An animal adaptation is a heritable characteristic that has arisen over time through the process of evolution. These traits are physical features, internal mechanisms, or specific behaviors that increase an animal’s “fitness,” meaning its ability to survive, find a mate, and successfully reproduce in its particular environment. Every living animal today possesses a suite of these specialized traits, which allows it to thrive in its ecological niche.
The Difference Between Adaptation and Acclimation
Adaptation is a genetic change that happens across multiple generations within an entire population or species. It is a permanent shift in the genetic makeup that results in a physical or functional trait, like the snow leopard’s permanently thick fur and large paws. This type of change is not reversible within the lifespan of an individual animal.
In contrast, acclimation is a short-term, temporary, and non-heritable adjustment that an individual organism makes to cope with a sudden environmental stressor. For example, when an animal moves to a higher altitude, its body might temporarily increase its red blood cell count to better capture oxygen from the thinner air. This physiological adjustment occurs rapidly and reverses when the animal returns to its original conditions.
The Process of Natural Selection
Adaptations arise through the process of natural selection. The process begins with variation because individuals within any population naturally exhibit differences in their traits, such as size, color, or behavior. This variation is heritable, meaning those differing traits are passed down from parent to offspring through their genes.
The next step is overproduction, where species produce more offspring than the environment can support, leading to a constant “struggle for existence” due to competition for limited resources like food and shelter. In this competition, a differential survival occurs, where individuals with traits better suited to the immediate environment are more likely to survive and successfully reproduce. For instance, if a prey animal happens to have slightly better camouflage due to random variation, it avoids predators and lives long enough to mate.
Over vast periods and countless generations, the advantageous, heritable traits accumulate in the population, gradually leading to the species becoming better suited to its environment. The environment essentially selects for the most beneficial traits, making them more common.
Three Main Types of Adaptation
Adaptations can be broadly categorized into three types based on whether the change affects the animal’s body structure, its behavior, or its internal workings.
Structural adaptations involve physical features of the animal’s body. A classic example is the giraffe’s long neck, which allows it to reach foliage unavailable to shorter herbivores. The thick layer of blubber and dense, specialized fur of a polar bear provides insulation against extreme cold.
Behavioral adaptations are the actions an animal takes to survive and reproduce. Examples include the long-distance migration of many bird species to find warmer climates and food sources in winter, or the hibernation of bears to conserve energy during periods of scarcity. Courtship rituals used to attract mates also fall under this category of survival-related actions.
Physiological adaptations relate to an animal’s internal body chemistry and function. The production of venom by certain snakes or spiders for defense and predation is a physiological adaptation. Another example is the ability of a ruminant, like a cow, to digest cellulose efficiently using a four-compartment stomach and specialized microbes.