Mar 26, 2018 in Case Studies

Galapos Islands as a Result of Volcanic Eruptions

Galapagos Islands, also referred to as Isla Encantadas are about 1000 km West of Ecuador. Volcanoes led to the formation of the Galapagos Island. The principal Islands came up from volcanoes, where the lava-flows project from the water. The giant volcanoes have impressive caldera on the summit. In geological terms, the highlands are young as the oldest is about 3-5 million years old. The shield volcanoes from the lava flows form a high point with gentle slopes. Charles Darwin explored Galapagos Island in 1831. After he "discovered" the islands, the attention of the world shifted to them and since then scientists have discovered many fascinating things. The greatest question is how the different species of plants and animals ended up in the islands. The Island has a wide range of biodiversity like an array of bird species, giant tortoises, sea lions, penguins, fur seals, and many plant species.

The most fascinating thing is the giant tortoises, which never drift away with ocean currents. During the rainy season, rafts of vegetation cut off and float on the seawater, and this made different plant species reach the islands. Light spores of a number of lower plants reached the Islands probably by wind, alongside the higher plants with lighter seeds. Plant seeds with hooks probably attach to the bodies of birds and get a free ride. Tiny land snails, spiders, and small insects also can reach the islands by wind.

Charles Darwin’s Galapagos finches consisted of an approximately fifteen species of birds, called the passerine birds. The dull-colored birds belong to the sub-family of Geospizinae, but no one has known its family. They are relatives of the true finches, and they inhabit only the Galapagos Islands. The finches range in sizes from 10-20 cm and weight of 8-38 grams. The Warbler finches are the smallest while the largest are the Vegetarian Finches. The differences, which exist among species, are in shape and size of the beaks, which adapt to different food sources. Besides the finches, Darwin’s opinion on fauna altered further when he encountered some giant tortoises moving along well-beaten tracks to their watering points. The three different types of plants and animals in Galapagos are native, endemic and introduced species. Endemic animals are like the marine iguana, native are in Galapagos and other places like the Frigate bird while the introduced got there through humans accidentally or intentionally, like the goat. The Island has a low biodiversity since it is far from the main land. The mammals in the Island are the rodents, bats, sea lions, whales, blackfish and dolphins. A part from Iguana lizards, other reptiles are lava lizards, harmless snakes, and geckos. Birds consist of the finches, frigate birds, gulls, pelicans, boobies, albatrosses, and Galapagos hawks.

Owing to the ecological pressures in the Island, organisms developed some unique features, which enable them to survive. The Islands species look more docile than their mainland counterparts do. Alternatively, the island species can grow smaller or larger like the case of giant tortoise, a situation known as island gigantism. After immigration, some reptiles, mammals, and birds grow larger and predatory, exhibiting intra-specific competition, where members of the same species actively compete for limited resources. In the case of mammals, large species decrease in size, while small species increase in size, an "island rule," which act to minimize energy expenditure. Other animals are poikilothermic, meaning they portray a withdrawn anti-predator behavior, low sexual selection in animals or loss of herbivore defenses, and a slow dispersal rate in plants.

The Ecosystem of Galapagos Islands

The ecosystem is unique since the plant and animal communities show some distinctive features like those of the finches. It is the ecosystem, which brings about variation, leading to evolution of species in order to adapt fully to the environment. The emergence of new islands and eventual isolation from the rest and the mainland provides unoccupied ecological niches, which species adapt. The fact that immigration of competitors and predators is persistent, most organisms can persist in the new niches, leading to high endemism, a situation where organisms are unique to an area, for instance, the islands have areas, which are endemic to birds. The adaptive radiation results in endemism. In this case, a single species inhabits or colonizes a locality then rapidly diversifies, eventually occupying available niches. A well-documented evidence of adaptive radiation is the finch species in the Galapagos Islands. The finches demonstrated adaptive radiation, when they evolved different beak sizes to exploit different types of seeds, which were in different Islands. The distributions of these individuals are just in the highlands, and are few compared to other bird species in the mainland, leading to lower genetic variation. The highland species, therefore, suffer the risk of extinction (Benz 83).

The survivals of species in the islands are due to such factors like natural selection, natural disturbances like volcanic eruptions and hurricanes, genetic variation, and human disturbances like habitat loss. Human disturbances are normally severe, and they can lead to extinction. Evidence from close continents supported the evolution of species across the islands. The compelling evidence from Darwin from the Galapagos Island confirmed this fact. Darwin evidence confirmed species evolve by natural selection in the sense that the variants that have better adaptation to the environments are likely to survive, reproduce, and pass down their genes to the next generation.

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On the animal behavior, Darwin and many other scientists demonstrated that the natural selection and random variation of organisms make them adapt to new habitats. This eventually affects their behavior like reproduction and sound production among the birds. Some of the noticeable features of birds are making homes in the cracks on the islands grounds. The bird predators also have a trick of waiting for their prey at the exit in order to capture. The giant tortoises also follow some paths to the watering points, and they can float on water, but cannot drown as a type of behavioral adaptation.

The predator snakes catch their prey and constrict them. This is because the Island’s snakes are not poisonous. The Galapagos hawks have good eyesight and then waylay the birds as the exit from their shelters then catch them with powerful claws and kill with the hooked beaks. The Galapagos penguins hunt small fish and crustaceans, and this foraging is normally at night. Under the water, the penguins can swim as fast as 40 km/hr, hence overpowering the prey. Most predators have better adaptations than their victims have, hence can easily capture them.

Conclusion

In conclusion, the Galapagos Islands came up because of volcanic eruptions, and it has a low biodiversity owing to its existing environmental pressures. Some of the endemic species in the Islands have some unique features, which are quite different from their counterparts in the mainland. The Galapagos finches, for example, have different types of beaks and are different with other birds from the mainland. The giant tortoise is also unique. The Galapagos ecosystems have led to variation of speciation, hence giving direction to evolution and speciation. Organisms undergo phenotypic changes in order to adapt well to the ecosystem. These changes affect their behaviors and the way of life. Predators like hawks, snakes, and penguins have significant adaptation of overpowering their prey.

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