In AP Biology, biotic factors are the living components of an ecosystem, like predators, prey, competitors, parasites, and food sources, that influence survival, reproduction, and the rate and direction of evolution in a population.
Biotic factors are the living things (or stuff that came from living things) that affect an organism in its environment. Think predators, prey, competitors, parasites, mates, plants, fungi, and bacteria. If it's alive or used to be part of something alive, it's biotic. The opposite is abiotic factors, which are the nonliving parts like temperature, water, sunlight, and soil chemistry.
In AP Bio, biotic factors matter because they create the pressure that drives natural selection and shape how populations grow. Competition for limited resources, getting eaten, finding a mate, fighting off disease, all of these are biotic interactions that decide who survives and reproduces. When the living environment shifts (a new predator shows up, a food source disappears), the rate and direction of evolution can change too.
Biotic factors show up in two different units, which is exactly why this term is worth understanding well. In Unit 7, learning objective [AP Bio 7.1.A] and [AP Bio 7.1.B] tie biotic factors to natural selection: competition for limited resources causes differential survival, and because biotic environments fluctuate, they affect the rate and direction of evolution. In Unit 8, [AP Bio 8.3.A] connects biotic factors to population growth dynamics, where interactions between organisms of the same species and between species influence birth rate and death rate. So the same idea (living things shaping each other) powers both the evolution story and the ecology story.
Keep studying AP Biology Unit 8
Abiotic Factors (Units 7-8)
Abiotic factors are the nonliving half of the same coin, things like temperature, water, and pH. Both biotic and abiotic factors fluctuate, and both can change the rate and direction of natural selection, so the exam often makes you sort which is which.
Competition (Units 7-8)
Competition is the classic biotic factor. When organisms fight over limited resources, individuals with more favorable phenotypes survive and reproduce more. That's the engine of natural selection in [AP Bio 7.1.A].
Carrying Capacity (Unit 8)
Biotic factors like food supply, predators, and disease are what slow a population down as it approaches carrying capacity. Reproduction without these constraints gives exponential growth (dN/dt = B - D), but biotic pressure is what eventually caps it.
Evolutionary Fitness (Unit 7)
Fitness is measured by reproductive success, and biotic factors are a big reason fitness varies. Surviving a predator or out-competing rivals for mates directly raises how many offspring you leave behind.
You'll most often see biotic factors in multiple-choice questions that ask you to sort biotic from abiotic, or to identify which factor 'directly influences population survival.' A predator, a competitor, or a disease is biotic; drought, soil salinity, and temperature are abiotic. On FRQs, biotic factors usually appear inside a larger natural selection or population growth argument. The 2026 anole lizard FRQ, for example, asks about genetically determined toe pad sizes, where biotic interactions like climbing and competition shape which traits get selected. Be ready to explain HOW a biotic factor causes differential survival, not just name it.
Biotic = living (predators, competitors, bacteria, plants). Abiotic = nonliving (water, temperature, sunlight, soil salinity). The quick test: was it ever alive or part of something alive? If yes, biotic. A drought reducing water availability is abiotic; a new predator eating your population is biotic.
Biotic factors are all the living components of an ecosystem, including predators, prey, competitors, parasites, and decomposers.
Competition for limited resources is a biotic factor that drives natural selection by causing differential survival and reproduction.
Because biotic environments fluctuate, they can change both the rate and the direction of evolution in a population.
Biotic factors like food supply, predators, and disease help slow population growth as a population nears its carrying capacity.
The fastest way to classify a factor: if it's alive or came from something alive, it's biotic; if it's nonliving, it's abiotic.
Biotic factors are the living parts of an ecosystem, such as predators, prey, competitors, plants, fungi, and bacteria, that affect an organism's survival and reproduction. On the AP exam they connect to natural selection in Unit 7 and population growth in Unit 8.
Abiotic. A drought reduces water availability and can raise soil salinity, and both are nonliving physical conditions. A biotic factor would be something living, like a predator, a competitor, or a disease-causing organism.
Biotic factors are living or come from living things (predators, competitors, bacteria), while abiotic factors are nonliving (temperature, water, sunlight, pH). The simple test is asking whether the thing was ever alive.
Biotic factors create competition for limited resources, which means not everyone survives. Individuals with more favorable phenotypes survive and reproduce more, passing those traits on, which is the core of natural selection in [AP Bio 7.1.A].
Yes. Biotic factors like food supply, predation, and disease influence birth rate and death rate, which feed into the population growth equation dN/dt = B - D and help determine carrying capacity in Unit 8.