MP Board · Class 12 · Biology · Organisms and PopulationsDiscuss the major abiotic factors that affect the survival and distribution of organisms in their environment.

Introduction to Abiotic Factors\nThe environment of an organism consists of biotic components (living beings) and abiotic components (non-living physical and chemical factors). The abiotic factors majorly dictate the adaptations, geographic distribution, and physiological functions of organisms on Earth. The four most crucial abiotic factors are:

1. Temperature

• Temperature is the most ecologically relevant environmental factor.
• It decreases progressively from the equator towards the poles and from plains to mountain tops.
• Eurythermal: Organisms that can tolerate a wide range of temperatures (e.g., mammals, birds).
• Stenothermal: Organisms restricted to a narrow range of temperatures (e.g., polar bears, penguins).
• Temperature affects enzyme kinetics, basal metabolic rate, and other physiological functions of living organisms.

2. Water

• Life on Earth originated in water and is unsustainable without it.
• Productivity and distribution of plants are heavily dependent on water.
• Salinity adaptations: Organisms are categorized based on their tolerance to salt concentration in water as euryhaline (tolerant of wide ranges of salinities, e.g., salmon) and stenohaline (restricted to narrow ranges, e.g., goldfish).

3. Light

• Plants depend on sunlight for photosynthesis, which is the only source of energy for almost all life on Earth.
• Many animals use the diurnal and seasonal variations in light intensity and photoperiod (day length) for timing their foraging, reproductive, and migratory activities.
• Deep-sea organisms (below 500m) do not receive solar light and have evolved specialized adaptations.

4. Soil

• The nature and properties of soil in different places depend on the climate, the weathering process, whether soil is transported or sedimentary, and how soil development occurred.
• Soil composition, grain size, and aggregation determine the percolation and water-holding capacity of the soils.
• These characteristics along with parameters such as pH, mineral composition, and topography determine to a large extent the vegetation in any area.