Any number of characteristics can vary among individuals of a given species— some may be larger, hairier, fight off infections better, or have smaller ears. These characteristics are largely determined by their genes, which are passed down from their parents and subsequently passed down to their own offspring. Some of these characteristics, or traits, provide competitive advantages like speed, strength, or attractiveness. If those traits are particularly helpful, individuals with those traits will produce more offspring than those without. Over generations, the number of individuals with that advantageous trait, or adaptation, will increase until it becomes a general attribute of the
species
.
Structural and Behavioral Adaptations
An adaptation can be structural, meaning it is a physical part of the organism. An
adaptation
can also be behavioral, affecting the way an organism responds to its environment.
An example of astructural
adaptation
is the way some plants have
adapted
to life in dry, hot deserts. Plants calledsucculents have
adapted
to thisclimateby storing water in their short, thick stems and leaves.
Seasonal migrationis an example of a
behavioral
adaptation
. Gray whales (Eschrichtius robustus) migrate thousands of kilometers every year as they swim from the cold Arctic Ocean in summer to the warm waters off the coast of Mexico to winter. Grey whale calves are born in the warm southern water, and then travel in groups called pods to thenutrient-rich waters of the
Arctic
.
Adaptations
that develop in response to one challenge sometimes help with or become co-opted for another. Feathers were probably first
adaptations
for tactile sense or regulating temperature. Later, feathers became longer and stiffer, allowing for gliding and then for flight. Such traits are called exaptations.
Some traits, on the other hand, lose their function when other
adaptations
become more important or when the
environment
changes. Evidence of these traits remain in a vestigial form— reduced or functionless. Whales and dolphins have
vestigial
leg bones, the remains of an
adaptation
(legs) that their ancestors used to walk.
Habitat
Adaptations
often develop in response to a change in the organisms’
habitat
.
A famous example of an animal
adapting
to a change in its
environment
is England's peppered moth (Biston betularia). Prior to the 19th century, the most common type of thismothwas cream-colored with darker spots. Few peppered moths were gray or black.
As theIndustrial Revolutionchanged the
environment
, the appearance of the peppered
moth
changed. The darker-colored
moths
, which were rare, began tothrivein theurbanatmosphere. Theirsooty color blended in with the trees, which were stained byindustrialpollution. Birds couldn’t see the dark
moths
as well, so they ate the cream-colored
moths
instead. The cream-colored
moths
began to make a comeback after the United Kingdom passed laws that limitedair
pollution
.
Speciation
Sometimes, an
adaptation
or set of
adaptations
develops that splits one
species
into two. This process is known as
speciation
.
Marsupials in Oceania are an example ofadaptive radiation, a type of
speciation
in which
species
develop to fill a variety of empty ecological niches.
Marsupials
, mammals that carry theirdeveloping youngin pouches after a short pregnancy, arrived in
Oceania
before the land split from Asia.Placental mammals, animals that carry their
young
to term in the
mother
’swomb, came todominateevery other continent, but not
Oceania
. Koalas (Phascolarctos cinereus), for instance,
adapted
to feed oneucalyptustrees, which are native to Australia. TheextinctTasmanian tiger (Thylacinus cynocephalus) was acarnivorous
marsupial
and
adapted
to the
niche
filled bybig cats, like tigers, on other
continents
.
Thecichlidfish found in many of Africa’s lakes exhibit another type of
speciation
,sympatric speciation.
Sympatric
speciation
is the opposite of physical isolation. It happens when
species
share the same
habitat
.
Adaptations
have allowed hundreds of varieties of
cichlids
to live in Lake Malawi. Each
species
of
cichlid
has aunique, specializeddiet: One type of
cichlid
may eat only insects, another may eat onlyalgae, another may feed only on other fish.
Coadaptation
Organisms sometimes
adapt
with and to other organisms. This is called
co
adaptation
. Certain flowers produce nectar to appeal to hummingbirds.
Hummingbirds
, in turn, have
adapted
long, thin beaks toextractthe nectar from certain flowers. When a
hummingbird
goes to feed, it inadvertently picks up pollen from the anthers of the flowers, which is deposited on the stigma of the next flowers it visits. In this relationship, the
hummingbird
gets food, while the plant’s
pollen
isdistributed. The
co
adaptation
is beneficial to both organisms.
Mimicry is another type of
co
adaptation
. In mimicry, one organism has
adapted
toresembleanother. The harmless king snake (sometimes called a milk snake) has
adapted
a color pattern that
resembles
the deadly coral snake. This mimicry keeps predators away from the king snake.
The mimic octopus (Thaumoctopus mimicus) has behavioral as well as structural
adaptations
. This
species
of octopus can copy the look and movements of other animals, such as sea snakes, flatfish, jellyfish, and shrimp.
Co
adaptation
can also limit an organism’s ability to
adapt
to new changes in their
habitat
. This can lead toco-extinction. In southern England, the large blue butterfly
adapted
to eat red ants. When humandevelopmentreduced the red ants’
habitat
, the local
extinction
of the red ant led to the local
extinction
of the large blue butterfly.
