Chapter 1
Invitation to Biology
Albia Dugger • Miami Dade College
1.1 The Secret Life of Earth
• Human activities are profoundly changing life on Earth
• Hundreds of new species are discovered each year – about
20 species become extinct every minute in rain forests alone
• What is a species, and why should discovering a new one
matter to anyone other than a scientist?
• These questions are part of biology, the scientific study of life
Foja Mountain Cloud Forest
New Cloud Forest Species
New Species of Spider
1.2 Life Is More Than the Sum of Its Parts
• Biologists study life by thinking about it at different levels of
organization
• Nature’s organization begins at the level of atoms, and
extends through the biosphere
• The quality of life emerges at the level of the cell
Emergent Properties
• Each level of organization in nature has emergent properties
– a characteristic of a system that does not appear in any of
its component parts
Same Parts, Different Organization
• Complex properties, including life, often emerge from the
interactions of much simpler parts
Stepped Art
p4
ANIMATION: Building blocks of life
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A Pattern in Life’s Organization
• Atoms
• Fundamental building blocks of all substances
• Molecules
• Consisting of two or more atoms
• Cell
• The smallest unit of life
• Tissue
• Specialized cells organized to perform a collective function
A Pattern in Life’s Organization
• Organ
• Structural unit of interacting tissues.
• Organ system
• A set of interacting organs
• Multicelled organism
• An individual consisting of one or more cells
A Pattern in Life’s Organization
• Population
• Individuals of the same species in the same area
• Community
• Populations of all species in the same area
• Ecosystem
• A community and its environment
• Biosphere
• All regions of the Earth where organisms live
Life’s Levels of Organization
atom
molecule
cell
tissue
organ
organ system
ANIMATED FIGURE: Life’s levels of
organization
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Take-Home Message: How do living things
differ from nonliving things?
• All things, living or not, consist of the same building blocks—
atoms; atoms join as molecules.
• The unique properties of life emerge as certain kinds of
molecules become organized into cells.
• Higher levels of life’s organization include multicelled
organisms, populations, communities, ecosystems, and the
biosphere.
• Emergent properties occur at each successive level of life’s
organization.
1.3 How Living Things Are Alike
• Continual inputs of energy and the cycling of materials
maintain life’s complex organization
• Organisms sense and respond to change
• All organisms use information in the DNA they inherited from
their parent or parents to develop and function
Energy and Life’s Organization
• Energy
• The capacity to do work
• Not cycled; flows through the world of life in one direction
• Nutrients
• Atoms or molecules essential in growth and survival that
an organism cannot make for itself
• Cycled between organisms and the environment
Producers and Consumers
• Producers
• Acquire energy and raw materials from the environment
• Make their own food (photosynthesis)
• Consumers
• Cannot make their own food
• Get energy by eating producers and other organisms
A Producers harvest energy
from the environment. Some
of that energy flows from
producers to consumers.
sunlight
energy
Producers
plants and other
self-feeding organisms
B Nutrients
that become
incorporated into the
cells of producers and
consumers are
eventually released by
decomposition. Some
cycle back to
producers.
Consumers
animals, most fungi,
many protists, bacteria
C All of the energy that enters the world
of life eventually flows out of it, mainly
as heat released back to the
environment.
Stepped Art
Figure 1-3b p6
ANIMATED FIGURE: One-way energy flow
and materials cycling
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Organisms Sense and
Respond to Change
• Organisms sense and respond to change both inside and
outside the body
• The body’s internal environment consists of all body fluids
outside of cells
• The internal environment must be kept within certain ranges
of composition, temperature, and other conditions
• By sensing and adjusting to change, organisms keep
conditions in the internal environment within a range that
favors cell survival (homeostasis)
Response to a Stimulus
Organisms Use DNA
• DNA is the basis of similarities in form and function among
organisms
• Details of DNA molecules differ – the source of life’s diversity
• DNA
• Deoxyribonucleic acid
• Carries hereditary information that guides development
and functioning
Development and Growth
• DNA guides ongoing metabolic activities that sustain the
individual through its lifetime
• Development
• Multistep process by which the first cell of a new individual
becomes a multicelled adult
• Growth
• In multicelled species, an increase in the number, size,
and volume of cells
Reproduction and Inheritance
• All organisms receive their DNA from one or more parents
• Reproduction includes various processes by which
individuals produce offspring
• Inheritance refers to the transmission of DNA to offspring
Take-Home Message:
How are all living things alike?
• A one-way flow of energy and a cycling of nutrients sustain
life’s organization.
• Organisms sense and respond to conditions inside and
outside themselves; they make adjustments that keep
conditions in their internal environment within a range that
favors cell survival, a process called homeostasis.
• Organisms develop and function based on information
encoded in their DNA, which they inherit from their parents.
DNA is the basis of similarities and differences in form and
function
1.4 How Living Things Differ
• Living things differ in their observable characteristics
• Various classification schemes help us organize this variation,
which we call Earth’s biodiversity
• biodiversity
• Scope of variation among living organisms
Basics of Classification
• Organisms can be classified into broad groups depending on
whether they have a nucleus
• Nucleus
• A sac with two membranes that encloses and protects a
cell’s DNA
Organisms With No Nucleus
• Bacteria and archaea are two types of organisms whose DNA
is not contained within a nucleus
• Bacteria
• The most diverse and well-known group of single-celled
organisms that lack a nucleus
• Archaea
• Single-celled organisms that lack a nucleus but are more
closely related to eukaryotes than to bacteria
Bacteria
Archaea
ANIMATED FIGURE: Life's diversity
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Eukaryotes
• Eukaryotes are organisms whose DNA is contained within a
nucleus
• Some eukaryotes live as individual cells; others are
multicelled
• Eukaryotic cells are typically larger and more complex than
bacteria or archaea
Protists
• Protists are the simplest eukaryotes
• As a group they vary a great deal, from single-celled
consumers to giant, multicelled producers
• Many biologists view “protists” as several major groups
Protists
Fungi
• Fungi are multicelled eukaryotes such as mushrooms
• Many are decomposers
• All are consumers that secrete substances that break down
food outside of the body and absorb the released nutrients
Fungi
Plants
• Plants are multicelled eukaryotes that live on land or in
freshwater environments
• Most are photosynthetic producers
• Plants and other photosynthesizers also serve as food for
most of the other organisms in the biosphere
Plants
Animals
• Animals
• Multicelled consumers that ingest tissues or juices of other
organisms
• Herbivores graze; carnivores eat meat; scavengers eat
remains of other organisms; parasites withdraw nutrients
from the tissues of a host
• Develop through stages that lead to the adult form
• Actively move about during at least part of their lives
Animals
Take-Home Message:
How do organisms differ from one another?
• Organisms differ in their details; they show tremendous
variation in observable characteristics, or traits
• Various classification systems group species on the basis of
shared traits
1.5 Organizing Information About Species
• Each type of organism, or species, is given a unique name
• We define and group species based on shared traits
• Taxonomy is the science of naming and classifying species
The Binomial System
• Carolus Linnaeus standardized a two-part naming system that
we use today
• The first part is the genus, a group of species that share a
unique set of features
• The second part is the specific epithet
• Genus name plus specific epithet designate one species
• Example: the dog rose Rosa canina
Taxonomic Classification
• We rank species into ever more inclusive categories: genus,
family, order, class, phylum, kingdom, and domain
• Each rank, or taxon is a group of organisms that share a
unique set of features
• Each higher taxon consists of a group of the next lower taxon
Taxonomic Classification
The Three-Domain System
The Six-Kingdom System
ANIMATED FIGURE: Classification systems
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A Rose by Any Other Name . . .
• A species is assigned to higher taxa based on some subset of
heritable traits it shares with other species
• Morphological traits (observable characteristics)
• Physiological traits (functional characteristics)
• Behavioral traits (responses to certain stimuli)
Traits
• Traits vary a little within a species
• There can be tremendous differences between species; such
species look very different, so it is easy to tell them apart
• Species that share a more recent ancestor may be harder to
tell apart
The Biological Species Concept
• Evolutionary biologist Ernst Mayr defined a species as groups
of individuals that potentially can interbreed, produce fertile
offspring, and do not interbreed with other groups
• This “biological species concept” is useful in many cases, but
it is not universally applicable
• For now it is important to remember that a “species” is a
convenient but artificial human construction
Four Butterflies, Two Species
Take-Home Message: How do we keep track of
all the species we know about?
• Each species has a unique, two-part scientific name.
• Classification systems group species on the basis of shared,
inherited traits
1.6 The Science of Nature
• Judging the quality of information before accepting it is called
critical thinking
• Scientists practice critical thinking by testing predictions about
how the natural world works
Thinking About Thinking
• Critical thinking is the deliberate process of judging the
quality of information before accepting it
• Critical thinking considers the supporting evidence,
alternative interpretations, and biases contained in a message
• Being conscious about learning can help you decide whether
to allow new information to guide your beliefs and actions
How Science Works
• Science is the systematic study of the observable world and
how it works
• Generally, a researcher observes something in nature and
uses inductive reasoning to form a hypothesis (testable
explanation) for it
• The researcher then uses deductive reasoning to make a
prediction about what might occur if the hypothesis is correct
Experiments
• Experiments are tests designed to support or falsify a
prediction
• Researchers investigate cause-and-effect relationships by
changing or observing variables
• An independent variable is defined or controlled by the
person doing the experiment
• A dependent variable is an observed result that is supposed
to be influenced by the independent variable
The Scientific Method
• Experiments are performed on an experimental group as
compared with a control group, and sometimes on models
• Conclusions are drawn from experimental results (data); a
hypothesis that is not consistent with data is modified
• Making, testing, and evaluating hypotheses is called the
scientific method
The Scientific Method
ANIMATION: Bacteriophage mice
experiment
Examples of Research
Take-Home Message:
What is science?
• The scientific method consists of making, testing, and
evaluating hypotheses
• It is a way of critical thinking, or systematically judging the
quality of information before allowing it to guide one’s beliefs
and actions
• Experiments measure how changing an independent variable
affects a dependent variable
1.7 Examples of Experiments in Biology
• Researchers unravel cause-and-effect relationships in
complex natural processes by changing one variable at a time
• When studying humans, isolating a single variable is not often
possible
Potato Chips and Stomach Aches
• Researchers tested the prediction that Olestra® in potato
chips causes cramps
• Experimental group: Olestra chips
• Control group: regular chips
A Hypothesis
Olestra® causes intestinal cramps.
B Prediction
People who eat potato chips made with Olestra will
be more likely to get intestinal cramps than those
who eat potato chips made without Olestra.
C Experiment
D Results
E
Control Group
Eats regular
potato chips
Experimental Group
93 of 529 people
get cramps later
(17.6%)
89 of 563 people
get cramps later
(15.8%)
Eats Olestra
potato chips
Conclusion
Percentages are about equal. People who eat
potato chips made with Olestra are just as likely to
get intestinal cramps as those who eat potato
chips made without Olestra. These results do not
support the hypothesis.
Stepped Art
Figure 1-10 p14
Butterflies and Birds
• Why does the peacock butterfly flick its wings when birds are
near?
• Researchers tested two hypotheses:
• Wing spots deter predatory birds
• Hissing and clicking sounds deter predatory birds
Peacock Butterfly Defenses
Against Predatory Birds
Results: Peacock Butterfly Experiment
Take-Home Message:
Why do biologists perform experiments?
• Natural processes are often very complex and influenced by
many interacting variables
• Experiments help researchers unravel causes of complex
natural processes by focusing on the effects of changing a
single variable
1.8 Analyzing Experimental Results
• Biology researchers often experiment on subsets of a group
• Results from such an experiment may differ from results of
the same experiment performed on the whole group
• Science is, ideally, a self-correcting process because
scientists check one another’s work
Sampling Error in Experiments
• Researchers often test or survey a subset of a population,
area, or event, then use the results to make generalizations
• Results may differ from results of the same experiment
performed on the whole group
• Sampling error is a difference between results from a subset
and results from the whole
• Small sample size increases the likelihood of sampling error
in experiments
Sample Size Affects Sampling Error
A Natalie,
blindfolded,
randomly plucks a
jelly bean from a jar.
The jar contains 120
green and 280 black
jelly beans, so 30
percent of the jelly
beans in the jar are
green, and 70
percent are black.
B The jar is hidden
from Natalie’s view
before she removes
her blindfold. She
sees one green jelly
bean in her hand and
assumes that the jar
must hold only green
jelly beans.
C Still blindfolded,
Natalie randomly
picks out 50 jelly
beans from the jar.
She ends up
picking out 10
green and 40 black
ones.
D The larger sample leads
Natalie to assume that
one-fifth of the jar’s jelly
beans are green (20
percent) and four-fifths
are black (80 percent).
This sample more closely
approximates the jar’s
actual green-to-black ratio
of 30 percent to 70 percent.
The more times Natalie
repeats the sampling, the
greater the chance she
has of guessing the actual
ratio.
Stepped Art
Figure 1-13 p16
Probability
• In cases like flipping a coin, it is possible to calculate
probability of an expected result
• Probability
• The measure, expressed as a percentage, of the chance
that a particular outcome will occur
• Depends on the total number of possible outcomes
• Analysis of experimental data often includes calculations of
probability
Statistical Significance
• If a result is very unlikely to have occurred by chance alone, it
is said to be statistically significant
• Statistically significant refers to a result that is statistically
unlikely to have occurred by chance
• In science, every result – even a statistically significant one –
has a possibility of being incorrect
Variability
• Variation in a set of data is often shown as error bars on a
graph
• Error bars may indicate variation around an average for one
sample set, or the difference between two sample sets
Error Bars in a Graph
Bias in Interpreting Results
• Experimenting with a single variable is not often possible,
particularly when studying humans
• Experiments are designed to yield quantitative results that
minimize the potential for bias
• Other scientists repeat the experiments and check the
conclusions drawn from them
How do scientists reduce
sampling error and bias in research?
Take-Home Message:
• Researchers minimize sampling error by using large sample
sizes and by repeating their experiments
• A statistical analysis can show the probability that a result has
occurred by chance alone
• Science is a self-correcting process because it is carried out
by an aggregate community of people systematically checking
one another’s ideas
1.9 The Nature of Science
• Scientific theories are our best descriptions of reality
• Science helps us to be objective about our observations, in
part because it is limited to the observable
“Theories” and “Laws”
• A scientific theory is a long-standing hypothesis that has not
been disproved after many years of rigorous testing
• Like all hypotheses, a scientific theory can be disproven by a
single observation that falsifies it
• A law of nature describes a phenomenon that has been
observed to occur consistently, but for which we do not have
a complete scientific explanation
The Limits of Science
• Science deals with observations of the natural world which
produce objective data that can be measured without bias
• Science does not measure moral, aesthetic, or philosophical
standards vary from one society to the next
• Neither does science address the supernatural, or anything
that is “beyond nature”
Take-Home Message:
Why does science work?
• Checks and balances inherent in the scientific process help
researchers to be objective about their observations
• Because a scientific theory is revised until no one can prove it
wrong, it is our best way of measuring reality