An organism's niche

##Abiotic factors influence the distribution of life

Abiotic factors determine where an organism can survive and live. This is evident in the organism’s range, which refers to the geographic area where an organism occurs throughout its lifetime.

##Abiotic factors form physical barriers to an organism

Some abiotic factors form physical barriers that restrict where an organism can be found and where it can go. For example, a terrestrial organism’s range may be limited by mountains or a desert. An aquatic organism may be restricted only to freshwater or saltwater environments. Natural phenomena such as floods, wildfires, and volcanic eruptions can also limit an organism’s range.

[[☃ image 1]]

##Abiotic factors affect the survival of an organism

Abiotic factors can determine whether or not an organism can survive. The most influential abiotic factors include temperature, light availability, and moisture.

• Organisms require specific temperatures to function. Temperatures that are too high or too low can decrease an organism’s metabolism (chemical activity in cells), movement, growth, and reproduction.

• Plants need light to photosynthesize. With too little light, plants will not have enough energy to survive and grow. However, too much light can damage leaves and slow the rate of photosynthesis.

• Water is essential to life; with too little water, organisms cannot function properly. Moisture is necessary to facilitate chemical reactions, transport nutrients, and maintain an organism’s body temperature.

Other important abiotic factors include chemical nutrients in soil (such as nitrogen, phosphorus, and potassium), salinity (saltiness of water), pH (a measure of an environment’s acidity), and dissolved oxygen in bodies of water.

[[☃ image 2]]

##Every organism needs specific abiotic factors

Every organism needs a specific set of abiotic factors to develop, survive, and reproduce successfully.

An organism’s tolerance is its ability to survive variation in abiotic factors, such as changes in temperature or sunlight. Each organism has a tolerance range for every abiotic factor in its environment.

• Optimal conditions are those within an organism’s tolerance range. When conditions are optimal, an organism can survive and reproduce successfully.

• Stressful conditions are those close to an organism’s lower and upper limits of tolerance. When conditions are stressful, an organism may survive, but it will likely produce fewer or no offspring.

• Extreme conditions are those beyond an organism’s limits of tolerance. When conditions are extreme, an organism will not survive.

[[☃ image 9]]

##Fundamental and realized niches

The tolerance ranges for all abiotic factors relevant to an organism make up the organism’s fundamental niche. In other words, the fundamental niche represents the environmental conditions in which an organism could exist.

Certain interactions (such as competition or predation) and resource availability can restrict an organism’s use of its environment. As a result, an organism may only use a portion of its fundamental niche. This is called the organism’s realized niche.

[[☃ image 11]]

In general, an organism’s niche refers to its realized niche. So, an organism’s niche includes both the abiotic factors it needs to survive as well as its interactions with other species and the environment.

An organism’s niche can change with its growth and development. For example, caterpillars (butterfly larvae) feed on plant leaves, whereas adult butterflies feed on nectar from flowers.

##Specialists and generalists

Specialist species are organisms that have narrow niches. Specialists typically have small tolerance ranges for abiotic factors, require specific resources to survive, and may have a restricted geographic range. For example, the Kirtland's warbler is a specialist bird species that only nests near young jack pine trees.

Generalist species are organisms that have broad niches. Generalists typically have large tolerance ranges for abiotic factors, can use many different resources to survive, and often have a wide geographic range. For example, raccoons are a generalist species; they live in many different environments (from forests to cities) and eat a variety of foods.

[[☃ image 12]]