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Principles of Evolution What is evolution? The accumulation of inherited changes within a POPULATION over time. Population: group of individuals of 1 species that live in the same geographic area at the same time. Species: organisms with similar structures, function & behavior that can interbreed. How do we know thing have changed? Fossils Remains of dead organisms which are preserved in rock Fossils develop in different ways. Uniformitarianism The hypothesis that the earth developed slowly through natural processes. Index Fossils Certain organisms that characterize a large geographical area. Index Fossils Use fossil layers to date rocks: index fossils Other ways to date fossils Radioisotopes Emit radiation & change into different elements as they decay Radioactive Decay Break down of radioisotope Uranium – 235 = Lead – 207 Half Life Time required for ½ an atom of radioisotope to change into a different atom Jean Baptiste Lamarck Developed the hypothesis of “Inheritance of Acquired Characteristics” This hypothesis stated that parents could pass along their acquired characteristics to their off spring. Could this work? Jean Baptiste de Lamarcke: Arranged all animals in a graduated sequence, beginning with mammals and working in order of decreasing complexity to to reptiles, fish, invertebrates, and eventually down to the polyps. This hierarchy represented the sequence of evolution, beginning with the simplest animals and proceeding, through small modifications, to produce all animals. He suggested four laws to explain why and how animal life might change: 1) The life force tends to increase the volume of the body and to enlarge its parts; 2) New organs can be produced in a body to satisfy a new need; 3) Organs develop in proportion to their use; 4) Changes that occur in the organs of an animal are transmitted to that animal's progeny. Males battle for females Charles Darwin (1809–1882) One of the best known figures of evolution. His famous trip on the H.M.S. Beagle gave him the data and background to form his hypothesis. Darwin Proposed that all species currently living on our planet arose from earlier ones by a process of gradual evolution. Natural Selection The process by which certain individuals have traits that make them more likely to reproduce. Natural Selection Modifies Populations Over Time Descent with modification. What does artificial selection do? Artificial selection is human-controlled breeding that is used to modify organisms. These cole crops are all the same plant species. Brassica oleracea has been bred to accentuate different traits: Leaves, roots, flowers, stems 4 Premises of Evolution by Natural Selection 1. Variation 2. Heredity 3. Differential Reproductive Success • Limits on Population Growth – Thomas Malthus 4. Population gene frequecies change Modern Synthesis (Synthetic Theory of Evolution) Combines Darwin’s theory of evolution by natural selection with modern genetics. Genetics explain how populations adapt to their environment. 5 Biological Measures of Evolution 1. Homologous Structures. 2. Homoplastic Structures 3. Vestigial Structures 4. Embryological similarity 5. Modern biochemical and genetics HUMAN CAT Humerus Homologous Structures Radius Ulna Carpal Metacarpal 1 1 Phalanges 5 4 3 2 54 3 2 Which of the following structures is NOT homologous to the others? 1. Alligator forelimb 2. Bird wing 3. Human arm 4. Insect wing 5. Bat wing Homoplastic Structures Different structures serve the same function These structures are known as Analogous Structures Convergent Evolution When populations with separate ancestors adapt in similar ways to similar environmental constraints. Vestigial Structures The existence of species of flightless birds with wings suggests that 1. they are not related to flying birds. 2. they are descended from flying birds. 3. they are ancestral to flying birds. 4. they are descended from a different group of dinosaurs than are flying birds. 5. birds did not evolve from dinosaurs. Embryonic Development Vertebrate embryos similar in the 1st stages Ancestral vertebrates possessed genes that directed development & genes still present. Biochemical & Genetic Relationships Molecular Structure Classification Nucleotide sequences of DNA (aka genotype) can be used to investigate relatedness. DNA sequencing of slow evolving genes works well for comparing distantly related organisms Structure of the chromosomes can also be examined, as well as chromosome number. The genetic code is common to virtually all organisms. Two important points of evolutionary changes: 1. The variations are produced by chance mutations. New variations can be good, bad, or neutral 2. Natural selection selects for organisms that are the best adapted to a particular environment. Can be bad if environment changes!!! What are mutations? Mutations are changes in the DNA sequence. Mutations are very rare!!! Mutations are NOT goal directed. If mutations are rare, how do they affect evolution? Changes in DNA result in a change in the genes that are expressed in an organism. New genes allow for new variations in a population on which evolution can work. Antibiotic Resistance Evolves by Natural Selection Some strains of bacteria are naturally resistant to antibiotics Natural selection acts on individuals, while populations are changed by evolution. Evolution is a change in the genetic makeup of a population. (NOT SPECIES!) Evolution is not always good or beneficial Most commercial pesticides are effective for only 2-3 years. This is because 1. new pests invade the area. 2. the chemicals induce mutations that convey immunity. 3. the chemicals mutate. 4. the pests learn to ignore the chemicals. 5. those pests with advantageous mutations will survive and reproduce. Evolutionary (Phylogenetic) Trees Used to show relatedness between groups (or individuals) of living things Common ancestor (A and B) Common ancestor (A, B and C) Phylogenetic Trees Most trees are MONOPHYLETIC Monophyletic Trees contain all of the living descendants of a common ancestor. Exception to Monophyletic Tree Reptiles aren’t monophyletic, because their current classification does not include the birds. Key Terms Taxonomy: science of "naming" organisms based upon relatedness Evolutionary Taxonomy: individual characteristics were used to determine relatedness Cladistics: classes of characteristics (shared derived features) are used to determine relatedness Cladistics Why aren’t reptiles considered to have a monophyletic grouping? 1. There is more than one type of reptile. 2. Crocodiles and turtles are not from the same ancestor. 3. They do not contain birds, which are from the same ancestor. 4. They do not contain frogs, which are from the same ancestor. 5. Nobody likes reptiles. Some Applications of Evolution Agriculture: evolution of pesticide resistance in insects and other pests Medicine: rapid evolution of disease-causing bacteria and viruses Conservation management: uses evolutionary principles of population genetics for rare and endangered species Bioremediation: evolution of oil-eating microorganisms in that can be used for clean-up after oil spills