Adaptation is key to the survival of species. Organisms are constantly evolving and adapting to changes in their environment in order to survive and pass on their genetic traits to future generations. Small changes over time called ‘microevolution’ can lead to dramatic transformations that allow organisms to thrive in new conditions.
In this comprehensive guide, we’ll explore how and why organisms undergo changes in behavior and physical characteristics to increase their chances of survival.
What is Adaptation?
Definition and examples of adaptation
Adaptation refers to the process where populations of organisms change over generations to improve their survival and reproduction in their environments. As the environment changes, genetic variations that help organisms survive and reproduce are selected for, while harmful variations are selected against.
Well-known examples of adaptations include:
- Desert plants having thick cuticles on their leaves to prevent water loss
- Arctic animals having thick fur or fat layers to withstand the cold
- Camouflaged insects that blend into their surroundings to avoid predators
Genetic variations and natural selection
Adaptation occurs through natural selection acting on genetic variations within a population. Mutations continuously generate new genetic variations, while sexual reproduction and genetic recombination shuffle existing variations into new combinations.
The genetic variations that improve survival and reproduction chances become more frequent over generations – this is natural selection. An example is the peppered moth evolving camouflaged wing coloration during England’s industrial revolution.
Microevolution vs macroevolution
Adaptation causes microevolution – small-scale changes within a species. Given enough time, the accumulation of microevolutionary changes can transform populations so drastically that new species emerge. This macroevolution produced the extraordinary diversity of organisms we see today.
While microevolution is easily observed over decades or centuries, macroevolution occurs over thousands to millions of years, as evidenced by fossil records.
Types of Adaptation
Structural adaptations
Structural adaptations are physical features of an organism that help it survive and reproduce in its environment. Here are some examples of structural adaptations:
- Camouflage – Animals like chameleons and stick insects have colors and patterns that help them blend into their surroundings to avoid predators.
- Mimicry – Some animals mimic the appearance of other species as a form of protection. For instance, non-venomous snakes like the milk snake have coloring similar to venomous coral snakes to ward off predators.
- Insulation – Animals living in cold climates often have thick fur or feathers, blubber, or fat layers that help conserve body heat.
- Streamlined bodies – Fish and whales have smooth, streamlined bodies that reduce water resistance when swimming.
- Cactus spines and thorns – These protect the plant from herbivores and also reduce water loss in dry environments.
Structural adaptations like these enhance the organism’s chances of survival and ability to reproduce in their habitat.
Behavioral adaptations
Behavioral adaptations refer to actions of an organism that enable it to survive in its environment. Some examples include:
- Migration – Birds, whales, and other animals migrate vast distances to find food, escape harsh weather, or reach breeding grounds.
- Hibernation – Bears and other animals go into a dormant state to conserve energy during winter months when food is scarce.
- Camouflage – Many animals use camouflage to blend into their surroundings and avoid detection by predators.
- Mimicry – Non-venomous species mimic poisonous ones to deter predation, like the viceroy butterfly mimicking the monarch.
- Pack hunting – Wolves and African wild dogs hunt in coordinated packs to take down large prey.
Behavioral adaptations increase the chances of finding food, avoiding predators, surviving extreme weather, and securing mates for reproduction.
Physiological adaptations
Physiological adaptations are internal changes to the biochemistry, anatomy, or functions of an organism that enable it to adapt. Examples include:
- Temperature regulation – Arctic foxes and penguins have countercurrent heat exchange in their legs to minimize heat loss.
- Water retention – Camels can go for long periods without water due to their ability to minimize fluid loss.
- Altitude tolerance – The bar-headed goose can fly at extreme altitudes over the Himalayas due to adaptations in its lungs and blood.
- Toxin resistance – The common garter snake has evolved resistance to toxic newt prey in its habitat.
- Salt excretion – Saltwater crocodiles have specialized glands to excrete excess salt from drinking salty water.
These internal adaptations allow organisms to maintain homeostasis and survive in extreme environments.
Causes of Adaptation
Climate change
Climate change can drive evolution and adaptation in organisms. As the global climate shifts due to rising temperatures, some environments experience changes in weather patterns, seasonal timing, and availability of resources like water.
Organisms must adapt to these changes or face reduced chances of survival and reproduction.
For example, some bird species like Great Tits have adapted their migration and breeding times to match earlier spring seasons caused by climate change. Tree frogs can survive freezing temperatures in the winter by producing higher levels of glucose in their blood, an adaptation to extreme cold.
Coral reefs that experience warming oceans may evolve heat-resistant strains or symbiotic relationships with algae that provide protection from heat stress.
Competition for resources
When multiple organisms in an ecosystem depend on the same limited resources like food, water, and territory, competition arises. Individuals with traits that allow them to secure resources more effectively will be more likely to survive and reproduce.
Over generations, adaptations that improve competitive ability become common in the population.
For example, giraffes developed extremely long necks to reach leaves high up in trees that shorter herbivores cannot access. Specialized beak shapes allow different bird species to access different food sources like seeds, insects, or nectar.
Territorial behaviors like vocalizing or ritual combat help some animals secure areas for breeding and feeding.
Predation and defense
The evolutionary arms race between predators and prey drives many adaptations. Predators evolve better camouflage, speed, toxins, or acute senses to capture prey, while prey develop defenses like warning coloration, spines, chemical deterrents, or behaviors that aid escape.
Successful adaptations give a reproductive advantage.
For example, some insects evolved to resemble sticks or leaves as camouflage from predators. Cane toads secrete toxic, milky poison from glands on their shoulders to deter predators. The hedgehog’s spines provide an effective defense against many predators.
These adaptations enhance survival against predation.
Reproductive success
Any adaptation that allows an individual to mate more successfully and produce more viable offspring will tend to persist in a population. Traits that attract mates, secure territories for breeding, provide care to offspring, or otherwise increase reproductive fitness give those individuals an advantage.
For example, elaborate plumage and courtship rituals in birds help attract mates. Some fish defend breeding sites where females lay eggs. Nurturing behaviors like nursing young and gathering food assist offspring survival. Successful reproduction perpetuates beneficial adaptations.
Case Studies and Examples
Peppered moths and industrialization
During the Industrial Revolution in England in the 1800s, peppered moths in areas with heavy industrial pollution experienced genetic changes that made them darker in color. The once predominantly light-colored moths now had more dark-colored individuals, which better camouflaged them against the soot-darkened trees and allowed them to avoid predation by birds.
This rapid genetic adaptation helped the moths survive in their changed environment.
Darwin’s finches on the Galapagos Islands
Charles Darwin studied different species of finches on the Galapagos Islands and found that their beaks had adapted to the different food sources available on each island. For example, finches with thicker, stronger beaks were able to crack open nuts and seeds, while those with longer, more slender beaks could reach nectar in flowers.
This was a key observation leading to Darwin’s theory of evolution by natural selection.
Bacteria developing antibiotic resistance
Bacteria have a remarkable ability to quickly evolve resistance to antibiotics. Through random genetic mutations and natural selection, populations of bacteria can rapidly become resistant to drugs that once killed them.
According to the CDC, antibiotic resistance is “one of the biggest public health challenges of our time,” as common infections are becoming difficult to treat (https://www.cdc.gov/drugresistance/about.html). Developing new antibiotics has become an arms race against bacteria’s ability to adapt.
Polar bears developing smaller body size
As Arctic sea ice declines due to climate change, polar bears have adapted with smaller average body size and cranial size. According to a 2010 study, polar bear skulls have become approximately 9% smaller since 1870.
The researchers theorized that the smaller body size requires less caloric intake, an advantage in their warming ecosystem with less access to food (https://academic.oup.com/jmammal/article/91/3/581/959173).
This gradual change shows how species morphologically adapt to rapid environmental changes within only a few generations.
Conclusion
In conclusion, the incredible diversity of life we see today is a result of ongoing adaptations that enable species to thrive in their ecological niches. While some changes are dramatic, most adaptations involve subtle shifts in behavior, anatomy, physiology or genetics that accumulate over time.
Understanding the mechanisms and drivers of adaptation provides key insights into how species can continue to evolve and survive amidst environmental pressures like climate change and habitat destruction caused by human activities.
