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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

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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

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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 mod

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