lab test 1

Question 1

What are the steps of the scientific method?

Answer 1

✓Making observations:
- You observe a phenomenon that is in some way
interesting or puzzling.
✓ Asking questions:
- You ask a question about your observation – why? how?
✓ Formulating a hypothesis:
- You make a guess as to the explanation of the
phenomenon and derive by inductive reasoning a possible answer to the question.
✓ Making a prediction:
- You make predictions about the results you would expect if the hypothesis is correct.
✓ Testing your hypothesis:
- You devise a test to show how likely the hypothesis is valid.
✓ Analysis of your results:
- You collect and analyze the data (results) generated from the experiment that tests the hypothesis.
✓ Deriving a conclusion:
- You then interpret the results to determine whether the hypothesis is supported by the data or falsified. This leads to a conclusion

Question 2

What is the independent variable?

Answer 2

Independent variable: Treatment or condition under study. It is the explanatory or
causal factor; the variable that you hypothesize is causing a particular response. In an
experiment, you manipulate this variable.

Question 3

What is the dependent variable?

Answer 3

Dependent variable: Treatment or condition that is measured or observed when the
results are collected. The dependent variable is dependent on the independent variable.
The dependent variable will change in response to changes in the independent variable.

Question 4

What are the controlled variables?

Answer 4

Controlled variables: All other factors that investigators attempt to keep the same for
all groups under study.

Question 5

What is a control group?

Answer 5

Control Group: Group of subjects not treated with the independent variable, or which
have a natural (i.e., not manipulated) level of the independent variable.

Question 6

What is an experimental group?

Answer 6

Experimental Group: Group of subjects treated with the independent variable, or where
the level of the independent variable is manipulated. The experimental group is also
called the treatment group.

Question 7

What is the t-test used for?

Answer 7

Two compare the means of 2 groups

Question 8

What are the 2 types of t-tests?

Answer 8

• Paired t-test
• Unpaired t-test

Question 9

What is a paired t-test?

Answer 9

Comparing random samples but measures taken as a pair of observations of a single subject (comparing at one condition and then at another)
- The 2 groups need to be the same size

Question 10

What is an unpaired t-test?

Answer 10

Comparing random samples even if the groups have different sizes
- 2 groups need to be independent, meaning they are no chances of them reacting the same way

Question 11

When is the one-tail p-value used?

Answer 11

• When your prediction is only based on one of the groups (i.e. larger than the mean of the control group)
• When not interested in the mean difference between the groups

Question 12

What are p-values for?

Answer 12

To evaluate the probability that the null hypothesis is correct.
- lower than 0.05= the null hypothesis is not considered
- higher than 0.05= sample is compatible with the null hypothesis

Question 13

What is the null hypothesis in a t-test?

Answer 13

That the independent variable has no effect on the dependent variable

Question 14

What does it mean when the p-value is low and when it’s high?

Answer 14

• When the p-value is low, the change brought by the independent is probably not due to chance
• When the p-value is high, then the effect of the dependant value on the dependent variable was probably by chance or didn’t do anything

Question 15

When is the χ-square test used?

Answer 15

• Tests non-parametric qualitative data; most often used with count data
• Used when there is a known expected distribution that can be tested for (often in genetics)

Question 16

What is the χ-square used for?

Answer 16

• Compares the observed distribution of a variable versus the expected distribution of
  the same variable

Question 17

What does the p-value mean if it’s under 0.05 and what does it mean if it’s over 0.05?

Answer 17

• Lower means that their is a big difference between the observed and the expected distribution
• Higher means that the expected and observed distribution are relatively close

Question 18

What is the regression test for?

Answer 18

To test if there is a linear relationship between 2 variables

Question 19

What does the r square value indicate?

Answer 19

R-squared value > 0.9 indicates that data are close to linear

Question 20

What is positive control?

Answer 20

When you know that the test with a certain substance is going to be positive (reference for other substances)

Question 21

What is negative control?

Answer 21

When a substance is predicted to have no reaction for a test (reference for other substances)

Question 22

What are the 3 steps for DNA isolation?

Answer 22

➢ Homogenization: Cellular structures must be broken down before DNA can be released from cells. This is done by homogenizing the onion tissue in a blender. Detergents in the homogenizing medium help to solubilize membranes and denature
proteins.
➢ Deproteinization: Chromosomal proteins must be stripped from the DNA by denaturation and precipitation from the homogenate that contains DNA.
➢ Precipitation of DNA: Ice-cold ethanol is added to the homogenate, causing all
components of the homogenate to stay in solution except DNA, which precipitates at the interface between the ethanol and the homogenate layers (Helms et al., 1998).

Question 23

What are the 4 biochemical tests

Answer 23

▪ Benedict’s test for reducing carbohydrates
▪ Lugol’s test for starch
▪ Emulsion test for lipids
▪ Biuret’s test for proteins

Question 24

What is the Benedict’s test for?

Answer 24

When added to a sugar solution, the alkaline solution will linearize any ringed monosaccharides present, making their carbonyl groups
available. The carbonyl groups will then reduce Cu2+ to Cu+, producing a red-colored precipitate (Figure 0-3). Thus, a positive Benedict’s test will form a red precipitate

Question 25

How does Lugol’s test (iodine/potassium iodide, I2KI) work?

Answer 25

Iodine complexes with helically-coiled, linear polysaccharide chains (such as the amylose form of starch), resulting in a black or dark blue color. Branched polysaccharides (such as glycogen or the amylopectin form of starch) form a less intense, red-violet color.

Question 26

What is the Emulsion test for?

Answer 26

Lipids dissolve in ethanol. If there are lipids dissolved in the ethanol, they will precipitate in the water, forming
a cloudy white (milk-like) emulsion (drops of liquid that can’t mix with the solvent).

Question 27

How does Biuret’s test work?

Answer 27

The copper ions in the Biuret reagent react with peptide bonds, converting the dye from a blue (negative result) to a violet color (positive result).

Question 28

What does Benedict’s test not detect?

Answer 28

Polysaccharides because they do not contain free carbonyl groups (aldehyde or ketone functional groups)

Question 29

What does Biuret’s test not detect?

Answer 29

Free amino acids do not react with the Biuret reagent

Question 30

DNA molecular visualization

Question 31

What is the field diameter formula?

Answer 31

1. Measure the diameter with a ruler in 4X (result in mm)
2. The use this formula: 𝑀𝑎𝑔𝑖 × 𝐹𝐷𝑖 = 𝑀𝑎𝑔𝑗 × 𝐹𝐷𝑗
   ex.: 𝑀𝑎𝑔4𝑋 × 𝐹𝐷4𝑋 = 𝑀𝑎𝑔10𝑋 × 𝐹𝐷10𝑋
   4 × 3.5𝑚𝑚 = 10 × 𝐹𝐷10𝑋
   𝐹𝐷10𝑋 = 4 × 3.5𝑚𝑚⁄10
   𝐹𝐷10𝑋 = 1.4𝑚𝑚

Question 32

How does Paramecium eat and move?

Answer 32

Nutrition: heterotrophic
Locomotion: cilia

Question 33

How does Trypanosoma eat and move?

Answer 33

Nutrition: heterotrophic
Locomotion:flagellum

Question 34

How does Amoeba eat and move?

Answer 34

Nutrition:heterotrophic
Locomotion: pseudopods

Question 35

How does Perdinium eat and move?

Answer 35

Nutrition:autotrophic
Locomotion:flagellum

Question 36

How does Volvox eat and move?

Answer 36

Nutrition:autotrophic
Locomotion:flagellum

Question 37

How does Diatoms eat and move?

Answer 37

Nutrition:autotrophic
Locomotion: transported by current of water

Question 38

L