
When did it first occur

Answer 4

• is a diverse genus (43 species) of tree and shrubs native to parts of the S.Hemisphere - Southern beach
• First appeared around 72 million years ago - found in Gondwanan fossils

Question 5

What is the modern distrubution of the Nothofagus

Answer 5

• Endemic to S.Hemisphere
• Common in: S.America, Australia, New Guinea (not western Australia tho)
• Not found in Africa
• Highly strange distribution

Question 6

What would explain the highly strange distribution of Nothofagus

Answer 6

Nothofagus (+ancestor) was only in SE Gondwana
Vicariance explanation is that the genus hasn’t moved much, but the contients have
i.e. the barriers arise after the taxon is in place
The current distribution is caused by the movement of the continents

Question 7

What is Vicariance

Answer 7

• A process by which the geographical range of an individual taxon (or a whole biota) is split into discontinuous parts by the formation of a physical or biotic barrier to gene flow or dispersal
• Eventually result in two/or more closely related species by reproductive isolation - allopatric speciation

Question 8

What is the opposite of Vicariance

Answer 8

Dispersal
A species disperses across an existing geographical barrier - hence the barrier arises first and then the species crosses it

Question 9

What is the ‘Dispersalist’ explanation for Nothofagus

Answer 9

• A pure dispersalist explanation would suggest that Nothofagus can travel very long distances across the ocean. Hard to think of any other explanation why Nothofagus would be on small oceanic isalnds in the middle of the Pacific - never connected to any other land
• Once dispersal has happened, allopatric speciation can occur

Question 10

How do Vicarianist argue against Dispersalist, when Nothofagus is found on Oceanic islands which have never been connected to any other land

Answer 10

Vicarianist propose that there was a land bridge
However this is very unlikely, and the overall distribtuion of Nothofagus is likely due to both reasons

Question 11

What is Zealandia

Answer 11

Is it a mainly submerged tectonic plate
Zealandia seems to be continental crust which is unusually heavy

Question 12

What is rather special about the biota in New Zealand

Answer 12

New Zealand has very distinctive biota - unique flora and fauna

Question 13

Explain using Vicariance, why New Zealand has ended up with a highly endemic species population

Answer 13

Gondwana broke up into difference pieces - Antarctica, Australia and New Zealand (continental drift)
The same species originally from Gondwana ended up on all three places but went extinct on Antarctica and Australia due to their climates BUT not is New Zealand

Question 14

Explain using Vicariance and allopatric speciation, why New Zealand has such high levels of endemic species

Answer 14

• Continental drift means species which existed on Gondwana are now on Antartica, Australia and New Zealand
• This species dies out in Antartica, but due to the different selectionary pressures in Australia and New Zealand, new species then form - anagenesis

Question 15

Explain using Vicariance, Dispersal and allopatric speciation, why New Zealand has high levels of endemic species

Answer 15

• We have an Ancestor X, which ends up on Australia through Vicariance
• Here through allopatric speciation, a new species is formed and disperses to New Zealand
• The original species dies out in Australia and is only endemic to New Zealand

Question 16

What is a clade

Answer 16

Groups of species from a single ancestor

Question 17

How do we know if Vicariance or Dispersal has occured

Answer 17

• Fossil evidence (e.g. for Nothofagus) can prove Vicariance
• Genetics can identify clades which may indicate dispersal instead (using genome sequencing)
• The closer the genomes are, the more recent the splitting was

Question 18

What is a molecular clock

Answer 18

Uses mutation rate of biomolcules to work out the time when two or more life forms diverged
The biomolecular data used are normally nucleotide sequences for DNA or amino acids sequences for proteins
We use bits of the genome which are not under selectionary pressure - mitocondria for example
Used to estimate times for speciation/radiation

Question 19

Why is there differences is dispersal rates between plants and animals

Answer 19

It is easier for plants to disperse due to the small distances between land masses
High dispersal rates are likely to be higher