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1、Theory of evolution,Many ideas were out there to explain how species change over time but the first published was,Charles Darwin in the H.M.S. Beagle traveled the world for 5 years and made observations of living and fossilized plants and animals. Started to notice relationships among species Most s
2、ignificant stop- the Galapagos Found many unique species similar but different then those of the mainland. IDEA CAN SPECIES CHANGE OVER TIME?,Now that an idea was formed DARWIN had to collect evidence,For two decades Darwin worked and experimented and read and borrowed from Thomas Malthus. Malthus i
3、dea was that human population grows faster than food supply Darwin idea was that individuals struggle to compete in changing environmental conditions. Which individuals survive?,Natural selection,Mechanism for change in populations. In Nature organisms produce more offspring than can survive Due to
4、independent assortment in any population individuals have variations Individual with useful variations will survive Over time offspring with certain variations make up most of the population and may look nothing like their ancestors In Indonesia Alfred Russell Wallace reached a similar conclusion bu
5、t Darwin was the first to publish.,Interpreting evidence after Darwin,Much data has been gathered but as Humans have only been here a short time and what happened before us is subject to interpretation.,Evidence for Evolution,Adaptation is variation that aids an organisms chance of survival in its e
6、nvironment. Structural adaptations Mimicry Camouflage Physiological adaptations Fossils Anatomy Homologous structure - Analogous structure Vestigial structure Embryology- viruses Biochemistry- Modern approach,Mechanisms of Evolution,What was missing from Darwins theory? Genes Who evolves Populations
7、 or individuals? Natural selection acts on the range of phenotypes Evolution occurs as a population genes and their frequencies change over time Gene pool How much (percentage) of any specific allele in the gene pool is called Allelic frequency,Genetic equilibrium,When the frequency of alleles remai
8、ns the same over generations Does it evolve?,Changes in genetic equilibrium,Mutation -most lethal but some. Are useful Genetic drift- change of allelic frequencies by chance events can greatly affect small populations making recessive alleles more common than in the larger population, Gene Flow- Can
9、 be affected by movement into and out of a population,Three types of natural selection that act on variation,Stabilizing-favors average individual in a population,Directional selection,Occurs when Natural selection favors on of the extreme variations of the trait,Disruptive selection,Individual with
10、 either extreme of a traits variation are selected for.,Physical barriers can prevent interbreeding rendering a new species (speciation) can no longer interbreed,Geographic isolation- When a physical barrier divides a population Reproductive isolation Change in chromosome numbers and speciation Spec
11、iation rates Gradualism- slow change over time Punctuated equilibrium- rapid change,Patterns of evolution,Adaptative radiation,Divergent evolution- become more dissimilar over time,Convergent evolution Unrelated species occupy similar environments which have similar pressures which make them look similar,Review,http:/www.ptpleasantbch.k12.nj.us/bridge/genbio/evolutiontaxon.html,
