A readable version of the review deck — every slide, in order. Tap a topic to jump to it.
Part 1
Characteristics of Life
ObjectivesWhat you should be able to do
Describe the nine properties common to living things.
Describe the levels of biological organization from atoms to the biosphere, and how they interrelate.
Define emergent properties and give an example.
Make an argument for or against a virus being non-living.
Explain how water's polarity leads to specific heat, surface tension, adhesion, cohesion, and how it interacts with other substances.
Explain the difference between polar and nonpolar covalent bonds (unequal vs equal sharing of electrons).
Identify polar and nonpolar molecules and how polarity affects interaction with water.
Define hydrophobic and hydrophilic interactions.
Identify polar and nonpolar bonds/regions in large molecules.
IntroWhat is biology?
bio- (Greek) = life, living. -logos = study.
Biology is the study of the diverse forms, processes, and systems of life — with many branches: zoology, botany, genetics, microbiology, ecology, biochemistry, and more.
Warm-upWhat are some examples of living things? What do they all have in common?
Core listThe 9 characteristics of life
Living things…
Are organized
Reproduce
Grow and develop
Acquire materials and energy
Respond to the environment
Regulate / maintain homeostasis
Are composed of cells (one or many)
Have genetic material
Evolve
Memory trickHold them in 3 buckets of 3 — build & continue (organized · cells · genes), run the machine (energy · homeostasis · respond), change over time (grow · reproduce · evolve).
1Living things are organized
Life is built in nested levels — each level is made of the one below it.
Emergent properties: complex traits or behaviors that arise from simpler interactions. Each level is more complex than the one before it — "the whole is greater than the sum of its parts." (Like separate bricks vs. a house.)
2Living things reproduce
Reproduction: the ability of an organism to copy itself.
Sexual: in most multicellular organisms, a sperm and egg fuse.
Asexual: some organisms simply split in two (e.g. bacteria, protozoa).
3Living things grow & develop
Inherited information carried by genes (DNA) controls an organism's pattern of growth and development.
Growth
Increase in mass and size of a body or organs — usually by cells multiplying.
Development
Physiological and functional maturation (e.g. tadpole → frog).
4Living things acquire materials & energy
For most organisms the ultimate source of energy is the sun.
Autotrophs (producers)
Capture the sun's energy through photosynthesis.
Heterotrophs (consumers)
Can't photosynthesize — must get nutrients from other sources.
See the diagrams pageEnergy flow, food chains & the decomposer loop are drawn out there.
5Living things respond to the environment
Organisms respond to stimuli — to get food (energy), for defense, and for survival. (A stimulus is detected by a receptor → sensory neuron → brain/spinal cord → motor neuron → effector.)
Phototropism
A response to the stimulus of light (a plant bending toward a lamp).
Geotropism
A response to the stimulus of gravity — shoots grow up (away), roots grow down (toward).
6Living things regulate their internal environment
Homeostasis: maintenance of stable internal conditions.
Example — jackrabbits have disproportionately large ears to deal with desert heat:
Large surface area for heat exchange.
Blood vessels widen so more warm blood circulates to the ears → more heat loss.
7Living things are composed of cells
Cell theory (1838, Schleiden & Schwann):
All life forms are made from one or more cells.
Cells only arise from pre-existing cells.
The cell is the smallest form of life.
8Living things have genetic material
What is a gene? A portion of a DNA and/or RNA molecule that codes for (makes) another molecule (RNA or protein).
🧬DNA→transcription📜RNA→translation🧶Protein
9Living things evolve
Species change over time. All living things are descendants of single-celled organisms.
One single origin? We may never know for sure — but the tree of life connects Bacteria, Archaea, and Eukaryotes back to a common root.
?Is a virus living?
Capsid: a protein shell that surrounds a virus's genetic material (DNA or RNA).
A virus lifecycle: ① attaches to a host cell → ② enters (capsid comes apart) → ③ hijacks the cell to copy its genome and make viral proteins → ④ new viruses assemble → ⑤ release, off to infect a new cell.
The debateA virus has genes and can evolve, but has no cells and no metabolism, and can't reproduce without a host. Argue a side. (Fully worked out on the diagrams page.)
Part 2
Chemistry: Water & Bonds
WaterProperties of water
Water is polar.
Water is an excellent solvent.
Water has cohesive and adhesive properties (surface tension; capillary action).
Water is less dense as a solid than as a liquid.
Water has high heat capacity (specific heat).
Water has high heat of vaporization.
Almost every special property below traces back to #1 — polarity.
WaterPolarity & why water dissolves things
Polarity: the distribution of electrical charge among the atoms connected by a chemical bond.
Water is a polar molecule: oxygen pulls the shared electrons closer, so O is slightly negative (δ−) and each H is slightly positive (δ+).
That polarity makes water a great solvent:
Solvents dissolve solutes, creating solutions.
Polar H₂O molecules surround + and − ions (e.g. Na⁺ and Cl⁻ from salt) and pull the crystal apart — forming "hydration shells."
WaterHydrophilic vs hydrophobic
💧 Hydrophilic — "water-loving"
Attracts water
Polar
🧈 Hydrophobic — "afraid of water"
Repels water
Nonpolar (e.g. butter, oil)
Like dissolves like: polar mixes with polar, nonpolar with nonpolar.
WaterCohesion & adhesion
Cohesion: hydrogen bonds between water molecules hold them together. Hydrogen bonds occur when H is bonded to N, O, or F.
Surface tension: the surface of a liquid resists an external force — strong enough to hold up a bug or water strider.
Adhesion: hydrogen bonds between water and other substances.
Capillary action: liquid moves through/along another material against an opposing force (gravity) — forms a meniscus; water climbs up towels/cloth or a flower stem.
WaterIce floats · specific heat
Less dense as a solid: in ice, hydrogen bonds lock molecules into a spacious, stable lattice — so ice is less dense than liquid water. That's why ice floats!
Specific heat: the heat required to raise the temperature 1 °C. Water's is high, so it resists temperature change and moderates Earth's temperatures (water heats/cools slower than sand).
Heat of vaporization: the energy needed to change one gram of a liquid to a gas at constant temperature. Water's is high too.
ChemistryElements of life
About 25 elements are essential for life. Six of them — CHNOPS — make up ~98% of living matter:
Trace elements (small amounts): Ca, K, Na, Mg, Mn, Fe, Co, Cu, Zn, Si, Cl.
BondsIntramolecular vs intermolecular forces
Intramolecular
Hold atoms together inside a molecule.
Ionic — attraction between oppositely charged ions (electrons transferred). Weaker; broken by water.
Covalent — sharing of electrons; can be polar (shared unequally) or nonpolar (shared equally).
Intermolecular
Hold different molecules together in a substance.
Hydrogen bonds
Hydrophobic interactions
Tip for the name:intra = "within" one molecule · inter = "between" molecules.
BondsBonds in biology
Whether a bond is polar depends on how equally the two atoms share electrons.
Polar (unequal sharing)
Nonpolar (equal sharing)
C–O
C–H
C=O
C–C
C–N
C=C
N–H
O=O
O–H
N–N
Amphipathic molecules have both polar and nonpolar regions. A fatty acid is the classic example: a polar –COOH "head" 💧 and a long nonpolar hydrocarbon "tail" 🧈.
BondsFunctional groups
Large biological molecules are generally built on a carbon skeleton (carbon + hydrogen). Extra atoms appear as functional groups that give the molecule its behavior.
Group
Structure
Property
Hydroxyl
R–OH
Polar
Methyl
R–CH₃
Nonpolar
Carbonyl
R–C(=O)–R′
Polar
Carboxyl
R–COOH
Charged; releases H⁺ → acidic
Amino
R–NH₂
Charged; accepts H⁺ → basic
Phosphate
R–OPO₃
Charged; releases H⁺ → acidic
Sulfhydryl
R–SH
Polar
PracticeWhich groups can you spot in glucose (lots of –OH hydroxyls) and testosterone (hydroxyl + carbonyl + methyls)?