Evidence for Evolution

• lines of investigation from direct observation, experimentation (eg. fossil evidence, continental drift) to indirect investigations Evidence examined are 1) fossil records (radiometric dating) 2) Biogeography (continental drift/theory of pangea) 3) anatomy (comparative embryology) 4) biochemistry 5) genetics 6) artificial selection: selective breeding is evolution in practice

• fossils form when an organism dies and is quickly buried by layers of sediment • over time the soft tissue decomposes but the hard bones, teeth, and shells remain and get replaced by minerals, the replacement is called petrification • molds and impressions can also form after and organism makes a print, it is filled with sediment hardens, and erodes over time and the print is revealed

• the fossil record shows the existence of organisms that inhabited the earth but don’t exist now; some bear resemblance to those who exist now • recent fossils resemble present day species; older fossils are more primitive • rocks are dated using radio-carbon dating, indicating the approximate time the organisms inhabited the Earth • fossil records are not complete, there are missing links (which is expected since the process of fossilization requires specific events) - in complete fossil records are accounted for

Archaepteryx - link between reptiles and birds - dinosaur like skeleton - reptilian features including jaws with teeth and long jointed tail but also had feathers and wings - Evolutionary ancestor that bridges the evolutionary split between higher primates and monkeys was recently discovered

1) different species lived on Earth at various times in past - very few species of today were alive 1 million years ago - almost all are now extinct 2) complexity of living organisms generally increases from most distant past to present - progression from very simple organisms to species of increased complexity 3) living species and their closely related matching fossils live in same geographic region

• mostly found in sedimentary rock = layered rock that is the oldest at the bottom • petrified fossils are organisms that have skeletal matter replaced with calcite • dated using a relative timescale; the geological time scale has major and minor corresponding with major evolutionary events • separated into: Eon Era Period Epoch

Observed geological stratification and fossils and suggested that most geological change was show and gradual and constant Based on - fossil deposits - geological processes of erosion and sedimentation Processes have been going on over vast expanses of time suggesting that the Earth is hundred of millions of years old

• prominent physicist that disagreed with Lyell • believed that Earth was gradually cooling from a molten state • used mathematical calculations for rates of cooling to estimate the age of Earth at 15-20 million years old • did not realize that the Earth’s core is a viscous fluid that acts as a source of heat • disproved by discovery of radioactive decay

The process of determining a specific date for an archaeological or paleontological or artifact Uses radioactive isotopes which decay at a constant rate, giving off radiation (radioactive decay) Because this rate is constant and unaffected by temperature, moisture, or other environmental conditions, it can be used to determine the age - radioactive=unstable Dating is based upon the half-life of an isotope The half-life is the time it takes for half of the atoms in the original element (parent isotope) to decay (daughter isotope) Only half of the atoms decay in one half-life; this can take between a few seconds or a million years depending on the element If parent isotopes of different radioactive elements are used, the dating becomes more reliable

• if we know the ratio of parent to daughter material, we can calculate the number of half-lives elapsed • from this info, the age of the sample can be calculated from the known length of the half-life of the radioisotope 1 - 50% 50% 2 - 25% 75% 3 - 12.5% 87.5% 4 - 6.25% 93.75%

• Biogeography: the study of the geographic distribution of life on Earth • patterns of distribution suggest that Earth’s continents were part of a single land mass 225 million years ago - broke apart resulting in continental drift • fossils dating back 150 million years ago and older were in the same geographic region but are now found at different continents • fossils younger than 150 million years are restricted to certain continents (endemic)

• pangea: 1 super continent existed 180 million years ago: broke off into two parts (Australia and Antarctica first) • similar organisms should evolve by natural selection if environment stressed are similar • marsupials in Australia resemble those from the rest of the world, also found marsupials in Antarctica • after Pangea broke up, the common ancestor evolved into mammals in the northern parts and into marsupials in the southern parts, yet similarities exist due to a similar environment • mammals: offspring developed in womb • marsupials: offspring developed in pouch

• islands are often products of volcanic activity but eventually get populated by unique species • islands have fewer species than their mainland counterparts • animals get to islands by flying, hitch a ride, swim, cross ice and land bridges, or raft on vegetation and ice floats • species native to remote islands are invariably and exclusively birds, insects, and potentially xobile - evidence for relationships between organisms on islands on other land masses is from genetic testing

Embryological similarities Embryology: the study of organisms in the early stage of development - embryos of many vertebrates are remarkably similar in the early stages - embryologists suggest this is because vertebrates evolve from a common ancestor - many embryonic structures are similar to those found in ancestors

• muscles/appendages that are considered useless • includes: tails, ear muscles, appendix, and limb bone of whale • thought to have once served a useful function but now are just remenants of a no-longer existing use • products of divergent evolution

• have common origins (in the embryo) (ex. gill slits), but many appear quite different in adults (divergent evolution) • have the same structure, but may have a different function • examples: human arm, cat leg, whale flipper, and bat wing

• similar structures but they are developed differently from an uncommon ancestor • example: wings of birds, insects, and bats • products of convergent evolution - homoplaysy • different origin and may have a different function

• the expression of proteins • many proteins are similar and share similar functions among very diverse organisms • this is particularly true for important proteins that carry out essential functions (i.e conserved) • some studies have shown that proteins from different organisms can function in the same role when expressed in others this is because of common ancestry • expression of proteins can influence the development of an organism and lead to diverse structures • instructions to encode proteins contain DNA • analysis of DNA and proteins show that animals may have remarkably similar DNA • differences arise by mutations accumulated overtime • the closer the “DNA fingerprint”, the more closely related the organisms are • 20 possible amino acid combinations but 64 different combos

• DNA: deoxyribnucleic acid • hereditary material in cells • Each DNA molecule contain many different genes • a gene is segment of DNA that performs a specific function • four nucleotide bases arranged in different sequences —> adanine, thymine, cytosine, guanine • DNA sequences from different species that code for the same protein vary in # and order of nucleotides • geneticists have found homologous + vestigal genes in DNA in virtually all species

• process of humans selecting and breeding individuals with desired traits • dramatic changes are produced in a species over a relatively short period of time • selectively influencing the “evolution” of desirable traits in different species • examples: broccoli, cauliflower, collard greens, brussel sprouts, cabbage, kale, and kohlrabi were made through natural selection with Brassica oleracea • breeds of dogs were made through selective breeding