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Introduction to ecosystems
Introduction to ecosystems

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3.2 Darwin’s thoughts on the iguanas

The marine iguanas of the Galápagos are the only marine lizards and occur nowhere else. They occupy a fragile ecosystem that is very vulnerable to changes in sea temperature. There is also a species of land iguana on the islands.

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Activity 2

Why, do you think, is the marine iguana so vulnerable to sea temperature changes?

What impacts of environmental change might make the land iguana vulnerable?

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The marine iguana feeds exclusively on a small number of species of seaweed. The seaweed needs relatively cool water and in some years, when the ocean currents reverse, the seas around the islands get too warm for the seaweed and it dies back. The marine iguanas then have no food and die in large numbers. Any prolonged warming of the seas would make the species highly vulnerable to extinction. Land iguanas get most of their water from prickly pear cacti and the rest from rain fall. Any prolonged period without rain due to changes in climate put land iguanas at risk.