25 SPECIATION THE FORMATION OF NEW SPECIES AS NEW SPECIES EVOVLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATEDREPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.
26 3 ISOLATING MECHANISMS…….. BEHAVIORAL ISOLATION- CAPABLE OF BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. MEADOWLARKS)GEOGRAPHICAL ISOLATION – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL)TEMPORAL ISOLATION – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT TIMES.
35 Fig. 23.6Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.
36 These squirrels live on opposite sides of the Grand Canyon These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.
37 Hawaiian Honeycreepers An example of adaptive radiation –these species all diverged from acommon ancestor (founder species)FOUNDER SPECIES
38 SPECIATION IN DARWIN’S FINCHES SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY:- FOUNDING OF A NEW POPULATION,- GEOGRAPHIC ISOLATION which led to -- REPRODUCTIVE ISOLATION andCHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.
50 Relative Dating Can determine a fossil’s relative age Performed by estimating fossil age compared with that of other fossilsDrawbacks – provides no info about age in years
51 Absolute dating Can determine the absolute age in numbers Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remainDrawbacks - part of the fossil is destroyed during the test
54 Big Bang TheoryA cosmic explosion that hurled matter and in all directions created the universe billion years agoEvidenceit explains why distant galaxies are traveling away from us at great speedsCosmic radiation from the explosion can be observedThe Big Bang theory probably will never be proven; consequentially, leaving a number of tough, unanswered questions.
55 What was early earth like? Earth was Hot!!Little or no oxygenGasses in atmosphere:Hydrogen cyanide (poison to you!)Hydrogen sulfideCarbon dioxideCarbon monoxideNitrogenwater
56 So how did the earth get oxygen? Some of that oxygen was generated by photosynthetic cyanobacteriaSome came from the chemical separation of water molecules into oxygen and hydrogen.
57 Others evolved ways of using oxygen for respiration Oxygen drove some life forms to extinctionOthers evolved ways of using oxygen for respiration
58 How did life begin? Miller and Urey’s Experiment Passed sparks through a mixture of hydrogen methane ammonia and waterThis produced amino acids – the building blocks of life
59 Miller’s experiment suggests that lightning could have produced amino acids
60 How can simple amino acids result in life? There are 3 theories 1. Formation of microspheresLarge organic molecules can sometimes form tiny proteinoid microspheresStore and release energy, selectively permeable membranes, may have acquired more characteristics of living cells
61 2nd Hypothesis for Life Evolution of RNA to DNA RNA was assembled from simple organic molecules in a primordial soupRNA was able to replicate itself and eventually form DNANot scientifically proven to be possible
62 3rd Theory of Life Endosymbiotic theory eukaryotic cells arose from living communities formed by prokaryotic organismsAncient prokaryotes entered primitive eukaryotic cells and remained there as organelles