Nature of Science Cont Lecture Notes Jan 18

Take online quizzes to stay up to date on the material
We can take online quizzes as many times as we want
For investigation problems
Hypothesis needs to be falsifiable
Positive and negative controls
Negative control: one field with no treatment
Positive: field you know is going to be destroyed
Most of the time will have to design experiment (most important part of question)
Need to be specific (don’t use words like: some, a lot)
Can workshop answers on wiki
Will need to know what would falsify hypothesis

Kinds of Selection
Stabilizing selection
Natural selection towards a mean
Ex: More advantageous to be average than very tall or short
Figure 22.13
Why two y-axes? Two graphs on one graph
Bars represent percent of population
Most babies born between 5-8 lbs – most of them live
Testable hypothesis between mortality and birth-weight: Babies of average birth weight have stronger hearts than babies either above or below the average birth weight.
Could falsify if: all the fetal heartbeat data is the same, no matter the birth weight
Does NOT lead to speciation

Disruptive selection
Advantageous to being an extreme – really big or really small; no advantageous to being average
Can lead to speciation by creating barriers to breeding
Speciation – population has been divided into two different species (can’t breed with each other)

Genetic drift and population bottlenecks
Population bottlenecks – most likely to occur in small, isolated populations. A small, random selection of a larger population results from a bottleneck. When this random selection breeds, the genetic makeup is different than the original population.
50 % of cats on Key West are polydactyl
dominant trait, but it’s very rare in most cats (less than 5 %)
Due to founder effect – Ernest Hemingway’s cat was polydactyl. They lived in Key West. The cat founded a new population of polydactyl cats.
Evolution vs. Intelligent Design
Evolution posits common descent plus natural selection on heritable variation
Evolution predicts: traits of organisms alive today are limited by genetic traits of ancestors; Organisms evolve workable, but not perfect, solutions to problems because of natural selection
Intelligent design posits that organisms were created as they recently appear by a super-intelligent designer
Intelligent design also predicts perfectly, or nearly perfect, working features of organisms

Why was the standard keyboard more fit than the Dvorak keyboard?
Dvorak keyboard jammed more often than standard
Why do we still use this keyboard design today?
Would have to relearn how to type

Can the eccoli become resistant to the T4 phages which kill them?
Falsifiable hypothesis: The eccoli will become resistant to the T4 phages (alternative hypothesis)
Eccoli will not become resistant (null hypothesis)

Make cultures – put T4 phages on petri dishes. Then add eccoli. Zone of inhibition will not form if the alternative hypothesis is correct.

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