The Rate of Evolution and The Rate of Evolution and ExtinctionExtinction

What affects how fast orgs evolve?

What leads to extinction?

Change is Everything!Change is Everything!

• Change in environment = Change in species!

• Failure to adapt to changes = possible extinction

Rate of EvolutionRate of EvolutionWhat affects how fast a species What affects how fast a species

evolves?evolves?

1.1. Rate of Rate of environmental environmental changechange

2.2. Rate of Rate of reproductionreproduction

Rate of Environmental ChangeRate of Environmental Change

• Rapid environmental Rapid environmental change = rapid change in change = rapid change in speciesspecies– Rapid changeRapid change

• ExEx. Modern horse: many . Modern horse: many changes over past million changes over past million yearsyears

– Slow changeSlow change• Ex.Ex. Horseshoe crab: Horseshoe crab:

nearly identical to nearly identical to ancestors from 300 myaancestors from 300 mya

Rate of ReproductionRate of Reproduction• The # of offspring produced can The # of offspring produced can

tell us how quickly a species can tell us how quickly a species can evolveevolve

– Few offspring = longer life = Few offspring = longer life = slowslow evolution evolution

• Ex.Ex. Humans, elephants Humans, elephants

– Many offspring = shorter life = Many offspring = shorter life = quickerquicker evolution evolution

• Ex.Ex. Bacteria, single celled Bacteria, single celled orgs, fishorgs, fish

Let’s look at bacteriaLet’s look at bacteria• Reproduce very Reproduce very quicklyquickly

• Millions exposed to antibioticMillions exposed to antibiotic– Very good chanceVery good chance a few will have a few will have resistantresistant genegene

due to random mutationdue to random mutation– These will live,These will live, THEN THEN pass on resistancepass on resistance– Pretty soon, large pop’n that have this resistancePretty soon, large pop’n that have this resistance– If same antibiotic used again, will increase If same antibiotic used again, will increase

resistanceresistance– Soon, a SUPER STRAIN of this bacteria has Soon, a SUPER STRAIN of this bacteria has

evolvedevolved

Brain Pop link

Lesson learned:Lesson learned:

• Only use antibiotics when necessaryOnly use antibiotics when necessary

• Many strains are resistant to Many strains are resistant to penicillin, the first antibiotic usedpenicillin, the first antibiotic used

• Humans are creating Super Strains Humans are creating Super Strains with continued misuse of antibioticswith continued misuse of antibiotics

• Similar occurrences with insects and Similar occurrences with insects and insecticidesinsecticides

What causes extinction?What causes extinction?1.1. Death rate higher than birth rateDeath rate higher than birth rate

• Usually due to rapid env. changesUsually due to rapid env. changes2.2. These env. changes cause major drop in These env. changes cause major drop in

pop’n size if species cannot adaptpop’n size if species cannot adapt• Variation drops!Variation drops!

• Less variation to pass onLess variation to pass on• Offspring essentially inbreeding, Offspring essentially inbreeding,

variation drops even morevariation drops even moreNO VARIATION = NO VARIATION =

NO ADAPTIVE VALUE = NO ADAPTIVE VALUE = EXTINCTIONEXTINCTION