Experimental Design
Briefly describe what an independent, dependent, and constant variable are.
IV: the variable the experimenter manipulates (changes)
DV: the variable the experimenter measures
Constant: the variable that stays the same amongst all groups.
What are antibiotics?
Medicine that kill bacteria.
What is the main difference between artificial and natural selection?
Artificial: initiated by humans
Natural: initiated by the environment
What is the name of the theory Darwin proposed?
Evolution by natural selection.
Why do we need both an experimental and a control group?
The control group ensures that a cause and effect relationship truly exists between the IV and DV.
What is the term for when bacteria don't die in the presence of antibiotics?
Antibiotic resistance.
What is evolution?
Change in a population over time?
BONUS: does this process happen in a short or long amount of time?
Name one of Darwin's influences.
Acceptable answers: HMS Beagle voyage. Finches, Earthquake (whale fossil), Glyptadonts vs Armadillos, Artificial Selection, Lyell and Hutton
Identify the IV, DV, constants, experimental group and control group in the following scenario:
A group of middle school students were given a short course in speed-reading. The instructor was curious if a monetary incentive would influence performance on a reading test taken at the end of the course. Half the students were offered $5 for obtaining a certain level of performance on the test, the other half were not offered money.
IV: amount of money given
DV: performance on test
C: same course, same test, same instructor
Experimental group: group that gets the incentive
Control group: group that does not get the incentive
What are some of the variables in our ZOI lab?
IV: presence of antibiotic
DV: ZOI diameter
Constants: same incubator, same incubator temperature, same plates, same bacteria, same broth
Identify the selective pressure in the following scenario:
A diverse population of fish lives in a freshwater river. The fish exhibit a variety of genetic traits, some of which confer resistance to a naturally occurring but rare aquatic toxin. Since the toxin is rare, the resistance trait provides no significant survival advantage, and the genes for resistance remain at a low frequency within the gene pool.
A nearby factory begins to release a low-level pollutant into the river. This pollutant is not immediately lethal but is chemically similar to the natural toxin that the fish have a pre-existing genetic resistance to. Over time, the cumulative effect of the pollutant makes the water toxic to most of the fish, leading to a decline in their numbers.
The presence of the pollutant in the river is the selective pressure because it influences the ability of the fish to survive.
What is natural selection?
Natural selection describes the process by which the environment "selects" for those with favorable traits to survive. Those that are best fit for their environment will reproduce and pass their traits on to their offspring, causing the population with that trait to increase over several generations.
Note: fit does not always mean bigger/stronger. Traits must be heritable.
What are the IV and DV in the following graph (to be pictured)?
IV: temperature
DV: light intensity of the candles
Use the hypothesis (if/then) framework to describe what we expected to happen in the ZOI lab.
Sample: If we expose bacteria to ampicillin, the diameter of the ZOI will decrease over several generations.
What introduces random traits/variations in populations?
Mutations.
What are the 4 steps of natural selection that we discussed in class?
1. Variation exists
2. Not everyone survives or reproduces
3. Some traits are better to have than others
4. Those with traits best fit for their environment will survive and pass those traits on to their offspring, causing the population with that trait to increase over several generations.