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Invitation to Biology
Chapter 1
1.1 Life’s Levels of Organization
 Nature has levels of organization
 Unique properties emerge at successively
higher levels
Organization Within An Organism
 Atoms are organized into molecules
 In multicelled species, cells are organized into
tissues, organs, and organ systems
 All organisms consist of one or more cells
 Emergent properties: Life emerges at the
cellular level
Organization of Groups of Organisms
 Population
• All individuals of one species in a specific area
 Community
• All populations in a specific area
 Ecosystem
• A community interacting with its environment
Organization of Life on Earth
 Biosphere
• All regions of Earth that hold life
• Land, water, and atmosphere
Levels of Organization
Levels of Organization
molecule
cell
tissue
organ
organ system
atom
Fig. 1.3a, p. 4
multicelled organism
population
community
ecosystem
biosphere
Fig. 1.3b, p. 4
KEY CONCEPTS:
LEVELS OF ORGANIZATION
 We study the world of life at different levels of
organization, from atoms and molecules to the
biosphere
 “Life” emerges at the level of cells
1.2 Overview of Life’s Unity
 Organisms require energy and materials to
sustain their organization and activities
• Nutrients are required for growth and survival
• Producers make their own food
• Consumers eat other organisms
Ecosystem:
Energy Flow and Material Cycling
Energy
input,
from
sun
Producers
Nutrient
cycling
Consumers
energy output (mainly metabolic heat)
Fig. 1.4, p. 6
Overview of Life’s Unity
 Organisms sense change
• Receptors respond to stimulation
• Responses keep internal conditions within ranges
that cells can tolerate (homeostasis)
Response to Stimulus
Overview of Life’s Unity
 Organisms grow and reproduce
• Based on information encoded in DNA
• Inheritance transmits DNA from parents to
offspring through reproduction mechanisms
• Development transforms first cell into an adult
Instructions Assemble Materials
Development
Fig. 1.7a, p. 7
Fig. 1.7b, p. 7
Fig. 1.7c, p. 7
Fig. 1.7d, p. 7
Fig. 1.7e, p. 7
KEY CONCEPTS:
LIFE’S UNDERLYING UNITY
 All organisms are alike in key respects:
• Consist of one or more cells
• Live through inputs of energy and raw materials
• Sense and respond to changes in their external
and internal environments
• Cells contain DNA (molecule that offspring inherit
from parents; encodes information necessary for
growth, survival, and reproduction)
Animation: Life's levels of organization
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Animation: One-way energy flow and
materials cycling
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Animation: Building blocks of life
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Animation: Insect development
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1.3 So Much Unity, So Many Species
 The world of life, past and present, shows great
diversity
 Classification systems organize species in ever
more inclusive groups
Genus and Species
 Species: One kind of organism
 Each species has a two-part name
• First part: Genus name
• Combined with the second part, it designates one
particular species
Domains
 Current classification groups all species into
three domains
• Bacteria (single-celled prokaryotes)
• Archaea (single-celled prokaryotes)
• Eukarya (protists, plants, fungi, and animals)
Bacteria and Archaea
Bacteria
Archaea
Eukarya
Eukarya
Eukarya
Eukarya
Life’s Three Domains
KEY CONCEPTS:
LIFE’S DIVERSITY
 The world of life shows great diversity
 Many millions of kinds of organisms (species)
have appeared and disappeared over time
 Each species is unique in at least one trait—in
some aspect of its body form or behavior
Animation: Three domains
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Animation: Life's diversity
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1.4 An Evolutionary View of Diversity
 Life’s diversity arises from mutations
• Changes in molecules of DNA which offspring
inherit from their parents
 In natural populations, mutations introduce
variation in heritable traits among individuals
Variation in Heritable Traits
 Some trait forms are more adaptive than others
• Bearers are more likely to survive and reproduce
 Over generations, adaptive forms of traits tend
to become more common in a population
• Less adaptive forms of the same traits become
less common or are lost
Evolution
 Populations evolve
• Traits that help characterize a population (and a
species) can change over generations
 Evolution
• Change which occurs in a line of descent
Selection
 Natural selection
• In natural populations
• Differential survival and reproduction among
individuals that vary in one or more heritable traits
 Artificial selection
• Breeding of captive populations
• Traits selected are not necessarily adaptive
Artificial and Natural Selection
KEY CONCEPTS:
EXPLAINING UNITY IN DIVERSITY
 Theories of evolution (especially a theory of
evolution by natural selection) help explain why
life shows both unity and diversity
 Evolutionary theories guide research in all fields
of biology
1.5 Critical Thinking and Science
 Critical thinking is a self-directed act of judging
the quality of information as one learns
 Science is a way of looking at the natural world
• Helps minimize bias in judgments
• Focuses on testable ideas about observable
aspects of nature
Evidence-Based Thinking
1.6 How Science Works
 Researchers generally
• Observe something in nature
• Form hypotheses (testable assumptions) about it
• Make predictions about what might occur if the
hypothesis is not wrong
• Test their predictions by observations,
experiments, or both
Experiments
 Tests used to support or falsify a prediction
• Variable characteristic is measured and changed
• In the control group, variables do not change
A Scientific Approach
Scientific Theory
 A well-tested hypothesis
• Explains a broad range of observations
• Can be used to make useful predictions about
other phenomena
 Opinion and belief are not scientific theory
Some Scientific Theories
1.7 The Power of Experiments
 Biological systems have many variables
 Experiments simplify observations of nature
• Focus on cause, effect, or function of one
variable at a time
 Researchers design experiments to minimize
potential bias in interpreting results
A Controlled Experiment
Hypothesis
Olestra® causes intestinal cramps.
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.
Experiment
Results
Control Group
Experimental Group
Eats regular
potato chips
Eats Olestra
potato chips
93 of 529 people
get cramps later
(17.6%)
89 of 563 people
get cramps later
(15.8%)
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.
Fig. 1.11, p. 14
Hypothesis
Olestra® causes intestinal cramps.
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
Experiment
Control Group
Eats regular
potato chips
Experimental Group
Eats Olestra
potato chips
Results
Control Group
Eats regular
potato chips
Experimental Group
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
Fig. 1-11, p. 14
a Wing spots
painted out
b Wing spots
visible; wings
silenced
c Wing spots
painted out;
wings silenced
d Wings painted
but spots visible
e Wings
cut but not
silenced
f Wings painted but
spots visible; wings
cut but not silenced
Stepped Art
Fig. 1-14, p. 18
Butterflies and Birds:
A Behavioral Experiment
Butterflies and Birds:
Results
1.8 Sampling Error in Experiments
 Small sample size increases the likelihood of
sampling error in experiments
 In such cases, a subset may be tested that is not
representative of the whole
Experiment: Sampling Error
KEY CONCEPTS:
HOW WE KNOW
 Biologists make systematic observations,
predictions, and tests in the laboratory and field
 They report their results so others may repeat
their work and check their reasoning
Animation: Sampling error
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