Abiotic factors affecting the abundance and distribution of organisms

These are important key terms:

  • An ecosystem is the interaction between a community of living organisms and their environment.
  • A community is two or more populations of organisms.
  • A population is all the organisms of the same or closely-related species in an area.
  • All organisms in an ecosystem depend upon each other. If the population of one organism rises or falls, then this can affect the rest of the ecosystem. This is interdependence.

Abundance and distribution

An abundance is the number of organisms in an ecosystem and their distribution is affected by abiotic factors. These are factors that are non-living.

They include:

Light intensity

Some plants have evolved for optimum growth in bright sunlight. An example of this is a cactus houseplant. Cacti originally come from deserts where they grow in bright sunlight. Other plants have evolved to grow in shade.

Many orchids, which are also kept as houseplants, grow on trees in the rainforest and have evolved for optimum growth in darker conditions. If you were to put an orchid on a bright windowsill and a cactus in a dark corner of your room, neither plant would grow well.


Both animals and plants have evolved to grow healthily at their optimum temperatures. If you planted either your cactus or orchid houseplants outside in cold temperatures, they would die. Similarly, animals that have evolved to live at the North Pole, such as the polar bear, could not survive in warmer conditions.

Moisture levels

Lots of people kill houseplants by overwatering rather than by under-watering them - plants cannot survive in waterlogged soils. Their roots are unable to respire, they rot and the plant dies. Other plants, such as pitcher plants, grow best in bogs where the moisture levels are high. Soil moisture meters can accurately determine how wet an area is.

Soil pH

The pH of soils can have a huge effect on the plants that are able to grow in them. Some plants, like azaleas, grow best in acidic soils and will quickly die if planted in alkaline soils. Others, like clematis, prefer alkaline soils. Some, like hydrangeas, can grow in both. Hydrangeas are unusual in that their flower colour changes in different soils. Just like universal indicator paper, hydrangea flowers are pink in acidic soils and blue in alkaline soils.

pH meter
pH meters can accurately determine the pH of soils

The pH of water can also affect the aquatic organisms that are found there. Different species have evolved to survive at different pH levels found within water.

A bar chart that shows the varying tolerance levels of pH in animalsThe graph highlights the various pH tolerances of different species found in water


The amount of salt in aquatic environments affects the organisms that are found there. Freshwater organisms could not survive in the salt water of the sea and the reverse for saltwater organisms.