Abiotic factors are non-living environmental conditions that affect the distribution and abundance of organisms. Free notes and 13 questions answered.
Updated 20 Mar 2026 · Revise Right Team
Physical Abiotic Factors in Ecosystems is part of Adaptations, interdependence and competition in GCSE AQA Higher Biology.
5 min
Reading time
36
Lessons in this topic
GCSE AQA Higher
Pathway
Reviewed by Revise Right
Content review
What this lesson covers
Abiotic factors are non-living environmental conditions that affect the distribution and abundance of organisms. Free notes and 13 questions answered.
Explain how light intensity affects the distribution and behaviour of organisms in ecosystems
Describe the impact of temperature on community structure and organism survival
Analyse how moisture levels influence where different species can live and thrive
Evaluate the effects of wind intensity and direction on ecosystem dynamics
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Use this lesson to stay inside Adaptations, interdependence and competition while connecting the detail back to the wider Ecology topic.
Ecology
Adaptations, interdependence and competition
GCSE AQA Higher Biology
Revision notes
Read the core explanations from Physical Abiotic Factors in Ecosystems before testing yourself from memory.
1. Why Physical Factors Control Life
Walk into a forest and you'll notice something obvious: different plants grow in different places. Ferns thrive in the shady undergrowth while oak trees dominate the sunny canopy. This isn't random — it's controlled by physical factors in the environment.
These non-living factors are called abiotic factors. They act like invisible filters, determining which organisms can survive where. Get the conditions wrong, and species can't establish themselves.
Trap: Many students think abiotic means 'dead things like fallen logs'. Actually, abiotic factors are environmental conditions — they were never alive in the first place. A rotting log is biotic because it was once living.
2. Light Intensity - The Energy Controller
Light intensity determines how much energy is available for photosynthesis. Think of it as the power supply for the entire ecosystem — without enough light, plants can't make glucose, and the whole food web collapses.
Different plants have evolved different light requirements. Shade-tolerant species like moss can photosynthesise in low light conditions, while sun-loving plants like sunflowers need intense, direct sunlight to thrive.
This creates distinct zones in ecosystems. Forest floors receive only 2-5% of the light that hits the canopy. That's why you find completely different plant communities at different heights — each adapted to their light environment.
3. Temperature - The Rate Controller
Temperature controls the speed of life itself. Every chemical reaction in living organisms — from photosynthesis to respiration — depends on temperature. Too cold, and reactions slow to a crawl. Too hot, and enzymes denature.
Most organisms have an optimal temperature range where they function best. Outside this range, they struggle to survive. This is why you find polar bears in the Arctic and camels in deserts — each is adapted to their temperature environment.
Temperature also affects water availability. Higher temperatures increase evaporation rates, making water scarcer even in areas with adequate rainfall. This double effect — direct temperature stress plus water stress — makes temperature a powerful ecological filter.
4. Moisture Levels - The Life Sustainer
Water is life. Every cell needs water for chemical reactions, transport, and structural support. Moisture levels in the environment determine which organisms can establish and maintain populations in an area.
Plants lose water constantly through transpiration — water evaporating from their leaves. In dry conditions, they must either reduce water loss (by closing stomata) or increase water uptake (with deeper roots). Each strategy comes with trade-offs.
Animals face similar challenges. Desert animals like kangaroo rats have evolved to need very little water, while amphibians like frogs require moist environments because they lose water rapidly through their permeable skin.
5. Wind Intensity and Direction - The Invisible Force
Wind might seem less important than light or water, but it's a major ecological force. Strong winds create physical stress, increase water loss, and can prevent certain species from establishing themselves.
On exposed hillsides and coastlines, constant wind creates stunted, wind-sculpted vegetation. Trees grow low and bent, shaped by years of wind pressure. Only the most wind-tolerant species survive in these harsh conditions.
Wind direction matters too. In the UK, prevailing south-westerly winds bring moist air from the Atlantic. The western sides of hills receive more rainfall (orographic precipitation), creating different plant communities on west-facing versus east-facing slopes.
Wind also affects seed dispersal and pollination. Some plants rely entirely on wind to spread their offspring, while others need calm conditions for insect pollinators to operate effectively.
6. How Abiotic Factors Work Together
Here's where it gets complex: abiotic factors don't work in isolation. They interact with each other to create unique environmental conditions. High temperature plus low moisture creates desert conditions. Low temperature plus high moisture creates bog conditions.
These interactions explain why ecosystems are so diverse. A small change in one factor can shift the entire balance, allowing new species to colonise while forcing others to retreat.
Worked example: Analysing Abiotic Factor Interactions
A student investigates why heather grows on acidic moorland but not in neutral grassland, even though both areas have similar temperature and rainfall. Explain the interaction of abiotic factors.
Soil pH: moorland is acidic (pH 4-5), grassland is neutral (pH 6-7) — This is the main abiotic factor that differs between the two habitats
Acidic soils have low nutrient availability due to reduced bacterial decomposition — Low pH slows down decomposer activity, reducing nutrient cycling
Heather is adapted to low-nutrient, acidic conditions with specialised root associations — Heather has mycorrhizal fungi that help extract nutrients from poor soil
In neutral grassland, fast-growing grasses outcompete heather for light and space — Higher nutrient availability favours rapid growth, giving grasses an advantage
Answer: Soil pH interacts with nutrient availability to create conditions that favour different plant communities. Heather thrives in low-nutrient, acidic conditions where it faces less competition, but cannot compete with faster-growing species in nutrient-rich, neutral soils.
Exam questions on abiotic factors often ask you to explain distribution patterns or predict how changes might affect communities. The key is linking the factor to its biological effect, then to the ecological outcome.
Common mistake: Students often describe what happens without explaining why. 'Plants grow better in higher light intensity' gets no marks. 'Plants grow better in higher light intensity because the rate of photosynthesis increases, providing more glucose for growth' gets full marks.
Sources and content standards
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Abiotic factors are non-living environmental conditions that affect the distribution and abundance of organisms in an ecosystem, including physical factors like temperature, light intensity, moisture levels and wind intensity and direction. They were never alive: a rotting log is biotic because it was once living.
What is light intensity measured in?
Light intensity is the amount of light energy reaching an area per unit time, measured in lux. It directly affects the rate of photosynthesis in plants.
Is a fallen log an abiotic factor?
A fallen, rotting log is biotic, not abiotic, because it was once living. Abiotic factors are environmental conditions that were never alive, such as temperature, light, moisture and wind.
How does light intensity affect plants in an ecosystem?
Light intensity, measured in lux, determines how much energy is available for photosynthesis, so it controls which plants can grow where. Forest floors receive only 2-5% of the light that hits the canopy, so shade-tolerant species like moss grow there, while sun-loving plants like sunflowers need intense, direct sunlight.
How does wind affect ecosystems?
Strong winds create physical stress and increase water loss, so exposed hillsides and coastlines have stunted, wind-sculpted vegetation where only wind-tolerant species survive. Wind direction also matters: in the UK, prevailing south-westerly winds bring more rain to western slopes, and wind affects seed dispersal and pollination.
How do moisture levels affect where organisms live?
Moisture levels determine which organisms can establish populations, because every cell needs water. In dry conditions plants close stomata or grow deeper roots; desert animals like kangaroo rats need very little water, while frogs need moist environments because they lose water rapidly through their permeable skin.
Why does heather grow on acidic moorland?
Heather grows on acidic moorland (pH 4-5) because low pH slows decomposers, giving low-nutrient soil, and heather is adapted to this with mycorrhizal fungi that help extract nutrients. In neutral grassland (pH 6-7), higher nutrient availability lets fast-growing grasses outcompete heather for light and space.
How much light reaches the forest floor?
Forest floors receive only 2-5% of the light that hits the canopy. This is why different plant communities grow at different heights, with shade-tolerant species like ferns and moss in the undergrowth and sun-loving species in the canopy.
Why do frogs need moist environments?
Frogs need moist environments because amphibians lose water rapidly through their permeable skin. Desert animals like kangaroo rats, however, have evolved to need very little water.
Why are trees bent on windy coasts?
Trees on exposed hillsides and coastlines grow low and bent, shaped by years of constant wind pressure. Strong winds create physical stress and increase water loss, so only the most wind-tolerant species survive.
How does wind direction affect plant communities in the UK?
In the UK, prevailing south-westerly winds bring moist air from the Atlantic, so the western sides of hills receive more rainfall. This creates different plant communities on west-facing and east-facing slopes.
How does temperature affect water availability?
Higher temperatures increase evaporation rates, making water scarcer even where rainfall is adequate. This double effect, temperature stress plus water stress, makes temperature a powerful ecological filter.
How do abiotic factors combine to make deserts and bogs?
Abiotic factors interact: high temperature plus low moisture creates desert conditions, while low temperature plus high moisture creates bog conditions. A small change in one factor can shift the whole balance of an ecosystem.