Modern Examples of Natural Selection Peppered Moth Antibiotic

Modern Examples of Natural Selection • Peppered Moth • Antibiotic Resistance • Pesticide/Insecticide Resistance

What happens when there is variation in a population? • the organisms in a population can be different • new traits may appear What do you think – COLOR – SHAPES – BEHAVIORS happens to organisms that have traits that are not good for survival? • some organisms may be able to survive better than the others • their DNA has a better chance of being passed on to offspring • the traits that helped them are more likely to show up in more and more organisms in future generations

Modern Examples of Natural Selection Peppered moth -two varieties of peppered moth existed, a light colored and a dark colored one. -Originally, the vast majority of peppered moths had light colouration, which effectively camouflaged them against the light-coloured trees and lichens which they rested upon. However, because of widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened by soot, causing most of the light-coloured moths, or typica, to die off from predation. -At the same time, the dark-coloured, or melanic, moths, carbonaria, flourished because of their ability to hide on the darkened trees. -the dark colored variety of the moth blended into the trees and increased in numbers, while the light colored moth was less adapted and decreased in numbers.

Antibiotic Resistance • Bacterial resistance to antibiotics: Bacteria not resistant to an antibiotic are killed by it, while resistant bacteria live to reproduce. • The antibiotic is a selecting agent for these bacteria.

Antibiotic Resistance

Pesticide/Insecticide Resistance • Insecticides kill insects not resistant to the insecticide, while insects resistant to the insecticide live to reproduce. • The insecticide acts as a selecting agent.

Pesticide/Insecticide Resistance

Why does this happen? • Variation due to mutations exists in both the population of bacteria and mosquito. • Those that possess the gene mutation that makes them resistant to the environmental factor will survive and reproduce. • They will pass this gene for resistance to their offspring! This gene for resistance is an adaptation!

Selecting agents and Natural Selection • A selecting agent is any characteristic or trait that gives one species an advantage over others • This trait becomes dominant as a species evolves.

Brainpop www. brainpop. com Antibiotic resistance http: //www. sumanasinc. com/scienceinfocus/sif_antibiotics. html Insecticide resistance http: //www. mhhe. com/biosci/esp/2001_gbio/folder_structure/ev/m 2/ s 1/evm 2 s 1_6. htm

What if there is NO VARIATION in a population? • The population would be asexually reproducing • All members would be very similar genetically • All members would have the same chance of survival • A sudden change in the environment could cause the population to go extinct

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