Habitat and environment Abiotic (non-living) environmental factors

Habitat and environment
An organism's habitat is the place where it lives. For example, swamps, deserts, the bark of a tree, cities and rivers are all habitats.

The environment is the set of conditions that exist within the habitat which affect the organism's survival.

Organisms thrive in habitats where they are best suited to the environmental conditions. They have features (adaptations) which have evolved over a long period of time which help them to survive under those conditions.

Changes in environmental factors (either natural or man-made) will affect the ability of some species to survive and therefore alter relationships within the food chains.

Abiotic (non-living) environmental factors

• Water availability
  Water is essential for life. This can be a major problem for land organisms! Water availability varies with climate, including total annual rainfall, frequency of rainfall, and relative humidity, as well as dehydration by winds and high temperatures. Water dictates which plants will grow and hence the number and type of consumers which can be supported. Desert plants have adaptations such as reduced leaf size, large root systems, waxy covers to reflect excess sunlight, internal water storage areas (e.g. cacti), and fewer stomata to reduce dehydration. Desert animals are often diurnal (active at dawn and dusk), burrow underground, produce concentrated urine, and have a reduced surface area to minimise water loss (see Adaptations). Ice and snow, though states of water, often reduce the amount of useable water available to organisms.
  
  
• Sunlight
  The total amount of production of food by plants (photosynthesis) depends on the intensity of sunlight and the relative length of day and night.. These factors change both with the season and geographical location. sunlight varies within layers of a natural community (e.g. very dim on the forest floor), and color of light can vary at depths in the sea due to differential absorption of some wavelengths. Pollution, cloud cover and smoke from forest burning (as has occurred recently in Indonesia) can drastically reduce light intensity.
  
  
• Temperature range
  This varies with latitude (distance from the Equator), altitude (height above sea-level) and the continental effect (distance from the stabilising influence of the sea). Water habitats are much less variable in temperature than land. Endothermic (warm-blooded) animals can survive better with temperature variation than ectothermic (cold-blooded) animals can.(See Needs of living things)
  
  
• Sub-stratum or soil
  Soil texture (sandy, clay, rock), drainage, mineral content, level of acidity (pH) and organic content all influence plant growth and microfauna (worms, helpful bacteria and so on) as well as burrowing or ground-nesting animals. In water habitats, the salt content can vary (salt, brackish, estuarine or fresh) as can the stability (currents, waves, tides).
  
  
• Geographical terrain
  Whether the area is flat, undulating, hilly or mountainous, will influence the organisms present. The aspect (position relative to north) will affect exposure to winds, Sun and rain. Caves and rock overhangs provide shelter from weather and predators. Altitude will affect temperature, and oxygen availability.
  
  
• Oxygen availability
  This is not generally a problem on land although oxygen levels are reduced at high altitudes. In water, however, limited oxygen availability may reduce survival. Oxygen is produced by water plants, but its solubility in water is greatly reduced by increased temperature, and reduced flow of the water (often caused by factories using streams for water cooling of machines). A dimly lit, still pond does not support much life at all.
  
  
• Exposure
  Tides, waves and winds all pose problems for organisms that depend on attachment to rocks. Deserts are very exposed environments affected greatly by winds because the lack of trees means little shelter.
  

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