The Galápagos Islands

Comprehension Activities


It’s home to the world’s only swimming iguanas… fish-eating snakes… and some little birds that changed the course of science. This is your Squiz Kids Shortcut to the Galápagos Islands —the podcast where we dive into the who, what, when, where, why and how of the big news stories. I’m Amanda Bower.

And I’m Bryce Corbett.

Bryce, way back in September 1835, a boat full of English explorers called the Beagle arrived at a rocky collection of islands in the middle of the Pacific Ocean. On board was a young scientist called Charles Darwin, and his observations of those islands would forever change our understanding of life on earth.

Today, we’ll take you through WHERE the Galápagos Islands are; WHY they are so important to science; and WHAT incredible creatures you’ll find there.

Listen carefully – there’s a Squiz at the end!

The Galápagos Islands are in the middle of the Pacific Ocean, about 1,000km off the coast of the South American country of Ecuador – and belong to Ecuador. Bryce, you may know this already – the word “Ecuador” means equator in Spanish. I’ll put a map in your episode notes – you’ll see that the equator runs right through the northern part of Ecuador, and if you follow it east across the Pacific, you’ll get to the Galápagos Islands.

The equator, of course, is the imaginary line that runs around our planet. If you imagine spinning the Earth like a beach ball, with the north pole on top and the south pole on the bottom, the equator runs around the exact middle – it’s the same distance from the equator to each pole.

Not only does the equator run through the Galápagos, but three major tectonic plates meet underneath the islands, at the bottom of the ocean. As we learned in our Shortcut to Earthquakes and Volcanoes, when the edges of the 17 tectonic plates that make up the earth’s outer shell move apart, or push against each other, volcanoes can emerge or erupt. All of the 127 islands in the Galápagos were formed by volcanoes.

So if an underwater volcano erupts enough, the lava that comes out will eventually rise up out of the water and create islands?

Exactly. Now compared with other volcanic islands in the world’s oceans, the Galápagos are just babies. I mean, in geological terms… the biggest and youngest of the islands are less than one million years old, and the oldest are no more than 5 million years old. When those islands were first created, they had absolutely no life on them. The process that got the plants and animals living there today is WHY the islands are so important to scientific history.

So Bryce, the Beagle was sent out from England to map the east coast of South America. Charles Darwin was on board as a geologist – someone who studies the physical structure of the Earth. But he was also very interested in animals and plants, and he’d been collecting a lot of specimens during the four years the Beagle had already been underway. When he arrived at the Galápagos in September 1835, Darwin was fascinated. He wrote in his notebook:

“It seems to be a little world within itself; the greater number of its inhabitants, both vegetable and animal, being found nowhere else”

Now it was a long intellectual journey for Darwin to go from collecting specimens to coming up with his theory of evolution, and I’ve put links in your episode notes if you’d like to explore it in greater detail. But essentially, what Darwin realised, along with the help of some other people, was that the plants and animals of the Galápagos had the same ancestors, which had come to the islands by swimming, or being carried in the ocean currents on rafts of plant life, or blown there by the wind. But when they landed on different islands, they’d evolved into different species, based on the environment of those islands. The animals that were the biggest help in him realising this were some sweet little birds, called finches.

Now at first glance, the finches of the Galápagos all look alike.

That’s right. Darwin observed 13 species of finch in the Galápagos, and they were all very similar in shape, size, and colour. But he noticed that each bird’s beak was different… and, importantly, that they all had different diets. Darwin figured that they’d all started out as the same bird – probably a South American grassquit – but a process called natural selection had led to them evolving as different species.

Natural selection is now accepted science, but at the time it was a new notion. Give us the basic gist of how it works, Amanda.

Okay. Every now and then, some animals are randomly born, or plants randomly grow, with a genetic difference. They might be a different colour; or shape; or size. But every so often, that random difference turns out to give the animal or plant an advantage in their environment.

Aha! So in the case of the finches, the change in their beak shape meant they could get to the specific food available on their island more easily.

Exactly. And because of that advantage, those finches got more food, which meant they were more likely to survive, and therefore were more likely to have babies. Those babies inherited that same difference… and so they were able to get more food… and were more likely to survive… and have their own babies. That process continued, until ALL the finches on that island had that new characteristic. And that’s how a new species evolves.

So from one common ancestor, there were now 13 different species of finch.

Yep! My favourite is the Vampire finch, which evolved to have a sharp, pointy beak. It pecks at bigger birds until they bleed… and then drinks the blood.

Love it! So WHAT are some of the other interesting animals to have evolved on the Galápagos Islands?

I think we should start with the marine iguana. Scientists figure that land iguanas from South America must have drifted out to sea millions of years ago on logs or other plant life, eventually landing on the Galápagos. But the best source of food on those brand new islands was underwater algae and seaweed… so they evolved to have a flattened tail to help them move like a crocodile through the water. The Galápagos islands are the only place in the world to have swimming iguanas.

Now Darwin wasn’t very kind when he first described them, was he?

“They are hideous-looking. The most disgusting, clumsy lizards.”

Okay, fine, they may not be pretty, but they have amazing adaptations! As well as that tail for swimming, they’ve evolved to have short, blunt noses and small, razor-sharp teeth to help them scrape the algae off rocks. And they’ve evolved to have dark colouring, so they can absorb sunlight after swimming in the freezing cold Galápagos waters.

And they’ve even evolved to be able to clean their blood of extra salt, which they eat while feeding in the water.

And get this: they’re believed to be the only species in the world that actually gets shorter when food is scarce. The smaller it shrinks, the less food it needs, the greater its chance of survival.


Then there’s the land-based racer snake, which on the island of Fernandina has evolved over time to be able to swim. No other land snake in the world has been observed swimming and catching fish to eat!

But the most famous animal is the one that gave these islands their name.

That’s right. Galápago is an old Spanish word for tortoise, and about two million years ago, giant tortoises arrived on the islands from mainland South America. They evolved into 14 different species on the islands … the ones that live on islands with lots of plants growing on the ground have dome-shaped shells, but giant tortoises on islands with less food have an upward curve to their shell, allowing them to stretch their head up to reach higher growing plants.

Now, didn’t sailors back in the bad old days capture those turtles and take them away on their ships?

Sadly, yes. One of the Galápagos giant tortoise’s adaptations is that they can survive for up to a year without food or water. So the sailors would take them on their long voyages, and kill them later as a source for fresh meat. Nowadays, the tortoises are also under threat from animals introduced to the islands by humans: rats, pigs and ants eat tortoise eggs; feral dogs attack adult tortoises; cattle and horses trample nests; and goats compete with tortoises for food.

Of those 14 species, two have gone extinct.

That’s right. I was in the Galápagos about 20 years ago and I saw Lonesome George, who was called that because he was the last remaining Pinta Island Giant Tortoise. Sadly, attempts to breed him failed, and he died in 2012. The Galápagos islands and the waters around them are one of the biggest protected areas in the world, but in some cases, the damage has already been done.

This is the part of the podcast where you get to test how well you’ve been listening…
1. Which ocean are the Galápagos Islands in?
2. Which type of animal helped Charles Darwin arrive at his theory of natural selection?
3. What is the old Spanish word for tortoise?