Scientific method quiz

What are the names of the software used to analyze the raw experimental data in this course?

Microsoft Excel and JMP

A cuckoo laying eggs in the nest of other bird species, is an example of __.

brood parasitism

Using the simple data analysis convention discussed in the Scientific Method Lecture, two treatments are thought to be significantly different if their standard error bars do not overlap.

True

A student wants to know how soil nutrients affect the growth of plants. For the experiment, she measures the height in millimeters of Arabidopsis thaliana plants grown in soils with no added nutrients, added phosphorus, and added nitrogen. She performed ten replicates of each treatment and calculated the mean height, standard deviation, and standard error for the treatments. She then graphed the results. Which of the following is a correct null hypothesis for this experiment?

Added nutrients will have no effect on the height of Arabidopsis thaliana.

After collecting raw experimental data, what is the next step in the scientific method?

Analyze the data

You take samples of water from one of the LSU lakes during the summer and bring them back to your lab for an experiment. A common organism found in the lakes is blue-green algae, which, when present in large amounts, often results in fish kills due to a lethal reduction in oxygen availability. Wanting to mimic this phenomenon, you create aquariums from each of your collected lake samples, each with ten red ear sunfish. Every day for a week, you add 0.25, 0.5, or 1 kg of blue-green algae to the respective aquariums in the morning and check to see how many fish are alive that night. What would be an appropriate control for your experiment?

Aquariums to which no algae is added.

An alternative hypothesis states the direction one expects to see in the difference between treatments, while the null hypothesis does not.

False

A student wants to know how soil nutrients affect the growth of plants. For the experiment, she measures the height in millimeters of Arabidopsis thaliana plants grown in soils with no added nutrients, added phosphorus, and added nitrogen. She performed ten replicates of each treatment and calculated the mean height, standard deviation, and standard error for the treatments. She then graphed the results. Which of the following is the best caption for the graph?

Figure 1. Bar graph of means with standard error bars for height in millimeters (mm) of Arabidopsis thaliana grown under three treatments. Measurements were taken from ten replicates per treatment.

After making observations, what is the next step in the scientific method?

Formulate research questions

Researchers are testing the effectiveness of various antibacterial soaps. Four different soaps are used on the same bacterium and a fifth petri dish receives no soap. Identify the independent (IV) and dependent variables (DV).

IV: the type of soap used, DV: the amount of bacterial growth

You take samples of water from one of the LSU lakes during the summer and bring them back to your lab for an experiment. A common organism found in the lakes is blue-green algae, which, when present in large amounts, often results in fish kills due to a lethal reduction in oxygen availability. Wanting to mimic this phenomenon, you create aquariums from each of your collected lake samples, each with ten red ear sunfish. Every day for a week, you add 0.25, 0.5, or 1 kg of blue-green algae to the respective aquariums in the morning and check to see how many fish are alive that night. What would be an appropriate prediction for your experiment?

Increasing the amount of blue-green algae present in the aquarium will cause a decrease in the percent survival of red ear sunfish at the end of the week.

What is wrong with the following research question? RQ: "How does the length of a tail change as age increases?"

It does not define its population.

It is well known that pine trees can get infected by a fungus called "tree-eater," which breaks down its bark and eats through its trunk. You test whether cypress and oak trees can also get infected by this fungus, and you find that they can! Now you want to test whether the fungus can infect the oak and cypress at the same rate as pine. Identify the control group(s) for this experiment.

Oak and cypress trees

It is well known that pine trees can get infected by a fungus called "tree-eater," which breaks down its bark and eats through its trunk. You test whether cypress and oak trees can also get infected by this fungus, and you find that they can! Now you want to test whether the fungus can infect the oak and cypress at the same rate as pine. Identify the treatment group(s) for this experiment.

Pine trees

You make a graph to show the rate of infection for pine, oak, and cypress trees, and you put the types of trees on the x-axis and the rate of infection on the y-axis. Identify the dependent variable.

Rate of infection

A biologist thinks that ginger lily (Hedychium coronarium), an invasive plant in tropical marshes throughout the world, is responsible for the reduction in diversity of native insects in Florida marshes. She records the diversity of insects in Florida marshes before and after the invasion of ginger lily under controlled conditions. Her null hypothesis is: The presence of ginger lily has no effect on the diversity of insects in Florida marshes. The bar graph of mean insect diversity with standard error bars is plotted below. Based on these results, what can the biologist conclude regarding the null hypothesis?

Since the error bars overlap, no difference was found between the treatments, so the biologist cannot reject the null hypothesis

You take samples of water from one of the LSU lakes during the summer and bring them back to your lab for an experiment. A common organism found in the lakes is blue-green algae, which, when present in large amounts, often results in fish kills due to a lethal reduction in oxygen availability. Wanting to mimic this phenomenon, you create aquariums from each of your collected lake samples, each with ten red ear sunfish. Every day for a week, you add 0.25, 0.5, or 1 kg of blue-green algae to the respective aquariums in the morning and check to see how many fish are alive that night. Which of the following is the independent variable in your experiment?

The amount of algae added to the aquarium.

Yeast is known to be a major food source for fruit flies (Drosophila melanogaster). A biologist was interested to see if feeding an excessive amount of yeast to fruit flies would affect their lifespan. She conducted an experiment where she fed different groups of flies varying amounts of yeast for a month. After a month, significantly more flies died after being fed an excessive amount of yeast compared to those fed less yeast. Write a null hypothesis using the information provided above.

The amount of yeast a fruit fly eats will not affect its lifespan

Yeast is known to be a major food source for fruit flies (Drosophila melanogaster). A biologist was interested to see if feeding an excessive amount of yeast to fruit flies would affect their lifespan. She conducted an experiment where she fed different groups of flies varying amounts of yeast for a month. After a month, significantly more flies died after being fed an excessive amount of yeast compared to those fed less yeast. Write an alternative hypothesis using the information provided above.

The amount of yeast eaten by a fruit fly will affect its lifespan

What does standard deviation indicate?

The spread of data points around the mean.

An experiment investigates the effects of the independent variable on the dependent variable.

True

A larger sample size will most likely result in __.

a smaller standard error

Captions are written __ the table and __ the figure.

above | below

A research question should always be __.

testable simple concise measurable

Biologists sometimes use different models or systems to represent things they cannot study directly.

true