The Rate of Evolution and Extinction What affects how fast orgs evolve? What leads to extinction?

Change is Everything! Change in environment = Change in species! Failure to adapt to changes = possible extinction 

Rate of Evolution What affects how fast a species evolves? 1.Rate of environmental change 2.Rate of reproduction

Rate of Environmental Change Rapid environmental change = rapid change in speciesRapid environmental change = rapid change in species –Rapid change Ex. Modern horse: many changes over past million yearsEx. Modern horse: many changes over past million years –Slow change Ex. Horseshoe crab: nearly identical to ancestors from 300 myaEx. Horseshoe crab: nearly identical to ancestors from 300 mya

Rate of Reproduction The # of offspring produced can tell us how quickly a species can evolve –F–F–F–Few offspring = longer life = slow evolution Ex. Humans, elephants –M–M–M–Many offspring = shorter life = quicker evolution Ex. Bacteria, single celled orgs, fish

Let’s look at bacteria Reproduce very quicklyReproduce very quickly Millions exposed to antibioticMillions exposed to antibiotic –Very good chance a few will have resistant gene due to random mutation –These will live, THEN pass on resistance –Pretty soon, large pop’n that have this resistance –If same antibiotic used again, will increase resistance –Soon, a SUPER STRAIN of this bacteria has evolved Brain Pop link Brain Pop link

Lesson learned: Only use antibiotics when necessaryOnly use antibiotics when necessary Many strains are resistant to penicillin, the first antibiotic usedMany strains are resistant to penicillin, the first antibiotic used Humans are creating Super Strains with continued misuse of antibioticsHumans are creating Super Strains with continued misuse of antibiotics Similar occurrences with insects and insecticidesSimilar occurrences with insects and insecticides

What causes extinction? 1.Death rate higher than birth rate Usually due to rapid env. changesUsually due to rapid env. changes 2.These env. changes cause major drop in pop’n size if species cannot adapt Variation drops!Variation drops! Less variation to pass onLess variation to pass on Offspring essentially inbreeding, variation drops even moreOffspring essentially inbreeding, variation drops even more NO VARIATION = NO ADAPTIVE VALUE = EXTINCTION