Biology Lab 1-3 Flashcards

What is the part of the microscope you look through to see the specimen?

Ocular lens (eyepiece).

Which microscope part adjusts the amount of light passing through the specimen?

Diaphragm.

Which knob moves the stage in large steps vs small steps?

Coarse adjustment (large steps), Fine adjustment (small steps).

What happens to the field of view as magnification increases?

It decreases (you see less area but in more detail).

What happens to depth of focus as magnification increases?

It decreases; only thin slices are in focus at once.

Define magnification.

The enlargement of an image using ocular and objective lenses.

Define field of view.

The circular area visible through the microscope.

If the ocular lens is 10x and the objective is 40x, what is total magnification?

400x.

Who invented the first simple microscope and what did he observe?

Anton van Leeuwenhoek; observed “animalcules” (microorganisms).

Who coined the term “cell”?

Robert Hooke, while observing cork cells.

List the correct order of viewing a specimen under the microscope.

• Start with 4x + stage up

• Place slide

• Adjust coarse focus

• Switch to 10x

• Adjust fine focus

• Switch to 40x

• Fine focus

• Reset to 4x

• Turn off the light.

Why is lab safety important?

Prevents contamination, protects people and equipment, ensures valid results.

Example of independent, dependent, and control group in an experiment?

Independent = variable manipulated

Dependent = what changes in response

Control = baseline group for comparison.

What is a scientific theory vs scientific principle?

Theory = supported explanation based on evidence

Principle = widely accepted, established scientific truth.

What is chromatography used for?

To separate mixtures into their individual components.

What are the stationary and mobile phases in paper chromatography?

Stationary Phase: The paper

Mobile Phase: The solvent

Define Rf value.

Distance traveled by solute ÷ distance traveled by solvent (from baseline).

What does it mean if two dyes have the same Rf value?

They are likely the same substance.

If Rf for dye A = 0.8 and dye B = 0.3, which is more soluble?

Dye A (higher Rf = moved farther in solvent).

Name two factors that influence migration in chromatography.

Solubility in solvent and size of solute molecules.

What is the independent and dependent variable in chromatography?

Independent = solvent (mobile phase); Dependent = distance traveled by solute.

Convert 7 × 10⁻¹ mm into meters.

0.07 m

What are the base units of the metric system for: length, mass, volume, time, temperature, amount of substance?

Meter (m), Gram (g), Liter (L), Second (s), Kelvin (K), Mole (mol).

Difference between accuracy and precision?

ccuracy = closeness to true value

Precision = consistency of repeated measurements.

Define an isotope.

Atoms of the same element with the same # protons but different # neutrons.

Define an ion.

Atom with unequal # of protons and electrons → carries a charge.

If an atom has 8 protons, 8 neutrons, and 5 electrons: neutral? ion? stable?

it is an unstable positive ion

Define polar covalent bond.

Bond where electrons are shared unequally due to differences in electronegativity.

What causes partial charges (δ⁺, δ⁻) in a molecule?

Unequal sharing of electrons.

What is a polar molecule? Give an example.

Molecule with unequal charge due to unequal sharing of electrons; Example: water (H₂O).

What is the pH of pure water?

7 (neutral; [H⁺] = [OH⁻]).

If a solution moves from pH 6 to pH 7, what happened to H⁺ concentration?

It decreased tenfold (less acidic).

Define strong acid vs weak acid.

Strong acid fully dissociates in water. Weak acid partially dissociates in water.

What is a buffer?

A solution that resists changes in pH when an acid or base is added. It is a weak acid/base system that resists large pH changes by absorbing H⁺ or OH⁻.

What is the role of phenolphthalein in titration?

pH indicator: colorless in acid, pink in base.

Why doesn’t pH rise immediately in titration of acetic acid with NaOH?

Added OH⁻ neutralizes H⁺ from acetic acid first; pH rises only after equivalence point.

What is the equivalence point in titration?

Point where moles of acid = moles of base; solution shifts sharply in pH.

What happens if more NaOH is added beyond equivalence point?

Excess OH⁻ makes solution more basic → pH rises sharply.

On a titration graph, which is the independent variable (x-axis) and dependent (y-axis)?

Independent = volume of NaOH; Dependent = pH.

What is depth of field in microscopy?

The vertical range that is in focus at one time

Why do scientists use the metric system in biology?

It’s universal, based on powers of 10, and allows consistent, precise measurements across experiments.

What’s the difference between a control group and an experimental group?

Control = baseline for comparison (no treatment or placebo). Experimental = group exposed to the independent variable.

What’s the relationship between pH and [H⁺] concentration?

pH = –log[H⁺]; as [H⁺] increases, pH decreases (more acidic).

Why does water form hydrogen bonds?

Because of its polarity: oxygen is partially negative, hydrogen is partially positive, so opposite charges attract between molecules.

Give an everyday example of a buffer and its importance.

Human blood (~pH 7.4). Buffers keep pH stable so enzymes and cells can function properly.

Ocular lens (eyepiece)

Where you look through; usually has 10x magnification.

Objective lenses

Provide different magnifications (commonly 4x, 10x, 40x, 100x). Rotates on the nosepiece.

nosepiece

Holds the objective lenses and allows you to switch between them.

Stage

Flat platform that holds the slide.

Stage clips

Secure the slide in place on the stage.

Coarse adjustment knob

Moves the stage up/down for rough focusing. Only used with 4x objective.

Fine adjustment knob

Makes small adjustments for sharp focus, used at higher powers.

Diaphragm (or iris)

Controls the amount of light that passes through the specimen.

Condenser

Focuses light onto the specimen for clearer viewing.

Illuminator (lamp)

Provides the light source for viewing specimens.

Arm

Connects the base and head; used to carry the microscope.

Base

Bottom support of the microscope.