AP Environmental Science Critical Knowledge Topics

Explain the difference between an organism and a molecule. Give an example of each.

An organism is a living thing made of cells (e.g., a tree, a bacterium); a molecule is two or more atoms bonded together (e.g., H₂O, glucose) — molecules are not alive.

photosynthesis equation

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

cellular respiration equation

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)

How are photosynthesis and cellular respiration related to each other?

They are reverse processes — the products of one are the reactants of the other, cycling matter and energy through ecosystems.

Explain the difference between aerobic and anaerobic decomposition. Which one produces methane?

Aerobic decomposition uses oxygen and produces CO₂; anaerobic decomposition occurs without oxygen and produces methane (CH₄).

Define heterotroph and autotroph. Do heterotrophs need organic or inorganic molecules to survive? What about autotrophs?

Heterotrophs need organic molecules (they consume other organisms for food). Autotrophs need only inorganic molecules (CO₂, water, sunlight) to make their own food.

What is the function of an enzyme in a biological reaction?

Enzymes speed up (catalyze) chemical reactions without being consumed.

What does it mean for an enzyme to become "denatured," and what commonly causes this?

Denaturation is when an enzyme loses its shape and stops functioning, commonly caused by high temperature or extreme pH.

Match each macromolecule to its basic function: proteins, carbohydrates, lipids, nucleic acids.

Proteins: structure/enzymes/transport.

Carbohydrates: short-term energy/structure.

Lipids: long-term energy storage/membranes.

Nucleic acids: store genetic information.

What atoms make up a carbohydrate? What atoms make up a protein (in addition to those)?

Carbohydrates: carbon, hydrogen, oxygen. Proteins: carbon, hydrogen, oxygen, plus nitrogen (and sometimes sulfur).

Explain the difference between an atom and a molecule, using carbon and carbon dioxide as an example.

Carbon is a single atom (element); carbon dioxide (CO₂) is a molecule made of one carbon atom bonded to two oxygen atoms.

Compare nitrogen (N₂) to ammonia and nitrate. Are they atoms, elements, or compounds?

Nitrogen gas (N₂) is an element/atom pair; ammonia (NH₃) and nitrate (NO₃⁻) are compounds/molecules containing nitrogen bonded to other elements.

Compare phosphorus to phosphate and phospholipid. What is the key structural difference?

Phosphorus is an element; phosphate (PO₄³⁻) is a molecule/ion containing phosphorus and oxygen; a phospholipid is a larger molecule built using a phosphate group attached to a lipid.

Give the chemical formula for nitric acid, sulfuric acid, and carbonic acid.

Nitric acid: HNO₃. Sulfuric acid: H₂SO₄. Carbonic acid: H₂CO₃.

Explain how natural selection can lead to speciation over time. What is the difference between a variation and an adaptation?

Natural selection favors individuals with helpful variations (adaptations), which are passed to offspring; over many generations this can cause populations to diverge enough to become separate species. A variation is any trait difference; an adaptation is a variation that improves survival/reproduction.

Define and give an example of the difference between an individual, a population, and a species.

Individual: one organism (one deer). Population: all members of one species in an area (all deer in a forest). Species: a group of populations capable of interbreeding (white-tailed deer as a whole).

In an experiment testing how fertilizer amount affects plant growth, identify the independent variable, the dependent variable, and the control group. Then explain what would need to be included on a properly labeled graph of this data (axes and title).

Independent variable: amount of fertilizer. Dependent variable: plant growth (e.g., height). Control group: plants receiving no fertilizer. Graph should have a clearly labeled x-axis (fertilizer amount), y-axis (plant growth, with units), and a scientific title describing the relationship shown (e.g., "Effect of Fertilizer Amount on Plant Growth").