Sampling & laboratory techniques
Practice Flashcards
Flip to reveal answersState the equation for an Rf value.
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 6 Flashcards — Sampling & laboratory techniques
Sign up free to track progress and get spaced-repetition review schedules.
Question
State the equation for an Rf value.
Answer
$R_f = \dfrac{\text{distance moved by the pigment}}{\text{distance moved by the solvent}}$ — both measured from the start line. It has **no units** and is always between **0 and 1**.
Question
A pigment moves 45 mm; the solvent moves 90 mm. What is the Rf?
Answer
Rf = 45 ÷ 90 = **0.50** (no units, because it is a ratio of two lengths).
Question
On a chromatogram, which pigment is the most soluble?
Answer
The one that travels **furthest** — it has the **highest Rf**. The lowest Rf is the least soluble.
Question
How do quadrats let you estimate a whole population?
Answer
Count in several quadrats, take a **mean per quadrat**, find the **density (number per m²)**, then **scale up** to the total habitat area. Using a mean of many quadrats improves reliability.
Question
What does gel electrophoresis separate, and how?
Answer
It separates **DNA fragments by SIZE**: DNA is negatively charged, so an electric field pulls it through the gel and the **smallest fragments travel furthest**.
Question
Which technique amplifies DNA, and which instrument measures respiration rate?
Answer
**PCR** amplifies (copies) DNA; a **respirometer** measures respiration rate (oxygen used per unit time).
Read the notes
Full study notes for Sampling & laboratory techniques
Topic 5.1 hub
Experimental and data skills
More from Topic 5.1
All flashcards in this topic
Biology exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free