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Transcript
Evolution Concepts Evidence for Evolution I. Fossils – Physical Remains of Organisms Found in Sedimentary Rock Relative Dating – estimate age by comparing it to other fossils. Radioactive Dating – Use of ½ life to determine age of sample. II. Anatomical and Physiological similarities -- Homologous structures -- implies similar genes III. Embryological Evidence -- Similarities in early development -- implies similar genes IV. DNA Sequences – All organisms have the same four bases – A, T, C, G V. Analysis of Amino Acid Sequences with proteins VI. Geographic distribution of living species – common ancestor Adaptation – An inherited characteristic that increases an organism’s chance for survival. Concept – Organisms with a given adaptation are more likely to survive and reproduce, their genes will be passed on to the next generation. -- This increases the frequency of the gene that caused the adaptation. In this way, species change over time or evolve. -- ORGANISMS THEMSELVES DO NOT EVOLVE --If an adaptation separates one group within a species from another group in such a way that they can no longer reproduce, the two groups may become different enough for scientists to consider them separate species. This is the process of speciation. --Dominant alleles do not always lead to an advantage; sometimes being homozygous recessive for a trait is advantageous. -- An adaptation which helps an organism in one environment may not prove to be advantageous in a different environment. Natural Selection – the process by which organisms that are better suited to their environment are more likely to survive and reproduce, thus passing on their gens. Darwin’s Theory of Natural Selection has four basic principles: 1. Variations exist among individuals in a population. 2. Variations can be inherited. 3. More offspring are produced than can survive. 4. Variations that increase an organism’s chance of surviving and reproducing are more likely to be passed on to the next generation.