Evolution by Natural Selection What started Evolutionary Thinking Plato 428 348 B C Introduced the concept of eidos the idea that everything had This kind of thinking is called Typological Thinking Based on its own significance designed by a creator that was unchanging the Idea that species are unchanging types and that variations within species are unimportant Aristotle 384 322 BC Created the Great Chain of Being ordered types of organisms into a linear bluleprint Also called The Scale of Nature The Great Chain of Being was ordered from least to most complex species with Humans at the top Claimed that the components within species did not change through time Aristotle s Ideas still popular in 1700 s Claims Species are established types unchanging Some species are higher hierarchy based on complexity of that species comparison to others C O M P L E X I T Y on in Lamarck Proposed a theory of Evolution That species are not constant Based on The Great Chain of but alter through time Being Living organisms form from nonliving matter move up the chain generating larger more complex better species were developed during lifespan Simplest organisms were product of Spontaneous Generation These simple organisms evolve or progress causing them to Lamarckian evolution is radical in sense of continuously Believed species changed due to inheritance of traits that Example Believed when short necked giraffes stretched their necks during their lifetime causing offspring to have longer necks Darwin and Wallace Emphasized the process of change in species occurring because of Change happened when individuals with certain traits produced more Consists of individuals of same species that are existing in variations among individuals in populations offspring than others a same area at one time unimportant variation was the major role to understanding the nature of species Darwin claimed that rather than being Population Thinking Population Theory of Evolution by Natural Selection 3 reasons why Theory of Evolution by Natural Selection was revolutionary 1 Reversed the idea that species are unchanging 2 Switched Typological Thinking with Population Thinking 3 Was Scientific Created opportunity for prediction that could be tested Typological Thinking Population Thinking Darwin Published his Theory in a book called On the Origins of Species by Means of Natural Selection in 1859 Explained the diversity of all living things Repeatedly expressed evolution as decent with modification passing traits from parent to offspring o Created 2 predictions about the nature of species Species change over time All species are related by Common Ancestor EVIDENCE Fossil Record indicates Extinction of Animals Law of Succession Transitional Features and Forms Vestigial Traits Fossils Fossils were classified by relative ages based on consideration of rock formation Form Layers Younger layers on top of older layers Used this knowledge to organize fossils based on relative position within rock layers Creating a Geologic Time Scale an arrangement of named intervals called eons eras and periods that depicted major events in Earth s history Geologic Record showed that Earth was substantially older than advocates of special creation believed Radiometric Dating In late 1800 s radioactivity was uncovered Realized that radioactive decay The spontaneous transformation of an unstable atomic nucleus into a lighter one was a way to produce absolute ages in the Geologic time scale Able to come to the conclusion that Earth is 4 6 billion years old and the earliest life emerged from rocks dating back to 3 4 3 8 billion years ago Fossils showed evidence of Extinct Species Darwin suggested from this evidence of extinction that species are dynamic Extinction followed by Replacement Law of Succession common observation that extinct species were followed in the same region by alike species Darwin saw this as a support for common ancestry Transitional Features Links existing species Transitional Feature A trait in a fossil species that in between those of old and young species Example fossils that show a transition between aquatic animals with fins to terrestrial animals with limbs Support hypothesis that an ancestor used sturdy lobed fins to move in shallow waters then moved onto land s 4 Footed organisms Slowly became Tetrapod Vestigial Traits Vestigial Traits reduced or incompletely matured structure that has no function or reduced function BUT is similar to functioning organs or construction in closely related species Examples Tailbones in humans which help many other animals balance Wisdom teeth in humans eyeless and blind aquatic animals having eyelids goosebumps in humans which help similar species keep warm etc Homology Homology a similarity that exists in species descended from a common ancestor 3 Interacting Levels of Homology Genetic Developmental Structural Genetic Homology species Similarities in DNA sequence in different Shows that different species have DNA similarities Developmental homology Similarities in embryos of different species Structural Homology Similarity in adult form The three types of homologies INTERACT o Genetic homologies lead the establishment of developmental homologies which lead to the structural homologies seen in adult species Genetic Developmental Structural How does Natural Selection Work Darwin broke the process of evolution by natural selection down into four steps or postulates o Individuals in a population vary among others with their traits Think about humans Nobody looks identical exception of twins o Some of these traits can be inherited by offspring o Some individuals will produce more offspring than others o Individuals with certain traits are more likely to survive and produce more offspring Natural Selection happens when individuals with these traits produce more offspring than others Heritable variation leads to differential success in survival and reproduction Biological Fitness The ability of an individual to produce offspring relative to that of other individuals Adaption increases fitness