Adaptations of organisms to the environment

Causes of adaptations and their structural basis

Any adaptive reactions arise under the action of specific environmental factors. Such factors are generally called adaptogenic, extreme, or stressors (from the English word stress, meaning tension or pressure).

All factors acting on the organism are classified into two major groups:

• Natural (including physical, chemical, and biological impacts).
• Social (characteristic of highly organized communities).

The structural basis for absolutely all adaptations is the formation of the so-called systemic structural trace. This means that adaptation does not arise out of nowhere: it is always based on specific structural changes in those organ complexes that are involved in the reaction to the stressor factor.

Types of adaptations by inheritance pattern

Depending on whether acquired traits are passed on to offspring, there are two main types of adaptations:

1. Phenotypic adaptations. They develop exclusively during the lifespan of a single generation. Such changes help a particular individual survive here and now, but they do not affect the genome and, consequently, are not inherited.
2. Genetically fixed adaptations. Unlike phenotypic ones, they form only if an extreme factor acts continuously on a population over many generations. The trait becomes fixed in the genotype and is passed on to descendants.

A striking example of genetically fixed adaptations is ecotypes (or geographical races). These are specific forms of species that have a very wide geographical distribution. In different parts of their range, they acquire genetically fixed adaptations to specific, local habitats.

Classification by manifested effects

According to how the adaptation manifests itself, adaptations are divided into three categories: morphological, physiological, and behavioral.

Morphological adaptations are associated with changes in body structure. Their aggregate, acquired by organisms for living in a similar environment, is called a life form. The significance of this concept is enormous: by looking at an organism's life form, a researcher can get a clear idea of its habitat.

Behavioral adaptations (or adaptive behavior) represent specific actions that organisms perform to adapt to environmental factors. These include:

• Migrations and movements.
• Stashing food for the future.
• Building nests and shelters.
• Parental care.
• Protective behavior.

Interestingly, behavioral reactions often turn out to be much more effective than physiological ones. Their main advantage is speed. Behavior makes it possible to respond to environmental changes very quickly (for example, instantly avoiding the impact of a harmful factor simply by leaving the dangerous zone). Higher animals develop the highest type of such reactions—conditioned reflexes, which are based on individual experience and the learning process.

Biological rhythms

It is worth highlighting biological rhythms separately, as they are also considered one of the most important forms of organism adaptation to the environment.

The essence of biorhythms is that they represent a regular change in the rate and general character of biological processes over time. This allows a living being to proactively adjust its internal homeostasis and activity to cyclical changes in external natural factors, thereby ensuring maximum survival.

Class and exam questions

What else to study on this topic

• Mechanisms of systemic structural trace formation in tissues
• Detailed analysis of examples of physiological adaptations
• Conditioned reflexes in higher animals as the basis of behavioral adaptations
• Specifics of ecotype (geographical race) formation with concrete examples
• Impact of social stress factors on population adaptation

Other topics in the "General Ecology" section

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