Unit 1 AP Bio test

Scientific Method

Steps used to investigate observations, solve problems, and test hypotheses.

Observation

Information gathered through the senses, often leading to a question.

Hypothesis

A testable explanation for an observation, written as "If…, then…" statements.

Experiment

A controlled procedure to test a hypothesis.

Independent Variable

The variable that is manipulated (changed) by the experimenter.

Dependent Variable

The variable that is measured in response to changes in the independent variable.

Control Group

The group that does not receive the experimental treatment; used as a baseline for comparison.

Experimental Group

The group that receives the experimental treatment.

Constants

Variables that are kept the same across all groups to ensure a fair test.

Qualitative Data

Descriptive data (colors, textures, behaviors, etc.).

Quantitative Data

Numerical data (counts, measurements).

Sample Size

The number of subjects in each group; larger sample sizes increase reliability.

Replication

Repeating an experiment to confirm results.

Bias

When results are influenced by personal opinions or expectations rather than data.

Conclusion

A statement that explains whether the hypothesis was supported or rejected.

Theory

A well-supported explanation of natural phenomena based on evidence.

Descriptive Statistics

Summarizes and describes data (e.g., mean, median, mode).

Mean

The average of a set of numbers.

Median

The middle value when numbers are ordered.

Mode

The most frequently occurring value in a data set.

Range

Difference between the highest and lowest values.

Variance

Measure of how spread out data values are from the mean.

Standard Deviation

Square root of variance; shows average distance from the mean.

Inferential Statistics

Makes predictions or inferences about a population from a sample.

Sampling

A subset of a population used to represent the whole.

Random Sampling

Each member of the population has an equal chance of being selected.

Population

The entire group of interest in a study.

Sample

A smaller group taken from the population for analysis.

Normal Distribution

A bell-shaped curve where most values are near the mean.

Skewed Distribution

When data is lopsided, not symmetrical around the mean.

Positive Skew

Distribution with a long tail to the right.

Negative Skew

Distribution with a long tail to the left.

Standard Error of the Mean (SEM)

Estimates how far the sample mean is from the population mean.

Confidence Interval (CI)

A range of values likely to contain the true population mean.

95% Confidence Interval

We are 95% confident the true mean lies within this range.

Statistical Significance

Indicates whether results are likely due to chance.

P-value

The probability results occurred by chance; <0.05 is often considered significant.

Correlation

Measure of the relationship between two variables.

Positive Correlation

As one variable increases, the other increases.

Negative Correlation

As one variable increases, the other decreases.

No Correlation

No relationship between variables.

Causation

When one variable directly affects another.

Outlier

A value much higher or lower than the others in a dataset.

Histogram

Graph showing frequency distribution of data.

Box Plot

Graph showing median, quartiles, and outliers.

Scatterplot

Graph showing the relationship between two variables.

Replication in Statistics

Repeating studies or trials to ensure reliability.

Polarity

A molecule with an uneven distribution of charges.

Cohesion

Water molecules sticking to each other due to hydrogen bonding.

Adhesion

Water molecules sticking to other polar molecules or surfaces.

Surface Tension

The inward pull of molecules at the surface of water, creating a thin film.

Capillary Action

Movement of water upward through narrow tubes due to cohesion and adhesion.

Meniscus

The curve of the surface of water in a container due to adhesion.

Concave Meniscus

Curves downward; adhesion is stronger than cohesion (e.g., water in glass).

Convex Meniscus

Curves upward; cohesion is stronger than adhesion (e.g., mercury in glass).

Specific Heat

The amount of energy required to raise the temperature of 1 gram of a substance by 1°C.

High Specific Heat of Water

Water absorbs and retains heat, moderating Earth's climate and body temperature.

Density

Mass per unit volume (g/mL or g/cm³).

Density of Ice

Ice is less dense than liquid water because hydrogen bonds form a crystalline structure.

Universal Solvent

Water dissolves many substances because of its polarity.

Solution

A homogeneous mixture where one substance is dissolved in another.

Solvent

The substance doing the dissolving (e.g., water).

Solute

The substance being dissolved (e.g., salt).

Hydrogen Bond

A weak attraction between a hydrogen atom and a more electronegative atom like oxygen.

Intermolecular Forces

Attractive forces between molecules.

Importance of Water’s Properties

Essential for life processes such as temperature regulation, nutrient transport, and habitat stability.

Atomic Number

The number of protons in an atom’s nucleus; defines the element.

Atomic Mass

The average mass of all isotopes of an element (protons + neutrons).

Isotopes

Atoms of the same element with different numbers of neutrons.

Periodic Table

A chart organizing elements by atomic number and showing repeating patterns.

Groups (Periodic Table)

Vertical columns; elements in the same group have the same number of valence electrons.

Periods (Periodic Table)

Horizontal rows; elements in the same period have the same number of electron shells.

Valence Electrons

Electrons in the outermost shell; determine chemical properties.

Chemical Bond

Force that holds atoms together to form compounds.

Covalent Bond

Bond formed when atoms share electrons.

Nonpolar Covalent Bond

Equal sharing of electrons (e.g., O₂).

Polar Covalent Bond

Unequal sharing of electrons, creating partial charges (e.g., H₂O).

Ionic Bond

Bond formed when electrons are transferred, creating charged ions (e.g., NaCl).

Role of Water in Life

Stabilizes climate, supports metabolism, and provides habitats.