Evidence for Evolution Professor Andrea Garrison Biology 3A Illustrations 2010 Pearson Education, Inc., unless otherwise noted
Fossil Evidence Fossil record Fossils accepted as evidence of once-living organisms that have been preserved Give idea of types of organisms living during the time rock was being deposited Date rocks to date fossils Evidence for Evolution 2
Fossil Evidence Give general picture of changes that have occurred in living forms over geologic history Oldest fossils less complex Younger fossils more similar to living species Trends support concept of change in species over time Variety of fossil types Evidence for Evolution 3
Fossil Evidence Trace fossils Evidence that organism was there Tracks, burrows, dung Tracks to right (identified as Chirotherium) are only known from the tracks do not know what dinosaur is associated with them Evidence for Evolution; picture http://en.wikipedia.org/wiki/trace_fossil 4
Fossil Evidence Mesolimulus walchi fossilized w/its tracks, (very rare to find together) Evidence for Evolution; picture http://en.wikipedia.org/wiki/trace_fossil 5
Fossil Evidence Arthropod tracks from late Cambrian Evidence for Evolution; picture http://en.wikipedia.org/wiki/trace_fossil 6
Fossil Evidence Trace fossils Coprolite: fossil dung Coprolite shown is from a carnivorous dinosaur (~13 inches long) Evidence for Evolution; picture http://en.wikipedia.org/wiki/coprolite, source USGS 7
Fossil Evidence Trace fossils Burrows shown below are believed to have been made by crustaceans during the middle Jurassic (145 200 MYA) Evidence for Evolution; picture http://en.wikipedia.org/wiki/file:thalassinoidesisrael.jpg 8
Fossil Evidence Compression fossils Carbon film: Original organic material altered to a carbon film in rock layers Evidence for Evolution; picture http://en.wikipedia.org/wiki/file:priscacara_liops_green_river_formation.jpg 9
Fossil Evidence Compression fossils Ginkgo biloba, Eocene (34-56 MYA) Evidence for Evolution; picture http://en.wikipedia.org/wiki/file:ginkgo_biloba_macabee_bc.jpg 10
Fossil Evidence Replacement fossils Original organic material replaced by another mineral Evidence for Evolution; picture http://en.wikipedia.org/wiki/file:petrifiedwood.jpg 11
Fossil Evidence Gives us lots of info about previous life Anatomy Structure relates to function Limbs method of locomotion Teeth & dung diet Nasal cavities sense of smell Special structures can surmise function Pollen reconstruct climate and habitat Evidence for Evolution 12
Interpreting Fossil Evidence Lambeosaurines (huge duckbilled dinosuars) Bony crests and huge nasal passages in skulls Weapons? Male adornment? Snorkels? Radiators to cool blood? Enhanced smell? Resonators for vocalizations? 2009: computer tomography showed the frequency of sounds from these chambers match the frequency their inner ears were designed to hear honking dinosaurs Evidence for Evolution; illustration 2014 Cengage Learning 13
Interpreting Fossil Evidence Evidence for Evolution; illustration 2014 Cengage Learning 14
Interpreting Fossil Evidence Fossil evidence indicates that different evolutionary lineages differ in the tempo (timing) of morphological change over time Phyletic gradualism hypothesis: most morphological change occurs gradually over long periods of time Evidenced by trilobites where there are only very small changes in related fossils found in different rock strata from different time periods Expect to find many transitional fossils Punctuated equilibrium hypothesis suggests that speciation usually occurs in isolated populations at the edge of a specie's geographical distribution Substantial genetic drift & distinctive patterns of natural selection Morphological changes occur in rapid bursts, followed by long periods of equilibrium Transition forms lived only for brief periods in very localized populations Discourages broad representation in fossil record Evidence indicates both occur, and some intermediate tempos, as well Evidence for Evolution; illustration 2014 Cengage Learning 15
Plate Tectonics Evidence for Evolution; picture http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php 16
Plate Tectonics Evidence for Evolution; picture http://en.wikipedia.org/wiki/file:tectonic_plate_boundaries.png, USGS 17
Plate Tectonics Evidence for Evolution; picture http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php 18
Plate Tectonics Pangaea (225 MYA) Tectonic plates brought continents together in supercontinent Gradually split apart (starting 180 MYA) About the time mammals show up in fossil record Formed current continental patterns Evidence for Evolution 19
Plate Tectonics Australia separated very early Mammals here unlike those of other plates Fossil records show common fossils during periods when continents touching Brazil and W. Africa show matching reptiles Can watch separate evolutionary patterns after the split Mammals vary between the continents (different selective pressures due to different environments on two sides of ocean) Evidence for Evolution 20
Biogeography Fossils in given area tend to be more closely related to living organisms only in that region, not in other regions with same climate Regions with similar environments have organisms which show similar adaptations, but are not related to one another (=convergent evolution) Evidence for Evolution; picture http://earthquake.usgs.gov/learn/topics/pl ate_tectonics/rift_man.php 21
Biogeography Convergent evolution Cactus in N. America and spurge in Africa show adaptations for desert environments, but are very different plants Evidence for Evolution; illustrations 2014 Cengage Learning 22
Biogeography Unusual mammals in Australia show the effects of being isolated from other continents for 55 million years Evidence for Evolution 23
Biogeography However, marsupial mammals in Australia and placental mammals in No. America show convergent evolution due to similar habitats and similar foods Evidence for Evolution; illustration 2014 Cengage Learning 24
Comparative Embryology Early developmental stages of organisms related at subphylum level or below have very similar embryology Evidence for Evolution 25
Comparative Anatomy Homologous structures show common anatomical theme Similar body parts derived from similar embryonic structures, even if used differently Evidence for Evolution 26
Comparative Anatomy Extinct whale with hind limbs (considered transitional) Evidence for Evolution 27
Comparative Biochemistry All living organisms have same types of molecules Proteins, carbohydrates, fats, nucleic acids Universal genetic code All living organisms have DNA as hereditary material Same 4 bases: A, T, C,G In almost all cases, the DNA codes for amino acids are the same Evidence for Evolution 28
Comparative Biochemistry Comparison of DNA sequences used to determine close relationships Argument assumes similar DNA implies close relationship Evidence for Evolution 29
Experimental Evolution Basic tenet of science is that it is observable and testable Should be able to observe and test evolutionary theory Difficult due to length of time required Some success with short-lived organisms Indiscriminate use of pesticides resistant insect strains Indiscriminate use of antibiotics resistant bacteria These are not new species, however Evidence for Evolution 30
Experimental Evolution New species of plant created in the lab Stebbins (1940s) induced doubling of chromosomes in Ehrharta erecta Resulting plant was new species Unable to mate with parent plant» Survived in environment in So. California for 40 years» Not as successful as parent plant in unchanging environment (tetraploids may have advantage in changing environments) http://www.calflora.org/cgibin/species_query.cgi?where-calrecnum=2895 Evidence for Evolution 31
Evidence of Evolution Lots of evidence for change within a species Evidence points to environment as being driving force for change Fossil record tells a lot Most of the changes we can observe occurring are not new species, but rather new strains Recent evidence indicates rate of change may vary over time Natural selection still best mechanism we have to explain what we see Evidence for Evolution 32