Planet earth supports a wide variety of life, ranging from the very tiniest of the microbes to the largest of the towering trees. Each living organism occupies a specific niche in its environment. Still, survival comes with a price in our world where resources such as food and space are often limited.
This is where adaptation — when an organism becomes better matched with its current environment — comes into play. In general, adaptations can be structural (meaning an organism undergoes bodily changes to survive) or behavioral (when a specific behavior increases an organism’s chances of survival) and it can occur in a few generations or take many generations to evolve.
A number of factors are responsible for adaptation such as environmental factors which include competition for resources, predation, infectious diseases, climate and seasonality. Some of these adaptive features include:
Though a mouthful of grass may not sound particularly tasty, the ability to digest it probably helped some animals survive in the past. Animals such as cattle and deer possess multi-chambered stomachs to break down tough plant matter into nutritious food. Researchers have found that eating grass and other vegetation high in cellulose requires animals to ferment food in their stomachs, where microbes help break down the compound though the evolution of a ruminant digestive system is a gradual and complex process.
Furthermore, a handful of animals have developed special saliva to process foods that their close ancestors couldn’t, for instance, the deers, some insects, squirrels and other rodents can consume varying levels of tannin (a chemical found in acorns and other plants) in environments where the compound is common. Teeth shape also allows certain animals to exploit food items.
Seed Dispersal in Plants
Life uses unique reproductive tactics to increase the chances of passing its genetics on to the next generation. Plants have developed interesting adaptations to spread their seeds . Some seeds possess tiny hooks that snag the fur or feathers of animals passing by, granting the seeds a free ride away from their parent plant. Others may look irresistible to hungry animals that consume and spread the seeds to other locations as droppings.
A study found that a species of weeds growing in small patches of soil in a new urban environment increased the amount of non-dispersing seeds, or ones deposited near the parent plant. Non-dispersing seeds deposited near the parent plant may have a better chance of surviving than dispersing seeds that can’t take root on concrete surfaces away from the parent plant. In this case, life rapidly adapted to its environment, especially considering that plants of the same species not living in urban settings don’t produce more non-dispersing seeds.
Some hermit crabs use empty shells to avoid drying up, or desiccating, between the ocean’s tides. Crabs that feed in these areas may get stuck in the sand during low tide, making them vulnerable to the sun or hungry beach predators. Grabbing an empty shell to live in is a behavioral adaptation that allows hermit crabs to better survive the inter-tidal environment, especially if they get stranded for a few hours.
Similarly, species of snails and bivalve mollusks grow their own shells to provide protection from the elements and predators. Scientists have found that the shape of physid freshwater snail shells depended on the type of predator present in the snails’ environments. Here, researchers attributed the shell diversity to the hunting strategies of the snails’ primary predators — crayfish and fish. The differences in shells are adaptive because they are shaped to avoid the attacks of predators found in their small habitats.
Like the physid snails, natural selection can also produce other adaptations in organisms.
As natural selection has shown us, many environmental pressures shape the genetics of a specific population. In these cases, organisms that survive to reproduce are the ones credited with adapting.
Look at pesticide use on insects, for instance. We initially thought using pesticides on insects would do the trick in getting rid of them. But a more complex phenomenon was at play. Since not every insect is genetically identical, there’s a chance that some insects will express resistance to the insecticide, survive encountering it and reproduce offspring with similar resistance. After using the same pesticide over and over, we learned that each new generation of insects became increasingly tolerant to the pesticide. Before you know it, an entire population of insects is resistant. Some call this process artificial selection.
Although we may not think of the human body as an “environment,” it’s surely home to living microorganisms set on survival. Adaptations can occur within us as well. In efforts to prevent creating antibiotic-resistant strains of bacteria, doctors prescribe antibiotics to patients with bacterial infections only when necessary.
Avoiding the Sun
In environments with extreme heat and little water, organisms including elephants, desert plants, reptiles and even humans, adapt to survive. Staying cool is vital. To achieve this, elephants adapt by
flapping their thin ears to dissipate heat and cool the blood running through them. To avoid drying up in a desert environment, organisms often store water in their bodies. The Gila monster, a desert lizard found in the southwestern United States, stores diluted water in its bladder after a several-minute drinking spree. We can also look to cactus plants and camels that use their bodies as vessels for water storage, too.
Believe it or not, our skin has an adaptation of its own — tanning. Humans adapt to the sun’s ultraviolet rays through the production of melanin, the pigment that gives skin its color. Melanin shields deeper layers of the skin and prevents the sun’s harmful rays from breaking down folic acid, an important vitamin that repairs blood cells in the body. As a short-term adaptation, most people develop a tan when exposed to the sun. In the long-term, human skin color reflects where your ancestors evolved, with the ancestors of darker-skinned humans having evolved closer to the equator and the ancestors of lighter-skinned humans having evolved in places with limited sunlight.
Although animals don’t use computers to complete tasks like humans, they still create innovative solutions by using tools. Usually, organisms use tools, or modified natural objects, to adapt to environmental constraints that may get in the way of accessing food.
Some species of hungry, dedicated birds fit this mold. The Egyptian vulture, for instance, is well-known for using its mouth and a stone to crack open ostrich eggs. Another type of bird, the woodpecker finch, has been observed placing a cactus spine in its mouth to prod delicious grubs out of tree holes. In addition, green herons have been observed “fishing” with bait by dropping small objects on the surface of water and waiting for fish to approach the object thinking it’s food.
These adaptations don’t have to be geographically widespread for them to take hold, either. Tools can be used for self defense as well. In one study, scientists reported a group of octopuses off the coast of Australia that suctioned coconut shells under their bodies in the event they’d need to use them for hiding from predators later.
Surviving With Little Oxygen
Much like humans, many organisms need oxygen to survive. Whether a marine organism holds its breath for several minutes or a llama travels high into the mountains, life can adapt to environments with little oxygen. For instance, marine mammals such as walruses have larger amounts of oxygen-rich blood circulating through their bodies in order to go on long dives without breathing. Animals also slow down their heart rate and blood circulation to conserve oxygen, too.
Altitude also determines the types of life that can survive in a given environment. Humans can adapt to gradual decreases in oxygen, and often people can acclimatize, or eventually adapt to high-altitude climates. To achieve this, the body creates more red blood cells and capillaries to help supply the body with more oxygen. There is, however, still a cost to this adaptation: fatigue and not being able to perform daily activities with the same rigor.
Over time, human populations have developed more permanent adaptations for living in high altitudes with little oxygen. For example, some high-altitude natives from Bolivia and Peru produce more hemoglobin in their blood, which carries additional oxygen in the bloodstream and allows people to take in extra oxygen through their lungs.
Life, particularly in the animal kingdom, is known for its masterful camouflages. Animals using camouflage disguise themselves to blend in with their surroundings or, sometimes, to mimic other animals in their environment. Camouflage is a useful adaptation because its users can avoid becoming dinner — and steer clear of being seen while trying to catch dinner, too. The chameleon stands as one of camouflage’s sterling examples, especially since the animal can change the pigmentation of its skin to match its surroundings. But other camouflage adaptations may not be as voluntary. Stick bugs are known for, well, their stick-liked appearance, while leaf insects are masters at blending into similarly colored foliage.
Changes in an organism’s appearance can also be shaped by other animals in its environment. For example, birds avoid eating the monarch butterfly because of its poisonous diet. Since birds identify monarch butterflies by their appearance, another species — the viceroy butterfly — has mimicked the appearance of monarch butterflies to avoid predation as well.
Surviving the Cold
As the seasons change, so do life’s adaptations. Just as some animals adapt to heat, others must survive the cold — whether it’s permanent or seasonal. Organisms living in cold climates naturally have larger bodies and thicker skin and fur. But many organisms adapt on a seasonal basis, too. Animals that hibernate, or enter a deep sleep of sorts, during winter use the behavior to survive periods of cold
temperatures when food is not widely available. Prior to hibernating, animals will stock up on fat to burn throughout the winter. In some cases, animals such as the American black bear can go 100 days without waking up, drinking, eating, defecating or urinating.
So far, multiple sources have claimed that climate change has negatively affected the cycles of hibernating animals, making them emerge from their winter slumber earlier than usual. These early arousals demonstrate how easily life can adapt to its changing environment. Rather than slumbering in a dedicated shelter, some
animals are adapted to freeze and thaw with the winter weather. The wood frog hibernates under leaves, where it can freeze and come back to life in the spring. Scientists credit the frog’s stealthy adaptive response to certain proteins and glucose that act as an antifreeze for the frog’s cells.
Humans and other primates heavily depend on their sense of vision to interpret the world around them. Other forms of life do this too, but often rely on other senses — some of which humans don’t even have. Bats rely on echolocation, or by emitting and receiving high-pitched sounds, to navigate their environments in the dark. This adaptation enables bats to fill an ecological niche as night dwellers.
The same can be said of birds of prey that possess acute vision at long distances or sharks’ abilities to pick up electromagnetic currents. Yet the “Use It or Lose It” idea seems to apply to some
sensory adaptations for animals. Like the ancestors of moles, which lost their sight gradually from living underground, one species of cave-fish lost its eyes altogether, according to a researcher’s findings. In a lab setting, the scientist crossbred the eyeless fish from different caves and found that some of the offspring possessed working eyes. The study revealed that the fish still had the genes to produce eyes, but they were not expressed because of the dark conditions of the
Of all the wonderful adaptations, perhaps the most important is the habit of living together in communal or family groups. Countless species engage in group living, either in herds, colonies, harems, complex societies or loose associations. Animals can derive a lot of
benefit from spending time with other members of the same species. They can help each other find food, defend against predators and care for young. Some other adaptations include flight, migration, artificial bigness in blowfish and nest paratism in cuckoo birds.