2 What is Evolution?Evolution is the process of biological change by which descendants come to differ from their ancestorsIt is the central theme in all fields of Biology
3 Carolus LinnaeusDeveloped a classification system for all types of organismsOrganisms were grouped by similarities but also reflected evolutionary relationships
4 Georges Louis Leclerc de Buffon Proposed that species shared ancestors instead of arising separatelySuggested that Earth was much older than 6,000 years old which was the common belief at the time
5 Erasmus Darwin Charles Darwin’s grandfather Proposed that all living things were descended from a common ancestor and that more-complex forms of life arose from less-complex forms
6 Early misconception by Jean-Baptiste Lamarck (1809) Proposed all organisms evolved toward perfection and complexityUse and Disuse of Organs Theory—organisms respond to their environment by developing new structures as neededThe more an organ was in use, the bigger it would become and vice versaInheritance of Acquired Traits—these traits are passed on to offspringEx. giraffes
8 Lamarck cont.In order for groups of organisms to have adapted over time, populations must have evolved rather than individuals.
9 Charles Darwin ( )An English scientist who formed ideas that are now the basis of modern evolutionary theoryWhen he was 21, Darwin took an apprenticeship on a 5-year scientific voyage on the HMS BeagleHe was the unofficial naturalist on the ship collecting many specimens along the way
10 Darwin’s voyage (Page 277) Darwin's journeyThe Galapagos Islands, off the coast of Ecuador, became the focal point in Darwin’s observations
11 In 1859, Darwin published his theories and ideas in the book On the Origin of Species by Natural Selection
12 Variation is the difference in the physical traits of an individual from those of other individuals in the group to which it belongsCan occur either among members of different species (interspecific) or same species (intraspecific)
13 Darwin believed that variation arose when species adapted to their surroundings. An adaptation is a feature that allows an organism to better survive in its environmentAn adaptation can lead to genetic change in a population over time
14 Artificial selectionDarwin also conducted many breeding experiments with pigeons and found that organisms with specific traits could be crossed to result in offspring that had those selected traits; this is called artificial selectionHumans are the selecting agent in artificial selection
15 In order for—artificial or natural—selection to occur, the trait must be heritable. Heritability is the ability of a trait to be passed down from one generation to the nextNatural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.The environment (nature) is the selective agent
16 Four main principles to the theory of natural selection VariationIndividuals in a population have varying characteristicsOverproductionOrganisms tend to produce more offspring than can survive to maturityAdaptationThe traits of survivors will become more common in a populationDescent with modificationSurviving individuals tend to reproduce more than others
18 Overview of the Evolution Theory Variation exists within the genes of every population or species (as a result of random mutation)In a particular environment, some individuals of a population or species are better suited to survive (a result of variation) and have more offspring (natural selection)
19 Overview cont.3. Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population4. There is a clear proof from fossils and many other sources that living species evolved from organisms that are extinct.
20 Natural selection acts on phenotypes or physical traits, rather than on genetic material itself.
21 Evidence for Evolution Fossil RecordGeographyEmbryologyBody Structures (Anatomy)Biochemistry (Genes and Proteins)
22 Fossil RecordFossils of animals show a pattern of development from early ancestors to their modern descendants“Intermediate” (missing links) species show how organisms evolved new adaptationsFossil Evidence Examples
26 Problems with fossilsIt is difficult to find fossils of soft-bodied organisms with no hard parts that can be left behindOrganisms decay at different rates and may not leave any traces
27 Geography Shows similarities among species living on different areas “Descent withmodification”
28 EmbryologyMost embryos look very similar and have gill slits and tails.This suggests a common ancestor.
29 AnatomyComparing structures of related organisms to find relationships between organismsEx. Homologous StructuresComparing Primate SkeletonsComparing common structures between unrelated organisms to find how natural selection affects organisms in similar environmentsEx. Analogous Structures
30 Homologous Structures Have a common evolutionary originSimilar structure but different functions
31 Analogous StructuresStructures that are similar in function but do not have a common evolutionary originDifferent structures but similar functionsEx. Bird wing and an insect wingShows that different species evolved similar traits to overcome similar selective agents
32 Homologous structures versus Analogous structures
33 Vestigial StructuresA body structure that has no function presently but was probably useful to an ancestorEven though the species does not need the feature, the structure is still passed on to offspringEx. Eyes on blind mole-rats, flightless wings on an ostrich, appendix/tonsils on humans
34 BiochemistryAs organisms evolve, the differences in the amino acids, DNA, and proteins they make should change graduallyThe more amino acid differences there are between two organisms, the more distantly related they are