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Factors affecting survival: Abiotic
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 theorganisms
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 shelte
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