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 is the name of the theory Darwin proposed?
Evolution by natural selection.
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 a clade?
A clade is a group of organisms that includes an ancestor and all of its descendants.
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 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 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?
Which group of animals have the closest evolutionary relationship with crocodiles? (Read a cladogram)
Birds
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 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.
What are the IV, DV and constant 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 including resistance to a rare aquatic toxin. Since the toxin is rare, the resistance trait provides no significant survival advantage.
A nearby factory begins to release a low-level pollutant into the river. This pollutant is chemically similar to the natural toxin that the fish have a pre-existing genetic resistance to. Over time, the pollutant's toxicity leads to a decline in fish numbers.
The presence of the pollutant in the river is the selective pressure because it influences the ability of the fish to survive.
What does a phylogenetic tree show?
The evolutionary history of a group of related organisms.
What are the IV and DV in the following graph (to be pictured)?
IV: light intensity
DV: rate of photosynthesis
What are the different pieces of evidence that support the theory of evolution?
Fossil record, biogeography, embryology, comparative anatomy
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 is the difference between homologous and analogous structures?
Homologous - Same structure, different functions (from common ancestor)
Analogous - Different structure, same function (from adapting to live in similar environments)
What features of organisms can be used to construct a phylogenetic tree?
1. Difference in DNA sequences between organisms
2. Physical traits of organisms
3. Differences in protein sequences between organisms