Abiotic Factors and Species Distribution

Abiotic Factors and Species

• Abiotic components of an environment encompass physical and chemical elements influencing metabolic and physiological processes, and regulate their functions.
• Abiotic factors are classified as resources, which can be consumed, or conditions, which affect growth and survival without being consumed.
• Abiotic factors determine a population's presence or absence in an area at the population level.
• A species' distribution size depends on prevailing physical environmental conditions when present in a community.
• Changes in the physical environment manifest as effects on the distribution of plants and animals.
• Abiotic factors can act as selective forces, which organisms adapt to for survival and reproduction (limiting factor).
• The Law of the Minimum and the Law of Tolerance describe the role of abiotic factors in determining where an organism can live

Law of the Minimum

• The Law of the Minimum concept of limiting factors was proposed in 1840 by Justus von Liebig.
• The success of an organism is determined by a crucial ingredient in the environment that is in short supply.
• Presence of an organism is defined by a critically limiting factor, even if other abiotic factors are abundant.
• An important ecology concept, it forms the basis for niche theory and competition.
• The growth of a plant is controlled by the scarcest resource and not by the amount of resource available.

Law of Tolerance

• In 1023, Victor Shelford expanded the minimum concept to the Law of Tolerance.
• This considers critical environmental factors and their upper limits and lower boundaries.
• Optimum range of any physical factor is where the organism exhibits the greatest number of individuals or biggest population size.

Physical Factors

• Physical factors are independent but interact with one another.
• Temperature and precipitation changes affect biotic distribution and abundance.
• Vegetation in high mountain altitude changes over time due to shifts in climatic factors.

Biogeography

• Plant and animal community composition changes as abiotic factors like temperature and altitude vary.
• Some species only exist in specific geographical areas, while others thrive in various areas, but no species is found globally.
• Temperature and precipitation change with altitude. As altitude increases, it gets cooler and wetter. Vertical zonation is applied to vegetation zones at different altitudes.

Abiotic Factors: Light

• Light is important and drives photosynthesis in pigmented or autotrophic organisms.
• The amount of light influences an ecosystem's productivity index.

Abiotic Factors: Temperature

• Temperature influences distribution because organisms must maintain a specific internal temperature.
• Species adapt through migration, hibernation, and estivation to deal with temperature fluctuations.
• Plants exemplify the impact of temperature, due to their sessile nature, on geographic ranges that are occupied by species.
• Saguaro Cactus (Cereus giganteus) show the precise temperature range limit in Sonoran Desert.
• The species dies if exposed to temperatures below freezing for over 36 hours.

Abiotic Factors: Water Abundance

• Water abundance also influences the distribution and abundance of many organisms.
• Water retention is vital to all living beings; adaptations have evolved within both terrestrial and aquatic species to minimize water loss.
• Redwoods (Sequoia sempervirens) are restricted to the fog belt of Northern California & Southern Oregon, where precipitation is high and fog adds moisture.
• In a desert, a wash channeling infrequent rains may support different and luxurious vegetation just a few meters away.

Abiotic Factors: Salinity

• Soil salinity can affect plant distribution.
• Plant species respond to the substrate gradient from a relatively non-saline substrate(higher elevation) to highly saline soils (valley bottoms).
• Species abundance is often greatly reduced in the saltier valley bottoms.
• Salinity affects the osmoregulatory ability of fishes.
• Invertebrates are isotonic; their internal fluids have a solute concentration equal to the concentration in sea water.
• Vertebrate fishes and marine mammals are generally hypotonic; their body fluids have a salt concentration lower than that of the surrounding water.

Abiotic Factors: Oxygen

• Most plants and animals use oxygen as a resource for energy metabolism.
• Anaerobes like E. coli, Staphylococcus, and Clostridium exist, and oxygen is toxic to them, forcing existence in oxygen-free habitats.
• Most plant roots obtain oxygen for respiration in soil. Mangroves breath oxygen from the air through pneumatophores.
• Animals assimilate oxygen from the environment and require the ability to absorb and transport it to tissues. Adaptation includes absorption through lungs or skin and delivery through the circulatory mechanism.
• An aquatic organism's oxygen content in the water determines to what degree oxygen is limited.

Abiotic Factors: pH

• Plants and aquatic animals have relatively wide pH tolerance limits.
• These pH tolerances can be directly or indirectly related to the effect of pH on metabolic physiology.
• pH can affect the ability of crayfish (Cambarus bartoni) to locate food.
• Crayfish prefer water with a pH of 7.5, and acid waters with a pH below 4.5 affect their olfactory senses, making finding food difficult.

Abiotic Factors: Nutrient Availability

• Nitrogen: A mineral element often limited in a body of water.
• Phytoplankton take up the nitrate form, and lush phytoplankton growth easily depletes this supply.
• For soil, nitrogen-fixing organism need to convert the atmospheric nitrogen into its usable form before it will be beneficial to plants.
• Phosphorus: An amount of around 0.02 ppm orthophosphate is sufficient to support phytoplankton growth.
• Higher levels (exceeding 1 ppm) can lead to algal blooms.
• Carbon: The backbone of every organic molecule and an essential element to all living organism.
• Limitation of carbon in water comes by way of carbon dioxide.
• Carbon dioxide would be higher near the sediments, where organic matter decomposition is highest, which has implications for the bottom fauna.
• In temperate swamps, high CO2 pressure may lead to a buildup of gas in fish tissues.

Recap

• Abiotic components can be further classified as resources and conditions.
• Environmental factors at a critical level in an ecosystem determine an organism's presence, absence, and population size.
• Factors that determine the presence/absence of a species in an area is called the limiting factor.
• The Law of the Minimum states that the growth of an organism is controlled by the minimum resource available.
• The Law of Tolerance states that upper limits of environmental factors are as critical as lower boundaries.

Conclusion

• Both biotic and abiotic components affect ecosystem structure.
• "Structure" refers to how the parts or components are organized and the way they relate to each other to make a whole.

Explore how abiotic factors like resources and conditions influence the distribution of species. Learn about the Law of the Minimum and the Law of Tolerance and how they determine where an organism can survive. Understand how these factors act as selective forces, shaping adaptation for survival and reproduction.