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 a structural adaptation is the way some plants have adapted to life in dry, hot deserts. Plants called succulents have adapted to this climate by storing water in their short, thick stems and leaves.

Seasonal migration is 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 the nutrient-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 this moth was cream-colored with darker spots. Few peppered moths were gray or black.


As the Industrial Revolution changed the environment, the appearance of the peppered moth changed. The darker-colored moths, which were rare, began to thrive in the urban atmosphere. Their sooty color blended in with the trees, which were stained by industrial pollution. 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 limited air 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 of adaptive radiation, a type of speciation in which species develop to fill a variety of empty ecological niches. Marsupials, mammals that carry their developing young in 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’s womb, came to dominate every other continent, but not Oceania. Koalas (Phascolarctos cinereus), for instance, adapted to feed on eucalyptus trees, which are native to Australia. The extinct Tasmanian tiger (Thylacinus cynocephalus) was a carnivorous marsupial and adapted to the niche filled by big cats, like tigers, on other continents.

The cichlid fish 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 a unique, specialized diet: One type of cichlid may eat only insects, another may eat only algae, another may feed only on other fish.

Coadaptation

Organisms sometimes adapt with and to other organisms. This is called coadaptation. Certain flowers produce nectar to appeal to hummingbirds. Hummingbirds, in turn, have adapted long, thin beaks to extract the 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 is distributed. The coadaptation is beneficial to both organisms.

Mimicry is another type of coadaptation. In mimicry, one organism has adapted to resemble another. 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.

Coadaptation can also limit an organism’s ability to adapt to new changes in their habitat. This can lead to co-extinction. In southern England, the large blue butterfly adapted to eat red ants. When human development reduced the red ants’ habitat, the local extinction of the red ant led to the local extinction of the large blue butterfly.

Adaptation and Survival

A koala hugs a tree while her baby clings to her back at the Lone Pine Koala Sanctuary near Brisbane, Queensland, Australia. Koalas have adapted to only eat the leaves of eucalyptus trees. Eucalyptus are very low in protein and toxic to many animal species. Being able to digest eucalyptus leaves is an adaptation that benefits the koala by providing it a food source for which there is little competition.

adapt
Verb

to adjust to new surroundings or a new situation.

Noun

a modification of an organism or its parts that makes it more fit for existence. An adaptation is passed from generation to generation.

adaptive radiation
Noun

process in which many species develop from the same ancestral species to fill a variety of different roles in the environment.

algae
Plural Noun

(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

Noun

region at Earth's extreme north, encompassed by the Arctic Circle.

behavioral adaptation
Noun

way an organism acts in order to survive or thrive in its environment.

big cat
Noun

large predators, including tigers, lions, jaguars, and leopards.

carnivorous
Adjective

meat-eating.

cichlid
Noun

spiny-finned freshwater fish.

climate
Noun

all weather conditions for a given location over a period of time.

coadaptation
Noun

the process in which organisms develop in close relationship to one another.

Noun

edge of land along the sea or other large body of water.

co-extinction
Noun

the process in which the loss of one species leads to the loss of another species.

Noun

one of the seven main land masses on Earth.

Noun

area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

Noun

growth, or changing from one condition to another.

Noun

foods eaten by a specific group of people or other organisms.

distribute
Verb

to divide and spread out materials.

dominate
Verb

to overpower or control.

environment
Noun

conditions that surround and influence an organism or community.

eucalyptus
Noun

tree native to Oceania.

exaptation
Noun

adaptation that developed for one purpose but is used for another.

extinct
Adjective

no longer existing.

extract
Verb

to pull out.

generation
Noun

group in a species made up of members that are roughly the same age.

genetic
Adjective

having to do with genes, inherited characteristics or heredity.

Noun

environment where an organism lives throughout the year or for shorter periods of time.

hummingbird
Noun

type of very small bird.

industrial
Adjective

having to do with factories or mechanical production.

Industrial Revolution
Noun

change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production.

inherit
Verb

to receive from ancestors.

isolation
Noun

state of being alone or separated from a community.

mammal
Noun

animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring.

marsupial
Noun

mammal that carries its young in a pouch on the mother's body.

migrate
Verb

to move from one place or activity to another.

Noun

movement of a group of people or animals from one place to another.

moth
Noun

flying insect.

Noun

sudden variation in one or more characteristics caused by a change in a gene or chromosome.

niche
Noun

role and space of a species within an ecosystem.

Noun

substance an organism needs for energy, growth, and life.

Oceania
Noun

region including island groups in the South Pacific.

placental mammal
Noun

animal (mammal) characterized by the fetus developing inside the body of the mother, in an organ called the placenta.

pollen
Noun

powdery material produced by plants, each grain of which contains a male gamete capable of fertilizing a female ovule.

Noun

introduction of harmful materials into the environment.

resemble
Verb

to look like.

Noun

process by which one or more populations of a species become genetically different enough to form a new species.

species
Noun

group of similar organisms that can reproduce with each other.

succulent
Noun

type of plant that has thick leaves and stems for storing water.

sympatric speciation
Noun

development of many similar species in a single habitat, each with a different specialization.

thrive
Verb

to develop and be successful.

unique
Adjective

one of a kind.

urban
Adjective

having to do with city life.

vestigial
Adjective

having to do with a body part, or remnant of a body part, that no longer serves any useful function.

womb
Noun

organ in which an embryo and fetus develops. Also called the uterus.

young
Noun

offspring or children.