bio lab quiz 2

what are the 7 steps of the scientific method

observation → question → hypothesis → prediction → experiment → analyze → report results

hypothesis

• tenatative answer to your question

• an explanation to an observation

• MUST be testable and falsifiable

control group

• everything is kept the same as the experimental group except for the independent variable

independent variable

what you change/control

• EX: the drug itself

dependent variable

what you measure/observe as a result

• EX: any changes that occur because of the drug

controlled variables

what you keep the same throughout the experiment so they don’t affact your results

peer-reviewed manuscript

scientific paper of a scientist’s research methods, findings, and interpretations, which is submitted to a scientific journal for publication

what are the 6 sections of a scientific paper

introduction → abstract → materials and methods → results → discussion → conclusion

review articles

summarize and comment on findings that were published as primary literature

Exercise A: How Penicillin Was Discovered

A.1. Identify the problem.

Bacteria were dying near the Penicillium mold.

A.2. What was Fleming's hypothesis?

Mold produced a chemical that killed the bacteria.

A.3. How was the hypothesis tested?

He grew the mold in a nutrient broth, removed the mold, and then transferred the broth onto a culture of bacteria. He observed whether the bacteria died.

A.4. Do the results indicate that the hypothesis should be rejected?

No. The bacteria died after being exposed to the broth, supporting Fleming's hypothesis.

A.5. This experiment led to the development of what major medical advancement?

Penicillin, one of the first antibiotics used to treat bacterial diseases.

Exercise B: Identify the Controls and Variables

1. Muhammad's special juice experiment

• Independent variable: Whether the workers drink the special juice

• Dependent variable: Number of stacks of papers produced

• Control group: Group B, which did not receive the special juice

• Experimental group: Group A, which received the special juice

• Conclusion: The special juice did not increase productivity because Group A made fewer stacks than Group B.

2. Sophia's coconut juice experiment

• Independent variable: Type of liquid used (coconut juice or water)

• Dependent variable: Amount/appearance of green slime after three days

• Control group: The half of the shower sprayed with water

• Experimental group: The half sprayed with coconut juice

• Conclusion: The results did not support the claim, since neither side showed a change.

3. Anh's anti-itch cream experiment

• Independent variable: Type of anti-itch cream used

• Dependent variable: How long it takes for the itching to return

• Control group: Subject A, using the original/leading anti-itch cream

• Experimental group: Subject B, using the new anti-itch cream

• Conclusion: The new cream did not perform as advertised. It lasted 1 hour 45 minutes compared with 2 hours for the original cream.

4. Lisa's Rogooti hair-growth experiment

A good experimental design would be:

• Independent variable: Whether Rogooti is applied to the hair/scalp

• Dependent variable: Speed/rate of hair growth

• Control group: Family members who do not use Rogooti

• Experimental group: Family members who use Rogooti

• Constants: Same length of experiment, measurement method, and ideally similar hair-care routines

• Hypothesis: Rogooti will increase the speed of hair growth.

Exercise C: Reporting Scientific Work

C.1 What is a primary reference?

An original scientific source that reports new research and experiments that the authors themselves conducted

C.2 Name two peer-reviewed scientific journals in the field of Biology.

nature and science

line graph

• showing how something changes over time

• independent variable is a continuous numerical value

bar graph

comparing different categories or groups

pH

measure of the acidity ot alkalinity (basicity)

the pH of a solution is

a measure of the concentration of hydrogen ions [H+]

In pure water

• the number of H+ ions = OH- ions

• 1 × 10^-7 M

• the product of both is 1 × 10^-14 M

pH lower than 7

acidic

pH above 7

basic/alkaline

the more completely an acid ionizes

the more H+ is released, the stronger the acid

a base is a substance that

decreases the number of H+ and increases OH- in solution

buffers

• solution that resists changes in pH when small amounts of acid or base are added

• can act as both an acid and base

[H+] equation 1

[H+] = concentration x degree of ionization

[H+] equation 2 (antilong)

[H+] = 10^-pH

[OH-] equation 1

[OH-] = concentration x degree of ionizaiton

[OH-] equation 2 with [H+]

[OH-] = 1 × 10^-14 / [H+]

pH equaiton

pH = -log[H+]

[H+] and [OH-] equation

[H+] x [OH-] = 1 × 10^-14

pOH equation

pOH = - log[OH-]

pH + pOH =

• 14

• pH = 14 - pOH