In AP Bio, abiotic factors are the non-living components of an environment, such as temperature, sunlight, water, pH, and wind, that act as selective pressures on organisms and limit how populations grow and survive.
Abiotic factors are the non-living parts of an environment that affect living things. Think temperature, sunlight, water availability, soil pH, wind, and salinity. They set the physical conditions an organism has to deal with just to stay alive.
Here's why they show up in two different units. In Unit 7 (Natural Selection), abiotic factors act as selective pressures. The College Board notes that biotic and abiotic environments can fluctuate, and those changes affect the rate and direction of evolution ([AP Bio 7.1.B]). A cold snap, a drought, or a shift in pH can favor one phenotype over another, so the favorable trait gets passed on. In Unit 8 (Ecology), abiotic factors shape population growth dynamics. Organisms have adaptations for obtaining and using energy and matter in a particular environment ([AP Bio 8.3.A]), and the abiotic conditions of that environment help determine birth rates, death rates, and ultimately how big a population can get.
Abiotic factors connect two big AP Bio ideas that students usually treat as separate. Under [AP Bio 7.1.B], they're a cause of natural selection, because a fluctuating non-living environment changes which phenotypes survive and reproduce. Under [AP Bio 8.3.A], they're a limit on population growth, because conditions like temperature and water availability affect death rates and constrain the exponential growth predicted by dN/dt = B - D. The connecting theme is the same: organisms succeed or fail based on how well their traits match the environment, living and non-living. That fitness-meets-environment logic runs through evolution, speciation, and ecology, so understanding abiotic factors pays off across the whole back half of the course.
Keep studying AP Biology Unit 8
Biotic Factors (Units 7-8)
Biotic factors are the living parts of an environment (predators, competitors, food), while abiotic factors are the non-living parts. Together they make up the total set of pressures an organism faces, and the AP exam routinely asks you to sort one specific example into the right bucket.
Evolutionary Fitness (Unit 7)
Fitness is measured by reproductive success, and abiotic conditions help decide who reproduces. When the non-living environment shifts, the phenotype with the highest fitness can shift right along with it, which is exactly the fluctuation [AP Bio 7.1.B] describes.
Carrying Capacity (Unit 8)
Carrying capacity (K) is partly set by abiotic limits like water, light, and temperature. A population can grow exponentially until those non-living resources run short, which is when the dN/dt curve flattens out.
Allopatric Speciation (Unit 7)
Abiotic features like rivers, mountains, or ocean barriers can physically separate populations. That geographic split, driven by the non-living landscape, lets two populations evolve independently until they become different species.
On multiple choice, the classic move is identifying whether a given example is abiotic or biotic and how it affects survival. You'll see stems like "Which abiotic factor affects population survival?" where the right answer is something non-living (temperature, water, sunlight) and the trap answers are living things. On FRQs, abiotic factors usually appear inside a natural-selection scenario. The 2026 anole lizard short FRQ, for instance, deals with genetically determined toe-pad size, the kind of trait whose advantage depends on the physical environment the lizard lives in. What you actually have to do: explain how a specific abiotic condition changes which phenotype survives and reproduces, or how it limits a population's growth using birth and death rates.
Abiotic means non-living; biotic means living. Temperature, sunlight, pH, and rainfall are abiotic. Predators, competitors, parasites, and food sources are biotic. The fast test: if it was never alive and can't die, it's abiotic. Both types can drive natural selection and limit populations, so the distinction is about what the factor IS, not what it does.
Abiotic factors are the non-living parts of an environment, including temperature, sunlight, water, pH, wind, and salinity.
In Unit 7, abiotic factors act as selective pressures, and when they fluctuate they change the rate and direction of natural selection ([AP Bio 7.1.B]).
In Unit 8, abiotic factors shape population growth dynamics by affecting birth and death rates and helping set carrying capacity ([AP Bio 8.3.A]).
The quickest way to distinguish abiotic from biotic is to ask whether the factor was ever alive; if not, it's abiotic.
On the exam, expect to label examples as abiotic or biotic and to explain how a non-living condition affects survival, reproduction, or population size.
Abiotic factors are the non-living parts of an environment that affect organisms, such as temperature, sunlight, water, soil pH, wind, and salinity. In AP Bio they matter as selective pressures in natural selection (Unit 7) and as limits on population growth (Unit 8).
Yes. Sunlight is non-living, so it counts as abiotic, along with temperature, water, wind, and pH. A predator or a competing plant would be biotic because those are living things.
Abiotic factors are non-living, and biotic factors are living. A common MCQ asks you to pick the abiotic example from a list, where the correct answer is something like temperature or water and the distractors are organisms like predators or competitors.
When the non-living environment changes, such as a drought, cold snap, or pH shift, it favors organisms whose phenotypes handle those conditions best. Those individuals survive and reproduce more, so the favorable trait gets passed on, which is exactly what [AP Bio 7.1.B] means by abiotic environments affecting the direction of evolution.
Abiotic factors are non-living (temperature, light, water, pH) and biotic factors are living (predators, competitors, food sources). Both can drive evolution and limit populations, so the only difference is whether the factor was ever alive.