Roaches
Storyboard Text
- There is variation in the cockroach population. Variation is the differences in a population, and the raw material of natural selection.
- Oh no! Jack is walking over here with the bug spray!
- These cockroaches are “bugging” me.
- Wow, that hurts my feelings
- Hey, we're alive? Why didn't we die?
- Hooray! I got rid of those cockroaches!
- I guess he didn't apply the pesticides correctly.
- Since we were the ones who didn't die, we must have genes that gave us a strong resistance to the pesticides.
- Yeah, that would mean the pesticide acts as a selective pressure. A selective pressure is something that puts pressure on an organisms fitness. Selection favors certain genotypes by acting on the organisms phenotype.
- Population: all members of the same species in a certain area
- The type of selection that happened to us is called directional selection. Directional selection occurs when individuals at a one end of the phenotypical range have a higher fitness than the rest. This can be seen in us since only the individuals with the highest pesticide resistance survived.
- Wait a minute. Since we all have high pesticide resistance, then our offspring must have high resistance too through inheritance of genes. We can create a new and evolved population. Well, what are we waiting for? Let's reproduce!
- Hooray! The pesticide has no effect on us anymore, and due to microevolution, this population will be staying for a while. Microevolution is a change in the allele frequencies over time in a population. In our case, the parent generation had a wide variety of alleles while the new generation has strong resistance alleles.
- 2 weeks later...
- I guess you could say we have un-bug-lievable strong resistance
- Now they will never die. I hate directional selection!
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