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NATURAL SELECTION OBSERVED TODAY • Peppered Moths • Microorganism s resistant to penicillin • Insects resistant to pesticides Examples Modern Examples of Evolution: 1. Peppered Moths • England, 1848 • Moths rest on Lichencovered tree barks. • There are more white moths in the population. Evolution In Action! • Why is Sexual reproduction better for a species than Asexual reproduction? The Peppered Moth: England 1848 INDUSTRIAL REVOLUTION Evolution Evolution 2. Antibiotic-Resistant Bacteria 2. Antibiotic-Resistant Bacteria Antibiotic-Resistant Bacteria –What was the selective pressure? –Who applied it? Antibiotic-Resistant Bacteria Antibiotic-Resistant Bacteria Did the antibiotic mutate the bacteria’s DNA? Did bacteria become resistant because they needed to? Did the bacteria get “used to” the antibiotic? WHY did one survive? Antibiotic-Resistant Bacteria Evolution Original Population New Population Would this have happened without antibiotics? Why does penecillin not work on bacteria anymore? 1. The bacteria that survived exposure to penicillin learned to avoid it. 2. During each generation, the bacteria modified their own DNA to increase their ability to resist penicillin and passed this ability on to their descendants. 3. Members of the original population of bacteria that were penicillin resistant survived and reproduced, creating a more resistant population. 4. The bacteria that caused the new outbreaks were from populations that had never been exposed to penicillin. Do NOT take antibiotics unless absolutely necessary! Antibiotics do NOT kill viruses. 3. DDT-Resistant Insects • DDT is an insecticide (bug-killer) that has been used to kill pests on crops. At first, DDT killed most of the pests. • But soon, the majority of the pest population had a DDT-resistance gene. • Explain (in at least 3 steps) the events that led to this evolution of pests. DDT also killed Falcons, Eagles, and Osprey by making the egg shells thinner. A large population of house flies was sprayed with a newly developed, fast-acting insecticide. The appearance of some house flies that are resistant to this insecticide supports the concept that: 1. species traits tend to remain constant 2. pesticides cause mutations 3. variation exists within a species 4. the environment does not change Evolution part 5 • Rates of evolution • Be able to explain gradualism vs punctuated equillibrium and why 2 beliefs exist. How fast does evolution occur? SLOW Evolution: Horseshoe Crab 150 millionyear old fossil Rate of Evolution How Fast Will a Species Change? Evolution will occur more quickly if: – Lots of VARIETY – High selective pressure (The environment changes.) – Lots of competition to survive and reproduce. How fast is evolution when… • The Environment stays stable? – SLOW • Selective pressure is applied? – FAST • Conditions are harsh? – FAST • Lots of competition? – FAST Time Frame for Evolution • Gradualism – evolution is slow, gradual and continuous Time Frame for Evolution • Punctuated Equilibrium- species have long periods of stability interrupted by brief periods of change (mutations), during which new species may evolve Extinction: Failure of a species to adapt to a changing environment. Fun Facts • Possibly 10 billion species have ever existed. • Of all species that ever inhabited the Earth over 99% of them are now extinct. • The primary reason for these extinctions is environmental change or competition. • They did not have the mutation that would have enabled them to survive.