BIOL 101 The Scientific Method Assignment solutions complete answers

BIOL 101 The Scientific Method Assignment solutions complete answers

 

Learn It: Describe the steps of the scientific method.
When an experiment is conducted to test a hypothesis and data are obtained, a conclusion can be made. The ability to make a valid conclusion depends, in part, however, on how well an experiment is designed. When testing the effects that a particular variable has on the subjects of an experiment, other variables must be controlled. Experiments typically manipulate only one variable—the independent variable—to determine if that specific manipulation has an effect on the system being observed. The subjects receiving the manipulated variable or treatment is called the experimental group. The other subjects being tested—the control group—differ from the experimental group by only that one independent variable.

As you may recall, scientific inquiry or the scientific method begins with observations. Let's consider an example. A researcher was growing pea plants to use for a future study on photosynthesis. To germinate (begin to grow) the seeds, the researchers wrapped the seeds in moistened paper towels, covered them with aluminum foil, and placed them on a countertop at room temperature (23 ℃). After five days, they came back to collect the sprouted seeds. They noticed that some of the seeds on the countertop were in direct sunlight coming in from a nearby window; this was unintended, but an important observation. The researchers also observed that the germination rate was higher in the seeds exposed to the sunlight coming through the window. Have you ever noticed that when you are sitting in direct sunlight, you feel warmer? Although, the seeds were wrapped in aluminum foil and shaded from direct sunlight, the researchers wondered if the germination rate was affected by sunlight heating the aluminum foil. Following their observations, they designed an experiment to test the following hypothesis:

If increased temperature stimulates seed germination, then seeds incubated at higher temperatures will have a higher germination rate than seeds incubated at lower temperatures.

Experiment:

Three paper towels, each with six evenly spaced seeds, were moistened with 1 ml of water and folded over the seeds. Each of the paper towels was then wrapped in aluminum foil, placed in a dark room, and incubated for five days at either 23 ℃, 26 ℃, or 29 ℃.

After five days, all seeds were removed, and seed germination was determined. The results are shown in the following table:

Incubation temperature (℃)
Number of seeds germinated/6
23
3
26
5
29
6
In this example, the researchers observed a higher germination rate among seeds warmed by sunlight. They predicted or hypothesized that the increased temperature caused the higher germination rate. To test their hypothesis, they incubated some seeds at room temperature, or 23℃ (the control group), and incubated other seeds at higher temperatures (the experimental group). Additionally, they controlled for other variables such as light availability, seed count, seed spacing, amount of water, and incubation time. By designing an experiment that controlled these other variables, the researchers were able to conclude that the difference in germination rate between the control group and the experimental group was most likely due to the independent variable.

 

What was the independent variable in the experiment?

 Temperature

 Incubation time

 Seed count

 Amount of water

 

What initial observation led the researchers to form a hypothesis?

 Moist paper towels increased germination rates.

 The germination rate was higher when seeds were directly exposed to sunlight.

 Seeds warmed by sunlight had higher germination rates.

 Pea plants are more efficient at photosynthesis.

 

What was the incubation temperature for the control group?

 23 ℃

 26 ℃

 29 ℃

 32 ℃

 

Which of the following conditions were kept the same between the control group and the experimental group? Select all that apply.

 Light availability

   Water availability

   Seed spacing

   Temperature

   Incubation time

 

The independent variable is manipulated by scientists over the course of an experiment.