Chapter 16: Evolutionary Theory Section 1: Developing a Theory Evolution: Artificial Selection: Evolution: I. A Theory to Explain Change Over Time B. Charles Darwin C. Theory: D. Modern evolutionary theory began when Darwin presented evidence that evolution happens and offered an explanation of how evolution happens Like most scientific theories this keeps developing and expanding II. Darwin s Ideas from Experience A. In Darwin s time most people did not think organisms or the Earth had changed B. C. 1
D. The Voyage of the Beagle Darwin collected evidence on a global voyage c. Galapagos Islands Collected several species of finches 1) 2) 3) Noticed species of plants and animals were similar to what he found in S. America 1) Determined species on Island were descended from species that came from S. America 2) Decent with Modification a) Idea that all finches descended from one ancestral finch and were changed due to the food they ate E. Years of Reflection Continued to study his findings and other sciences F. Breeding and Selection Darwin s insight If find a specific trait they like they can produce more individuals that have desirable traits c. Artificial Selection 1) Process of selecting desirable traits by humans not by nature 2
III. Darwin s Ideas from Others A. Darwin was influenced by ideas from numerous fields 3. B. People who influenced Darwin 3. 4. C. Lamarckian Inheritance Organisms change over time as they adapt to changing environments 3. Had incorrect idea a) b) i.e. Person s muscles may decrease or increase in size due to use or disuse - Lamark thought offspring could inherit this change D. Population Growth Food supplies were increasing linearly number of people was increasing exponentially 3. 3
All kinds of populations produce more offspring than can survive E. Geology and an Ancient Earth Geology 3. Cuvier argued that fossils in rock layers showed differences in species over time Did not see species changing gradually over time thought changes occurred suddenly 4. Hutton and Lyell geologic processed work gradually and constantly Section 2: Applying Darwin s Ideas Natural Selection: process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals Adaptation: Fossil: Homologous: describes a character that is shared by a group of species because it is inherited from a common ancestor I. Evolution by Natural Selection A. 4
B. Natural Selection Evolution is a change in the inherited characteristics of a population from one generation to the next C. Steps of Darwin s Theory Theory of Evolution by Natural Selection Overproduction 3. Variation 4. Selection In given environment, having a particular trait can make individuals more or less likely to survive and have successful offspring 5. Adaptation D. Selection and Adaptation Darwin s theory explains why living things vary in form yet fit their environment 3. Each species evolves because of the selection of those individuals that survive 5
4. 5. E. Publication of the Theory Darwin s Book: II. What Darwin Explained A. The Fossil Record B. Biogeography Study of the locations of organisms around the world Find geography separates populations C. Developmental Biology Ancestry of organisms evident in ways multicellular organisms develop from embryos Embryology D. Anatomy Homologous structures are characteristics that are E. Biochemistry Evidence of hereditary relationships among species in proteins and amino acids 6
Section 3: Beyond Darwinian Theory Speciation: I. Darwin s Theory Updated A. Discoveries since Darwin s time, especially in genetics, have been added to his theory to explain the evolution of species. B. Some parts of Darwin s theory have been modified, and new parts have been added. But mostly, Darwin s theory has been supported. C. D. Survival and reproduction can be limited by chance or by the way that genes work E. Natural Selection F. Migration Migration can change the numbers and types of alleles in a population. 3. Mate Choice Parents are paired up randomly in a population, a random assortment of traits will be passed on to the next generation. G. Mutation H. Genetic Drift 7
Some alleles may become more or less common in a population, especially in a small population. I. Coevolution A. Organisms are part of one other s environment Species that live in close contact often have clear adaptations to one another s existence. J. Adaptive Radiation A. As this splitting repeats, one species gives rise to new species The process speeds up when a new species enters environment that contains few other species K. Extinction Few of their descendants survived and evolved into the species present today L. Graduated Equilibrium M. Punctuated Equilibrium Species remain stable for long periods until environmental changes create new pressures 3. 8