Download Adaptations of Species

Adaptations of Species
Giraffes are unique animals because they have such long necks.
The neck of a modern day giraffe is much longer than the neck of
an ancient giraffe that lived long ago. How and why did the giraffe
change in such a way? What are the advantages of having a long
neck?
Natural Selection and Species Survival
Structures of living organisms demonstrate adaptations that
allow for specific functions. For example, the giraffe’s long neck is
an adaptation because it allows the giraffe to reach leaves further
up on trees. This provides an advantage because the giraffe can
reach food that other animals cannot reach. Since a longer neck
provides an advantage, giraffes with this trait are more likely to
survive, reproduce, and pass the trait to their offspring. This is
called natural selection. It is the process by which, over
generations, favorable traits become more common in a species
or population and unfavorable traits become less common.
adaptations: structures
or behaviors in organisms
that help them survive in
their environment
Plants also have adaptations that help them survive. Water lilies,
for example, have large, thin leaves. The structure of these
leaves helps water lilies float so they can get enough sunlight for
photosynthesis. Because floating has an advantage, plants that
have this leaf structure can produce more food during
photosynthesis. The extra food helps the plants make more
seeds and pass on this trait to the next generation.
Some plants, like tulips, store food in structures called bulbs. The
bulbs grow underground. During winter (or other harsh conditions like a drought), the aboveground structures of the plant (stem, flower, leaves) die, but the bulb stays alive. It produces a new
stem, new leaves, and new flowers in the spring. This adaptation helps the plant survive difficult
environmental conditions.
One challenge for animals that live in water is getting enough
oxygen. Animals that live on land use lungs to get oxygen from
the air. Fish have gills to help them take in enough oxygen from
the water. Fish gills can be difficult to see because they are inside
the animal.
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Adaptations of Species
Amphibians also have gills during the time that they live in water. These gills can be found on the
outside of the animal, as shown in the picture of the salamander on the previous page. They look
like feathery structures on each side of the body. Gills are adapted to have many fringes to
increase the area that can absorb oxygen from the water.
An internal adaptation in plants is the xylem. The xylem is a
structure that moves water through the plant. Plants that do not
have xylem, like the mosses shown in the image on the right,
are limited to wet climates. Xylem is an adaptation that allows
plants to grow in drier climates because the xylem can draw
water up from deep in the soil.
If you examined a chicken or turkey bone, you would notice that
the bone is lightweight and hollow. In fact, most birds have hollow
bones. Why do you think this is so? What adaptive advantage do
hollow bones provide to a bird?
Behavioral Adaptations
The adaptations discussed so far have been structural, or
physical, adaptations. In the example above of hollow bones in
birds, the hollow structure of the bones allows birds to fly.
Therefore, birds can fulfill a role in the environment that most other organisms cannot fill.
Animals also have behavioral adaptations. For example, humpback whales use unique songs to
communicate with one another. These songs can help a mother find her lost calf. They can also be
used to claim a territory and keep other whales at a distance. Or, the songs can be used to find a
mate. Whales that are better at communicating have many advantages. A whale that is better able
to attract a mate through song is more likely to breed and pass that trait on to the next generation.
Squirrels and some other animals hibernate to help them
get through times of the year during which temperatures are
cold and food is limited. Animals that hibernate do not eat
and rely on stored body fat for energy. Thus, the timing of
hibernation is important. An animal that hibernates too long
may run out of fat reserves. An animal that awakes from
hibernation too soon may not find food. Producing enough
fat reserves is also an essential component of this
adaptation. Animals that have more fat reserves when they
enter hibernation are more likely to survive the winter.
hibernate: a process during
which an organism undergoes
a slowed physiological state
to survive long periods of cold
temperature or reduced food
supplies
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Adaptations of Species
Monarch butterflies and many species of
birds have a different behavioral
adaptation for surviving cold winters.
They leave the area. These animals
migrate from northern areas in the
summer to southern areas in the winter.
migrate: to move to a
different geographical
or climatic region where
food is more available
Natural selection does not have a goal. Organisms cannot plan to have “better” offspring.
Organisms that are born with more favorable traits are more likely to survive and reproduce than
organisms born with less favorable traits. Those organisms that survive and reproduce pass their
traits on to the next generation. What makes a trait more or less favorable? Many times it depends
on the environment. A trait that is favorable for living in the arctic may not be favorable for living in
the desert.
Genetic Variation
Natural selection is possible because of genetic variation
among organisms within a population. In a population of
giraffes, for example, individuals vary in height (as well as
other traits.) Some of these individuals have more
favorable sets of traits; others have less favorable sets of
traits. The individuals with the most favorable set of traits
will survive and reproduce to pass on those traits. It is the
variation between individuals that allows for natural
selection.
population: members of the
same species that live in the
same geographical area; may
be distinctly different than
populations living elsewhere,
due to the spread of local
adaptations within a population
The process of natural selection has changed nearly every species found on Earth. For example,
the Galapagos Medium Ground Finch has developed a unique beak shape allowing it to fill a
specific role in its environment and improve its ability to survive. The ground finches of the
Galapagos (a group of islands in the Pacific Ocean) feed mainly on seed. Several different species
of finches evolved from a common ancestor that was a seed-eating ground finch with a relatively
small, pointy beak. Each species specializes in feeding based on beak size. For example, the large
ground finch (Geospiza magnirostris) has a large beak and feeds mainly on large seeds. The small
ground finch (Geospiza fuliginosa) has a small beak and feeds mainly on small seeds. The
medium ground finch (Geospiza fortis) as a medium-sized beak. This allows the bird to be more of
a generalist; it is able to eat either large or small seeds. The medium-sized beak provides an
advantage because it has increased options for feeding, so its chances of survival are greater.
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Adaptations of Species
Populations and species demonstrate unique variations
and inherited traits, which have gradually changed over
time as they were passed from one generation to the
next. Changes in external features, internal features,
and behaviors of organisms, through natural selection
can enhance the survival of a species or produce desired
genetic traits.
Scientists in the Spotlight: Peter and Rosemary
Grant
Peter and Rosemary Grant are biologists who studied
the Galapagos finches. They were able to observe
natural selection over the course of a few generations of
the finches when the environment dramatically changed.
For example, in 1977 a drought resulted in more large seeds and fewer small seeds. The average
beak size of medium ground finches was larger after the drought than before the drought. After a
particularly wet year in 1985, the average finch beak was smaller. Smaller seeds were more
plentiful and the smaller-beaked finches were more successful at survival and reproduction that
year.
This data is important because it helps scientists measure and describe natural selection.
Obtaining the data took years of careful measuring and weighing. Peter and Rosemary Grant spent
a few months each year on the Galapagos Islands. They measured the finches and collected
weather data for many years. This dedication resulted in a long-term study that showed natural
selection in action.
Everyday Life: Selective Breeding
In selective breeding, the favorable traits to be passed on to
offspring are chosen by a breeder. Selective breeding of
domestic animals, like dogs, has led to incredible diversity from
their wolf ancestor. Dogs are as diverse as the Great Dane and
Chihuahua; yet they had a common ancestor. People who
selectively breed animals select for particular traits and breed
only the animals that have those
traits. After many generations, each
domestic: related to
breed has highly specific traits that
the household
have been selected for. Some breeds
are the result of breeding for a good
sense of smell, a good protective instinct, unique fur patterns, or
a particular body shape.
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Adaptations of Species
People also selectively breed plants. Wild corn, for example,
has very small kernels. Over many years of breeding,
humans have created modern corn with the large kernels
like we expect to see in the grocery store. People prefer to
purchase the larger kernels. Therefore, farmers plant the
seeds that produce the desired traits. Other crops, like
wheat, have also been selectively bred to produce desirable
traits. Modern wheat crops are more resistant to harsh
weather and produce more wheat per growing season.
Some modern crops are even bred to contain more vitamins!
What do you know?
The chart on the next page lists examples of adaptations in different organisms. For each example,
state whether the adaptation is likely the result of natural selection or selective breeding. Then,
describe at least one advantage for the adaptation. Be accurate, but creative! Many items in the
chart have more than one answer.
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Adaptations of Species
Example of Adaptation
Apples with large, sweet fruit
Natural Selection or
Selective Breeding?
Advantage(s) of
Adaptation
Cacti with sharp spines
Bats that can fly
Crabs that can hide in the sand
Tomato plants that can grow in
salty environments
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Adaptations of Species
Artificial Selection at the Grocery Store
To help your child learn more about
adaptations, investigate selective breeding
(also called artificial selection) by taking a trip
to the grocery store or farmer’s market. If you
are unable to travel to the market together, try
to find samples of fruits and vegetables in
your refrigerator or search for pictures on the
Internet.
the potential for frost or herbivore damage.
Larger fruit can be advantageous by attracting
dispersing animals, but it also requires a lot of
energy from the fruit- producing plant. Some
traits, however, are entirely of benefit to
humans and not the plant. Seedless plants,
for example, would not be selected for by
natural selection.
Selective breeding is common in food crops;
these crops are often called genetically
modified crops. Breeders can select for
a variety of traits, such as leaf size in lettuce,
fruit size in tomatoes, root size and vitamin
content in carrots, and flower size in
cauliflower. Choose at least six different fruits
and/or vegetables to discuss. Most of the
traits selected for by breeders can be
beneficial in the wild within the limits of a
particular range of variability. For example,
larger leaves help a plant by increasing
photosynthesis, but they can also increase
Here are some questions to discuss with the
student:
•
Which traits do you think were artificially
selected for in each fruit or vegetable?
Why do you think these traits were
selected?
•
Would similar adaptations be beneficial or
harmful in the wild?
•
Which type of environmental conditions
would be most favorable for these plants?
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