Organisms and their responses to the changing environmental conditions (Defense mechanisms)


Organisms are the cumulative expression of their interaction with the surrounding environment (external and internal factors). Some of the external factors like harsh climatic conditions, excessive drought, unexpected natural disasters such as floods may result in habitat destruction, and disease causation. Such factors demand a certain degree of defence mechanisms from its inhabitants to ensure their survival. The failure to adapt or respond can lead tot eh death of the organisms. Hence , all organisms must be prepared to respond to the inadvertent conditions presented by nature from time to time. Different organisms respond differently as each one exhibits its own skills and abilities in order to survive. Organism`s responses are the expression of their natural or artificial coping skills depending upon the fitness and morphological advantage that they possess. Following are some of the responses the living organisms can exhibit while they are exposed to the danger.  



1. Homeostasize or regulate

This is the most common response of an individual against the unexpected threat from the environment. This is mostly adopted by the organisms with advanced evolutionary features as they tend to defend well in order to survive. Homeostasis is the consequence of physiological, morphological or biochemical modification that brings in a certain behavioural change in the organisms, for example, we produce shivering during the cold weather. Shivering produces the vigorous movement of our body to generate more heat to protect us against the harsh cold. Evolutionary biologists conclude that a successful organism is capable of defending against the adverse conditions every time.



2. Confirm

Confirmation is evident in the organisms found at the bottom of the food chain. Conformers are the weaker individuals who compromise themselves against unexpected environmental changes as these organisms cannot guard themselves against the threat. The majority of the animal and plant population are conforming or compromising with the available set of conditions. Conforming may not help the individuals survive longer however they are great for time-being. 



3. Migrate

This is a temporary movement ( change in the location) of the organisms in response to the potential or actual threat. It is commonly seen in the bird population. Birds are capable of sensing the menace in advance so that they can take a long trip to the safest zones on the earth. Birds sometimes travel up to thousands of miles to protect themselves. Most of the organisms migrate is due to either one or many factors among extreme cold, increased seasonal predators, drought and the shortage of food around their habitats. For example, Cranes from Siberia migrate to India during their winter season.



4. Suspend

Some organisms have the ability to modify their morphology or bodily features when a threat is evident. Some bacteria tend to develop a spore-like structure that protects them from external threats. Bears moving into hibernation during the winter is also an example of suspend.



Organism`s adaptations

Adaptations are the basic skills of organisms that help them protect against unusual threats. They are the innate or acquired ability of organisms to temporarily modify the behaviour, anatomy and the physiology. This happens when the organisms encounter threat such as the predators, adverse climatic conditions, shortage of food and water, etc. For example, both the polar bear and sheep develop thick fur to protect against the cold in the antarctic regions. Adaptations can be behavioural, defensive, physiological, or morphological in nature. They generally tend to be same over the generations (For example, long neck in a giraffe or fish with gills never change over a period of time). However, over the long run, a slight change is seen in as the organisms evolve. Following section is meant to explain various types of adaptations by the organisms.



Different forms of adaptations

1. Structural adaptations

These are the type of physical adaptation of organisms in response to an external threat or a known stressor. The physical change of an organism is often related to a modification in the physical outlook of an organism. For example, an owl joins in camouflages (change its body colour according to it`s living background)  in order to hide from the predators. Some of the structural adaptations are; developing long wings to fly, a long neck (giraffe), fins for aquatic creatures ( fish) and powerful legs to run quickly ( ostrich)  and camouflaging in some species.



2. Behavioural Adaptations

These are the actions, attitudes and the behavioural responses of the individuals that aid in protecting the organisms during the times of crisis. Behavioural adaptations could be triggered by a change in the immediate environment such as shortage of food. For example, birds fly south in the winter because they can find enough food in the south during winter.



3. Physiological Adaptations

Physiological adaptations are the same as structural adaptations, but they affect the functional pattern of the organism rather than the structure. For example, animal fur turns erect to fully cover the body while they are exposed to cold conditions.



Further reading



Species on the earth and their diversity


Introduction to Ecosystems


Animal Kingdom




  1. Mention the defences that the organisms adapt.

  2. Explain the role of migration.

  3. When do organisms suspend?

  4. What kind of defence is camouflaging? Explain.

  5. Explain the role of behavioral adaptations with an example.





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