Theory of Evolution What is evolution? A change over time; a change in species over time. Who was Jean-Baptiste de Lamarck? A French naturalist who was the first to recognize evolution. • He said things change over time. • He believed that organisms change because of an “inborn” will to change. • He believed that organisms could change their body structure by using or not using body parts • Lamarck was incorrect. Who was Charles Darwin? A British naturalist who developed the current theory of evolution by natural selection. • He traveled for 5 years on the HMS Beagle to South America, the Galapagos Islands and South Pacific • Darwin wrote the Origin of Species, in which he presented a lot of evidence to support his ideas of evolution. Who was Alfred Russel Wallace? A naturalist who gave Darwin his paper on natural selection. They presented their papers together at a scientific meeting. How Are We Doing? Who thought that an organism could ‘want’ something enough to evolve? Wallace or Lamarck. Who was the first to ‘write’ about natural selection? Darwin or Wallace. What is Natural Selection? A mechanism for change in populations. • it occurs when individuals with more favorable variations for a particular environment survive and pass on these traits • those without favorable variations are ‘selected’ to die What are the major points of natural selection? 1. Variations (differences among individuals of a species) exist within populations. 2. Some variations are more advantageous (adaptations) 3. Organisms produce more offspring than can survive. 4. Over time offspring of survivors will make up larger proportions of the population as those selected for death disappear. How Are We Doing? List two of the parts of the natural selection mechanism. Why does natural selection suggest one organism dies instead of another? Adaptations better for the environment or a random dying individual. Artificial Selection • Nature provided the variation, and humans selected those variations that they found useful. Adaptation • Any inherited characteristic that increases an organisms chance of survival. • Individuals that are better suited to their environment survive and reproduce most successfully. Known as Survival of the Fittest. Principle of Common Descent • All species living and extinct were derived from common ancestors. What are some of the supporting data for evolution? 1. Fossils • They are remains or traces of organisms that lived long ago. 2. Anatomy • Comparing body structures of living organisms. • Homologous Structures: structures in different species that have the same evolutionary origin. • Vestigial organs- small or incomplete organs that have no apparent function. 3. Embryo Development • Early stages in the development of some organisms also provide evidence of common ancestry. 4. Chemical Evidence (DNA) • By studying the sequence of amino acids in proteins we can see how closely related certain species are to each other. How are we doing? List 2 types of evidence supporting evolution. Gene Pool • Consists of all the genes, including all the different alleles that are present in a population. Section 16-1 Figure 16–2 Relative Frequencies of Alleles Sample Population 48% heterozygous black 16% homozygous black 36% homozygous brown Frequency of Alleles allele for brown fur allele for black fur Single Gene and Polygenic Traits • Single gene trait- controlled by single gene with two alleles. • Polygenic traits-controlled by two or more genes and alleles. Results in many different phenotypes and genotypes. Section 16-1 Figure 16–3 Phenotypes for Single-Gene Trait 100 Frequency of Phenotype (%) 80 60 40 20 0 Widow’s peak Phenotype No widow’s peak Generic Bell Curve for Polygenic Trait Frequency of Phenotype Section 16-1 Phenotype (height) Directional Selection • Individuals at one end of the curve have higher fitness than individuals in the middle or at the other end. Section 16-2 Figure 16–6 Graph of Directional Selection Key Directional Selection Food becomes scarce. Low mortality, high fitness High mortality, low fitness Stabilizing Selection • When individuals near the center of the curve have a higher fitness than individuals at either end of the curve. Section 16-2 Figure 16–7 Graph of Stabilizing Selection Stabilizing Selection Key Low mortality, high fitness High mortality, low fitness Birth Weight Selection against both extremes keep curve narrow and in same place. Disruptive Selection • Individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle. Section 16-2 Figure 16–8 Graph of Disruptive Selection Disruptive Selection Low mortality, high fitness High mortality, low fitness Population splits into two subgroups specializing in different seeds. Beak Size Number of Birds in Population Key Number of Birds in Population Largest and smallest seeds become more common. Beak Size What affects speciation? (formation of a new species) When two groups in a population become isolated from each other. 1. Geographical isolation: • When a physical barrier cuts a single breeding population in two 2. Reproductive isolation: When a barrier to interbreeding caused by varied breeding times. How Are We Doing? Reproductive and geographical __________ affects speciation. Does speciation take place rapidly? Yep or Nope. Distinguish between the process of adaptive radiation and convergent evolution (adaptive convergence) 1. Adaptive radiation • A type of evolution of many diverse species deriving from a single, ancestral species. 2. Convergent Evolution (Adaptive convergence) • A type of evolution in which unrelated species produce descendents with similar traits. How fast does evolution occur? 1. Gradualism • Showing a steady, slow and continuous change of one species into new species. 2. Punctuated equilibrium • The process that shows the rapid change of a species caused by the mutation of just a few genes. Gradualism vs. Punctuated Equilibrium How Are We Doing? What are the two models describing how long evolution takes? Gradualism/Punctuated Equilibrium or Adaptive/Convergent Radiation. Does evolution take a long time? Yes or No.