The Galapagos

by
Nancy A. Schiller
Science and Engineering Library
Clyde Freeman Herreid
Dept. of Biological Sciences
University at Buffalo, State University of New York

Take five and twenty heaps of cinders dumped here and there in an outside lot;
imagine some of them magnified into mountains and the vacant lot the sea;
and you will have a fit idea of the general aspect of the Encantadas.
--Herman Melville

PART I - IN THE BEGINNING

Kate stood on the edge of the caldera and peered down into the shadows. She could barely make out the movement a thousand feet below. But there, she was sure, was the tortoise she had named Alfredo, slowly making his way among the lava rocks toward the water pool. All 500 pounds of him.

Kate marveled at the volcanoes around her. Before she had started this journey, she had read about the Galapagos and their volcanic origins. But she hadn't expected to be so emotionally moved by the islands themselves, by their stark scenery.

A young graduate student, she was about to embark on a four-year study of the biology of the longest living animals. Alfredo had been around long before Darwin had arrived in the islands--and here he was still, ambling among the lava.

The origins of the Galapagos were similar to the origins of the Hawaiian Islands, but the Galapagos clearly were younger, more stark and barren. Kate had read that the Galapagos were a chain of islands, some of which no longer broke the surface of the water. How were these islands formed, she wondered. Was it from a hot spot at the bottom of the ocean bubbling up magma at periodic intervals? Somewhere in the sea nearby in the Galapagos Rift there were hydrothermal vents belching sulphurous gases. Some biologists believed that these vents were the sites of the origin of life.

It had been a long-time dream of Kate's to visit the Galapagos Islands, and they hadn't disappointed her. Made up of 13 large islands and dozens of smaller ones, the Galapagos straddle the Equator in the eastern Pacific Ocean, some 600 miles off the coast of mainland Ecuador. Large, jagged outcroppings of lava alternated with small sandy beaches along the shorelines. Isolated patches of mangroves along the shore gave way to cactus in the arid lowlands of the islands, then lush cloud forests in the moist upper regions, and finally tree ferns and scrubby grasses in the otherwise barren uplands.

But it was the astonishing array of animals that took Kate's breath away. Like every other visitor to the islands, from the first Europeans to set foot on these shores to Darwin some 300 years later in 1835, she was struck by the strangeness and tameness of the fauna. On shore, scores of sea lions lazily sunned themselves on the beaches. Masked boobies courted practically under foot.

Among the rocks at the water's edge lived the black iguana, the only marine lizard in the world. In the surrounding seas were stingrays, white-tipped sharks, sea turtles, and the Galapagos penguin. Dozens of endemic species were found here and nowhere else on earth.

And here she was, standing where Charles Darwin had stood 150 years before. Darwin's theories of evolution had depended heavily on his insights into the origins of the life forms on the Galapagos. He had questioned where these animals had come from. How could the flora and the fauna of islands so near one another be so different and yet strangely so similar? Each island seemed to have its own variety of tortoise, its own type of marine iguana, even its own form of prickly-pear cactus.

The finches were particularly interesting. These relatively nondescript birds had beaks with amazing adaptations to eat different types of food. Although most of them were seed-eaters, Darwin had discovered that one of the finches had specialized by using small sharp sticks to probe the recesses of cactus plants for grubs. A woodpecker finch he called it. How could these animals and plants be due to simple creation? Wasn't it more reasonable to think that mainland species had arrived on the islands eons ago and became specialized for different environmental conditions on the different islands?

Kate knew the answers now to Darwin's questions, and yet the islands didn't seem old enough to account for the spectacular diversity she saw all around her. She knew that the Grants, the husband and wife team from Princeton University, were working on a nearby island to resolve the question of the speed of evolution. She had heard at the Charles Darwin Research Station that they had been impressed with the rapid changes that seemed to be brought about by the El Nino climate shifts in the last couple of decades. She resolved to look into this more closely. But right now she had to get back to the research station--gray storm clouds were closing in fast.

Study Questions

  1. How did the Galapagos Islands come into existence?
  2. Were plate tectonics involved?
  3. How old are the Galapagos Islands?
  4. What kinds of animals and plants are endemic to the islands?
  5. How do species become endemic?
  6. Where did the original colonists come from and how did they get to the Galapagos?
  7. What kind of special adaptations do the animals and plants have? How do adaptations evolve?
  8. How did these islands figure into Darwin's ideas on evolution?

References

Internet Sites

Image Credits::

Blue-footed Booby, Sea Lion, and Marine Iguana, photographs by Clyde F. Herreid. Used with permission.

GO TO Part II: The Galapagos: Darwin's Finches



Date Case Posted: 12/1/99 nas