The fifteen ideas the test is built on, how the questions work, and every term you need.
Take the practice test first. It will tell you which topics are weak. Then come here and read only those sections closely, rather than starting at the top and drifting.
This page is a summary, which means it is shorter than the unit. Use it to organize what you know and to find your gaps, then go back to your notes, the slide deck, your model tracker, and the case file for the detail. If you can read a section here and explain it out loud without looking, you know it. If you can only recognize it, you do not know it yet.
Everything on the quiz comes out of these. The line at the bottom of each one tells you how it tends to get asked.
The early Earth had the right ingredients and energy for simple organic molecules to form, in warm pools and around hydrothermal vents. Nobody was there to watch, so this is the part of the unit built on inference rather than observation.
On the quiz: You get asked what conditions mattered and why this step is a hypothesis supported by evidence rather than something witnessed.
A protocell is a membrane bubble that can enclose chemicals, grow, and split. That is already enough for selection to act, because the bubbles varied, some copies survived, and resources ran short.
On the quiz: You get asked to tell a protocell from a true cell, and to explain why selection could start before real cells existed.
LUCA is the last universal common ancestor, the population every living thing today descends from. Plenty of life existed before LUCA and alongside it. LUCA is just the branch all surviving lineages trace back to.
On the quiz: The trap is calling LUCA the first life ever. Also know that we have no fossil of LUCA, since it is inferred from what all living things share.
DNA as the information molecule, ribosomes to build proteins, and nearly the same genetic code. An identical system across all life is the single strongest argument for one common ancestor.
On the quiz: You get asked why coincidence and convergence fail to explain it. Convergence produces similar solutions, not identical ones.
Bacteria, Archaea, and Eukarya. Bacteria and Archaea are both prokaryotic, but the surprise is that Archaea are more closely related to us than they are to Bacteria.
On the quiz: You get asked to sort a mystery organism by its features, and the archaea result is the one students miss.
Protista, Fungi, Plantae, Animalia. All four have cells with a nucleus and membrane bound organelles, and all four sit inside one domain.
On the quiz: The trap is sliding Bacteria or Archaea into the kingdom list. They are domains and they sit outside Eukarya entirely.
A large cell engulfed a smaller bacterium and did not digest it. The bacterium kept working inside, both benefited, and over a very long time they became a single organism. That is where mitochondria came from, and chloroplasts the same way later.
On the quiz: You get asked to put the steps in order, and to explain why engulfing without digesting is the key move.
Four things give it away. Two membranes, its own circular DNA, its own bacteria sized ribosomes, and it divides on its own schedule rather than with the cell.
On the quiz: You get asked which observation supports the theory, and the trap is a fact that is true but irrelevant, like mitochondria making ATP.
Once cells stayed together and stopped each doing every job, they could specialize. Specialized cells make tissues, tissues make organs, and that is what a complex body is.
On the quiz: You get asked what specialization buys an organism, and how it connects to the size and complexity of Cambrian animals.
In a few million years, a geological blink, most major animal body plans appear in the fossil record. Rising oxygen and the energy from aerobic respiration are what made bodies that expensive possible.
On the quiz: You get asked what it was and what made it possible. The trap answers call it the origin of life or a mass extinction.
Homologous means the same underlying structure inherited from a shared ancestor, like a bat wing and your arm. Analogous means the same job from similar pressure with different internals, like a bird wing and an insect wing. Vestigial means a shrunken leftover that no longer does its old job.
On the quiz: This is the most tested distinction in the unit. Ask what the structure is made of, not what it is used for.
The fewer differences between two species in the same gene, the more recently they shared an ancestor. This is why whales come out closest to hippos even though they look like fish.
On the quiz: You get a table and have to rank relatedness. The trap is saying one living species evolved from another, when both descend from a shared ancestor that is neither of them.
A trait marked on the tree appeared once, and every branch after that mark inherits it. The organism sharing the fewest traits branches off first, and a trait everybody has marks the base rather than any later split.
On the quiz: You get a trait table and have to build or read the tree. Count shared derived traits and work from fewest to most.
Fossils show traits appearing and disappearing at different times, which is what a transition looks like. Biogeography shows that related species cluster where geography put them, like the sloths.
On the quiz: You get a dated fossil table and have to read down the age column, or a map question about why relatives live where they do.
Four conditions: variation, more offspring than can survive, differences in survival and reproduction, and the trait being inherited. Fitness means surviving and reproducing, not being strong or fast.
On the quiz: You get a scenario missing one condition and have to name which. Any answer where an individual changes its own genes is wrong.
This fills in as you mark the ideas above. Work from the top down. Nothing here is saved, so print it or write it down before you close the tab.
Nothing marked yet. Go back up and rate each of the fifteen ideas honestly. Guessing high here only costs you later.
Expect questions that ask what each activity was modelling, and what it was evidence of.
You started as a micelle and worked toward becoming a prokaryote. That phase was modelling abiogenesis, the move from a lipid bubble to a cell that could copy itself and run its own chemistry.
You engulfed another cell instead of eating it. That is endosymbiosis, and it is where mitochondria came from. The payoff was a huge jump in available energy.
You merged with cells like yourself and specialized. That is multicellularity, and specialization is what makes tissues, organs, and eventually Cambrian bodies possible.
Each station was one line of evidence. The python leg bones were vestigial structures. The DNA strips put whales nearest hippos, showing molecules beat body shape. The sloth station was biogeography. The sorting station was telling convergent from divergent. Archaeopteryx was a transitional fossil. Be able to say what each one proved, not just what was on the table.
Different tools competing for the same seeds is natural selection running in front of you. Variation in beak type, competition for limited food, and differences in who got enough to survive. Every condition of natural selection is in that activity.
The content is half the battle. These are the habits that pick up the other half.
Homologous or analogous is decided by internal structure. A bat wing and a bird wing both fly, but the bones tell you one story is shared ancestry and the other is convergence.
Body shape can be produced by the environment, so it can mislead. Sequence differences record descent. The whale and hippo result is the example to carry into the test.
Cross out any answer where an organism develops a trait because it needed one, or changes its own body and passes that change on. Those are wrong every single time.
Selection shifts how common a trait is across generations. If an answer has one organism transforming itself, it is wrong no matter how reasonable the rest sounds.
Many selection questions describe a population where one of the four conditions is absent. Check each one against the scenario before you look at the choices.
On a fossil or sequence table, pick the one column the question turns on and read it top to bottom. Look for where a value stops changing, or where a trait appears or disappears.
The hardest wrong answers are true statements that do not answer the question. Mitochondria do make ATP, but that tells you nothing about where they came from.
You should be able to give a one sentence definition of each of these without hesitating.
| Abiogenesis | The origin of life from nonliving chemistry. |
| Protocell | A membrane bubble that could grow and divide, but was not yet a true cell. |
| LUCA | The last universal common ancestor, the population all living things descend from. |
| Prokaryote | A cell with no nucleus and no membrane bound organelles. Bacteria and Archaea. |
| Eukaryote | A cell with a nucleus and membrane bound organelles. |
| Domain | The broadest group in classification. There are three: Bacteria, Archaea, Eukarya. |
| Kingdom | The group below domain. Eukarya has four: Protista, Fungi, Plantae, Animalia. |
| Endosymbiosis | One cell engulfing another and keeping it alive until the two become one organism. |
| Mitochondrion | The organelle that makes most of a cell's ATP. Descended from an engulfed bacterium. |
| Chloroplast | The organelle that performs photosynthesis. Also descended from an engulfed bacterium. |
| Multicellularity | Cells staying together as one organism instead of living separately. |
| Specialization | Cells taking on different jobs instead of each doing everything. |
| Cambrian explosion | The rapid appearance of most major animal body plans in the fossil record. |
| Common ancestor | A species that two or more later species both descend from. |
| Homologous structure | A structure shared by different species because it was inherited from an ancestor. |
| Analogous structure | A structure that does the same job in unrelated species, from similar pressures. |
| Vestigial structure | A reduced leftover of a structure that functioned in an ancestor. |
| Convergent evolution | Unrelated species evolving similar traits because they face similar conditions. |
| Divergent evolution | Related species becoming more different as they adapt to different conditions. |
| Transitional fossil | A fossil showing a mix of traits from an older group and a newer one. |
| Biogeography | The study of where species live, and what that reveals about their history. |
| Cladogram | A branching diagram showing how species are related by shared derived traits. |
| Phylogenetic tree | A diagram of evolutionary relationships, often including time. |
| Derived trait | A trait that appeared in one lineage and is shared by everything descended from it. |
| Natural selection | The process where heritable traits that help survival and reproduction become more common. |
| Variation | The differences between individuals in a population. |
| Adaptation | An inherited trait that improves survival or reproduction in a given environment. |
| Fitness | How well an organism survives and reproduces in its environment. |
| Struggle for existence | More offspring are produced than the environment can support, so they compete. |
| Descent with modification | Traits passing to offspring with changes, so populations shift over generations. |
| Speciation | The formation of a new species, usually when groups can no longer interbreed. |
| Reproductive isolation | When two populations can no longer produce fertile offspring together. |
You do not have to memorize these. You need to read one and explain what it shows, and what conclusion it supports.
If you can answer all of these out loud, you are ready.