AP Biology Unit 1 — Scientific Inquiry, Chemistry & Macromolecules

Complete 280-card review for AP Biology Unit 1.

What is scientific inquiry?

The process scientists use to investigate questions and develop explanations about the natural world.

What is the general process of scientific inquiry?

Observation → Question → Hypothesis → Experiment → Analyze results → Conclusion.

Does scientific inquiry always follow one fixed sequence?

No. Scientific investigations can follow different sequences depending on the question and experiment.

What is an observation?

Information gathered using the senses or measurements.

What is a qualitative observation?

A descriptive, non-numerical observation.

What is a quantitative observation?

An observation involving numbers or measurements.

What is an inference?

A logical interpretation or explanation based on observations.

What is inductive reasoning?

Using specific observations to develop a general conclusion. Specific → general.

What is deductive reasoning?

Using a general principle to make a specific prediction. General → specific.

What is a hypothesis?

A testable explanation or prediction based on observations or existing evidence.

What characteristics should a good hypothesis have?

It should be testable, evidence-based, and capable of being supported or rejected.

Can a hypothesis be permanently proven?

No. Evidence can support or fail to support a hypothesis.

What is a scientific theory?

A broad explanation supported by a large body of scientific evidence.

Is a scientific theory just a guess?

No. Scientific theories are strongly supported by evidence.

What is a scientific law?

A description of a consistent pattern observed in nature, often expressed mathematically.

Hypothesis vs. theory vs. law?

Hypothesis = testable explanation; theory = broad, well-supported explanation; law = describes a consistent natural pattern.

What is a null hypothesis (H₀)?

A hypothesis stating that there is no significant difference, effect, or relationship between variables.

What is an alternative hypothesis (H₁ or Hₐ)?

A hypothesis stating that there is a difference, effect, or relationship between variables.

What is an independent variable (IV)?

The factor intentionally manipulated or changed by the researcher.

What is an easy way to remember independent variable?

IV = I change.

What is a dependent variable (DV)?

The response that is measured or recorded.

What are constants?

Conditions intentionally kept the same so they do not influence the results.

Why are constants important?

They help ensure that changes in the dependent variable are caused by the independent variable rather than another factor.

What is a control group?

A group or condition used as a baseline for comparison with the experimental treatment.

What is a positive control?

A treatment known to produce an expected response, showing that the experimental system can produce a result.

What is a negative control?

A treatment expected to produce no response, establishing a baseline for comparison.

What are examples of negative controls?

A placebo, untreated group, no fertilizer, or another condition expected to cause no experimental effect.

Do experiments always require both positive and negative controls?

No. The appropriate controls depend on the experiment.

Why are repeated trials important?

They increase reliability and reduce the influence of random variation.

Why is adequate sample size important?

Larger samples generally provide more reliable estimates of the population and reduce standard error.

What is a population?

The entire group scientists want to understand or draw conclusions about.

What is a sample?

A smaller group collected from a population and used to make inferences about the population.

What is a normal distribution?

A roughly symmetrical, bell-shaped distribution centered around the mean.

In a normal distribution, about what percentage of data is within ±1 SD?

About 68%.

About what percentage is within ±2 SD?

About 95%.

About what percentage is within ±3 SD?

About 99.7%.

What is the mean?

The arithmetic average: sum of all values ÷ number of values.

How do outliers affect the mean?

The mean can be strongly shifted by extreme values.

What is the median?

The middle value when observations are arranged from smallest to largest.

How do you find the median with an even number of values?

Average the two middle values.

Is the median strongly affected by outliers?

Usually much less than the mean.

What is the mode?

The value occurring most frequently.

Can a dataset have multiple modes?

Yes. It can have one mode, multiple modes, or no mode.

What is range?

Maximum value − minimum value.

What does a larger range generally indicate?

Greater spread or variability in the data.

What is standard deviation (SD)?

A measure of how spread out individual observations are around the mean.

What does a small standard deviation mean?

The observations are clustered relatively close to the mean.

What does a large standard deviation mean?

The observations are more spread out from the mean.

What is standard error (SE)?

A measure of the uncertainty or precision of a sample mean as an estimate of the population mean.

What is the standard error formula?

SE = s/√n, where s = sample standard deviation and n = sample size.

What happens to SE when sample size increases?

SE decreases.

What does a smaller SE indicate?

A more precise estimate of the population mean.

What is the key difference between SD and SE?

SD = spread of individual observations. SE = precision/uncertainty of the sample mean.

What are error bars?

Graphical representations of variability or uncertainty around a measured value such as a mean.

What does ±2 SE represent approximately under common assumptions?

Approximately a 95% confidence interval.

For our class, what does overlapping error bars generally indicate?

The difference is generally treated as not statistically significant.

For our class, what do non-overlapping error bars generally suggest?

The difference may be statistically significant.

What is matter?

Anything that has mass and occupies space.

What is an element?

A substance that cannot be broken down into simpler substances by ordinary chemical reactions.

Approximately how many naturally occurring elements are there?

About 92.

What is a compound?

A substance consisting of two or more different elements chemically combined in a fixed ratio.

What are examples of compounds?

H₂O and NaCl.

What does CHONPS stand for?

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur.

Why are essential elements important?

They help build biological structures and participate in essential chemical reactions.

What are trace elements?

Elements required by organisms in very small amounts.

Why are trace elements important?

They can be necessary for enzymes, hormones, metabolism, and other normal biological functions.

What charge does a proton have and where is it located?

Positive charge; located in the nucleus.

What charge does a neutron have and where is it located?

No charge; located in the nucleus.

What charge does an electron have?

Negative charge.

Where are electrons located?

In orbitals/electron shells surrounding the nucleus.

What is the atomic number?

The number of protons in an atom.

In a neutral atom, how do protons and electrons compare?

Number of protons = number of electrons.

How many electrons can the first shell hold in the simplified model?

2.

How many electrons can the second shell hold in the simplified biological model?

8.

What are valence electrons?

Electrons in an atom's outermost occupied shell.

Why are valence electrons important?

They largely determine chemical reactivity and bonding behavior.

Why do elements in the same periodic-table group often have similar chemical properties?

They have similar valence-electron configurations.

What does a Bohr model show?

The nucleus and electrons arranged into energy levels/shells.

What does a Lewis dot structure show?

The element symbol surrounded by its valence electrons.

Why do atoms form chemical bonds?

Bonding can produce more chemically stable electron arrangements.

What is a covalent bond?

A bond formed when atoms share electrons.

What is a single covalent bond?

One shared pair of electrons.

What is a double covalent bond?

Two shared pairs of electrons.

What is a triple covalent bond?

Three shared pairs of electrons.

What is a nonpolar covalent bond?

A covalent bond in which electrons are shared approximately equally.

What is a polar covalent bond?

A covalent bond in which electrons are shared unequally.

What causes unequal electron sharing?

A difference in electronegativity between bonded atoms.

What is electronegativity?

An atom's ability to attract shared electrons toward itself.

What is the general electronegativity trend across the periodic table?

It generally increases left → right and bottom → top.

Why is water polar?

Oxygen is more electronegative than hydrogen, so electrons are shared unequally.

What partial charge does oxygen have in water?

δ−

What partial charge do the hydrogens have in water?

δ+

What is an ionic bond?

An attraction between oppositely charged ions formed after electrons are transferred.

What is a cation?

A positively charged ion that has lost electrons.

What is an anion?

A negatively charged ion that has gained electrons.

What happens to Na when NaCl forms?

Na loses an electron and becomes Na⁺.