Abiotic factors are the non-living conditions of an ecosystem. When an abiotic factor is close to the optimum for a species, individuals survive and reproduce well, and the carrying capacity is high. When conditions move away from the optimum, fewer individuals survive and the population is smaller.Temperature
Enzymes work fastest near their optimum temperature. In ectotherms, such as insects, and in plants, body temperature follows the environment, so low temperatures slow metabolism and growth, while high temperatures can denature enzymes. Endotherms, such as mammals, keep their body temperature constant, but in cold conditions they use more energy to stay warm, leaving less for growth and reproduction.Light
Light is needed for photosynthesis. More light increases the rate of photosynthesis and plant growth, which increases the food available to the animals that feed on the plants. Light also affects the timing of behaviour such as flowering and breeding.pH
pH affects enzyme action. Each species has an optimum pH, so the pH of soil or water affects which species can live there and how large their populations are.Water and humidity
Water is essential for all organisms. Where water is scarce, only species with adaptations to reduce water loss can survive in large numbers. Humidity affects the rate of transpiration in plants and of evaporation from animals such as woodlice.Other abiotic factors include oxygen concentration, mineral ions in the soil, wind speed and salinity. Several factors act at once, and the one furthest from the optimum usually has the greatest effect.
Enzymes work fastest near their optimum temperature. In ectotherms, such as insects, and in plants, body temperature follows the environment, so low temperatures slow metabolism and growth, while high temperatures can denature enzymes. Endotherms, such as mammals, keep their body temperature constant, but in cold conditions they use more energy to stay warm, leaving less for growth and reproduction.Light
Light is needed for photosynthesis. More light increases the rate of photosynthesis and plant growth, which increases the food available to the animals that feed on the plants. Light also affects the timing of behaviour such as flowering and breeding.pH
pH affects enzyme action. Each species has an optimum pH, so the pH of soil or water affects which species can live there and how large their populations are.Water and humidity
Water is essential for all organisms. Where water is scarce, only species with adaptations to reduce water loss can survive in large numbers. Humidity affects the rate of transpiration in plants and of evaporation from animals such as woodlice.Other abiotic factors include oxygen concentration, mineral ions in the soil, wind speed and salinity. Several factors act at once, and the one furthest from the optimum usually has the greatest effect.