Density Independent Factors

Edexcel A-level BiologyThe Nature of EcosystemsLesson 24 of 39

A density-independent factor affects the same proportion of a population whatever its density. Most are abiotic (non-living) factors, such as:
- temperature, for example a severe frost or a heatwave
- rainfall, causing drought or flooding
- natural events such as fire, volcanic eruption or storms
- human activities such as pollution or habitat destruction

For example, a hard winter might kill 60% of a population of garden snails whether there are 50 of them or 5000. A forest fire destroys the same fraction of a population regardless of how crowded it is.

More in The Nature of Ecosystems

• Parasitism and Disease
• Case Study: Snowshoe Hare and Lynx
• Case Study: Red Grouse and Parasites
• Density Dependent Factors
• Competition
• Intraspecific Competition
• Interspecific Competition
• Species Abundance

All 39 lessons in The Nature of Ecosystems · All Edexcel A-level Biology topics