L22 - Panama

Question 1

What is the Isthmus of Panama?

Answer 1

• Dry land connection between North and South America.
• First complete link between the Americas since the breakup of the Pangaea.

Question 2

How was the Isthmus of Panama created ~3Ma?

Answer 2

• Complex movements of Caribbean plate tectonics in different directions
• Creation of mountains & volcanoes at plate boundaries
• Created a barrier to trans-oceanic circulation

Question 3

What were the changes to ocean circulation?

Answer 3

• Circum-tropical circulation of warm water is blocked
• Warm current then deflected north in Atlantic

Question 4

What were the implications of these circulation changes?

Answer 4

• Increased temperature difference between warm Caribbean/Gulf of Mexico and cool Pacific.
• The deflection of Gulf Stream increases moisture in northern latitudes = snow and glaciation.

Question 5

What were the direct and indirect effects of Isthmus of Panama on the biological systems?

Answer 5

• Direct:
  
  • Land bridge as a barrier to dispersal (oceanic dispersal)
  • Land bridge as a corridor for dispersal (land dispersal)
• Indirect:
  
  • Climatic changes, geological changes lead to subsequent changes in distribution, ecology

Question 6

What are the lines of evidence for the closing of Isthmus?

Answer 6

• Changes in trade winds’ patterns, upwellings’ patterns and nutrients concentrations
• Fossils
• Shell formations

Question 7

What was a consequences of the isolation of marine biota?

Answer 7

Speciation

Question 8

What were the two types of environments created following the barrier?

Answer 8

1. Pacific:
   - deeper waters.
   - movement of nutrients, recycling of nutrients.
   - food chains due to energy sources.
   - high production due to high nutrients.
2. Caribbean:
   - shallow waters.
   - high diversity.
   - low nutrients.
   - construction = slow biological material created.

Question 9

What was the fauna of North and South America before Isthmus?

Answer 9

• Both continents had diverse fauna of large and small mammals, birds…
• All usual terrestrial niches were filled
• But the species filling these niches in North America were almost entirely different to the ones in South America

Question 10

What is convergent evolution?

Answer 10

• Unrelated species subject to similar environmental and ecological conditions will evolve to resemble each other
• Selective pressures will promote certain traits and eliminate others

Question 11

What are heralds and legions?

Answer 11

• Heralds: early colonizers - island hopping
• Legions: main invasion group - walkers and crawlers

Question 12

What is the aftermath of the exchange of species between North and South America?

Answer 12

• At least 50% of South American mammals are descendants of ancestors that came from North America.
• Several extinctions in South America mammal fauna due to competition & predation.
• Birds, reptiles, amphibians not as affected.

Question 13

What are new barriers between North and South America?

Answer 13

• North and South America have very different vegetation patterns (rainforest, cloud forest vs grassland, desert or scrub forest).
• Isthmus is no longer a complete barrier: Panama Canal completed in 1914, mainly to move ships through