How Chapter 22 Descent with Modification A Darwinian View of Life Charles Darwin published The Origin of Species which ushered in a scientific revolution Evolution Descent with modification used by Darwin to say that current day species are descendants of ancestral species 22 1 THE DARWINIAN REVOLUTION CHALLENGED THE TRADITIONAL VIEWS OF A YOUNG EARTH INHABITED BY UNCHANGING SPECIES SCALA NATURAE AND CLASSIFICATION OF SPECIES Aristotle was a philosopher who believed that organisms were created as perfect for their environments unchanging Each form of life had its allotted rung on the ladder which was a scale of increasing complexity Carolus Linnaeus classified life s diversity by developing a two part binomial format for naming species e g Homo Sapiens IDEAS ABOUT CHANGES OVER TIME Darwin came up with his theory of descent with modification by adapting on the work of scientists studying fossils Fossils are found on sedimentary rock on the bottom of seas lakes and swamps New layers of sediment cover older layers of sediment and compress them into a layers of rock called strata Paleontolgy was developed by Georges Cuvier Cuveir noticed that older fossils were more different to current life forms than newer fossils Cuvier noted that each layer separating strata marked a sudden catastrophic event e g flood James Hutton proposed that Earth s geologic features could be explained by gradual mechanisms Charles Lyell stated that the same geologic processes are operating at the same rate today as in the past This influenced Darwin and led him to conclude that if geologic processes occur gradually then Earth may be older than a few thousand years LAMARCK S HYPOTHESIS OF EVOLUTION Lamarck proposed a new theory for evolution He compared living species with fossil forms and found several lines of descent He used the idea of USE AND DISUSE and INHERITANCE OF ACQUIRED CHARCTERISTICS USE AND DISUSE states that parts of the body that are used extensively become larger and stronger while the ones not used deteriorate THE theory of INHERITANCE OF ACQUIRED CHARCTERISTICS states that an organism could pass these modifications to its offspring This turns out to be incorrect as traits acquired by use during an individual s life are not inherited in the way proposed by Lamarck 22 2 DESCENT WITH MODIFICTION BY NATURAL SELECTION EXPLAINS THE ADAPTATIONS OF ORGANISMS AND THE UNITY AND DIVERSITY OF LIFE THE VOYAGE OF THE BEAGLE During this voyage Darwin explained the features of organism that made them well suited to such diverse environments He also found that fossils found in South America looked more similar to South American species than European species Also he notes that geologic evidence did not support the idea that Earth was only a few thousand years old Darwin concluded that Galapagos finches were finches that strayed from South America and adapted to each individual island DARWINS FOCUS ON ADAPTATION Darwin discovered many ADAPTATIONS inherited characteristics of organisms that enhance their survival and reproduction in specific environments He started thinking that an accumulation of adaptations could lead to the creation of new species He then decided to use his idea of adaptations to develop a theory called NATURAL SELECTION which states that organisms that tend to survive and reproduce at higher rates tend to do so because of their traits Darwin was the first scientist to develop a theory that had a plausible scientific mechanism THE ORIGIN OF SPECIES DESCENT WITH MODIFICATION This book amassed evidence that showed the unity of life diversity of life and match between organisms and their environments resulted from descent with modification by natural selection Darwin perceived unity in life and attributed to the descent of all organisms from a common ancestor that lived in the past Also Darwin concluded that as descendants lived in various habitats they gradually accumulated diverse modifications that fit their specific ways of life ultimately leading to the diversity we see today Darwin viewed the history of life as a tree with multiple branching s from a common trunk In his diagram the twigs with letters represent today s species while the unlabeled ones represent extinct organisms ARTIFICAL SELECTION NATURAL SELECTION AND ADAPTATION Natural Selection as a mechanism was used to justify Evolution Artificial Selection was used to justify natural selection Artificial Selection allows humans to selectively breed things for the traits they want e g Wild Mustard and various vegetables Nature undergoes a process very similar to artificial selection Darwin used two observations and inferences to justify natural selection His first observation was that members of populations vary in inherited traits Observation 2 is that all species can produce more offspring than their environment can support and many of these offspring die This leads to the survivors having a higher probability of passing on their genes and leave more offspring Ultimately this leads to an accumulation of favorable traits in the population over generations and thus the transformation Malthus stated that human suffering occurred due to the ability for populations to reproduce faster than the rate of food supplies and resources and Darwin used this to connect to natural selection as all species overproduce NATURAL SELECTION A SUMMARY Process by which organisms with favorable traits survive and reproduce at a higher rate than other individuals because of those traits Over time organisms become more adept to live in their current environments If environments change or a population moves to a new environment natural selection may compel populations to adapt new conditions and ultimately lead to new species 22 3 Evolution is supported by an overwhelming amount of scientific evidence DIRECT OBSERVATIONS OF EVOLUTIONARY CHANGE NATURAL SELECTION IN RESPONSE TO INTRODUCED SPECIES SOAPBERRY BUGS Feeds on seeds of native plants the balloon vine Balloon vines became rare Soapberry Bugs now feed on seeds of golden rain tree species introduced from Asia Soapberry Bugs feed most effectively when beak length closely matches depth at which seeds are found within fruit Golden rain tree fruit has seeds located closer to surface than Balloon vines Researchers predict that population that feeds on golden rain tree would lead to bugs having shorter beaks Correct Same experiment done with larger fruit bugs developed longer beak THE EVOLUTION OF DRUG