Lab Exam Biol 213

Selective Pressures

Environmental factors that influence survival and reproduction, including abiotic factors (light, temperature, humidity, pH, sugar, nutrients, salt, antimicrobial agents) and biotic factors (competition).

Independent Variable (Explanatory)

The variable manipulated by the experimenter or used to define groups/conditions expected to explain variation in another variable; plotted on the horizontal (x) axis.

Dependent Variable (Response)

The outcome or response variable measured in an experiment; plotted on the vertical (y) axis.

Categorical Variable

A variable that places observations into discrete groups or categories (e.g., Sex, Diet_Type, Sun_Exposure, Exercise_Level, Disease_Diagnosis).

Continuous Numerical Variable

A numerical variable that can take any value within a continuous range (e.g., BMI, Hemoglobin, Serum Vitamin D, Chlorophyll concentration).

Discrete Numerical Variable

A numerical variable with distinct, countable whole-number values (e.g., Age, Symptoms_Count, number of plants).

Tidy Data

A standardized dataset format where each row represents a single observation, each column represents a single variable, and each cell contains a single value.

Aseptic Technique

Sterile laboratory practices used to prevent contamination of yourself, your bench, and your cultures (e.g., wearing buttoned lab coats, wiping benches with disinfectant, working within a Bunsen burner's sterile field).

Sterile Field

An area of upward thermal airflow (~20–30 cm around a lit Bunsen burner) that reduces airborne microbial contamination.

Bacterial Lawn

A uniform, continuous field of bacterial growth across an agar plate produced by spreading liquid culture evenly; represents an uninterrupted population rather than isolated clonal colonies.

Clonal Colony

A discrete cluster of genetically identical bacteria arising from a single progenitor cell on an agar surface.

Micropipette First Stop

The point of initial resistance on a micropipette plunger used when measuring and aspirating the exact target volume of liquid.

Micropipette Second Stop

The point past the initial resistance pressed only when dispensing liquid to completely evacuate all liquid from the tip.

Zone of Inhibition (ZOI)

A clear circular region around an antimicrobial-infused disk on an agar lawn where bacterial growth is prevented; its diameter measures antimicrobial effectiveness.

Factors Affecting ZOI Size

Compound solubility (diffusion capacity through agar matrix), molecular size (larger molecules diffuse slower and yield smaller ZOIs), and chemical stability/volatility (e.g., rapid evaporation of alcohols).

PICO Framework

A research question structure consisting of Population, Intervention, Comparison (control), and Outcome.

Standard Deviation (SD)

A summary statistic describing the spread or variability of individual raw observations around their sample mean.

Standard Error of the Mean (SEM)

A measure of the precision of an estimated sample mean relative to the true population mean; calculated as SD divided by the square root of sample size (n).

SEM Formula

SEM = SD / sqrt(n)

Mean

The arithmetic average of a dataset; calculated in Excel using =AVERAGE(range).

Median

The middle value of an ordered dataset; calculated in Excel using =MEDIAN(range).

Histogram

A graph used to visualize the distribution, center, spread, shape, and frequency of a single continuous numerical variable grouped into bins.

Bin Width

The range interval of continuous data grouped into each bar of a histogram; setting it too wide hides underlying patterns, while setting it too narrow creates visual noise.

Scatter Plot

A graph displaying paired continuous numerical variables as individual points to evaluate associations or correlations (without connecting points).

Line Graph

A graph displaying continuous data points connected by line segments; appropriate only when the x-axis has a natural, continuous, ordered sequence (e.g., time series).

Box Plot

A statistical chart displaying the distribution of a continuous variable across categories by showing the median, interquartile range (box), spread (whiskers), and potential outliers.

Two-Dimensional Pivot Table

An Excel table that cross-tabulates two categorical variables (rows and columns) while calculating a summary statistic (e.g., average, count) for a numerical variable in each intersection cell.

Excel Custom Error Bars

A chart feature used to display uncertainty (e.g., SEM) by pointing custom positive and negative error amounts to specific calculated cell ranges (e.g., =Plots!$C$2:$C$4).

Eutrophication

The process by which an aquatic ecosystem becomes enriched with excess nutrients (primarily N, P, and K), leading to dense algal blooms, reduced light penetration, oxygen depletion during decomposition, and potential ecosystem collapse.

Oligotrophic

An aquatic ecosystem characterized by low nutrient availability, clear water, low primary productivity, and high dissolved oxygen.

Primary Fertilizer Nutrients (N-P-K)

Nitrogen (N) and Phosphorus (P) for proteins and nucleic acids (DNA/RNA); Potassium (K) for turgor pressure and enzyme activation.

Cyanobacteria vs Green Algae

Cyanobacteria can fix atmospheric nitrogen gas (N2) into bioavailable forms, enabling them to thrive in nitrogen-poor environments where eukaryotic green algae cannot.

Phytoplankton

Microscopic photosynthetic aquatic organisms (including cyanobacteria and eukaryotic microalgae) forming the base of aquatic food webs.

Zooplankton

Microscopic floating aquatic animals/protozoans that feed on phytoplankton and serve as primary consumers.

Microcosm

A miniature, self-contained experimental ecosystem modeling natural field (terrestrial) and pond (aquatic) interactions.

Lugol's Iodine

A chemical stain added to biological samples to fix and kill planktonic cells rapidly, enabling accurate microscopic counts.

Palmer-Maloney Counting Slide

A specialized microscope slide with a precise 100 µL reservoir chamber (0.4 mm depth, 0.02 mm² field area at 10X) used for quantifying cell density.

Zooplankton Dilution Correction

In cell counting, multiplying the per-slide cell count by 2 corrects for the 1:1 dilution caused by adding an equal volume of Lugol's iodine.

Spectrophotometry

An analytical technique measuring light absorbance at specific wavelengths to quantify solute concentration based on Beer-Lambert relationships.

Chlorophyll Absorption Maxima

Chlorophyll a exhibits peak absorption at 665 nm; Chlorophyll b exhibits peak absorption at 649 nm.

Spectrophotometric Blank

A cuvette containing only the solvent (e.g., pure ethanol) used to calibrate the spectrophotometer to zero absorbance before reading experimental samples.

CURE Project Objective

Course-based Undergraduate Research Experience evaluating long-term evolutionary dynamics and bacterial adaptation/resistance to antimicrobial agents over successive generations.

Mutagenic UV Exposure

Brief exposure (e.g., 15 seconds) to ultraviolet radiation used to induce random DNA mutations in bacterial populations to accelerate genetic variation for selection experiments.

CURE Experimental Controls

Distilled water (DW) disks serve as negative controls for antimicrobial assays; non-UV treated (Wild Type/Control) bacterial strains serve as controls against UV-mutated strains.

Biohazardous Waste

Contaminated biological materials, including used agar plates and bacterial cultures, disposed of in designated yellow biohazard or autoclave bins for decontamination.

Sharps Waste

Items capable of puncturing skin (e.g., clean broken glass, scalpels, needles) disposed of in rigid sharps containers.

Excel Function =COUNT(range)

Calculates the total number of numeric entries within a selected range of cells.

Correlation vs Causation

A statistical association between two continuous variables on a scatter plot does not establish that changes in one variable directly cause changes in the other.

Excel Mean Formula

=AVERAGE(range)

Excel Median Formula

=MEDIAN(range)

Excel Count Formula

=COUNT(range)

Excel Maximum Formula

=MAX(range)

Excel Minimum Formula

=MIN(range)

Excel Standard Deviation Formula

=STDEV.S(range)

Excel Standard Error of the Mean Formula

=STDEV.S(range)/SQRT(COUNT(range))

Palmer-Maloney Slide Volume

0.1 mL (or 100 mm³)

Palmer-Maloney Cell Count Formula (Per Slide)

num_cells_per_slide = total_cells_counted * (100 mm³ / (area_of_FoV_at_10X * depth_of_slide_reservoir * num_fields_counted))

Simplified Palmer-Maloney Formula (10X, 5 Fields)

num_cells_per_slide = total_cells_counted * (100 mm³ / (0.02 mm² * 0.4 mm * 5))

Lab 3 Initial Zooplankton Density Formula

# cells per mL of pond water = (num_cells_per_slide * 2 * 5) / 750 mL

Lab 7 Final Zooplankton Density Formula

# cells per mL of pond water = num_cells_per_slide * 20

Spectrophotometer Chlorophyll a Formula

Chlorophyll a (µg/mL) = (13.95 * A665) - (6.88 * A649)

Spectrophotometer Chlorophyll b Formula

Chlorophyll b (µg/mL) = (24.96 * A649) - (7.32 * A665)

Total Plant Chlorophyll Formula

Total Chlorophyll (µg/mL) = Chlorophyll a + Chlorophyll b

Delta Plant Biomass/Height Formula

Δ Value = Final Measurement - Initial Measurement (Lab 3)

Negative Frequency-Dependent Selection

A form of natural selection where a phenotype's fitness increases as it becomes rarer in a population (e.g., predators hunting common morphs).

Negative Assortative Mating

Mating between individuals with different phenotypes, which acts to increase overall population heterozygosity.

Intersexual Selection

Sexual selection driven by mate choice, typically where individuals of one sex (often females) choose mates based on specific traits.

Gene Flow Effect

The movement of alleles between populations, which acts to make separate populations more genetically similar over time.

Stabilizing Selection

Natural selection that favours intermediate phenotypes and selects against both extreme ends of a trait spectrum.

Founder Effect

A form of genetic drift occurring when a small subset of a population colonizes a new area, establishing a population with reduced genetic diversity.

Genetic Drift Genetic Effects

Random changes in allele frequencies that reduce overall genetic variation by increasing homozygosity and decreasing heterozygosity.

Scatter Plot Variable Types

Used specifically to analyze relationships between two continuous numerical variables.

Two-Dimensional Pivot Table Function

An Excel tool used to calculate summary statistics for a numerical variable cross-tabulated across two categorical variables simultaneously.

Correlation vs Causation in Graphs

A scatter plot showing a positive association indicates that high values of two variables tend to occur together, but does NOT prove one variable causes the other.

Tidy Dataset Row Unit

In a tidy dataset, each individual row represents a single observation (e.g., one participant).

Histogram Primary Purpose

Visualizes the shape, frequency, and distribution of values for a single continuous numerical variable.

Optimal Fill Handle Action

Double-clicking the fill handle in Excel to automatically apply a formula down an entire column.

Standard Graph Axis Conventions

The independent (explanatory) variable is placed on the x-axis; the dependent (response) variable is placed on the y-axis.

Comparing Group Means Graph

A column graph (bar chart) is used to compare summary statistics like means across distinct categorical groups.

Connecting Graph Points Criteria

Lines connecting points imply progression or time series; independent continuous paired observations should remain unconnected in a scatter plot.

Standard Deviation (SD) Definition

A metric describing the variation or spread of individual observations around their sample mean.

Overlapping SEM Error Bars Meaning

Visual overlap of SEM error bars does NOT conclusively determine statistical significance or lack thereof without formal hypothesis testing.