11/3/2023 0 Comments Facts about alfred russel wallace![]() It is difficult and time-consuming to document and present examples of evolution by natural selection. His book outlined in considerable detail his arguments for evolution by natural selection.įigure 2: Both (a) Charles Darwin and (b) Alfred Wallace wrote scientific papers on natural selection that they presented together at the Linnean Society in 1858. The following year Darwin’s book, On the Origin of Species, was published. In 1858, Darwin and Wallace (Figure 2) presented papers at the Linnean Society in London that discussed the idea of natural selection. It is the only mechanism known for adaptive evolution. Ultimately, natural selection leads to greater adaptation of the population to its local environment. This will lead to change in populations over generations in a process that Darwin called descent with modification. Because characteristics are inherited, these traits will be better represented in the next generation. Darwin and Wallace reasoned that offspring with inherited characteristics which allow them to best compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Third, offspring vary among each other in regard to their characteristics and those variations are inherited. Both Darwin and Wallace’s understanding of this principle came from reading economist Thomas Malthus’ essay that explained this principle in relation to human populations. Thus, there is competition for those resources in each generation. ![]() The capacity for reproduction in all organisms outstrips the availability of resources to support their numbers. Second, more offspring are produced than are able to survive, so resources for survival and reproduction are limited. Although no one, including Darwin and Wallace, knew how this happened at the time, it was a common understanding. First, most characteristics of organisms are inherited, or passed from parent to offspring. Natural selection, Darwin argued, was an inevitable outcome of three principles that operated in nature. Over time, only long-necked tortoises would be present in the population. Consequently, long-necked tortoises would be more likely to be reproductively successful and pass the long-necked trait to their offspring. In times of drought when fewer leaves would be available, those that could reach more leaves had a better chance to eat and survive than those that couldn’t reach the food source. These tortoises were “selected” because they could reach more leaves and access more food than those with short necks. This leads to evolutionary change.įor example, Darwin observed a population of giant tortoises in the Galápagos Archipelago to have longer necks than those that lived on other islands with dry lowlands. Natural selection, or “survival of the fittest,” is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. Darwin called this mechanism natural selection. Wallace and Darwin both observed similar patterns in other organisms and they independently developed the same explanation for how and why such changes could take place. He postulated that ancestral species’ beaks had adapted over time to equip the finches to acquire different food sources. For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey.įigure 1: Darwin observed that beak shape varies among finch species. Upon further study, he realized that each finch’s varied beaks helped the birds acquire a specific type of food. Darwin imagined that the island species might be species modified from one of the original mainland species. He observed that these finches closely resembled another finch species on the South American mainland. The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. For example, the ground finches inhabiting the Galápagos Islands comprised several species with a unique beak shape (Figure 1). On these islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences. Darwin’s journey, like Wallace’s later journeys to the Malay Archipelago, included stops at several island chains, the last being the Galápagos Islands west of Ecuador. Wallace traveled to Brazil to collect insects in the Amazon rainforest from 1848 to 1852 and to the Malay Archipelago from 1854 to 1862. Beagle, including stops in South America, Australia, and the southern tip of Africa. From 1831 to 1836, Darwin traveled around the world on H.M.S. Importantly, each naturalist spent time exploring the natural world on expeditions to the tropics. ![]() In the mid-nineteenth century, two naturalists, Charles Darwin and Alfred Russel Wallace, independently conceived and described the actual mechanism for evolution.
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