Chapter 1 A View of Life

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Chapter 1A View of Life
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A View of Life H1N1
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H1N1

• H1N1 influenza attracted global attention in
  April 2009, when more than 200 countries around
  the world reported confirmed cases within a few
  months
• Pandemics such as H1N1 affect many aspects of
  life, including global economy, travel, tourism,
  and education

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Biology

• Biologists are making new discoveries that affect
  every aspect of our lives, including health,
  food, safety, relationships with humans and other
  organisms, and the environment of our planet
• biology
• The science of life

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1.1 THREE BASIC THEMES

• LEARNING OBJECTIVE
• Describe three basic themes of biology

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Three Basic Themes of Biology

• Evolution
• Evolution results in populations changing over
  time
• Explains how the ancestry of organisms can be
  traced back to earlier forms of life
• Information transfer
• Information must be transmitted within cells,
  among cells, among organisms, and from one
  generation to the next
• Energy transfer
• Life requires continuous input of energy from the
  sun

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KEY CONCEPTS 1.1

• Basic themes of biology include evolution,
  information transfer, and energy transfer

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1.2 CHARACTERISTICS OF LIFE

• LEARNING OBJECTIVE
• Distinguish between living and nonliving things
  by describing the features that characterize
  living organisms

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Organisms are Composed of Cells

• cell theory
• A fundamental unifying concept of biology
• Every living organism is composed of one or more
  cells
• New cells are formed only by division of
  previously existing cells
• Simple, unicellular life-forms consist of a
  single cell
• Complex, multicellular organisms depend on
  coordinated functions of cells that are organized
  to form tissues, organs, and organ systems

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Unicellular and Multicellular Life-Forms

• Paramecium

• African buffalo, plants

(a) Unicellular organisms consist of one
intricate cell that performs all the functions
essential to life. Ciliates, such as this
Paramecium , move about by beating their hairlike
cilia.
(b) Multicellular organisms, such as this African
buffalo (Syncerus caffer) and the plants on which
it grazes, may consist of billions of cells
specialized to perform specific functions.
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Cell Structure

• A plasma membrane protects the cell and regulates
  passage of materials between the cell and its
  environment
• Specialized molecules usually deoxyribonucleic
  acid (DNA) contain genetic instructions and
  transmit genetic information
• Internal structures (organelles) are specialized
  to perform specific functions

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Two Types of Cells

• prokaryotic cells
• Exclusive to bacteria and archaea
• Structurally simple they do not have a nucleus
  or other membrane-enclosed organelles
• eukaryotic cells
• Typically contain a variety of organelles
  enclosed by membranes, including a nucleus, which
  houses DNA

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Organisms Grow and Develop

• Biological growth involves an increase in size of
  individual cells of an organism, in number of
  cells, or in both
• Some organisms (e.g. trees) grow throughout their
  lives
• Many animals have a growth period that ends at
  adult size
• Development includes all changes during an
  organisms life
• Example A human develops from a fertilized egg
  into a multicellular organism with structures and
  body form adapted to specific functions

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Organisms Regulate Their Metabolic Processes

• Metabolism includes all chemical activities that
  take place in an organism, including chemical
  reactions essential to nutrition, growth and
  repair, and conversion of energy
• Homeostatic mechanisms carefully regulate
  metabolic processes to maintain an appropriate,
  balanced internal environment (homeostasis)
• Example Regulation of blood sugar (glucose)

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Organisms Respond to Stimuli

• Organisms respond to physical or chemical changes
  in their external or internal environment
  (stimuli)
• Responses typically involve movement
• Unicellular organisms may move by slow oozing of
  the cell (amoeboid movement), by beating tiny,
  hairlike extensions of the cell (cilia) or longer
  structures (flagella)

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Flagella

• Bacteria equipped with flagella for locomotion
• Helicobacter pylori have been linked to stomach
  ulcers

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Organisms Respond to Stimuli (cont.)

• Most animals move by contracting muscles
• Complex animals have highly specialized cells
  that respond to specific types of stimuli, such
  as light
• Plants respond to light, gravity, water, touch,
  and other stimuli

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Plants Respond to Stimuli
Fig. 1-3a, p. 4
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Organisms Reproduce

• asexual reproduction
• Offspring have the same genes as the single
  parent
• Variation occurs only by mutations
• sexual reproduction
• Offspring are produced by fusion of egg and sperm
• Genes are typically contributed by two parents

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Asexual and Sexual Reproduction
Fig. 1-4, p. 5
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Populations Evolve and BecomeAdapted to the
Environment

• As populations evolve, they become adapted to
  their environment
• Adaptations may be structural, physiological,
  biochemical, behavioral, or a combination of all
  four
• adaptations
• Inherited characteristics that enhance an
  organisms ability to survive in a particular
  environment

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Adaptations

• Burchells zebras (1) are behaviorally adapted to
  watch for predators, (2) have stripes for visual
  protection against predators, (3) have stomachs
  adapted to coarse grass (enlarged cecum)

Fig. 1-5, p. 5
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KEY CONCEPTS 1.2

• Characteristics of life include
• cellular structure
• growth and development
• self-regulated metabolism
• response to stimuli
• reproduction

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1.3 LEVELS OF BIOLOGICAL ORGANIZATION

• LEARNING OBJECTIVE
• Construct a hierarchy of biological organization,
  including levels characteristic of individual
  organisms and levels characteristic of ecological
  systems

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Organisms Have Several Levels of Organization

• Atoms and molecules form cells
• Cells associate to form tissues
• Tissues organize into functional structures
  (organs)
• In animals, major biological functions are
  performed by a coordinated group of tissues and
  organs (organ system)
• Organ systems function together to make up a
  complex, multicellular organism

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Several Levels of EcologicalOrganization Can Be
Identified

• population
• All members of one species living in the same
  geographic area at the same time
• community
• Populations of various types of organisms living
  and interacting with one another in a particular
  area
• ecosystem
• A community together with its nonliving
  environment

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Levels of Organization (cont.)

• All of Earths ecosystems together are known as
  the biosphere
• The study of how organisms relate to one another
  and to their physical environment is called
  ecology

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Hierarchy of Biological Organization
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Stepped Art
Fig. 1-6, p. 7
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KEY CONCEPTS 1.3

• Biological organization includes chemical, cell,
  tissue, organ, organ system, and organism levels
• Ecological organization includes population,
  community, ecosystem, and biosphere levels

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1.4 INFORMATION TRANSFER

• LEARNING OBJECTIVE
• Summarize the importance of information transfer
  within and between living systems, giving
  specific examples

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DNA Transmits Information fromOne Generation to
the Next

• A DNA molecule consists of two chains of atoms
  twisted into a helix
• Each chain is made up of a sequence of chemical
  subunits called nucleotides

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DNA

• DNA is the hereditary material that transmits
  information from one generation to the next
• The sequence of nucleotides makes up the genetic
  code

Fig. 1-7, p. 8
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Information is Transmitted by Chemical and
Electrical Signals

• Genes control development and function of every
  organism
• The DNA that makes up genes contains instructions
  for making all the proteins required by the
  organism
• proteins
• Large molecules important in determining the
  structure and function of cells and tissues

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Communication Between Cells

• Cells use proteins and other molecules to
  communicate with one another
• Hormones and other chemical messengers signal
  cells in distant organs to secrete a required
  substance or change a metabolic activity
• Animals nervous systems transmit information by
  electrical impulses and chemical compounds
  (neurotransmitters)

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KEY CONCEPTS 1.4

• Information transfer includes
• DNA transfer of information from one generation
  to the next
• Chemical and electrical signals within and among
  the cells of every organism
• Chemicals, visual displays, and sounds that allow
  organisms to communicate with one another and to
  interact with their environment

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1.5 THE ENERGY OF LIFE

• LEARNING OBJECTIVE
• Summarize the flow of energy through ecosystems
  and contrast the roles of producers, consumers,
  and decomposers

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Energy and Metabolism

• Life depends on continuous input of energy from
  the sun
• Whenever energy is used to perform biological
  work, some is converted to heat and dispersed
  into the environment
• All energy transformations and chemical processes
  within an organism are referred to as its
  metabolism

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Cellular Respiration

• All cells require nutrients that contain energy
• During cellular respiration, cells capture energy
  released by nutrient molecules through a series
  of carefully regulated chemical reactions
• Cells use this energy to do work, including
  synthesis of new cell components

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Energy in Ecosystems

• Ecosystems also depend on continuous energy input
• Ecosystems include three types of organisms
  (producers, consumers, decomposers) and their
  physical environment
• There is a one-way flow of energy through
  ecosystems
• Organisms can neither create energy nor use it
  with complete efficiency
• During every energy transaction, some energy
  disperses into the environment as heat

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The Producers

• Plants, algae, and some bacteria are producers
  (autotrophs) that produce their own food from
  simple raw materials
• Most producers use sunlight as energy for
  photosynthesis, which transforms light energy
  into chemical energy stored in chemical bonds of
  food molecules
• Photosynthesis synthesizes food molecules such as
  glucose (sugar) from carbon dioxide and water,
  and releases oxygen
• carbon dioxide water light ? glucose oxygen

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The Consumers

• Animals are consumers (heterotrophs) that obtain
  energy by breaking down food molecules produced
  in photosynthesis
• Primary consumers eat producers secondary
  consumers eat primary consumers
• Chemical bonds are broken in the process of
  cellular respiration, and stored energy is made
  available
• glucose oxygen ? carbon dioxide water energy

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The Decomposers

• Most bacteria and fungi are decomposers,
  heterotrophs that obtain nutrients by breaking
  down nonliving organic material such as wastes,
  dead leaves and branches, and bodies of dead
  organisms
• In the process of obtaining energy, decomposers
  make the components of these materials available
  for reuse

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Energy Flow Within and Among Organisms
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Light energy
Photosynthesis captures light energy
Oxygen
Energy stored in glucose and other nutrients
Carbon dioxide and water
Oxygen
Energy
Cellular respiration releases energy stored in
glucose molecules
Synthesis of needed molecules and structures
Other Life Activities Homeostasis Growth
and development Reproduction Movement of
materials in and out of cells Movement of body
Fig. 1-8, p. 9
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Energy Flow Through the Biosphere

• During every energy transaction, some energy is
  lost to biological systems, dispersing into the
  environment as heat

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Light energy
Heat
Heat
Food
Heat
Primary consumer (caterpillar)
Secondary consumer (robin)
Heat
Producer (plant)
Dead bodies
Plant litter, wastes
Decomposers (bacteria, fungi)
Soil
Fig. 1-9, p. 10
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1.6 THE BASIC CONCEPTS OF BIOLOGY

• LEARNING OBJECTIVES
• Demonstrate the binomial system of nomenclature
  using specific examples, and classify an organism
  in its domain, kingdom, phylum, class, order,
  family, genus, and species
• Identify the three domains and the kingdoms of
  living organisms, and give examples of organisms
  in each group
• Give a brief overview of the scientific theory of
  evolution and explain why it is the principal
  unifying concept in biology
• Apply the theory of natural selection to any
  given adaptation and suggest a logical
  explanation of how it may have evolved

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Evolution

• evolution
• Process by which populations of organisms change
  over time
• Involves passing genes for new traits from one
  generation to another, leading to differences in
  populations

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Biologists Use a Binomial Systemfor Naming
Organisms

• Systematics is the field of biology that studies
  the diversity of organisms and their
  relationships
• Taxonomy, is the science of naming and
  classifying organisms

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Binomial System

• The binomial system of nomenclature is used to
  name each species, it is called such because each
  species has a two-part name
• The first part of the name is the genus
• The second part, the specific epithet, designates
  a particular species in that genus
• Example The domestic dog, Canis familiaris (or
  C. familiaris), and timber wolf, Canis lupus (C.
  lupus), are in the same genus

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Species and Genus

• A species is a group of organisms with similar
  structure, function, and behavior
• Closely related species are grouped into a genus
  (genera)

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Taxonomic Classificationis Hierarchical

• Related genera are grouped in a family
• Families are grouped into orders, orders into
  classes, and classes into phyla (phylum)
• Phyla are assigned to kingdoms, and kingdoms are
  grouped in domains
• Each level is a taxon (taxa)

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Classification of the Cat, Human,and White Oak
Tree
Table 1-1, p. 11
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DOMAIN
Eukarya
KINGDOM
Animalia
PHYLUM
Chordata
CLASS
Mammalia
ORDER
Primates
FAMILY
Pongidae
GENUS
Pan
SPECIES
Pan troglodytes
Fig. 1-10, p. 12
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Three Domains

• Most biologists assign organisms to three domains
  and several kingdoms
• There are two domains of organisms with
  prokaryotic cells (prokaryotes) Bacteria and
  Archaea
• Kingdom Archaea corresponds to domain Archaea
• Kingdom Bacteria corresponds to domain Bacteria
• All other organisms belong to the domain Eukarya

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Domain Eukarya

• Organisms with eukaryotic cells (eukaryotes) are
  classified in domain Eukarya
• Protists (including five supergroups) are
  unicellular, colonial, or simple multicellular
  eukaryotic organisms
• Kingdom Plantae (plants) are complex
  multicellular organisms adapted for
  photosynthesis
• Kingdom Fungi (yeasts, mildews, molds, and
  mushrooms) do not photosynthesize they obtain
  nutrients by secreting digestive enzymes into
  food and absorbing it
• Kingdom Animalia includes complex multicellular
  organisms that obtain nutrition by eating other
  organisms

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Three Domains of Life
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Stepped Art
Fig. 1-11, p. 13
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Species Adapt in Response to Changes in Their
Environment

• Every organism is the product of numerous
  interactions between environmental conditions and
  genes inherited from its ancestors
• If all individuals of a species were exactly
  alike, any change in the environment might be
  disastrous to all, and the species would become
  extinct
• Adaptations to changes in the environment occur
  as a result of evolutionary processes that take
  place over time and involve many generations

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Natural Selection An Important Evolutionary
Mechanism

• Charles Darwin and Alfred Wallace proposed a
  theory of evolution and suggested a mechanism
  natural selection
• Darwins book, On the Origin of Species by
  Natural Selection (1859), supported his
  hypothesis that present forms of life descended,
  with modifications, from previously existing forms

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Darwins Four Observations

• Darwin based his theory on four observations
• Individual members of a species vary from one
  another
• Organisms produce many more offspring than will
  survive to reproduce
• More individuals are produced than the
  environment can support, so organisms must
  compete for necessary, but limited, resources
  also, some are killed by predators, disease
  organisms, or unfavorable natural conditions
• Individuals with characteristics that enable them
  to withstand prevailing environmental conditions
  and challenges are more likely to survive and
  reproduce

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Adaptation

• Survivors that reproduce pass their adaptations
  for survival on to their offspring
• The best-adapted individuals leave, on average,
  more offspring than other individuals
  (differential reproduction)
• The environment selects the best-adapted
  organisms of a population for survival
• Adaptation involves changes in populations, not
  individuals

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Mutation and Variation

• Most variations among individuals result from
  different varieties of genes that code for each
  characteristic
• The ultimate source of these variations is random
  mutations (chemical or physical changes in DNA
  that can be inherited)
• Mutations modify genes and provide the raw
  material for evolution

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Populations Evolve Due to Selective Pressures
from Environmental Changes

• All genes in a population make up its gene pool
  (a reservoir of genetic variation)
• Natural selection acts on individuals within a
  population
• Selection favors individuals with genes for
  traits that allow them to respond effectively to
  environmental pressure these individuals are
  most likely to survive and produce offspring
• Over time, members of a population become better
  adapted to their environment and less like their
  ancestors new species may evolve

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1.7 THE PROCESS OF SCIENCE

• LEARNING OBJECTIVES
• Design a study to test a given hypothesis, using
  the procedure and terminology of the scientific
  method
• Compare the reductionist and systems approaches
  to biological research

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Process of Science

• Science is a way of thinking, and a method of
  investigating, the natural world in a systematic
  manner
• The process of science is investigative, dynamic,
  and often controversial observations,
  questions, and experimental design depend on the
  creativity of the individual scientist
• Science is influenced by cultural, social,
  historical, and technological contexts, so the
  process changes over time

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Scientific Method

• The scientific method involves a series of
  ordered steps
• Make careful observations
• Ask critical questions and develop hypotheses
• Make predictions that can be tested by making
  further observations or by performing experiments
• Gather information (data) that can be analyzed
• Interpret the results of experiments and draw
  conclusions

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Careful Observations and Chance

• 1928 Alexander Fleming did not set out to
  discover penicillin
• When a blue mold invaded one of his bacterial
  cultures, he noticed that the contaminated area
  was surrounded by a zone where bacterial colonies
  did not grow
• Fleming benefited from chance, but his mind was
  prepared to make observations and formulate
  critical questions

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A Hypothesis is a Testable Statement

• A hypothesis is a tentative explanation for
  observations or phenomena
• A good hypothesis has three characteristics
• It is reasonably consistent with well-established
  facts
• It is capable of being tested and test results
  should be repeatable by independent observers
• It is falsifiable (can be proven false)

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A Falsifiable Hypothesis Can Be Tested

• A well-stated hypothesis can be tested
• If no evidence is found to support it, the
  hypothesis is rejected
• The hypothesis can be shown to be false
• A hypothesis can be supported by data, but it
  cant really be proven true

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Models Are Important in Developing and Testing
Hypotheses

• Hypotheses may be derived from models that
  scientists develop to provide a comprehensive
  explanation for a large number of observations
• Examples Model of the structure of DNA model of
  the structure of the plasma membrane
• The best design for an experiment can sometimes
  be established by performing computer simulations

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Many Predictions canbe Tested by Experiment

• Scientists make predictions (deductive, logical
  consequences of a hypothesis) that can be tested
  by experiments
• Some predictions can be tested by controlled
  experiments in which an experimental group
  differs from a control group only with respect to
  the variable being studied

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Key Experiment

• Scientists observed that the nucleus was the most
  prominent part of the cell, and predicted that
  cells would be adversely affected if they lost
  their nuclei
• Experiment
• Experimental group Nucleus was removed
• Control group A microloop was inserted into the
  cell to simulate removal, but the nucleus was
  left inside
• Result The control group lived the experimental
  group died

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Key Experiment (cont.)
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Amoeba dies
(a) Experimental group. When its nucleus is
surgically removed with a microloop, the amoeba
dies.
Fig. 1-17a, p. 18
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Amoeba lives
(b) Control group. A control amoeba subjected to
similar surgical procedures (including insertion
of a microloop), but without actual removal of
the nucleus, does not die.
Fig. 1-17b, p. 18
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Researchers Must Avoid Bias

• In scientific studies, researchers must try to
  avoid bias or preconceived ideas of what should
  happen
• In a double-blind study neither patient nor
  physician knows who gets an experimental drug and
  who gets a placebo
• Not all experiments can be so neatly designed
  it is often difficult to establish appropriate
  controls

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Scientists Interpret Results and Make Conclusions

• Scientists gather data in an experiment,
  interpret results, and draw conclusions from them
• In the amoeba experiment, investigators concluded
  that data supported the hypothesis that the
  nucleus is essential for the survival of the cell
• Results that falsify a hypothesis also may be
  valuable and may lead to new hypotheses

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Sampling Error and Repeatability

• One reason for inaccurate conclusions is sampling
  error
• Not all cases can be observed or tested
• If the sample is too small, it may not be
  representative because of random factors
• Scientists try to state that any specific
  conclusion has a certain statistical probability
  of being correct
• Experiments must be repeatable by other scientists

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Statistical Probability
Fig. 1-19, p. 21
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Curtain
Single selection
Marbles
produces
Assumption
100 blue
Actual ratio 20 blue 80 white
(a) Taking a single selection can result in
sampling error. If the only marble selected is
blue, we might assume all the marbles are blue.
Fig. 1-19a, p. 21
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Curtain
Multiple selections
Marbles
produce
Assumption
30 blue 70 white
Actual ratio 20 blue 80 white
(b) The greater the number of selections we take
of an unknown, the more likely we can make valid
assumptions about it.
Fig. 1-19b, p. 21
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A Theory is Supported by Tested Hypotheses

• A scientific theory is an integrated explanation
  of some aspect of the natural world, based on a
  number of hypotheses, each supported by
  consistent results from many observations or
  experiments
• By showing relationships among classes of facts,
  a scientific theory clarifies our understanding
  of the natural world

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Paradigm Shifts Allow New Discoveries

• A paradigm is a set of assumptions or concepts
  that constitute a way of thinking about reality
• As new facts are discovered, biologists have to
  make paradigm shifts they change their view of
  reality to accommodate new knowledge
• Systems biology is a field of biology that builds
  on information provided and integrates the
  different levels of information

86
Science Has Ethical Dimensions

• Honesty is particularly important in science
  science tends to correct itself through
  consistent use of the scientific process
• Scientists face many societal and political
  issues surrounding areas such as genetic
  research, stem cell research, cloning, and human
  and animal experimentation
• Human genome research raises ethical concerns
  about the privacy of genetic information and the
  ethical, legal, and social implications of its
  findings

87
KEY CONCEPTS 1.7

• Biologists ask questions, develop hypotheses,
  make predictions, and collect data by careful
  observation and experiment
• Based on their results, they come to conclusions