Organic Evolution Natural Selection Scientific Explanations must be

Organic Evolution & Natural Selection

Scientific Explanations ► must be natural ► must be supported by available data ► must be testable & falsifiable ► subject to revision or refinement or negation ► should be predictive ► OE and NS meet all of these requirements

Student Concerns ► Theological conflict § natural cause vs. special cause ► Relationship of humans and animals ► Difficult/impossible to observe ► Only a “theory”

Science & Religion ► St. Augustine: He was concerned that if believers asserted religious explanations that contradicted experience with natural phenomena, potential converts would reject the spiritual message. ► Isaac Newton: Believed nature operates according to God’s laws. ► Stephen J. Gould: Separate magesteria.

Science & Religion ► Stances on Evolution vary widely ► Roman Catholic Church – no problems ► Lutheran Church ►ELCA – no problems ►Missouri Synod – no evolution, Earth is only a few thousand years old and essentially created as it appears today ► Need to ask

Theory & Hypothesis ► Hypothesis § a working explanation or “educated guess” § competing hypotheses are often investigated simultaneously ► Theory § the best explanation supported by a preponderance of the evidence § the best a scientist can hope for

Organic Evolution ► changes in life through time ► development of complex life forms ► development of a variety of life forms

Natural Selection ► mechanism responsible for organic evolution ► through mutation and selection ► survival of the § fittest (for a niche) § luckiest § combination

Terminology ► species - reproductively isolated group of living organisms ► population - all the members of a species living in an area ► community – all of the populations in an area ► habitat – organism’s physical location within a community ► niche – organism’s place (duties) within a habitat

Organic evolution: observations ► sedimentary rocks § deposited in layers § oldest layers are on the bottom § layers may be correlated with layers in other areas ► results § relative time scale § the Earth is very old

Organic evolution: observations ► fossil record § oldest rocks have only simple fossils § younger rocks have more organisms similar to those living today (at levels from species to kingdom) § fossils record includes appearances and extinctions of many species

Organic evolution: observations ► geographic distribution of organisms § many organisms are similar but unique § they are confined to specific areas (islands, continents, water bodies) § includes modern and fossil organisms § distribution has changed through time

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Organic evolution: observations ► anatomy § cell structure is similar in all living organisms § embryology - embryos of mammals, birds, and reptiles are very similar § homologus organs - similar organs, different functions § vestigal organs - no purpose in one, purpose in another

Organic evolution: observations ► genetics § structure of DNA and RNA is the same in all living organisms § similarity in genetic code varies between organisms (some organisms are more similar than others)

Organic evolution: observations ► cladistic analyses § statistical examination using ►anatomy ►DNA ►behavior § indicates strength of affinity between species

Organic evolution: conclusions ► the characteristics of populations of living organisms have changed through time § life has become more complex § life has become more diverse § all life is related ► this is accepted as a factual observation

Evolutionary trends ► divergence ► speciation & extinction ► convergent evolution ► phylogeny ► phyletic gradualism & punctuated equilibrium

Organic evolution: concerns ► What about “missing links” § the “link” between two fossil species OR between a fossil species and a living species § many found, yet none found § each “gap” filled creates two new “gaps”

Question ► What is the mechanism that resulted in the evolution of life?

Natural selection: observations ► populations of organisms display a variety of characteristics § characteristics may be useful, not useful, or detrimental § the variety is reflected in an organisms genes ► new genes § provide variety § produced by mutation, duplication, exchange of genes, symbiotic relationships § passed to offspring during reproduction

Natural selection: observations ► artificial selection § domesticated plants and animals can be bred to favor certain characteristics § populations of wild and domestic plants and animals develop characteristics that favor their survival

Natural selection: observations ► the natural environment § provides opportunities and stresses for living organisms § a new niche or stress on an existing niche will enhance selection

Natural selection: observations ► populations isolated of a species may become § by geography or behavior § provides new opportunities and stresses § isolates the population from the larger gene pool

Natural selection: conclusion ► the natural environment provides conditions (opportunities and stresses) that result in evolution through the process of natural selection ► populations of organisms display variety as a result of genetic change and symbiogenesis

Natural selection: conclusion ► organisms with favorable characteristics for their niche are more likely to thrive and reproduce while organisms with unfavorable characteristics are less likely to thrive and reproduce ► over time, favorable characteristics can accumulate in a population until the members of the population can no longer reproduce with the population from which they became isolated

Evolutionary trends ► divergence ► speciation & extinction ► convergent evolution ► phylogeny ► phyletic gradualism & punctuated equilibrium

Natural selection: speciation ►a population has a gene pool ► members of the population interbreed ► the population may become isolated from others of a species § § § development of niches & resource partitioning migration development of physical barriers ► populations may § by stress § by opportunity ► isolation be selected may result in genetic divergence

Natural selection: extinction ► stress on limiting factors reduce or destroy a population ► evolution into subsequent species (pseudo-extinction)

Phylogeny ► relationships between organisms can be determined using § genetics § anatomy & physiology (esp. for sybiogenesis) § fossils

Phyletic Gradualism & Punctuated Equilibrium ► gradualism § slow, steady change ► equilibrium & punctuation § long periods with little change § short bursts of rapid change ► evolutionary rates

How did it start? ► Chemical evolution? ► Where? § deep ocean vents? § tidal pools? § ice surface? § clay surface?

Randomness ► evolution is not random ► natural selection is not random ► mutations are random ► favorable mutations survive through reproduction

End point ► Evolution has no end