Unit One Evolution and Animal Diversity 05 14 2012 Introduction to Evolution and the Scientific Process Evolution by Natural Selection o Nylon 1935 invented A novel non organic material 1975 nylon eating bacteria discovered o Malaria Kills 3 million each year 17th century Quinine 20th century Chloroquine 21st century Quinine and others o Show things develop across time evolution of resistance o Evolution Mean change literally unfolding Charles Darwin evolution is descent with modification Process Contemporary species have arisen from a succession of ancestors Mechanism natural selection Darwin famous for Species has branches which branch off from the original ancestral line Natural selection a population of organisms can change over successive generations if individuals having certain heritable traits that make them more likely to survive and successfully reproduce leave more offspring than organism with traits that hinder their existence Evolution of super bugs If Variation individuals in a population a group of organisms of the same species living together in the same geographic area vary in character values Differential Fitness relative ability of an organism to survive and reproduce individuals with different character values have different propensities to survive and reproduce Selection the frequencies of individuals with different character values will change Inheritance the character values of parents and offspring are correlated Then And if Then Evolution Frequencies of individual with different character values will change between generations Additional conditions Struggle for existence many more individuals must be born than can survive for this process to work efficiently EX Beetles Variation different colors Differential fitness predators eats individuals with certain traits i e white Selection environmental pressure mostly non white beetles left Inheritance reproduction of survivors Evolution next generation of beetles has higher frequency of traits that enhance survival and reproductive fitness higher differential fitness Evolution is a historical process and does not entail Directionality Unfolding of any predetermined patterns Inaccurate Evolution is JUST a theory The common use of the term theory implies speculation or assumption that has not been verified or has limited proof The scientific definition of a theory is a set of statements devised to explain a group of facts or phenomena has been repeatedly tested is widely accepted and can be used to make predictions about natural phenomena Law an established principle thought to be universal and invariable based of empirical evidence Darwin s accomplishments Establishing the fact of evolution Proposing a theory of natural selection to explain the mechanism of evolution Is there a conflict between evolution religion Can coexist Religion doesn t belong in science class because can t be tested with the scientific Evolution deals with the origin of species NOT the Evolution was around before Darwin he put the theory together Darwin s theory requires Time for gradual change to occur over Ever present mechanism is now and has always been operating Many more individuals born than survive Variation population thinking Characters are heritable later demonstrated by Mendel Buffon process origin of life History Studied fossils and suggested similar environments different regions have distinct plants and animals Earth is older than was thought iron cooling Similarities between particular fossils and living animals but not exactly alike Concluded that types of animals not created for specific types of environment Earth much older than 6 000 years Fossil forms are ancient versions of living species Lamarck Suggested explanation for Buffon s finding was live evolved Hypothesis Progress towards increasing biological complexity evolutionary process caused by acquired inherited characters mechanism incorrect Hutton Lyell Malthus Uniformatarianism the same natural laws and processed that operate today have always operated in past and apply everywhere in the universe Gradualism small changes over long periods of time can have big results Interested in population sixe and its increase or decrease in response to various factors Populations SHOULD grow exponentially but there are malfusion parameters food sources water etc which checks human population growth when widespread mortality occurs Wallace Darwin Decided Malthus theories must also be true for other organism Asked what allowed some to survive 5 year journey on the HMS Beagle Galapagos Islands had specific animal species with slight variations May or may not have borrowed from Wallace Achieved four things o Documented the fact of evolution beyond reasonable doubt o Proposed natural selection as the first plausible explanation for adaptation o Introduced population thinking to biology o Presented testable hypotheses See lecture slides for summary of history Microevolutionary Processes Microevolution small o The change in gene frequencies of a population from one generation to the next o Often associated with adaptation Macroevolution big over many generations o Major changes in history of life o Origin of new species o The descent of different species from a common ancestor Microevolution change of gene frequencies over time o Gene frequency the frequency of occurrence of an allele in relation to that of other alleles of the same gene in a population o Population o Adaptation o Analyzing gene frequencies Allele an alternative form of a gene Gene a discrete unit of hereditary info consisting of a specific nucleotide sequence in DNA Genotype the genetic makeup of an organism Phenotype the expressed trait of an organism o H W Equilibrium when a population is NOT evolving Allele and genotype frequencies do not change over generations o Types of natural selection Directional selection end of a trait range Stabilizing selection Natural selection that favors individuals on one Natural selection that favors intermediate variants by acting against individuals with extreme traits stabilizes mean Diversifying selection Natural selection that favors individuals with extreme over intermediate trait values Could be beginning process leading to speciation two new species Sexual selection Natural selection on traits related to obtaining mates for sexual reproduction Genetic drift a change in the gene frequencies of a population from one generation to the next due to chance operates more often
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