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SCIENCE

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Title: SCIENCE


1
SCIENCE
  • The intellectual process using all available
    mental and physical resources to better
    understand, explain, quantitate, and predict
    normal as well as unusual natural phenomena
  • The goal of science is to investigate and
    understand the natural world, to explain events
    in the natural world, and to use those
    explanations to make useful predictions
  • Organized way of using evidence to learn about
    the natural world
  • Body of knowledge that has been built up over the
    years

2
Scientific Method
  • Observation
  • Measurement
  • Accumulation and analysis of verifiable data

3
Scientific Method
  • Observation
  • Process of gathering information about events or
    processes in a careful, orderly way
  • Generally involves using the senses, particularly
    sight, hearing, touch, smell, and taste

4
Scientific Method
  • The information gathered from observations is
    called data
  • Observations and measurements that are made in an
    experiment
  • There are two main categories of data
  • Quantitative data are expressed as numbers,
    obtained by counting or measuring
  • Qualitative data are descriptive and involve
    characteristics that can't usually be counted
  • The researcher might make the qualitative
    observations that the scar appears old and the
    animal seems healthy and alert.

5
Inference
  • Scientists may use data to make inferences
  • Inference is a logical interpretation based on
    prior knowledge or experience
  • Example
  • Researcher might be testing water in a reservoir
    Because he/she cannot test all the water, he/she
    collects water samples from several different
    parts of the reservoir
  • If all the samples are clean enough to drink, she
    may infer that all the water is safe to drink

6
Explaining and Interpreting Evidence
  • Scientists try to explain events in the natural
    world by interpreting evidence logically and
    analytically
  • Suppose
  • That many people contract an unknown disease
    after attending a public event
  • Public health researchers will use scientific
    methods to try to determine how those people
    became ill

7
Explaining and Interpreting EvidenceHYPOTHESIS
  • After initial observations
  • Researchers will propose one or more hypotheses
  • A hypothesis is a proposed scientific explanation
    for a set of observations (educated guess)
  • Scientists generate hypotheses using prior
    knowledge, or what they already know logical
    inference and informed, creative imagination
  • For the unknown disease, there might be several
    competing hypotheses, such as these
  • (1) The disease was spread from person to person
    by contact
  • (2) The disease was spread through insect bites
  • (3) The disease was spread through air, water, or
    food

8
Test Hypothesis
  • Scientific hypotheses must be proposed in a way
    that enables them to be tested
  • Some hypotheses are tested by performing
    controlled experiments, as you will learn in the
    next section
  • Other hypotheses are tested by gathering more
    data
  • In the case of the mystery illness, data would be
    collected by studying the location of the event
    by examining air, water, and food people were
    exposed to and by questioning people about their
    actions before falling ill
  • Some hypotheses would be ruled out
  • Others might be supported and eventually
    confirmed

9
Designing an Experiment
  • People's ideas about where some living things
    come from have changed over the centuries
  • Exploring this change can help show how science
    works
  • Remember that what might seem obvious today was
    not so obvious thousands of years ago.

10
Stating the ProblemObservation
  • For many years, observations seemed to indicate
    that some living things could just suddenly
    appear
  • Maggots showed up on meat mice were found on
    grain and beetles turned up on cow dung
  • People wondered how these events happened. They
    were, in their own everyday way, identifying a
    problem to be solved by asking a question How do
    new living things, or organisms, come into being?

11
Hypothesis
  • For centuries, people accepted the prevailing
    explanation for the sudden appearance of some
    organisms, that some life somehow arose from
    nonliving matter
  • The maggots arose from the meat
  • Mice from the grain
  • Beetles from the dung
  • Scholars of the day even gave a name to the idea
    that life could arise from nonliving
    matterspontaneous generation
  • In today's terms, the idea of spontaneous
    generation can be considered a hypothesis

12
Redis Experiment
  • In 1668, Francesco Redi, an Italian physician,
    proposed a different hypothesis for the
    appearance of maggots
  • Redi had observed that these organisms appeared
    on meat a few days after flies were present
  • He considered it likely that the flies laid eggs
    too small for people to see
  • Thus, Redi was proposing a new hypothesisflies
    produce maggots
  • Redi's next step was to test his hypothesis

13
Setting Up a Controlled Experiment 
  • In science, testing a hypothesis often involves
    designing an experiment
  • The factors in an experiment that can change are
    called variables
  • Examples of variables include
  • Equipment used
  • Type of material
  • Amount of material
  • Temperature
  • Light
  • Time

14
Setting Up a Controlled Experiment
  • Suppose you want to know whether an increase in
    water, light, or fertilizer can speed up plant
    growth
  • If you change all three variables at once, you
    will not be able to tell which variable is
    responsible for the observed results
  • Whenever possible, a hypothesis should be tested
    by an experiment in which only one variable is
    changed at a time
  • All other variables should be kept unchanged, or
    controlled
  • This type of experiment is called a controlled
    experiment
  • The variable that is deliberately changed is
    called the manipulated variable
  • The variable that is observed and that changes in
    response to the manipulated variable is called
    the responding variable.

15
Redis Experiment
  • Based on his hypothesis, Redi made a prediction
    that keeping flies away from meat would prevent
    the appearance of maggots
  • To test this hypothesis, he planned the
    experiment shown at right
  • Notice that Redi controlled all variables except
    one
  • Whether or not there was gauze over each jar
  • The gauze was important because it kept flies off
    the meat.

16
Redis Experiment
17
Redis Experiment
  • The manipulated variable was the presence or
    absence of the gauze covering
  • The results of this experiment helped
  • Disprove the hypothesis of spontaneous generation

18
Recording and Analyzing Results 
  • Scientists usually keep written records of their
    observations, or data
  • In the past, data were usually recorded by hand,
    often in notebooks or personal journals
  • Sometimes, drawings recorded certain kinds of
    observations more completely and accurately than
    a verbal description could
  • Today, researchers may record their work on
    computers. Online storage often makes it easier
    for researchers to review the data at any time
    and, if necessary, offer a new explanation for
    the data
  • Scientists know that Redi recorded his data
    because copies of his work were available to
    later generations of scientists
  • His investigation showed that maggots appeared on
    the meat in the control jars
  • No maggots appeared in the jars covered with
    gauze

19
Drawing a Conclusion 
  • Scientists use the data from an experiment to
    evaluate the hypothesis and draw a valid
    conclusion
  • That is, they use the evidence to determine
    whether the hypothesis was supported or refuted
  • Redi's results supported his hypothesis
  • He therefore concluded that the maggots were
    indeed produced by flies
  • As scientists look for explanations for specific
    observations, they assume that the patterns in
    nature are consistent
  • Thus, Redi's results could be viewed not only as
    an explanation about maggots and flies but also
    as a refutation of the hypothesis of spontaneous
    generation

20
Publishing and Repeating Investigations
  • A key assumption in science is that experimental
    results can be reproduced because nature behaves
    in a consistent manner
  • When one particular variable is manipulated in a
    given set of variables, the result should always
    be the same
  • In keeping with this assumption, scientists
    expect to test one another's investigations
  • Thus, communicating a description of an
    experiment is an essential part of science
  • Today's researchers often publish a report of
    their work in a scientific journal
  • Other scientists review the experimental
    procedures to make sure that the design was
    without flaws
  • They often repeat experiments to be sure that the
    results match those already obtained
  • In Redi's day, scientific journals were not
    common, but he communicated his conclusion in a
    book that included a description of his
    investigation and its results.

21
Microscope Discovery
  • About the time Redi was carrying out his
    experiment, Anton van Leeuwenhoek (LAY-vun-hook)
    of the Netherlands discovered a world of tiny
    moving objects in rainwater, pond water, and
    dust
  • Inferring that these objects were alive, he
    called them animalcules, or tiny animals
  • He made drawings of his observations and shared
    them with other scientists
  • For the next 200 years or so, scientists could
    not agree on whether the animalcules were alive
    or how they came to exist (Spontaneous
    Generation?????)

22
Needham's Test of Redi's Findings 
  • In the mid-1700s, John Needham, an English
    scientist, used an experiment involving
    animalcules to attack Redi's work
  • Needham claimed that spontaneous generation could
    occur under the right conditions
  • To prove his claim, he sealed a bottle of gravy
    and heated it
  • He claimed that the heat had killed any living
    things that might be in the gravy
  • After several days, he examined the contents of
    the bottle and found it swarming with activity
  • These little animals, he inferred, can only
    have come from juice of the gravy. (SPONTANEOUS
    GENERATION)

23
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24
Spallanzani's Test of Redi's Findings 
  • An Italian scholar, Lazzaro Spallanzani, read
    about Redi's and Needham's work
  • Spallanzani thought that Needham had not heated
    his samples enough and decided to improve upon
    Needham's experiment
  • The figure shown at right illustrates that
    Spallanzani boiled two containers of gravy,
    assuming that the boiling would kill any tiny
    living things, or microorganisms, that were
    present
  • He sealed one jar immediately and left the other
    jar open
  • After a few days, the gravy in the open jar was
    teeming with microorganisms
  • The sealed jar remained free of microorganisms

25
Spallanzanis Experiment
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27
Spallanzanis Experiment
  • Spallanzani concluded that nonliving gravy did
    not produce living things
  • The microorganisms in the unsealed jar were
    off-spring of microorganisms that had entered the
    jar through the air
  • This experiment and Redi's work supported the
    hypothesis that new organisms are produced only
    by existing organisms

28
Challenge 
  • Well into the 1800s, some scientists continued to
    support the spontaneous generation hypothesis
  • Some of them argued that air was a necessary
    factor in the process of generating life because
    air contained the life force needed to produce
    new life
  • They pointed out that Spallanzani's experiment
    was not a fair test because air had been excluded
    from the sealed jar

29
Pasteur's Test of Spontaneous Generation
  • In 1864, an ingenious French scientist, Louis
    Pasteur, found a way to settle the argument
  • He designed a flask that had a long curved neck,
    as shown in the figure at right
  • The flask remained open to the air, but
    microorganisms from the air did not make their
    way through the neck into the flask
  • Pasteur showed that as long as the broth was
    protected from microorganisms, it remained free
    of living things
  • About a year after the experiment began, Pasteur
    broke the neck of the flask, and the broth
    quickly became filled with microorganisms
  • His work convinced other scientists that the
    hypothesis of spontaneous generation was not
    correct
  • In other words, Pasteur showed that all living
    things come from other living things
  • This change in thinking represented a major shift
    in the way scientists viewed living things

30
Pasteurs Experiment
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33
The Impact of Pasteur's Work 
  • During his lifetime, Pasteur made many
    discoveries related to microorganisms
  • His research had an impact on society as well as
    on scientific thought
  • He saved the French wine industry, which was
    troubled by unexplained souring of wine, and the
    silk industry, which was endangered by a silkworm
    disease
  • Moreover, he began to uncover the very nature of
    infectious diseases, showing that they were the
    result of microorganisms entering the bodies of
    the victims
  • Pasteur is considered one of biology's most
    remarkable problem solvers.

34
How a Theory Develops
  • As evidence from numerous investigations builds
    up, a particular hypothesis may become so well
    supported that scientists consider it a theory
  • That is what happened with the hypothesis that
    new organisms come from existing organisms
  • This idea is now considered one of the major
    ideas in science
  • It is called biogenesis, meaning generating from
    life

35
Theory
  • You may have heard the word theory used in
    everyday conversations as people discuss ideas
  • Someone might say, Oh, that's just a theory, to
    criticize an idea that is not supported by
    evidence
  • In science, the word theory applies to a
    well-tested explanation that unifies a broad
    range of observations
  • A theory enables scientists to make accurate
    predictions about new situations

36
Theory
  • A useful theory may become the dominant view
    among the majority of scientists, but no theory
    is considered absolute truth
  • Scientists analyze, review, and critique the
    strengths and weaknesses of theories
  • As new evidence is uncovered, a theory may be
    revised or replaced by a more useful explanation
  • Sometimes, scientists resist a new way of looking
    at nature, but over time new evidence determines
    which ideas survive and which are replaced
  • Thus, science is characterized by both continuity
    and change

37
BIOLOGY
  • The word biology means the study of life
  • The Greek word bios means life, and -logy means
    study of
  • Biology is the science that seeks to understand
    the living world
  • A biologist is someone who uses scientific
    methods to study living things
  • The work of biologists can be quite varied,
    because organisms are complex and vary so greatly

38
Characteristics of Life
  • Living things share the following
    characteristics
  • Living things are made up of units called cells
  • Living things reproduce
  • Living things are based on a universal genetic
    code
  • Living things grow and develop
  • Living things obtain and use materials and energy
  • Living things respond to their environment
  • Living things maintain a stable internal
    environment
  • Taken as a group, living things change over time

39
Made Up of Cells 
  • Living things, or organisms, are made up of
    small, self-contained units called cells
  • A cell is a collection of living matter enclosed
    by a barrier that separates the cell from its
    surroundings
  • Cells are the smallest units of an organism that
    can be considered alive
  • Cells can grow, respond to their surroundings,
    and reproduce
  • Despite their small size, cells are complex and
    highly organized
  • Many living things consist of only a single cell
    and are therefore called unicellular organisms
  • The Latin prefix uni- means one, so unicellular
    means single-celled
  • Many of the microorganisms involved in
    Spallanzani's and Pasteur's experiments were
    unicellular organisms

40
Made Up of Cells
  • The organisms you are most familiar withfor
    example, animals and plantsare multicellular
  • The Latin prefix multi- means many
  • Thus, multicellular means many-celled
  • Multicellular organisms contain hundreds,
    thousands, or even trillions of cells
  • The cells in these organisms are often remarkably
    diverse, existing in a variety of sizes and
    shapes
  • In some multicellular organisms, each type of
    cell is specialized to perform a different
    function
  • The human body alone is made up of at least 85
    different cell types

41
Reproduction
  • All organisms produce new organisms through a
    process called reproduction
  • There are two basic kinds of reproduction sexual
    and asexual
  • The vast majority of multicellular organismsfrom
    maple trees to birds and humansreproduce
    sexually
  • In sexual reproduction, cells from two different
    parents unite to produce the first cell of the
    new organism
  • In asexual reproduction, the new organism has a
    single parent
  • In some forms of asexual reproduction, a
    single-celled organism divides in half to form
    two new organisms
  • In another type of asexual reproduction known as
    budding, a portion of an organism splits off to
    form a new organism

42
Based on a Genetic Code 
  • Offspring usually resemble their parents
  • With asexual reproduction, offspring and their
    parents have the same traits
  • With sexual reproduction, offspring differ from
    their parents in some ways
  • However, there are limits to these differences
  • Flies produce flies, dogs produce dogs, and seeds
    from maple trees produce maple trees
  • Explaining how organisms inherit traits is one of
    the greatest achievements of modern biology
  • Biologists now know that the directions for
    inheritance are carried by a molecule called
    deoxyribonucleic acid, or DNA
  • This genetic code, with a few minor variations,
    determines the inherited traits of every organism
    on Earth

43
Growth and Development 
  • All living things grow during at least part of
    their lives
  • For some single-celled organisms, such as
    bacteria, growth is mostly a simple increase in
    size
  • Multicellular organisms, however, typically go
    through a process called development
  • During development, a single fertilized egg cell
    divides again and again to produce the many cells
    of mature organisms
  • As those cells divide, they change in shape and
    structure to form cells such as liver cells,
    brain cells, and muscle cells
  • This process is called differentiation, because
    it forms cells that look different from one
    another and perform different functions
  • For many organisms, development includes periods
    of rapid and dramatic change
  • In fact, although you will not sprout wings, your
    body is currently experiencing one of the most
    intense spurts of growth and development of your
    entire life!

44
Need for Materials and Energy 
  • Think of what an organism needs as it grows and
    develops
  • Just as a building grows taller because workers
    use energy to assemble new materials, an organism
    uses energy and a constant supply of materials to
    grow, develop, and reproduce
  • Organisms also need materials and energy just to
    stay alive
  • The combination of chemical reactions through
    which an organism builds up or breaks down
    materials as it carries out its life processes is
    called metabolism

45
Need for Materials and Energy
  • All organisms take in selected materials that
    they need from their surroundings, or
    environment, but the way they obtain energy
    varies
  • Plants, some bacteria, and most algae obtain
    their energy directly from sunlight
  • AUTOTROPHS
  • Through a process called photosynthesis, these
    organisms convert light into a form of energy
    that is stored in certain molecules
  • That stored energy is ready to be used when
    needed

46
Need for Materials and Energy
  • Most other organisms rely on the energy stored
    during photosynthesis
  • HETEROTROPHS
  • Some organisms, such as grasshoppers and sheep,
    obtain their energy by eating plants and other
    photosynthesizing organisms (Herbivore)
  • Other organisms, such as birds and wolves, get
    energy by eating the grasshoppers or sheep
    (Carnivore)
  • And some organisms, called decomposers, obtain
    energy from the remains of organisms that have
    died

47
Response to the Environment 
  • Organisms detect and respond to stimuli from
    their environment
  • A stimulus is a signal to which an organism
    responds
  • External stimuli, which come from the environment
    outside an organism, include factors such as
    light and temperature
  • For example, when there is sufficient water and
    the ground is warm enough, a plant seed responds
    by germinating
  • The roots respond to gravity and grow down into
    the soil
  • The new leaves and stems grow toward light
  • Internal stimuli come from within an organism
  • The level of the sugar glucose in your blood is
    an example of an internal stimulus
  • If this level becomes low enough, your body
    responds by making you feel hungry

48
Maintaining Internal Balance 
  • Even though conditions in the external
    environment may vary widely, most organisms must
    keep internal conditions, such as temperature and
    water content, fairly constant to survive
  • The process by which they do this is called
    homeostasis (hoh-mee-oh-STAY-sis)
  • Homeostasis often involves internal feedback
    mechanisms that work in much the same way as a
    thermostat
  • Just as a thermostat in your home turns on the
    heat when room temperature drops below a certain
    point, you have an internal thermostat that
    makes your body shiver if your internal
    temperature drops too low
  • The muscle action involved in shivering produces
    heat, thus warming your body
  • In contrast, if you get too hot, your biological
    thermostat turns on air conditioning by causing
    you to sweat.
  • Sweating helps to remove excess heat from your
    skin
  • When birds get cold, they hunch down and adjust
    their feathers to provide maximum insulation
  • Often internal stimuli help maintain homeostasis
  • For example, when your body needs more water to
    maintain homeostasis, internal stimuli make you
    feel thirsty

49
Evolution
  • Although individual organisms experience many
    changes during their lives, the basic traits they
    inherited from their parents usually do not
    change
  • As a group, however, any given kind of organism
    can evolve, or change over time
  • Over a few generations, the changes in a group
    may not seem significant
  • But over hundreds of thousands or even millions
    of years, the changes can be dramatic
  • Scientists study deposits containing the remains
    of animals that lived long ago to learn about the
    evolution of organisms
  • From the study of very early deposits, scientists
    know that at one time there were no fishes in
    Earth's waters
  • Yet, in more recent deposits, the remains of
    fishes and other animals with backbones are
    abundant
  • The ability of a group of organisms to change
    over time is invaluable for survival in a world
    that is always changing

50
Branches of Biology
  • Living things come in an astonishing variety of
    shapes, sizes, and habits
  • Living systems also range in size from groups of
    molecules that make up structures inside cells to
    the collections of organisms that make up the
    biosphere
  • No single biologist could study all this
    diversity, so biology is divided into different
    fields
  • Some fields are based on the types of organisms
    being studied
  • Zoologists study animals
  • Botanists study plants
  • Other fields study life from a particular
    perspective
  • Example
  • Paleontologists study ancient life

51
Branches of Biology
  • Some fields focus on the study of living systems
    at different levels of organization, as shown in
    the table at right
  • Some of the levels at which life can be studied
    include molecules, cells, organisms, populations
    of a single kind of organism, communities of
    different organisms in an area, and the biosphere
  • At all these levels, smaller living systems are
    found within larger systems
  • Molecular biologists and cell biologists study
    some of the smallest living systems
  • Population biologists and ecologists study some
    of the largest systems in nature
  • Studies at all these levels make important
    contributions to the quality of human life

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53
Biology in Everyday Life
  • Biologists do not make the decisions about most
    matters affecting human society or the natural
    world citizens and governments do
  • In just a few years, you will be able to exercise
    the rights of a voting citizen, influencing
    public policy by the ballots you cast and the
    messages you send public officials
  • With others, you will make decisions based on
    many factors, including customs, values, ethical
    standards, and scientific knowledge
  • Biology can provide decision makers with useful
    information and analytical skills
  • It can help them envision the possible effects of
    their decisions
  • Biology can help people understand that humans
    are capable of predicting and trying to control
    their future and that of the planet

54
A Common Measurement System
  • Because researchers need to replicate each
    other's experiments and most experiments involve
    measurements, scientists need a common system of
    measurement
  • Most scientists use the metric system when
    collecting data and performing experiments
  • The metric system is a decimal system of
    measurement whose units are based on certain
    physical standards and are scaled on multiples of
    10
  • A revised version of the original metric system
    is called the International System of Units, or
    SI
  • The abbreviation SI comes from the French Le
    Système International d'Unités.
  • Because the metric system is based on multiples
    of 10, it is easy to use
  • Notice in the table at right how the basic unit
    of length, the meter, can be multiplied or
    divided to measure objects and distances much
    larger or smaller than a meter. The same process
    can be used when measuring volume and mass

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Metric
  • POWER DECIMAL
  • OF TEN EQUIVALENT PREFIX SUFFIX SYMBOL
  •  
  • 1012 1,000,000,000,000 tera
    T
  • 109 1,000,000,000 giga
    G
  • 106 1,000,000 mega M
  • 103 1,000
    kilo k
  • 102 100 hecto h
  • 10 10 deka da
  • 1
    meter/liter/gram m/l/g

57
Metric
  • POWER DECIMAL PREFIX SUFFIX SYMBOL
  • OF TEN EQUIVALENT
  • 1 meter/liter/gram
    m/l/g
  • 10-1 0.1 deci d
  • 10-2 0.01 centi
    c
  • 10-3 0.001 milli
    m
  • 10-6 0.000 001 micro
    u
  • 10-9 0.000 000 001 nano
    n
  • 10-12 0.000 000 000 001
    pico p
  • 10-15 0.000 000 000 000 001 femto f
  • 10-18 0.000 000 000 000 000 001 atto
    a
  • to express the units you combine the prefix
    and suffix

58
Metric
  • DIMENSIONAL ANALYSIS
  • Now that you know the basic units of the
    metric/SI system, it is important that you
    understand how to go from one unit to another.
    The skill of converting one unit to another is
    called dimensional analysis
  • Dimensional analysis involves determining in what
    units a problem is given, in what units the
    answer should be, and the factor to be used to
    make the conversion from one unit to another.

59
Metric
  • To perform dimensional analysis, you must use a
    conversion factor
  • A conversion factor is a fraction that equal 1.
  • Example
  • 1 kilometer equals 1000 meters
  • So the fraction 1 kilometer / 1000 meters equals
    1
  • So does the fraction 1000 meters / 1 kilometer
  • The top number in a fraction is called the
    numerator
  • The bottom number in a fraction is called the
    denominator
  • In a conversion fraction the numerator always
    equals the denominator so that the fraction
    always equals 1

60
Metric
  • Lets see how dimensional analysis works. Suppose
    you are told to convert 2500 grams to kilograms.
    This means that grams are your given unit and you
    must express your answer in kilograms. The
    conversion factor you choose must contain a
    relationship between grams and kilograms that has
    a value of 1. You have two possible choices
  • 1000 grams / 1 kilogram 1
  • or
  • 1 kilogram / 1000 grams 1 
  • To convert one metric unit to another, you must
    multiply the given value times the conversion
    factor. Remember that multiplying a number by 1
    does not change the value of the number. So
    multiplying by a conversion factor does not
    change the value, just the units.

61
Metric
  • Now, which conversion factor should you use to
    change 2500 grams into kilograms? Since you are
    going to multiply by the conversion factor, you
    want the unit to be converted to cancel out
    during the multiplication. This is just what will
    happen if the denominator of the conversion
    factor has the same units as the value you wish
    to convert. Since you are converting grams into
    kilograms, the denominator of the conversion
    factor must be in grams and the numerator in
    kilograms. The first step in dimensional
    analysis, then, is to write out the value given,
    the correct conversion factor, and a
    multiplication symbol between them

62
Metric
  • 2500 grams X 1 kilogram / 1000 grams  
  • The next step is to cancel out the same units 
  • 2500 X 1 kilogram / 1000  
  • The last step is to multiply 
  • 2500 kilograms / 1000
  •   2500 kilograms / 1000 2.5 kilograms

63
Metric
  • MASS VALUES
  • 1 kilogram (kg) 1,000 grams (g)
  • 1 hectogram (hg) 100 grams (g)
  • 1 dekagram (dag) 10 grams (g)
  • 1 gram (g) 1 gram (g)
  • 1 decigram (dg) 0.1 gram (g)
  • 1 gram (g) 10 decigram (dg)
  • 1 centigram (cg) 0.01 gram (g)
  • 1 gram (g) 100 centigram (cg)
  • 1 milligram (mg) 0.001 gram (g)
  • 1 gram (g) 1000 milligram (mg)
  • 1 microgram (ug) 0.000001 gram (g)
  • 1 gram (g) 1,000,000 microgram (ug)
  • 1 nanogram (ng) 0.000000001 gram (g)
  • 1 gram (g) 1,000,000,000 nanogram (ng)

64
Metric
  • LIQUID VALUES
  • 1 kiloliter (kl) 1,000 liters (l)
  • 1 hectoliter (hl) 100 liters (l)
  • 1 dekaliter (dal) 10 liters (l)
  • 1 liter (l) 1 liter (l)
  • 1 deciliter (dl) 0.1 liter (l)
  • 1 liter (l) 10 deciliter (dl)
  • 1 centiliter (cl) 0.01 liter (l)
  • 1 liter (l) 100 centiliter (cl)
  • 1 milliliter (ml) 0.001 liter (l)
  • 1 liter (l) 1000 milliliter (ml)
  • 1 microliter (ul) 0.000001 (l)
  • 1 liter (l) 1,000,000 microliter (ul)
  • 1 nanoliter (nl) 0.000000001 (l)
  • 1 liter (l) 1,000,000,000 nanoliter (nl)

65
Metric
  • LENGTH VALUES
  • 1kilometer (km) 1,000 meters (m)
  • 1hectometer (hm) 100 meters (m)
  • 1dekameter (dam) 10 meters (m)
  • 1meter(m) 1 meter (m)
  • 1decimeter (dm) 0.1 meter (m) 1meter
    (m) 10 decimeter (dm)
  • 1centimeter (cm) 0.01 meter (m)
  • 1meter (m) 100 centimeter (cm)
  • 1millimeter (mm) 0.001 meter (m)
  • 1meter (m) 1000 millimeter (mm)
  • 1micrometer (um) 0.000001 meter (m) 1meter
    (m) 1,000,000 micrometer (um)
  • 1nanometer (nm) 0.000000001 meter (m)
  • 1meter (m) 1,000,000,000 nanometer (nm) 

66
Metric
  • Do the following conversions for homework. All
    work and individual steps MUST be shown !
  • as you will see later the volume measurement
    of 1 ml is equivalent to 1 cubic centimeter or 1
    cc or 1 cm 3

67
Metric
  • CONVERSIONS
  • 3 m _______ cm 3 m x 100 cm / 1 m _________
    cm
  •  
  • 1,500 ml ______ l 1,500 ml x 1 l / 1000 ml
    ________ l
  •  
  • 0.015 g _______ mg 0.015 g x 1000 mg / 1 g
    _________ mg
  •  
  • 0.25 km _______ m 0.25 km x 1000 m / 1 km
    ________ m
  •  
  • 2.5 l __________ ml 2.5 l x 1000 ml / 1 l
    _________ ml
  •  
  • 2,750 mg _______ g 2,750 mg x 1 g / 1000 mg
    ________ g
  •  
  • 2 mm _________ um
  • 2 mm x 1000 um / 1 mm __________ um
  •  
  • 2 mm _________ nm
  • 2 mm x 1,000,000 nm / 1mm ____________ nm

68
Microscopes
  • Microscopes are devices that produce magnified
    images of structures that are too small to see
    with the unaided eye
  • Light microscopes produce magnified images by
    focusing visible light rays
  • Electron microscopes produce magnified images by
    focusing beams of electrons
  • Since the first microscope was invented,
    microscope manufacturers have had to deal with
    two problems What is the instrument's
    magnificationthat is, how much larger can it
    make an object appear compared to the object's
    real size? And how sharp an image can the
    instrument produce?

69
Light Microscopes 
  • The most commonly used microscope is the light
    microscope
  • Light microscopes can produce clear images of
    objects at a magnification of about 1000 times
  • Compound light microscopes allow light to pass
    through the specimen and use two lenses to form
    an image
  • Light microscopes make it possible to study dead
    organisms and their parts, and to observe some
    tiny organisms and cells while they are still
    alive
  • Biologists have developed techniques and
    procedures to make light microscopes more useful
  • Chemical stains, also called dyes, can show
    specific structures in the cell
  • Fluorescent dyes have been combined with video
    cameras and computer processing to produce moving
    three-dimensional images of processes such as
    cell movement

70
Electron Microscopes 
  • All microscopes are limited in what they reveal,
    and light microscopes cannot produce clear images
    of objects smaller than 0.2 micrometers, or about
    one-fiftieth the diameter of a typical cell
  • To study even smaller objects, scientists use
    electron microscopes
  • Electron microscopes use beams of electrons,
    rather than light, to produce images
  • The best electron microscopes can produce images
    almost 1000 times more detailed than light
    microscopes can

71
Electron Microscopes
  • Biologists use two main types of electron
    microscopes
  • Transmission electron microscopes (TEMs) shine a
    beam of electrons through a thin specimen
  • TEMs can reveal a wealth of detail inside the
    cell
  • Scanning electron microscopes (SEMs) scan a
    narrow beam of electrons back and forth across
    the surface of a specimen
  • SEMs produce realistic, and often dramatic,
    three-dimensional images of the surfaces of
    objects
  • Because electron microscopes require a vacuum to
    operate, samples for both TEM and SEM work must
    be preserved and dehydrated before they are
    placed inside the microscope
  • This means that living cells cannot be observed
    with electron microscopes, only with the light
    microscope

72
Cell Cultures 
  • To obtain enough material to study, biologists
    sometimes place a single cell into a dish
    containing a nutrient solution
  • The cell is able to reproduce so that a group of
    cells, called a cell culture, develops from the
    single original cell
  • Cell cultures can be used to test cell responses
    under controlled conditions, to study
    interactions between cells, and to select
    specific cells for further study

73
Cell Fractionation 
  • Suppose you want to study just one part of a cell
  • How could you separate that one part from the
    rest of the cell?
  • Biologists often use a technique known as cell
    fractionation to separate the different cell
    parts
  • First, the cells are broken into pieces in a
    special blender
  • Then, the broken cell bits are added to a liquid
    and placed in a tube
  • The tube is inserted into a centrifuge, which is
    an instrument that can spin the tube
  • Spinning causes the cell parts to separate, with
    the most dense parts settling near the bottom of
    the tube
  • A biologist can then remove the specific part of
    the cell to be studied by selecting the
    appropriate layer.
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