Abiotic factors affecting the abundance and distribution of organisms

The abundance is the number of organisms in an ecosystem. A community is all of the living organisms within a habitat. Communities are affected by abiotic factors. Abiotic factors are non-living.

They include:

  • light intensity
  • temperature
  • moisture levels
  • pH of soil

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 an orchid was put on a bright windowsill and a cactus in a dark corner of a room neither plant would grow well.

Temperature

Both animals and plants have evolved to grow healthily at their optimum temperatures. If you planted either a 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

a soil pH meter
A soil pH meter

More people kill houseplants by overwatering than by underwatering them. Many plants cannot survive in waterlogged soils because there is little oxygen. The cells in their roots are unable to respire, meaning that the roots 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.

pH of soil

The pH of soil can have a huge effect on the range of plants that are able to grow. 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 the hydrangea, can grow in both. These plants 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.

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. pH meters can accurately determine the pH of soils.

A bar chart that shows the varying tolerance levels of pH in animalspH tolerances of different species found in water