Darwin's Magic Island
During Darwin's circumnavigation of the globe, he reached an important island: the Galapagos Islands, west of South America, near the equator in the central Pacific Ocean. Tiny ground finches, huge tortoises, unique tropical penguins, iguanas shaped like small dinosaurs... Darwin found solid evidence of evolution in the archipelago, and Galapagos became famous for Darwin. On the occasion of the 150th anniversary of the publication of On the Origin of Species, let's follow in darwin's footsteps and set foot in the Gallapags Archipelago in search of the unique creatures there.
Tortoise Fortress
The bulky tortoises are the "big stars" of Galapagos animals, growing up to 1. 5 meters long and weighing nearly half a ton, it is the largest tortoise in the world. The first Spanish navigators to arrive here called the giant tortoise "Galapagos" and later simply called the entire archipelago by this name.
It's not easy to support a heavy body, and these continental tortoises have thick limbs like elephants, and they will stand slowly like lifts, and after standing firmly, they will slowly step forward. They often take a few steps to pause, look up at the surroundings, or simply lie down and rest for a while. Darwin once tested the speed of giant turtles, they can only walk 300 meters per hour, deducting the time to eat and sleep, giant turtles can only walk two or three kilometers a day.
Darwin loved these docile tortoises, sometimes even joking with them. The giant turtle's hearing is not good, it is not easy to detect the things behind them, but Darwin quietly approached from behind them, and then jumped in front of the giant turtle, frightening it to lie on the ground quickly, and its head was as small as possible into the shell. Young Darwin jumped on its back, stomped his feet, and the giant turtle would get up and move on. Darwin said in his notes that it was not easy to stand on the back of a turtle and maintain balance.
Vegetarian "live dinosaurs"
The dark reef on the seashore is suddenly moving! It moved forward a few steps, then "poofed" and jumped into the water. Slender body, short limbs, long tail is both a paddle and a rudder, swinging from side to side, swimming in the water very flexible and relaxed.
The marine iguana is a unique type of lizard, and Darwin called them more like "small crocodiles." Every morning, sea iguanas lie in groups on the reefs on the coast, basking motionless in the sun, and when they are warm, they jump into the water and dive to the bottom of the sea to eat the seaweed on the rocks. The diving skills of the iguanas are very good, they can stay in the sea for 40 minutes at a time, and they can be considered masters.
Darwin did not like sea iguanas very much, calling them fierce in appearance and dirty skin, but he still observed and studied sea iguanas - Darwin said that sea iguanas never make bites, and when frightened, they will drip a little liquid from their nostrils instead of jumping into the water to escape. The act of diving, just for food, is darwin's conclusion for the sea iguana. By dissecting the stomachs of sea iguanas, Darwin discovered that these unsightly reptiles, which only ate aquatic grasses and seaweed, had a rougher and more extensive digestive system than their terrestrial carnivorous relatives.
Museum of Evolution
On the land of the Galapagos Islands, relatives of the sea iguana live one by one. Land iguanas can grow to more than 1 meter, perhaps climbing and climbing more requires more strength, their body shape is much thicker than the sea iguana, and the weight can reach more than 10 kilograms. Darwin summed up two major characteristics of the life of the land iguana: drilling holes and herbivorous. Land iguanas usually do not stay away from their burrows, and their food is mostly plant-based. Sometimes you can see land iguanas clumsily climbing up cacti to eat tender and juicy leaves, and their coarse skin and flesh make the sharp edges used by cacti for self-defense useless.
Darwin believed that the magic of the Galapagos was that the sea iguana, land iguana and various turtle species were extremely abundant, and they occupied the main space. Nowhere else in the world did reptiles so bizarrely replace herbivorous mammals — this is Darwin's assessment of the importance of reptiles on the island.
Modern scientists have used the amino acids in hemoglobin for comparison and found that the galapagos marine iguana and the land iguana have a common ancestor: the green iguana from the South American continent. Scientists have deduced that about 5 million to 7 million years ago, there was a huge storm, a large number of trees on the South American continent were destroyed, they fell into the sea, drifted with the waves to the Galapagos Islands. On these trees, there are many animals such as land turtles and green iguanas.
Later in life, some green iguanas settled in the seashore, practiced swimming skills, and gradually adapted to the life of "sea and land amphibious", evolving into the current sea iguanas; Some green iguanas climbed the mountains and fed on cacti and other plants, becoming today's land iguanas. It is the existence of these unique species of independent evolution that once again provides conclusive evidence for evolution, and the Galapagos Islands have been evaluated as "living museum of biological evolution."
A big bird that flies over the world
When Darwin landed on the islands, he was impressed by the overwhelming number of birds. The most notable is the large warship bird. The frigate birds have a wingspan of up to 3 meters, named after their fondness to follow long-range warships, and they are one of the world's most flying birds, which can fly 1600 kilometers away from home to find food.
This bird, which can fly long distances on the surface of the sea, also has many special behaviors that attract attention. The most famous feature of the frigate bird is that during the breeding season, the male will inflate the throat sac and bulge into a bright red "balloon".
They use this method to attract the attention of females. In addition, the frigate bird has a bad habit: roadblocks and robberies. When other seabirds catch fish and are trying to fly back to the island to eat it, the frigate bird can attack in the air. The seabird was frightened, its mouth was loose, the fish fell from its mouth, and the frigate bird could immediately fly below to catch it.
It is the that are often bullied by the frigate birds. are slightly smaller, and in order to cope with the evil deeds of warship birds, they often go out in large groups, and when they encounter the enemy, everyone shouts together, which is enough to scare the other party away.
Penguins on the equator
Among the birds of the Galapagos Islands, the most unique and adorable are the penguins. penguin? That's right, there are the world's only penguins living in equatorial regions– the Galapagos penguins.
Penguins are often associated with the icy Antarctica, but the Galapagos, located in the tropical ocean, does have a unique penguin. They are less than half a meter tall and wear the iconic black and white "tunic" and are a small species in the penguin family.
Galapagos penguins are able to come to tropical islands thanks to ocean currents. The penguins traveled north with the Peruvian Cold Current and other ocean currents, and eventually stayed in the Galapagos Islands, and then gradually adapted to the local environment and settled on the island. Compared to their relatives in cold regions, Galapagos penguins are not as fat, and they do not need thick fat to withstand the cold. Nor are they like the penguins of Antarctica, which huddled together in large flocks to keep warm to each other. The little penguins here usually haunt alone and seem a little lonely. From their stature to their habits, these tropical penguins are another example of an environmentally modified species.
Darwin's confusion
When Darwin set foot on the Galapagos Islands, the real confusion came not from strange-looking creatures, but from some inconspicuous birds, a type of bird called "ground finches". Due to its petite size, it is impossible to fly continuously for thousands of kilometers on the sea, so the space for the finches is limited to the island.
Different species of ground finches have small differences in morphology, and these differences can only evolve slowly in the long-term island life. The ground finches that catch small insects have shorter and thicker mouths so that they can kill their prey at once when they hunt; ground finches that feed on flowers and fruits should have small and delicate mouths, which is conducive to reaching into flowers or branches and choosing suitable food. The length of the ground finches' feathers is related to the area where they live, and areas with strong winds or lack of food require stronger flight ability, and the wings of the ground finches here are stronger.
Food and living environment have created different shapes for different species of ground finches. This was a conclusion that disturbed and excited Darwin. Through the study of these birds, the most important idea of evolution was formed in Darwin's mind: it was not God who created these animals, but their "creators" were the islands themselves, and the adaptation to the environment was the power to produce new species.