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Evolution, the Themes of
Biology, and Scientific inquiry

1

Figure 1
...
1

the study of life reveals unifying
themes

1
...
3

in studying nature, scientists
make observations and form
and test hypotheses

1
...
This mouse has a
much darker back, side, and face than mice of
the same species that inhabit sand dunes
...
However, the
beach mice that live there have light, dappled fur, allowing them to blend into
their surroundings (Figure 1
...
Mice of the same species (Peromyscus polionotus)
also inhabit nearby inland areas
...
For both beach mice and
inland mice, the close color match of coat (fur) and environment is vital for survival, since hawks, herons, and other sharp-eyed predators periodically scan the
landscape for prey
...
Evolution is the
fundamental principle of biology and the core theme of this book
...
Posing questions about the living world and seeking answers through
scientific inquiry are the central activities of biology, the scientific study of
life
...
They may ask how a single tiny cell

When you see this blue icon, log in to MasteringBiology
and go to the Study Area for digital resources
...
2 reminds
us that the living world is wondrously varied
...

The first part of the chapter provides a panoramic view of
the biological “landscape,” organized around some unifying
themes
...
Next, we look at
scientific inquiry—how scientists ask and attempt to answer
questions about the natural world
...


becomes a tree or a dog, how the human mind works, or
how the different forms of life in a forest interact
...
More than anything else, biology is a quest, an ongoing inquiry about the nature of life
...
Yet the phenomenon we call life defies a
simple, one-sentence definition
...
Figure 1
...


Figure 1
...

▼ Order
...


▲ Regulation
...
The overall
surrounding air
...

Such adaptations evolve over countless
generations by the reproductive
success of those individuals with
▼ Reproduction
...

things) reproduce
their own kind
...
This
butterfly obtains fuel in
the form of nectar from
flowers
...


animation: Signs of Life
Video: Sea horse Camouflage

▲ Growth and development
...


CHaPTeR 1

▲ Response to the
environment
...


Evolution, the Themes of Biology, and Scientific Inquiry

3

COncEpT  1
...


the study of life reveals
unifying themes




Biology is a subject of enormous scope, and exciting new
biological discoveries are being made every day
...


Figure 1
...


exploring Levels of Biological organization
◀1

The Biosphere

Even from space, we can see signs of Earth’s life—in the green mosaic of the forests, for
example
...


◀2

Ecosystems

Our first scale change brings us to a North American mountain
meadow, which is an example of an ecosystem, as are tropical
forests, grasslands, deserts, and coral reefs
...


▶3

Communities

The array of organisms inhabiting a particular
ecosystem is called a biological community
...
Each of these forms of
life belongs to a species—a group whose members can
only reproduce with other members of the group
...
For example, our
meadow includes a population of lupine (some
of which are shown here) and a population of
mule deer
...


4

CHaPTeR 1

Evolution, the Themes of Biology, and Scientific Inquiry

▲5

Organisms

Individual living things
are called organisms
...


theme: new Properties emerge at Successive
Levels of Biological organization
ORGaniZaTiOn The study of life on Earth extends from
the microscopic scale of the molecules and cells that make up
organisms to the global scale of the entire living planet
...
In Figure 1
...
This journey, depicted as a series of numbered steps,
highlights the hierarchy of biological organization
...
A leaf is an example of an
organ, a body part that is made up of multiple
tissues and has specific functions in the body
...
Within an organ,
each tissue has a distinct
arrangement and contributes
particular properties
to organ function
...
Some
organisms consist
of a single cell,
which performs
all the functions
of life
...
Here we see
a magnified view of a cell in a
leaf tissue
...
Within these tiny cells are even
smaller green structures called
chloroplasts, which are responsible
for photosynthesis
...
This method is so named because it reduces
complex systems to simpler components that are more
manageable to study
...
For example, by studying the molecular structure
of DNA that had been extracted from cells, James Watson
and Francis Crick inferred the chemical basis of biological
inheritance
...


Tissues

Viewing the tissues of a leaf requires a microscope
...
The leaf shown
here has been cut on an angle
...
The jigsaw
puzzle–like “skin” on the surface of the
leaf is a tissue called epidermis (right
side of photo)
...


50 μm

10 μm

▼9

Organelles

▼ 10

Chloroplasts are examples
of organelles, the various
functional components
present in cells
...


Chloroplast

CHaPTeR 1

1 μm

Molecules

Our last scale change drops us into
a chloroplast for a view of life at the
molecular level
...

Chlorophyll is the
pigment that makes a
leaf green, and it
absorbs sunlight
during photosynthesis
...


Evolution, the Themes of Biology, and Scientific Inquiry

5

Emergent Properties
Let’s reexamine Figure 1
...
This approach allows us to
see novel properties emerge at each level that are absent from
the preceding one
...
For example, although photosynthesis occurs in
an intact chloroplast, it will not take place in a disorganized
test-tube mixture of chlorophyll and other chloroplast molecules
...

Isolated components of living systems—the objects of study
in a reductionist approach—lack a number of significant
properties that emerge at higher levels of organization
...
A box of bicycle
parts won’t transport you anywhere, but if they are arranged
in a certain way, you can pedal to your chosen destination
...

To fully explore emergent properties, biologists today
complement reductionism with systems biology, the
exploration of a biological system by analyzing the interactions among its parts
...
By examining and modeling the dynamic behavior of an integrated network of components, systems biology
enables us to pose new kinds of questions
...


Structure and Function
At each level of the biological hierarchy, we find a correlation
of structure and function
...
3: Its thin,
flat shape maximizes the capture of sunlight by chloroplasts
...
Conversely,
knowing the function of something provides
insight into its structure and organization
...
For example, the
hummingbird’s anatomy allows the
wings to rotate at the shoulder, so
hummingbirds have the ability,
unique among birds, to fly
backward or hover in place
...
The elegant
match of form and function in the structures of life is explained
by natural selection, which we’ll explore shortly
...

The so-called Cell Theory was first developed in the 1800s,
based on the observations of many scientists
...
In fact, the actions of organisms are all
based on the functioning of cells
...
Even a process that occurs
on a global scale, such as the recycling of carbon atoms, is the
product of cellular functions, including the photosynthetic
activity of chloroplasts in leaf cells
...
For instance, every cell
is enclosed by a membrane that regulates the passage of materials between the cell and its surroundings
...

The cells of two groups of single-celled microorganisms—
bacteria (singular, bacterium) and archaea (singular, archaean)—
are prokaryotic
...

A eukaryotic cell contains membrane-enclosed organelles
(Figure 1
...
Some organelles, such as the DNA-containing
nucleus, are found in the cells of all eukaryotes; other organelles
Figure 1
...

The cells are shown to scale here; to see a larger
magnification of a prokaryotic cell, see Figure 6
...

Eukaryotic cell
Membrane

Prokaryotic cell

DNA
(no nucleus)
Membrane

Cytoplasm

Nucleus
(membraneenclosed)
Membraneenclosed organelles

DNA (throughout
nucleus)

1 μm

ViSUAL SKiLLS Measure the scale bar and use its length to estimate the
length of the prokaryotic cell and the longest dimension of the eukaryotic cell
...
For example, the chloroplast
in Figure 1
...
In contrast to eukaryotic cells, a
prokaryotic cell lacks a nucleus or other membrane-enclosed
organelles
...
4
...
6  inherited
dNA directs development
of an organism
...
In cells that are preparing
to divide, the chromosomes may be made visible using a dye
that appears blue when bound to the DNA (Figure 1
...

infORmaTiOn

Embryo’s cells
with copies of
inherited DNA
Offspring with
traits inherited
from both parents

10 μm

Figure 1
...


Nucleus

Figure 1
...


DNA

Cell
A
C
Nucleotide

T
A

DNA, the Genetic material

T

Before a cell divides, the DNA is first replicated, or copied, and
each of the two cellular offspring inherits a complete set of
chromosomes, identical to that of the parent cell
...
Transmitted from parents to offspring, genes
are the units of inheritance
...

You began as a single cell stocked with DNA inherited from
your parents
...
As the cells grew
and divided, the genetic information encoded by the DNA
directed your development (Figure 1
...

The molecular structure of DNA accounts for its ability to
store information
...
Each chain
is made up of four kinds of chemical building blocks called
nucleotides, abbreviated A, T, C, and G (Figure 1
...
Specific
sequences of these four nucleotides encode the information

A

CHaPTeR 1

C
C
G
T
A
G
T
A
(b) Single strand of DNA
...
This
geometric shapes and letters are
model shows the atoms
simple symbols for the nucleoin a segment of DNA
...
Genetic
of building blocks called
information is encoded in specific
nucleotides, a DNA molecule
sequences of the four types of
takes the three-dimensional
nucleotides
...

abbreviated A, T, C, and G
...
The way DNA encodes information is analogous to
how we arrange the letters of the alphabet into words and
phrases with specific meanings
...
We can think of
nucleotides as a four-letter alphabet
...
For instance, a given bacterial gene may
specify a particular protein (an enzyme) required to break
down a certain sugar molecule, while a human gene may
denote a different protein (an antibody) that helps fight off
infection
...

Protein-encoding genes control protein production indirectly, using a related molecule called RNA as an intermediary (Figure 1
...
The sequence of nucleotides along a gene
is transcribed into mRNA, which is then translated into a
linked series of protein building blocks called amino acids
...
The entire process by
which the information in a gene directs the manufacture of a
cellular product is called gene expression
...
Differences between organisms reflect differences
between their nucleotide sequences rather than between
their genetic codes
...
Comparing
the sequences in several species for a gene that codes for a
particular protein can provide valuable information both
about the protein and about the relationship of the species
to each other
...
8 is translated into a protein,
but other cellular RNAs function differently
...
Recently, scientists have discovered whole new classes
of RNA that play other roles in the cell, such as regulating the
functioning of protein-coding genes
...
By carrying the instructions for making proteins and
RNAs and by replicating with each cell division, DNA ensures
faithful inheritance of genetic information from generation to
generation
...
8  Gene expression: Cells use information
encoded in a gene to synthesize a functional protein
...
How
do lens cells make crystallin
proteins?

Lens
cell

(b) A lens cell uses information in DNA to make crystallin proteins
...


DNA
(part of the
crystallin gene)

A

C

C

A A

A

C

C

G A

G

T

T

G

G

T

T

G

G

C

C

A

U G

G

U U

U G

G

C

U

C

A

The cell translates the information in the
sequence of mRNA nucleotides to make a
protein, a series of linked amino acids
...
A typical human cell has two
similar sets of chromosomes, and each set has approximately
3 billion nucleotide pairs of DNA
...


TRANSCRIPTION

mRNA

T

Protein
Crystallin protein

The chain of amino
acids folds into the
specific shape of a
crystallin protein
...


Figure Walkthrough

8

CHaPTeR 1

Evolution, the Themes of Biology, and Scientific Inquiry

size of those you are now reading, the genomic text would fill
about 700 biology textbooks
...

The genome sequence—the entire sequence of nucleotides
for a representative member of a species—is now known for
humans and many other animals, as well as numerous plants,
fungi, bacteria, and archaea
...

Rather than investigating a single gene at a time, researchers
study whole sets of genes (or other DNA) in one or more
species—an approach called genomics
...
(The entire set of proteins expressed by a given
cell, tissue, or organism is called a proteome)
...
One is “highthroughput” technology, tools that can analyze many biological samples very rapidly
...
The third development is the formation of interdisciplinary research teams—groups of diverse
specialists that may include computer scientists, mathematicians, engineers, chemists, physicists, and, of course, biologists
from a variety of fields
...


Figure 1
...
There
is a one-way flow of energy in an
ecosystem: During photosynthesis,
plants convert energy from
sunlight to chemical energy (stored
in food molecules such as sugars),
which is used by plants and other
organisms to do work and is
eventually lost from the ecosystem
as heat
...


theme: Life requires the transfer and
transformation of energy and matter
EnERGY and MaTTER A fundamental characteristic of
living organisms is their use of energy to carry out life’s
activities
...

The input of energy, primarily from the sun, and the transformation of energy from one form to another make life
possible (Figure 1
...
When a plant’s leaves absorb sunlight, molecules within the leaves convert the energy of
sunlight to the chemical energy of food, such as sugars, in
the process of photosynthesis
...

Consumers are organisms, such as animals, that feed on
other organisms or their remains
...
As a result, energy
flows through an ecosystem in one direction, usually entering
as light and exiting as heat
...
9)
...
Eventually, these chemicals
will be returned to the environment by decomposers such as
bacteria and fungi that break down waste products, leaf litter,
and the bodies of dead organisms
...


ENERGY FLOW

LC
EMICA YCLING
CH

Plants
convert
sunlight to
chemical
energy
...


Organisms use
chemical energy
to do work
...


Chemicals

CHaPTeR 1

Chemicals in
plants are passed
to organisms that
eat the plants
...


Decomposers
such as fungi and
bacteria break
down leaf litter
and dead
organisms,
returning
chemicals to the
soil
...
10  Feedback regulation
...
This figure shows negative
feedback: The response to insulin reduces the initial stimulus
...


At any level of the biological hierarchy, interactions between the components of the system ensure smooth
integration of all the parts, such that they function as a whole
...


molecules: Interactions Within Organisms

Negative feedback

inTERacTiOnS

2 Insulin circulates in the
blood throughout the body
...
This lowers glucose
cells, and molecules—are crucial to their smooth operation
...

Consider the regulation of blood sugar levels, for instance
...

down and storage
...

the initial stimulus that is reduced by the response?
In feedback regulation, the output or product of a process regulates that very process
...
As seen in the examleaves and fruit (Figure 1
...
Interactions between organple of insulin signaling (Figure 1
...
Insulin, in turn, causes body
in which one species benefits and the other is harmed (as
cells to take up glucose and liver cells to store it, thus decreaswhen a lion kills and eats a zebra)
...
This eliminates the stimulus for insubetween species, both are harmed—for example, when two
lin secretion, shutting off the pathway
...

process negatively regulates that process
...
11  interactions of an African acacia tree with other organisms
regulated by negative feedback, there are
and the physical environment
...

Leaves absorb light
Leaves take in
The clotting of your blood in response to
energy from the sun
...
When a blood vesfrom the air and
sel is damaged, structures in the blood
release oxygen
...
Positive feedback occurs as chemicals released by the platelets attract more
Leaves fall to the
ground and are
platelets
...

return minerals

to the soil
...

For instance, an acacia tree interacts
with soil microorganisms associated
10

CHaPTeR 1

Water and
minerals in the
soil are taken
up by the
tree through
its roots
...


Interactions among organisms help regulate the functioning of the ecosystem as a whole
...
The leaves of a tree, for example,
absorb light from the sun, take in carbon dioxide from the air,
and release oxygen to the air (see Figure 1
...
The environment is also affected by organisms
...
On a global scale, plants and other photosynthetic organisms have generated all the oxygen in the atmosphere
...
Our interactions sometimes have dire consequences: For example, over the past 150 years, humans have
greatly increased the burning of fossil fuels (coal, oil, and
gas)
...
29)
...
At the current rates
that CO2 and other gases are being added to the atmosphere,
global models predict an additional rise of at least 3ºC before
the end of this century
...
But global warming is not the only way the
climate is changing: Wind and precipitation patterns are
also shifting, and extreme weather events such as storms
and droughts are occurring more often
...
For example, polar bears have lost much of the ice
platform from which they hunt, leading to food shortages
and increased mortality rates
...
As a result, the populations of many species are
shrinking in size or even disappearing (Figure 1
...
This
Figure 1
...
A warmer
environment causes lizards in the
genus Sceloporus to spend more
time in refuges from the heat,
reducing time for foraging
...
Surveys show
that 12% of the 200 populations
in Mexico have disappeared
since 1975
...
30
...

As we’ll discuss in greater detail in Concept 56
...

Having considered four of the unifying themes (organization, information, energy and matter, and interactions),
let’s now turn to evolution
...


COncEpT CHEck 1
...
Starting with the molecular level in Figure 1
...
” Continue
with organelles, moving up the biological hierarchy
...
identify the theme or themes exemplified by (a) the
sharp quills of a porcupine, (b) the development of a
multicellular organism from a single fertilized egg,
and (c) a hummingbird using sugar to power its flight
...
WHAT iF? For each theme discussed in this section,
give an example not mentioned in the text
...


COncEpT  1
...
As the
fossil record clearly shows, life has been evolving on Earth for
billions of years, resulting in a vast diversity of past and present organisms
...
For example, while sea horses,
jackrabbits, hummingbirds, and giraffes all look very different, their skeletons are organized in the same basic way
...
As a result of descent with modification, two species share certain traits (unity) simply because
they have descended from a common ancestor
...
An abundance of evidence of different types supports the occurrence
of evolution and the theory that describes how it takes place,
which we’ll discuss in detail in Chapters 22–25
...
” To understand Dobzhansky’s statement,
we need to discuss how biologists think about the vast diversity of life on the planet
...
Biologists have so far identified
and named about 1
...
Each
species is given a two-part name: The first part is the name
of the genus (plural, genera) to which the species belongs,
and the second part is unique to the species within the genus
...
)
To date, known species include at least 100,000 species
of fungi, 290,000 plant species, 57,000 vertebrate species
(animals with backbones), and 1 million insect species
(more than half of all known forms of life)—not to mention
the myriad types of single-celled organisms
...
Estimates
of the total number of species range from about 10 million to
over 100 million
...
Biologists face
a major challenge in attempting to make sense of this variety
...
In the last few
decades, new methods of assessing species relationships, such
as comparisons of DNA sequences, have led to a reevaluation
of the classification of life
...
13)
...
All the eukaryotes
(organisms with eukaryotic cells) are in domain Eukarya
...
The
three kingdoms are distinguished partly by their modes of
nutrition: Plants produce their own sugars and other food
molecules by photosynthesis, fungi absorb nutrients in

Figure 1
...


2 μm

(b) Domain Archaea

2 μm

(a) Domain Bacteria

Bacteria are the most diverse and widespread prokaryotes and are
now classified into multiple kingdoms
...


Domain Archaea includes multiple kingdoms
...
Each
round structure in this photo is an archaeal cell
...


100 μm

▲ Kingdom Plantae (land
plants) consists of terrestrial
multicellular eukaryotes that
carry out photosynthesis, the
conversion of light energy to
the chemical energy in food
...


12

CHaPTeR 1

▶ Protists are mostly
unicellular eukaryotes
and some relatively
simple multicellular
relatives
...
Scientists are currently debating how to classify protists
in a way that accurately reflects their evolutionary relationships
...
Animalia is, of
course, the kingdom to which we belong
...
Although
protists were once placed in a single kingdom, they are now
classified into several groups
...


fossils and other evidence, is the saga of a changing Earth
billions of years old, inhabited by an evolving cast of living
forms (Figure 1
...

Figure 1
...
Paleontologists carefully
excavate the hind leg of a long-necked dinosaur (Rapetosaurus krausei )
from rocks in Madagascar
...

Consider, for example, the similar skeletons of different
animals and the universal genetic language of DNA (the
genetic code), both mentioned earlier
...
For example, unity is obvious in many features
of cell structure, even among distantly related organisms
(Figure 1
...

How can we account for life’s dual nature of unity and
diversity? The process of evolution, explained next, illuminates both the similarities and differences in the world of life
...
The history of life, as documented by
Figure 1
...
Cilia (singular,
cilium) are extensions of cells that function in locomotion
...
Even organisms so different share a common architecture for
their cilia, which have an elaborate system of tubules that is striking in
cross-sectional views
...
The cilia of
the single-celled Paramecium
propel the organism through
pond water
...
1 μm

CHaPTeR 1

Cilia of windpipe cells
...


Evolution, the Themes of Biology, and Scientific Inquiry

13

Figure 1
...

His revolutionary book On
the Origin of Species was first
published in 1859
...
17  Unity and diversity among birds
...
For example, each has
feathers, a beak, and wings
...

▼ Red-shouldered hawk

▼ American flamingo
aBC news Video: exploring evolution in the Solomon islands

▲ European robin

Charles Darwin and the theory
of natural Selection
An evolutionary view of life came into sharp focus in
November 1859, when Charles Darwin published one of the
most important and influential books ever written, On the
Origin of Species by Means of Natural Selection (Figure 1
...

The Origin of Species articulated two main points
...
Darwin called this
process “descent with modification
...
17)
...

Darwin developed his theory of natural selection from
observations that by themselves were neither new nor profound
...
He
started with the following three observations from nature:
First, individuals in a population vary in their traits, many
of which seem to be heritable (passed on from parents to offspring)
...
With more
individuals than the environment is able to support, competition is inevitable
...
For instance, a common adaptation among birds
that eat mostly hard seeds is an especially strong beak
...
He reasoned that individuals
14

CHaPTeR 1

▲ Gentoo penguin

with inherited traits that are better suited to the local environment are more likely to survive and reproduce than less wellsuited individuals
...
Evolution occurs as the unequal reproductive
success of individuals ultimately leads to adaptation to their
environment, as long as the environment remains the same
...
The
example in Figure 1
...
We
see the products of natural selection in the exquisite adaptations of various organisms to the special circumstances of
their way of life and their environment
...
19 are an excellent example of adaptation
...
18  Natural selection
...
Initially, the population varies extensively
in the inherited coloration of the individuals, from very light gray to charcoal
...


1 Population with varied
inherited traits

2 Elimination of
individuals with certain
traits

3 Reproduction of
survivors

dRAW iT Over time, the soil will gradually become lighter in color
...
Write a caption for
this new step
...


Figure 1
...
Bats,
the only mammals capable of active flight, have
wings with webbing between extended “fingers
...


the tree of Life
Take another look at the skeletal architecture of the bat’s
wings in Figure 1
...
These wings are not like those of feathered birds; the bat is a mammal
...
Indeed, all mammalian forelimbs are anatomical variations of a common architecture
...
The diversity
of mammalian forelimbs results from modification by natural
selection operating over millions of years in different environmental contexts
...


CHaPTeR 1

4 Increased frequency
of traits that enhance
survival and reproductive success

hhmi Video: the making of the Fittest:
natural Selection and adaptation
(rock Pocket mouse)

Darwin proposed that natural selection, by its cumulative
effects over long periods of time, could cause an ancestral
species to give rise to two or more descendant species
...
In
these separate arenas of natural selection, one species could
gradually radiate into multiple species as the geographically
isolated populations adapted over many generations to different sets of environmental factors
...
Darwin
collected specimens of these birds during his 1835 visit to
the remote Galápagos Islands, 900 kilometers (km) off the
Pacific coast of South America
...

The Galápagos finches are believed to have descended from
an ancestral finch species that reached the archipelago from
South America or the Caribbean
...

Years after Darwin collected the finches, researchers began to
sort out their evolutionary relationships, first from anatomical
and geographic data and more recently with the help of DNA
sequence comparisons
...
20  descent with
modification: adaptive radiation of
finches on the Galápagos islands
...

Note the different beaks, which are adapted
to different food sources on the different
islands
...


Green warbler finch
Certhidea olivacea
(insect-eater)
Vegetarian finch
Platyspiza crassirostris
(fruit-eater)

ANCESTRAL
FINCH

Woodpecker finch
Camarhynchus pallidus
(insect-eater)

hhmi Video: the origin of Species:
the Beak of the Finch

Small tree finch
Camarhynchus parvulus
(insect-eater)

Branch point: where
lineages diverge
from a common
ancestor
...


as in Figure 1
...
Tree diagrams make sense: Just as an individual has a genealogy that can be diagrammed as a family tree,
each species is one twig of a branching tree of life extending
back in time through ancestral species more and more remote
...
Through an ancestor that lived
much farther back in time, finches are related to sparrows,
hawks, penguins, and all other birds
...
Trace life back far enough, and we reach
the early prokaryotes that inhabited Earth over 3
...
We can recognize their vestiges in our own cells—in
the universal genetic code, for example
...


COncEpT CHEck 1
...
Explain why “editing” is a metaphor for how natural
selection acts on a population’s heritable variation
...
Referring to Figure 1
...

3
...
2 can be represented in the tree of life as the
three main branches, with three subbranches on the
eukaryotic branch being the kingdoms Plantae, Fungi,
and Animalia
...

For suggested answers, see Appendix A
...
3
in studying nature, scientists make
observations and form and test
hypotheses
Science is a way of knowing—an approach to understanding the natural world
...
The word science is derived from a Latin verb meaning
“to know
...

At the heart of science is inquiry, a search for information
and explanations of natural phenomena
...
As in all quests, science
includes elements of challenge, adventure, and luck, along
with careful planning, reasoning, creativity, patience, and
the persistence to overcome setbacks
...
That said, it is possible to highlight certain characteristics that help to distinguish science from other ways of
describing and explaining nature
...
The process is necessarily
repetitive: In testing a hypothesis, more observations may
inspire revision of the original hypothesis or formation
of a new one, thus leading to further testing
...


Figure 1
...
Goodall recorded her observations in field
notebooks, often with sketches of the animals’ behavior
...
For example, what causes the roots of a plant
seedling to grow downward? In fine-tuning their questions,
biologists rely heavily on the scientific literature, the published contributions of fellow scientists
...
Identifying
publications relevant to a new line of research is now easier
than at any point in the past, thanks to indexed and searchable electronic databases
...
In gathering information, they often use tools
such as microscopes, precision thermometers, or high-speed
cameras that extend their senses or facilitate careful measurement
...
For example, a series of detailed
observations have shaped our understanding of cell structure, and another set of observations is currently expanding
our databases of genome sequences from diverse species
and databases of genes whose expression is altered in various diseases
...
Put another way,
data are items of information on which scientific inquiry
is based
...

But some data are qualitative, often in the form of recorded
descriptions rather than numerical measurements
...
21)
...
Quantitative data are generally
expressed as numerical measurements and often organized
into tables and graphs
...

All results presented in this text have been shown to be
statistically significant
...
Through induction, we derive generalizations
from a large number of specific observations
...
And so is “All organisms are
made of cells
...


Forming and testing hypotheses
After carrying out preliminary observations and collecting and analyzing data, scientists begin to form tentative
answers to their original questions and to test their hypothetical explanations—that is, their hypotheses
...
Said another
way, a hypothesis is an explanation on trial
...
A scientific hypothesis must lead to predictions that can
be tested by making additional observations or by performing
experiments
...

We all make observations and develop questions and
hypotheses in solving everyday problems
...
That’s an observation
...
Each of
these alternative hypotheses leads to predictions you can test
with experiments
...
22  A simplified view of the scientific process
...

Observation: Desk lamp doesn’t work
...


Hypothesis #2:
Bulb is burnt out
...


Prediction: Replacing
bulb will fix problem
...


Test of prediction:
Replace bulb
...

Hypothesis is not supported
...

Hypothesis is supported
...
Figure 1
...
Figuring things out in this way by trial and error is a
hypothesis-based approach
...
While induction entails reasoning
from a set of specific observations to reach a general conclusion, deductive reasoning involves logic that flows in the
opposite direction, from the general to the specific
...
In the scientific process, deductions usually take the form of predictions of results that will be
found if a particular hypothesis (premise) is correct
...
This
deductive testing takes the form of “If
...
In the
case of the desk lamp example: If the burnt-out bulb hypothesis is correct, then the lamp should work if you replace the
bulb with a new one
...
First, one
can always devise additional hypotheses to explain a set of
observations
...
Although you could design an experiment to test
this hypothesis, you can never test all possible hypotheses
...
Based
on the experiments shown in Figure 1
...
For example, even
if replacing the bulb fixed the desk lamp, it might have
been because there was a temporary power outage that just
happened to end while the bulb was being changed
...
Often, rounds of
hypothesis formulation and testing lead to a scientific
consensus—the shared conclusion of many scientists that
a particular hypothesis explains the known data well and
stands up to experimental testing
...
A scientific hypothesis must be testable; there must
be some observation or experiment that could reveal if
such an idea is likely to be true or false
...

Not all hypotheses meet the criteria of science: You
wouldn’t be able to test the hypothesis that invisible ghosts
are fooling with your desk lamp! Because science only deals
with natural, testable explanations for natural phenomena,
it can neither support nor contradict the invisible ghost
hypothesis, nor whether spirits or elves cause storms, rainbows, or illnesses
...
Science and religion are not mutually exclusive or contradictory; they are simply concerned
with different issues
...
22 traces an idealized
process of inquiry sometimes called the scientific method
...
For example, a scientist may start to design an
experiment, but then backtrack after realizing that more
preliminary observations are necessary
...
For example, scientists

Evolution, the Themes of Biology, and Scientific Inquiry

could not unravel the details of how genes encode proteins
until after the discovery of the structure of DNA (an event
that took place in 1953)
...
23
...

This core set of activities is the reason that science does so
well in explaining phenomena in the natural world
...
23) and influenced by interactions with other scientists and with society more generally

EXP
LO

• Predicting results
• Doing experiments and/or
making observations
• Gathering data
• Analyzing results
Interpreting Results
Data may…
• Support a hypothesis
• Contradict a hypothesis
• Inspire a revised or new
hypothesis

COMM
UN

F

SOC
IET
A

TESTING HY
PO
AND
G
TH
IN
ES
Testing Ideas
M
E
R
O • Forming hypotheses

LYSIS AN
ANA
D
Y
F
T
I
• Feedback and
peer review
• Replication of
findings
• Publication

ACK
DB
EE

• Developing
technology
• Informing policy
• Solving problems
• Building
knowledge

• Observing nature
• Asking questions
• Reading the
scientific literature

S

ES
OM
TC

EFITS AND O
EN
B
U
L

N AND DIS
TIO
CO
RA

RY
VE

Figure 1
...
In reality, the process
of science is not linear, but is more circular,
involving backtracking, repetitions, and
interactions of different parts of the
process
...
understandingscience
...


(lower circles)
...

Similarly, societal needs—such as the push to cure cancer or
understand the process of climate change—may help shape
what research projects are funded and how extensively the
results are discussed
...


• Consensus
building

CHaPTeR 1

Evolution, the Themes of Biology, and Scientific Inquiry

19

A Case Study in Scientific Inquiry:
investigating Coat Coloration in mouse
Populations
Our case study begins with a set of observations and inductive generalizations
...
What accounts for such variation? As you may
recall, the two mice depicted at the beginning of this chapter are members of the same species (Peromyscus polionotus),
but they have different color patterns and reside in different environments
...
The inland mouse lives on darker,
more fertile soil farther inland (Figure 1
...
Even a brief
glance at the photographs in Figure 1
...
The natural
predators of these mice, including hawks, owls, foxes, and
coyotes, are all visual hunters (they use their eyes to look for
prey)
...

As obvious as the camouflage hypothesis may seem, it still
required testing
...
Figure 1
...

The researchers built hundreds of models of mice and spraypainted them to resemble either beach or inland mice, so that

the models differed only in their color patterns
...
The mouse models resembling the native mice in the habitat were the control group (for
instance, light-colored mouse models in the beach habitat),
while the mouse models with the non-native coloration were
the experimental group (for example, darker models in the
beach habitat)
...
Judging by the shape of the predators’ bites and
the tracks surrounding the experimental sites, the predators
appeared to be split fairly evenly between mammals (such as
foxes and coyotes) and birds (such as owls, herons, and hawks)
...

The results were clear-cut: Camouflaged models showed much
lower predation rates than those lacking camouflage in both the
beach habitat (where light mice were less vulnerable) and the
inland habitat (where dark mice were less vulnerable)
...


experimental Variables and Controls
In carrying out an experiment, a researcher often manipulates one factor in a system and observes the effects of this
change
...
25 is an example of a controlled experiment, one
that is designed to compare an experimental group (the noncamouflaged mice models, in this case) with a control group
(the camouflaged models)
...
24  different coloration in beach and inland populations of Peromyscus
polionotus
...


20

CHaPTeR 1

Inland population

Members of the same species living about 30 km inland have dark fur
on their backs, camouflaging them against the dark ground of their
habitat
...
25

inquiry  Does camouflage affect predation rates on two populations
of mice?
Experiment  Hopi Hoekstra and colleagues tested the hypothesis that coat coloration provides
camouflage that protects beach and inland populations of Peromyscus polionotus mice from
predation in their habitats
...
The next morning, they counted damaged or missing models
...
In both habitats, the models whose pattern did not
match their surroundings suffered much higher “predation” than did the camouflaged models
...
But that’s
impossible in field research and can be
very difficult even in highly regulated
laboratory environments
...

animation: introduction to
experimental Design

100

theories in Science

50

“It’s just a theory!” Our everyday use of
the term theory often implies an untested
Light models
Dark models
Light models
Dark models
speculation
...
What is
a scientific theory, and how is it different from a hypothesis or from mere
speculation?
Camouflaged
Non-camouflaged
Non-camouflaged
Camouflaged
First, a scientific theory is much
(control)
(experimental)
(experimental)
(control)
broader in scope than a hypothesis
...

Thus, the experiment supports the camouflage hypothesis
...
” But
this is a theory: “Evolutionary adaptaData from  S
...
Vignieri, J
...
Larson, and H
...
Hoekstra, The selective advantage of crypsis in mice, Evolution
64:2153–2158 (2010)
...
” This
iNTERPRET THE dATA The bars indicate the percentage of the attacked models that were either light
theory proposes that natural selection
or dark
...
For the beach habitat, how many were
is the evolutionary mechanism that
light models? Dark models? Answer the same questions for the inland habitat
...

Second, a theory is general enough
to spin off many new, testable hypotheses
...
In our example, the color of the mouse model
the theory of natural selection motivated two researchers
was the independent variable—the factor being manipuat Princeton University, Peter and Rosemary Grant, to test
lated by the researchers
...

dent variable; in this case, the researchers measured the preda(Their results supported their hypothesis; see the introduction rate in response to variation in color of the mouse model
...
)
Ideally, the experimental and control groups differ in only one
And third, compared to any one hypothesis, a theory is
independent variable—in the mouse experiment, color
...
The
Without the control group, the researchers would not
theory of natural selection has been supported by a vast quanhave been able to rule out other factors as causes of the more
tity of evidence, with more being found every day, and has
frequent attacks on the non-camouflaged mice—such as
not been contradicted by any scientific data
...
The clever experimental design left
of natural selection and the theory of gravity) explain a great
coloration as the only factor that could account for the low
diversity of observations and are supported by a vast accumupredation rate on models camouflaged with respect to the
lation of evidence
...

0

CHaPTeR 1

Evolution, the Themes of Biology, and Scientific Inquiry

21

In spite of the body of evidence supporting a widely
accepted theory, scientists will sometimes modify or even
reject theories when new research produces results that don’t
fit
...
When new methods
for comparing cells and molecules could be used to test such
relationships, the evidence led scientists to reject the theory
that bacteria and archaea are members of the same kingdom
...


COncEpT CHEck 1
...
What qualitative observation led to the quantitative
study in Figure 1
...
Contrast inductive reasoning with deductive reasoning
...
Why is natural selection called a theory?
4
...
Mice are found in both sandy and rocky areas, and
owls are known predators
...
How
would you use this ecosystem to further test the camouflage hypothesis?
For suggested answers, see Appendix A
...
4
Science benefits from a cooperative
approach and diverse viewpoints
Movies and cartoons sometimes portray scientists as loners in white lab coats, working in isolated labs
...
Most scientists work
in teams, which often include both graduate and undergraduate students
...
Research results have no impact until
shared with a community of peers through seminars, publications, and websites
...
The examples of scientific
inquiry described in this book, for instance, have all been
published in peer-reviewed journals
...
’Tis much better to do a little with certainty, and
leave the rest for others that come after you
...
In fact, Hopi
Hoekstra’s experiment benefited from the work of another

22

CHaPTeR 1

researcher, D
...
Kaufman, 40 years earlier
...

Scientific results are continually scrutinized through the
repetition of observations and experiments
...
If scientific colleagues cannot repeat experimental
findings, this failure may reflect some underlying weakness in
the original claim, which will then have to be revised
...
Integrity and adherence to high
professional standards in reporting results are central to the
scientific endeavor, since the validity of experimental data is
key to designing further lines of inquiry
...
Some scientists enjoy the challenge
of being first with an important discovery or key experiment,
while others derive more satisfaction from cooperating with
fellow scientists working on the same problem
...
Often it is a widely used model organism—a
species that is easy to grow in the lab and lends itself particularly well to the questions being investigated
...
For example, genetic studies of the
fruit fly Drosophila melanogaster have taught us a lot about
how genes work in other species, even humans
...
As you read through this book, note the many
contributions that these and other model organisms have
made to the study of life
...
Some biologists focus on ecosystems, while others
study natural phenomena at the level of organisms or cells
...

Yet any given problem can be addressed from many perspectives, which in fact complement each other
...
Her lab includes biologists specializing in different biological levels, allowing links to be made between the
evolutionary adaptations she focuses on and their molecular
basis in DNA sequences
...
You can develop
this skill by noticing when certain topics crop up again and
again in different units
...
W
...
He also hypothesized that the contrast would be
affected by the amount of moonlight
...


How the Experiment Was done  Pairs of mice (Peromyscus
polionotus) with different coat colors, one light brown and one
dark brown, were released simultaneously into an enclosure that
contained a hungry owl
...
if the owl did not catch
either mouse within 15 minutes, the test was recorded as a zero
...
The presence or absence of moonlight during each assay was recorded
...
W
...


descendants
...
In addition, we
have designed a number of figures that make connections
between the content in different chapters, as well as questions that ask you to make the connections yourselves
...


Science, technology, and Society
The research community is part of society at large, and the
relationship of science to society becomes clearer when we
add technology to the picture (see Figure 1
...
Though

CHaPTeR 1

1
...
Graph A shows data from
the light-colored soil enclosure
and graph B from the darkcolored enclosure, but in all
other respects the graphs are
the same
...
What are the independent variables, the variables that were tested by the researcher?
Which axis of the graphs has the independent variables? (b) What
is the dependent variable, the response to the variables being
tested? Which axis of the graphs has the dependent variable?
2
...

3
...

4
...
(a) What combination of independent variables led to the highest predation level in enclosures with light-colored soil? (b) What
combination of independent variables led to the highest predation level in enclosures with dark-colored soil?
6
...

7
...
Which
condition is optimal for predation by the owl? Explain
...


science and technology sometimes employ similar inquiry
patterns, their basic goals differ
...

Biologists and other scientists usually speak of “discoveries,”
while engineers and other technologists more often speak of
“inventions
...

The potent combination of science and technology can
have dramatic effects on society
...
For
example, discovery of the structure of DNA by Watson and

Evolution, the Themes of Biology, and Scientific Inquiry

23

Figure 1
...
In 2011,
forensic analysis of DNA samples from a crime scene led to the release
of Michael Morton from prison after he had served nearly 25 years
for a crime he didn’t commit, the brutal murder of his wife
...
The photo shows Mr
...
The details of forensic analysis of DNA will
be described in Chapter 20
...
26)
...

The directions that technology takes depend less on the
curiosity that drives basic science than on the current needs
and wants of people and on the social environment of the
times
...
” With advances in technology
come difficult choices
...

Ethical issues raised by such questions have as much to
do with politics, economics, and cultural values as with science and technology
...
The relationship between science, technology, and society increases the significance and value of any
biology course
...
For example, the printing press, which
helped spread knowledge to all social classes, was invented
by the German Johannes Gutenberg around 1440
...
Paper traveled along trade routes from
China to Baghdad, where technology was developed for its
mass production
...
We have the cross-fertilization of diverse cultures to thank for the printing press, and
the same can be said for other important inventions
...
But just how diverse a population
are scientists in relation to gender, race, ethnicity, and
other attributes?
The scientific community reflects the cultural standards
and behaviors of the society around it
...

Over the past 50 years, changing attitudes about career
choices have increased the proportion of women in biology
and some other sciences, so that now women constitute
roughly half of undergraduate biology majors and biology
Ph
...
students
...
This lack of diversity hampers the
progress of science
...
The authors of this text welcome
all students to the community of biologists, wishing you
the joys and satisfactions of this exciting field of science
...
4
1
...
MAKE CONNECTiONS The gene that causes sickle-cell
disease is present in a higher percentage of residents
of sub-Saharan Africa than among those of African
descent living in the United States
...
Discuss an evolutionary process that
could account for the different percentages of the
sickle-cell gene among residents of the two regions
...
2
...


1

Chapter Review

Go to MasteringBiology™ for Videos, Animations, Vocab Self-Quiz,
Practice Tests, and more in the Study Area
...
1

The study of life reveals unifying
themes (pp
...
Plants take
up nutrients from the soil and
chemicals from the air and use
energy from the sun
...
gl/6u55ks
at Successive Levels of Biological Organization
The hierarchy of life unfolds as follows:
biosphere 7 ecosystem 7 community 7
population 7 organism 7 organ system 7 organ
7 tissue 7 cell 7 organelle 7 molecule 7 atom
...

In an approach called reductionism, complex
systems are broken down to simpler components that are more manageable to study
...

Structure and function are correlated at all levels of biological
organization
...
Cells are either prokaryotic or eukaryotic
...
Prokaryotic cells lack such organelles
...
2

The Core Theme: Evolution accounts
for the unity and diversity of life (pp
...
It is DNA that
transmits heritable information from parents
to offspring
...
Gene expression also produces
RNAs that are not translated into protein but
serve other important functions
...

Bioinformatics uses computational tools
to deal with huge volumes of sequence data
...
It also explains
evolutionary adaptation—the match of
organisms to their environments
...
Domain Bacteria and domain Archaea consist of prokaryotes
...
As diverse as life is, there is also evidence of remarkable
unity, revealed in the similarities between different species
...
Natural
selection is the evolutionary process that occurs when a population is exposed to environmental factors that consistently cause
individuals with certain heritable traits to have greater reproductive success than do individuals with other heritable traits
...
All organisms must
AL CYC
perform work, which requires
EMIC
LIN
CH
energy
...
(The rest is lost from the
ecosystem as heat
...


Evolution of adaptations in the population


G

Each species is one twig of a branching tree of life extending back
in time through more and more remote ancestral species
...


?

How could natural selection have led to the evolution of adaptations
such as camouflaging coat color in beach mice?

COncEpT  1
...
In negative feedback, accumulation of the
end product slows its production
...

CHaPTeR 1

in studying nature, scientists make observations
and form and test hypotheses (pp
...

Deductive reasoning makes predictions that can be used to

Evolution, the Themes of Biology, and Scientific Inquiry

25





test hypotheses
...
Hypotheses can be tested by conducting
experiments or, when that is not possible, by making observations
...

This endeavor is influenced by exploration and discovery, community analysis and feedback, and societal outcomes
...

A scientific theory is broad in scope, generates new hypotheses,
and is supported by a large body of evidence
...
4

Science benefits from a cooperative approach
and diverse viewpoints (pp
...
The work of each scientist builds on
the work of others who have come before
...
Biologists
approach questions at different levels; their approaches complement each other
...

The impact of basic research is not always immediately obvious
...


?

Explain why different approaches and diverse backgrounds among
scientists are important
...
Which of the following is an example of qualitative data?
(A) The fish swam in a zigzag motion
...

(C) The temperature decreased from 20°C to 15°C
...

7
...

(B) If my prediction is correct, it will lead to a testable
hypothesis
...

(D) If my hypothesis is correct, I can expect certain test results
...
dRAW iT  With rough sketches, draw a biological hierarchy
similar to the one in Figure 1
...
Include all levels in the hierarchy
...
EVOLUTiON CONNECTiON  A typical prokaryotic cell has about
3,000 genes in its DNA, while a human cell has almost 21,000
genes
...
Based on your understanding of evolution, explain how
such different organisms could have this same subset of 1,000
genes
...
SCiENTiFiC iNQUiRY  Based on the results of the mouse
coloration case study, suggest another hypothesis researchers
might use to further study the role of predators in the natural
selection process
...
SCiENTiFiC iNQUiRY  Scientists search the scientific literature
by means of electronic databases such as PubMed, a free online
database maintained by the National Center for Biotechnology
Information
...


TEST YOuR UndERSTandinG
Level 1: Knowledge/Comprehension
1
...

(A) an ecosystem
...

(D) a taxonomic
domain
...
gl/CUYGKD

2
...

(B) simplify complex problems by reducing the system into
smaller, less complex units
...

(D) build high-throughput machines for the rapid acquisition
of biological data
...
WRiTE ABOUT A THEME: EVOLUTiON  In a short essay
(100–150 words), discuss Darwin’s view of how natural selection
resulted in both unity and diversity of life on Earth
...
(See a suggested grading
rubric and tips for writing good essays in the Study Area of
MasteringBiology under “Write About a Theme
...
SYNTHESiZE YOUR KNOWLEdGE
Can you pick out the
mossy leaf-tailed gecko
lying against the tree
trunk in this photo?
How is the appearance
of the gecko a benefit in
terms of survival? Given
what you learned about
evolution, natural
selection, and genetic
information in this
chapter, describe how
the gecko’s coloration
might have evolved
...
Which of the following best demonstrates the unity among all
organisms?
(A) emergent properties
(C) the structure and function
(B) descent with
of DNA
modification
(D) natural selection
4
...

(B) tests experimental and control groups in parallel
...

(D) keeps all variables constant
...
Which of the following statements best distinguishes
hypotheses from theories in science?
(A) Theories are hypotheses that have been proved
...

(C) Hypotheses usually are relatively narrow in scope; theories
have broad explanatory power
...


26

CHaPTeR 1

For selected answers, see Appendix A
...
You can use them to study on
your smartphone, tablet, or computer anytime, anywhere!



---