Chapter 22 Descent with Modification- Evolution- change in a population of organism over a long period of timeo Change in genetic composition of a population  Change in any aspect of an organism under genetic control (biochemistry, morphology behavior)- Scala naturae- scale of nature that life forms were organized by increasing complexity - St. Augustine of Hippo (354-430)o Rationalized Christianity o Philosopher who proposed that god created the universe in a form unlike today but with the potential to develop into present day conditions Would take a long time “programed universe”o Problems with his model Supernatural- cannot be tested- Catastrophism- events in the past happened suddenly and were caused by mechanisms different from those operating in the present- Lamarck’s idea of evolution (First testable theory of evolution)o “inheritance of acquired characteristics”o Use and disuse- parts of the body used more often will become larger and stronger Snakes stopped using legs so they became weaker and eventually disappearedo Organisms can pass these traits to their offspringo Organisms have an innate desire to become more complexo Testing of the model Use and disuse does work to an extent: muscles will get larger with more use Only changes in the germ cells can be passed down- Darwin (1809-1882) o Beagle went to map the coast of south America and ended up at the Galapagos Saw 13 species of finch vs 1 species on the mainland Wallace came up with the same idea and they published togethero Adaptations-inherited characteristics of organisms that enhance survival and reproduction in specific environmentso Natural selection- process by which individuals that have traits that allow them to survive and reproduce at higher rates Underlying case of descent with modificationo Artificial selection- humans have manufactured species by breeding those with specific traitso Influences on Darwin Lamarck- evolution occurs, new species appear Lyell- Uniformitarianism- mechanisms of change are the same over time- Enough time for biological change to occur Malthus-we are going to outgrow our food supply- Competition for resource Selective breeding (plant/animals) – saw how fast evolutiono Observations: Resources are limited Members of a population often vary in inherited traits All species can reproduce more than what their environment can support and many fail to survive and reproduceo Inferences: Individuals whose traits give them a higher probability of surviving and reproducing in a given environment tend to have more offspring than other individuals This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in a population over generationso Natural selection requires variability o Favorable traits vary with environment: no perfect variationSupport for evolution- Evolution doesn’t create changes, changes occur and natural selection selects those that are most favorable (Relies on local environment)- Homology- underlying similarities yet differing functions among organisms indicating a common ancestoro Analogy- similar functions but different ancestry Flight organs of a bug vs a birdo Homologous structures- variations on a structural theme present in a common ancestor (differences in the details) Embryos all have tails and gill like structures Vertebral forelimbo Homologous genes also found The homeobox- used in the body patterns of all animals- Regulatory genes- Vary in where and to what extent it is expressedo Vestigial structures- features that are no longer used but were once used by ancestors Ear wiggling muscles in humans, pelvis in whales At the molecular level- DNA/RNA /Genetic code is universal- Pseudogenes are like vestigial organs- Embryologyo Primitive ancestral structures seen in embryos that are not seen in later developmental stageso Phylotype state- all vertebrate embryos have pharyngeal pouches (gill slits) that develop into other organs around the neck Humans have a tail that is lost at later stages Not the same as vestigial organs Suggests a common ancestor- Evolutionary tree- diagram that reflects the relationships among groups of organisms- Convergent evolution- when 2 species resemble one another but aren’t relatedo Sugar glider vs flying squirrel- Fossils- preserved parts/traces of plants or animals that were once alive o Provide a record of evolution: appearances and disappearance and changes over timeo Hardest parts most likely to be preservedo Footprints could show behavioro Amber preserves the actual tissueo Macro evolution- Repeated branching speciation events (adaptive radiations) followed by selective survival and extinctions Horse evolution- Went from a small, delicate teethed shrub eating forest dweller with 4 toes to a hooved 1 toed grass eatero Teeth slowly got largero Remnants of toes in skeletono Larger body size- Many horse like species in each layer, only a few escaped extinctiono Horses actually went extinct in north America and had to be reintroducedo Paleontology- study of fossilso Age of fossils Relative dating- stratigraphy- Strata- superimposed layers of rock- The lower the strata the older the fossil- Index fossils- common forms (mollusks/arthropods common fossils usuallyfound at the edge of the sea) unique to a geologic period and worldwide in distributiono Used as markerso Need to apply dates through absolute dating Absolute dating- radioactive decay- We know the probability of decay and that the rates of decay cannot be influenced by ambient physical or chemical environments/treatments- Carbon 14 has a half-life of 5730 yearso Half-life- amount of time it takes for ½ of the original amount to decayo Good for only organic materials(not fossils because the fossils have beenreplaced by rock)o Rate of 14C is not constant Calibrated against bristlecone pine wood samples Cannot test anything past the 50s- Calculations:-T =−1λ∗ln ⁡(NtN0)o T= age of specimeno λ=decay constant =0.693 t1/2 o t1/2=half-life of isotopeo Nt=amount of isotope at time To N0=amount of isotope at T=0- Ex:o Soapberry bugs- beak lengths varybased on which fruit they eat Very speedy evolutiono Drug resistant bacteria MRSA resistant to antibiotics Overuse of antibiotics- Biogeography- geographic distribution of species o Influenced by continental drifto Pangaea- all land masses in one spot Explains