Key Concept 1: Plants and animals have specific structures and
functions that enable them to be successful in their environments.
Adaptations help a plant or animal survive. The English naturalist Charles
Darwin realized over 150 years ago that physical features (structures) and
how they are used (functions) took many generations to develop. He
observed that those species of animals and plants that were able to
survive and reproduce were those which had best adapted to the
challenges of their environments. He called this natural ability to adapt
natural selection.
Plant Adaptations - In the rain forest with its heavy green foliage, the
competition is not for water, but for sunlight. As a result, plants in rain
forests adapt by growing taller and faster than neighboring plants to
reach the sunlight. Those plants that are in deep shade areas will have
darker green and red leaves to absorb as much light as possible. In Arctic
regions, although there is plenty of sunlight during the summer, the wind
blows unmercifully in the unprotected landscape. As a result, trees grow
very low to the ground, sometimes no more than a few inches tall, to
avoid the howling wind. The plants are also smaller than similar species at
lower latitudes because of a shorter growing season farther north.
Many factors determine which adaptations will ensure survival. Plants
release moisture through their leaves. However, in the desert where water
is scarce, plants like cacti have leaves that resemble sharp spines so that a
minimum amount of leaf surface area is exposed to transpiration. The
spines also act as protection, since the cacti are so rich in water under the
waxy coating. Cacti can store gallons of water in their trunks to be used
sparingly during periods of no rain. Desert plants have roots that spread
wide and extend deep into the ground to capture every valuable drop of
water. Even a houseplant, when placed near sunlight, will grow toward the
light source in an adaptation to its environment. Every part of a plant,
root, stem or trunk, leaf, flower or fruit, is vital to the survival of the plant,
and as such has been adapted to respond to the effects of the
environment around it.
Feet Adaptations - Animals, too, are products, or reflections, of their
environments. Many animals that live in an aquatic environment have
webbed feet to aid swimming both in cold and warm water. Beyond that,
many waterfowl, such as ducks and geese, and even polar bear and otter
feet are webbed. The flaps of skin between the toes of webbed feet allow
the animal to push against the water with greater force for faster
swimming to catch food or to escape from predators. Sharp claws are an
adaptation of many animals that need running speed, climbing ability,
digging prowess, or hunting skills. Hooves on horses and antelopes allow
them to run faster and more easily over hard prairie ground. A hoof is
simply one large, modified toenail that supports the entire foot and leg.
The sucker-like feet on a Gecko lizard allow it to cling to objects to hide
from predators or to wait for food. The grasping feet of tree monkeys
allow them to swing from limb to limb.
Limb Adaptations - Flippers on penguins and seals are adaptations that
allow these animals to swim rapidly, either to find food or to escape a
predator. The strong back legs of rabbits, kangaroos, and cheetahs allow
the animals to leap and run long distances, either to escape predators or
to catch prey.
Mouth Adaptations - An animal’s teeth will often indicate its source of
food. Sharp teeth reveal a carnivore (meat eater), while broad, flat teeth
for grinding food belong to an herbivore (plant eater). The beaks of birds
vary according to diet. The crane has a long, narrow beak to reach deep
into water for small fish, while a finch has a short, powerful beak for
cracking nuts and seeds. Predators, such as eagles and hawks, have
curved, sharp beaks for tearing chunks of flesh from their prey.
Defense Adaptations - By having a color or shape that blends with the
environment (camouflage), the organism is better able to hide from its
enemies and stalk its prey. A lizard can change skin color to blend in with
its environment. A baby deer has spots to hide it from predators. An
arctic hare is white in the winter to blend in with the snow-covered
terrain. Sometimes, an animal resembles another organism or its
surroundings to better survive (mimicry). Some insects look like leaves,
while other insects resemble a stick to hide themselves. The Dragon
Seahorse resembles a leafy aquatic plant in order to hide from predators.
Some animals try to appear larger to scare off predators, such as a cat
arching its back.
Temperature Adaptations - In the frigid regions of the North or South
Poles, animals like polar bears or seals have thick layers of blubber
underneath thick skins to protect them from the ice and freezing water. In
hot desert environments, animals have adapted to a small size, such as
the kangaroo mouse, or thick skins, such as scorpions, to prevent water
loss. Migration (seasonal movement of an organism from one place to
another) is an adaptation to extreme temperatures and reduced food
supplies during winter. Many birds migrate to southern areas to wait out
frigid temperatures.
The Monarch butterfly travels to central Mexico, over thousands of miles,
during winter. The Arctic tern, gray whale, and African elephant are other
examples of animals that migrate long distances due to seasonal changes.
Hibernation (when an animal becomes still in an enclosed space, and
reduces body functions to save energy) is another adaptation to seasonal
changes. For example, bears, bats, squirrels, and frogs slow down their
metabolism (body functions) to hibernate during winter.