Responses To Abiotic Factors - Organisms And Populations

Responses to abiotic factors are the ways in which living organisms react and adapt to changes in the non-living components of their habitat. There are majorly four abiotic factors, namely, Temperature, Water, Light and Soil which affect living organisms. Living organisms show responses to these abiotic factors in several ways depending on, the type of organisms, duration of unfavourable conditions etc.

What are Abiotic Factors?

Abiotic factors refer to the non-living components of an ecosystem that influence living organisms. These factors include Temperature, Light, Water Availability, Soil Composition, and Wind.

Temperature

Temperature is an important abiotic factor that affects the physiology and behaviour of organisms. Different species have specific temperature ranges within which they can survive, while extreme temperatures can lead to adverse effects or even mortality. There are two types of organisms based on tolerance to a range of temperatures- Eurythermal and Stenothermal. Eurythermal can tolerate a wide range of temperatures while Stenothermal can tolerate a narrow range of temperatures.

Light

Light is essential for photosynthesis in plants and plays a crucial role in determining daily and seasonal patterns of activity for many organisms. It impacts processes such as reproduction, migration, and feeding behaviours.

Water Availability

Water is a life-sustaining resource, and its availability profoundly influences the distribution and abundance of living organisms. For aquatic life, the quality of water matters more than quantity. Adaptations in desert plants show the importance of water.

Soil Composition

The chemical and physical properties of soil impact plant growth and the availability of nutrients for various organisms. Soil pH, texture, and nutrient content play significant roles in shaping the community structure.

Wind

Wind affects the dispersal of seeds, pollen, and spores, influencing the colonization of new areas and the reproductive strategies of many plants. 

Responses to Abiotic Factors

Living organisms show responses to changes in abiotic factors in several ways depending on the duration of unfavourable conditions. Organisms show responses such as migration and suspension if unfavourable conditions are present for a shorter duration. They show adaptation and extinction if unfavourable conditions are present for a longer duration.

Case 1: If unfavourable conditions are present for a shorter duration:

Migration:

Migration refers to the movement of organisms from unfavourable (hostile) conditions to favourable (hospitable) conditions for shelter and reproduction. Organisms come back when normal conditions resume. Examples include:

• Migration of Grasshoppers in winter for food
• Migration of Siberian crane in winter from Siberia to Keolado National Park, Rajasthan, India. 
• Migration of Cyclostomes from Oceans to fresh water for reproduction. 
• Migration of Arctic Tern from North Pole to South Pole. 

Suspension

Those organisms which are not able to migrate, suspend their activity and become less metabolically active. This is known as suspension. Examples include:

• Seed dormancy- seed suspends growth
• Hibernation (Winter sleep)- Polar bears suspend their activities and go to sleep to escape time. 
• Aestivation- In summer, fish and snails go to deeper layers in water bodies. 
• Diapause- Zooplanktons enter into suspended growth. 
• Spore Formation- Algae, Fungi and Bacteria contains spores that can survive for thousands of years. 

Case 2. If unfavourable conditions are present for a longer duration:

Adaptation

Adaptation is a change in any attribute like behaviour, morphology, anatomy, and physiology for survival and reproduction. With time, adaptations are genetically fixed. Organisms adapt by physiological or behavioural means.

Physiological Adaptations

Desert

1. Kangaroo Rat- It releases concentrated urine and produces metabolic water inside the body by internal fat oxidation. 
2. Plants- Leaves have thick cuticles to prevent loss of water. Also, leaves are modified into spines and the stem becomes flat and photosynthetic. Stomata are sunken and open at night. Such plants in which stomata open at night are known as Crassulacean Acid Metabolism (CAM) plants. 

Colder climate

1. Plants- In colder climates, plants do not have many adaptations. 
2. Animals- Whales, seals and other aquatic mammals have blubber which is a thick fat layer to provide insulation. Also, animals in colder climates have shorter ears and limbs to avoid heat loss. This is known as 'Allen's rule'. 

High altitude

When we move to high altitudes like Rohtang pass (>3500m) from plains, altitude sickness (Headache, vomiting, nausea, heart palpitations) occurs due to low atmospheric pressure. This altitude sickness is overcome by physiological adaptations such as increased breathing rate, increased RBC production, and decreased affinity of haemoglobin with oxygen. 

Behavioural Adaptations

Lizards are cold-blooded animals. They lack physiological adaptations for thermoregulation. Thus, they adapt behaviorally according to ambient conditions. When the outside temperature is lower than body temperature, they bask in the sun and when the outside temperature is higher than body temperature, they move into burrows. 

Extinction

Extinction refers to the complete disappearance of a species or a group of organisms from the Earth. Those organisms that can not adapt, get extinct. Examples include:

• Dodo (Flightless bird) from Mauritius
• Thylacine from Australia
• Quagga from Africa
• Stellar sea cow from Russia
• Bala, Javan, Caspian- Subspecies of Tiger