Download Reading Science! - O. Henry Science

7.11BC/.12A: Adaptation of Species
Organisms and Environment
Reading Science!
Name: ____________________________________ Date: _____________________
Darwin’s Fancy with Finches
Lexile 1190L
1
Whales are mammals that live in water and
can hold their breath underwater for a long
time, yet need to breathe air from the surface
of the ocean in order to live. Evidence
suggests that the modern-day whale’s
ancestors lived on land. White hair in animals
is due to the loss of chemical that causes the
hair to be colored. Biologists declare that the
ancestors to polar bears lost their dark pelt
1. Geospiza magnirostris. 2. Geospiza fortis.
over time to a theory known as natural
3. Geospiza parvula.
4. Certhidea olivacea
selection. This theory was defined in Charles
Finches from Galapagos Archipelago
Darwin’s book On the Origin of Species by
Means of Natural Selection in 1859. Natural selection is the process that is
responsible for the evolution of adaptations of organisms to their
environment over time. Evolution is changes in inherited features of a
species. Natural selection plays a role in the origin of new species. Essentially,
natural selection means that the organisms with the strongest dominate
traits are the ones that will be able to sustain the environmental conditions
over time, thus survive.
2
Charles Darwin was a mere 22 years old in 1831. He developed his theory of
evolution as a result of a survey he conducted while sailing as a naturalist
aboard the HMS Beagle His job was to search for and collect samples of
plants and animals he found on the ship’s journey around the world. He was
particularly amazed by the unusual animals and plants he found in the
Galápagos Islands, located 600 miles west of the coast of Ecuador. Darwin
was especially fascinated by fourteen types of a small bird he identified as
varieties of finch. He pondered upon how there could be so many different,
1
Reading Science!
7.11BC/.12A: Adaptation of Species
Organisms and Environment
yet similar, species of finches living in such close proximity of each other in
this chain of islands. For twenty years after his voyage, Darwin studied his
collection of animals and plants. His findings resulted in a hypothesis that
eventually became known as the theory of evolution by natural selection.
Even today, this theory is one of the most important concepts in studying life
science.
3
Four factors govern natural selection: 1) In general, organisms produce more
offspring than can survive; 2) variations of a species are found among
individuals; 3) these variations contribute to the survival and reproduction of
individuals; and 4) over time, with the succession of generations, variations
that enhance survival and reproduction in the offspring will become
increasingly widespread in the population.
4
This is particularly true when variations provide a survival advantage to
individuals within the environment. Variations result from changes in an
organism’s DNA, which is also known as mutation. Variations may include the
organisms’ color, chemical make up, shape, and size. Camouflage coloring, for
example, is a protective adaptation that allows the organism to blend in with
its environment, which affects its ability to avoid predators. Those individuals
that successfully survive and produce offspring, will pass on those variations
through their genes. This process is what is referred to as an adaptation of
species.
5
Darwin’s finches are the classic example of illustrating how this can happen.
He examined the variations in the beak sizes and shapes of the Galápagos
finches. All fourteen species of these finches are closely related, and they live
in a changing environment. The environment underwent periods of severe
drought as well heavy, prolonged rains of El Niño. These impacted the
geography, climate, and vegetation of the islands. Those finches that couldn’t
adapt, perished. Human activity was generally absent, and therefore had no
effect on these species. Thus, biologists conclude that the key factors that
shaped adaptations in the finches could be attributed strictly to the forces of
environmental change and natural selection. Darwin marveled most at the
size of the beaks and varied diets of the different species of the finch he
2
Reading Science!
7.11BC/.12A: Adaptation of Species
Organisms and Environment
found on the islands. His theory included evidence supporting how one
species of finch, a “common ancestor,” had likely evolved into many different
species is Galápagos and the surrounding islands. His finches’ main
adaptation appeared in the shape and type of beak as the birds adapted to
the local food sources on each island. The food types that grew on each
island were driven by environmental conditions.
6
Today, adaptations of species is clearly seen in our every day lives. For
example, some insects evolved over hundreds of years to resist various
chemicals used to exterminate them. Their resistance to various insecticides
has mad it more and more difficult to control them, resulting in financial loss
for the agricultural industry and, in some cases, an inability to control the
destruction of crops. Adaptations also show up in human health. Biologists
have seen how harmful bacteria and viruses have evolved increasing
resistance to antibiotics or other drugs used against them. The most obvious
example is the epidemic spread of the HIV virus, which medical scientists
testify is capable of evolving rapidly to resist drugs that once were effective
against it. This antibiotic resistance is another excellent example that
illustrates Darwin’s natural selection process.
3
Reading Science!
7.11BC/.12A: Adaptation of Species
Organisms and Environment
1
A
2
3
Natural selection is −
a process that happens in the
absence of environmental
conditions.
Darwin, through his collection of
samples and findings, taught us that
natural selection is how species −
A
survive over time.
B
a single process of adaptation
within an individual.
B
evolve by adapting to their
environment over time.
C
the survival of the fittest.
C
D
an ability to predict the
outcome of a defined species
over time.
plays a role in the origin of new
species.
D
Both B and C
In 1859, Darwin’s controversial book,
On the Origin of Species by Means of
Natural Selection, illustrates −
A
4
the importance of variations in
organisms.
B
the explanation of design in
nature.
C
how species evolve by adapting
to their environment.
D
All the above
4
Darwin concluded that the chief
reason his finches did not become
extinct was due to −
A
ample food supply.
B
climate control.
C
absence of predators.
D
the lack of human activity on
the islands.
Reading Science!
7.11BC/.12A: Adaptation of Species
Organisms and Environment
5
6
This reading suggest that the factors
governing natural selection include
all except which of the following:
A
B
C
D
From the reading of this passage,
you now know that examples of
natural selection would include −
Organisms successfully
reproduce themselves
A
Organisms produce more
offspring than can survive
the whale, a mammal who lives
in the water.
B
some insects resistant to
pesticides.
C
antibiotic resistance in the
human body as seen in HIV
patients.
D
All the above
Over time, variations in the
offspring will become
increasingly widespread in the
population
Variations are found in an
individual
5