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Science of Biology
• The scientific study of life
• Nature is not neatly packaged into the
individual life sciences.
• Organisms and their environment are
natural systems to which the basic
concepts of chemistry and physics apply.
• Biology is a multidisciplinary science,
drawing on the insights from other
What is Life?
• Life resists a simple, one-sentence
definition, yet we can recognize life by
what living things do.
• All organisms share a common set of
features or properties
Properties of Life
• Form high degree of ordered structures
• Regulate internal conditions
Properties of Life
• Harvest and use energy
• Reproduce and evolve
Properties of Life
• Grow and develop
• Respond to environmental stimuli
Organizational Hierarchy
• Life can be
organized into a
hierarchy of
structural levels.
• At each successive
level additional
emergent properties
Florida coast
All organisms on
the Florida coast
Group of brown
Brown pelican
Spinal cord
Organ system
Nervous system
Nervous tissue
Nerve cell
Fig. 2.1
The hierarchy of Life
Organ systems
Biologists investigate the full
spectrum of life, from the
biosphere to the biochemical
reactions within a cell.
Emergent Properties
• Life’s basic characteristic is a high degree of
• Biological organization is based on a hierarchy
of structural levels, each building on the levels
• Novel properties emerge at each step upward
• Emergent properties result from interactions
between components
• Emergent properties reflect importance of
structural arrangement and organization
• The complex organization of life presents a
dilemma to scientists seeking to understand
biological processes.
• We cannot fully explain a higher level of organization
by breaking it down into parts.
• At the same time, it is futile to try to analyze something
a complex as an organism or cell without taking it
• Reductionism - Reducing complex systems to
simpler components, is a powerful strategy in
• Reductionism is balanced by the longer-range
objective of understanding emergent properties.
Unity and Diversity
• Biology can be viewed as having two
• A “vertical” dimension covering the size scale
from atoms to the biosphere
• A “horizontal” dimension that stretches across
the diversity of life.
• The latter includes not only present day organisms
but those throughout life’s history.
Diversity - Hallmark Of Life
• At present, biologists have identified and
named about 1.5 million species.
• This includes over 280,000 plants, almost
50,000 vertebrates, and over 750,000 insects.
• Thousands of newly identified species are
added each year.
• Estimates of the total diversity of life range
from about 5 million to over 30 million
• Underlying the diversity
of life is a striking unity,
especially at the lower
levels of organization.
• The universal genetic
language of DNA unites
prokaryotes, like
bacteria, with
eukaryotes, like humans.
• Among eukaryotes, unity
is evident in many
details of cell structure.
Fig. 1.12
Unity and Diversity
• Evolution is the key to understanding biological diversity
• The evolutionary connections among all organisms
explain the unity and diversity of life
• Descent with modification accounts for both the unity
and diversity of life.
• In many cases, features shared by two species are due to their
descent from a common ancestor.
• Differences are due to modifications by natural selection
modifying the ancestral equipment in different environments.
• Evolution is the core theme of biology - a unifying thread
that ties biology together.
• Can explain the unity and
diversity of life
• Charles Darwin synthesized the theory
of evolution by natural selection, his
book on evolution presented two
important concepts.
• Species evolved from ancestors,
and there was modification in the
process or, as Darwin stated,
“descent with modification.”
• Natural selection occurs as
heritable variations are exposed
to environmental factors that favor
the reproductive success of some
individuals over others.
Darwin’s Observations
• Individual Variation - Individuals in a population
of any species vary in many heritable traits
• Differential reproductive success –
• Any population can potentially produce far more
offspring than the environment can support
• This creates a struggle for existence among variant
members of a population.
• Darwin inferred that those individuals with traits best
suited to the local environment will generally leave
more surviving, fertile offspring
Natural Selection
• Natural selection is an
editing mechanism
• Occurs when populations
or organisms, having
inherited variations, are
exposed to environmental
factors that favor the
reproductive success of
some individuals over
Struggle for Existence
• Struggle for existence: A population produces
many more offspring than can survive long
enough to reproduce. This idea was based on
Thomas Malthus’s Essay on the Principle of
Population – populations tend to increase faster
than their food supply.
• This leads to competition and is of great
consequence in differential reproductive success
Natural Selection
• Natural selection, by its cumulative effects
over vast spans of time, can produce new
species from ancestral species.
• For example, a population may be fragmented
into several isolated populations in different
• What began as one species could gradually
diversify into many species.
• Each isolated population would adapt over
many generations to different environmental
Finches Of The Galapagos Islands
• Diversified after an initial colonization from the mainland to exploit
different food sources on different islands.
Descent With Modification
• Descent with modification accounts for
both the unity and diversity of life.
• In many cases, features shared by two
species are due to their descent from a
common ancestor.
• Differences are due to modifications by
natural selection modifying the ancestral
equipment in different environments.
• Evolution is the core theme of biology - a
unifying thread that ties biology together.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• The product of natural
selection is adaptation,
the collection of
favorable modifications
in a population over
• All organisms have
adaptations that have
evolved by means of
natural selection
The Process Of Science
• Scientists use two main approaches to
learn about nature
• Discovery Science - Scientists describe some
aspect of the world and use inductive
reasoning to draw general conclusions
• Hypothesis-Based Science - Scientists
attempt to explain observations by testing
The Process Of Science
• There are no absolute truths in science
• All that we understand about nature
comes from our ability to observe the
world around us.
• Scientists do not “believe” in something
• Instead scientists have levels of
confidence in explanations for natural
Scientific Theory
• Broad in scope, generates hypotheses,
supported by massive body of evidence.
Theories constantly challenged through
testing of the specific, falsifiable
hypotheses they generate.
• Einstein’s Theory of General Relativity
• Darwin’s Theory of Evolution
• Lemaître’s Big Bang Theory of the Universe
Hypothesis-based Science
• Hypothesis-based science involves:
• Observations, questions, hypotheses as
tentative answers to questions
• Deductions leading to predictions, and
then tests of predictions to see if a
hypothesis is falsifiable
What is a hypothesis?
• A hypothesis is a tentative or educated guess at
an answer to a problem or question that is being
• A good hypothesis makes predictions that can
be tested.
• Part of the process of hypothesis-based science
uses deductive reasoning, which flows from a
general premise to a specific premise.
• The important aspect of this process is that the
deduction can be tested.
Hypothesis-based Science
• A Case Study from Every day Life
• Deductive reasoning is used in testing hypotheses as follows
Hypothesis # 1:
Dead batteries
Hypothesis # 2:
Burnt-out bulb
Replacing batteries
will fix problem
Replacing bulb
will fix problem
Test prediction
Test falsifies hypothesis
Test prediction
Test does not falsify hypothesis
Hypothesis-based Science
Two important qualities of the
hypothesis-based science illustrated in
the flashlight example
A hypothesis must be testable.
A hypothesis must be falsifiable
If a hypothesis is correct, and we test it,
then we can expect a particular outcome
Key Steps in the Scientific Method
• Make observations, may come from others or results of
earlier tests
• Ask questions about aspects of the observations: How?
Why? When?
• Generate hypotheses; explanations of the phenomena,
phrased in such a way as to be testable.
• Derive predictions; logical, testable outcomes of the
• Developed by the use of deductive reasoning
• Predictions take the form of if (statement of hypothesis) is true,
then (predictions).
• Test the predictions; performed to determine if the
predictions are supported (fail to falsify) or falsified
• A hypothesis becomes credible when repeated attempts
to disprove it fail
In Science and Medicine, We use
the Metric System!
Base Units
Unit of length: meter
Unit of mass: kilogram
Unit of volume: liter
Unit of temperture: degree Celsius
SI Base Units of Measurement
• Mass = gram = g
• 1 gram ≈ 1/28 ounce
• Length = meter = m
• 1 meter ≈ 1.094 yard
• Volume = liter = l
• defined as 1000 cubic centimeters
• 1 liter ≈ 1.057 quart
• Temperature = degrees Celsius; oC
• The metric system uses prefixes to
represent units
• smaller and larger than the
fundamental unit by factors of 10.
• For example, a centimeter is 1/100 of a
meter, and a kilometer is 1000 times a
• For very large numbers, we use the
powers-of-ten notation, e.g. 102 = 100,
106 = 1,000,000, 10-2 = 0.01
• One of the clever ideas behind the system was to use only
multiples of ten.
Converting Between Metric Units
• To convert from a LARGER unit of measure to a
SMALLER unit of measure, MULTIPLY by the
“order-of-magnitude difference” between the units.
• Example: 1.2 mg = ______ g
• 1 mg = 1000 g
• 1.2 mg = 1.2 x 1000 g = 1200 g
• Remember to check if your answer is logical.
• It should take a GREATER NUMBER of SMALL
• A microgram is smaller than a milligram (by a
factor of 1000), so a given number of
milligrams should be equal to many more
micrograms (1000 times as many).
Converting Between Metric Units
• To convert from a SMALLER unit of measure to a
LARGER unit of measure, DIVIDE by the “order-ofmagnitude difference” between the units.
• Example: 250 ml = ______ l
• 1 l = 1000 ml
• 250 ml = 250 ÷ 1000 l = 0.25 l
• Is your answer is logical?
• It should take a LESSER NUMBER of LARGE
UNITS to equate to a GREATER NUMBER of
• A liter is larger than a milliliter (by a factor of 1000), so
a given number of milliliters should be equal to fewer
liters (1/1000 as many).
Thinking in Metric Units of
1 kilometer = ~0.62 or ~5/8 mi
1 meter = 1.09 yard = 39.4 in
1 centimeter = ~4/10 inch
1 angstrom = 1/10 nm or 10-10m
1 mile = ~1.6 km
1 yard = ~0.91 m
1 foot ~30.5 cm
1 inch = ~2.54 cm
Thinking in Metric Units of Volume
• 1 liter = ~1.06 quart
• 1 milliliter = 1 cubic cm (1cc)
~"a thimble full"
• Examples
1 teaspoon ≈ 5ml
12 oz. soda ≈ 360 ml
2-liter bottle of soda
1 gallon = ~3.8 l
1 quart = ~0.95 l
1 pint = ~0.47 l
1 cup = ~240 ml
1 fluid oz. ~30 ml
2 liters~1/2 gal.
Thinking in Metric Units of Mass
• 1 kilogram = 2.2 pounds
• 1 gram = ~"a thimble
full" of water
• Examples
• 70 kg human = 154 lbs.
• 1 ml of water weighs ~1 g
• 1 pound = 454 g
• 1 ounce = ~28 g
• The length of:
• your bare foot
• your driveway
• The volume of:
• a coffee cup
• a bottle of shampoo
• The mass of:
• a steak
• a dog
Celsius: The Metric Temperature Scale
• Also called the centigrade scale.
• Definitions
• 0 Celsius = 32 Fahrenheit = water
• 100 Celsius = 212 Fahrenheit = water
• Therefore, 1C = 1.8F
• Conversions
•  Celsius = 5/9 x ( Fahrenheit - 32)
•  Fahrenheit = (9/5 x  Celsius) + 32
Thinking in Celsius
-10 Celsius = frigid (14 F)
0 Celsius = cold (32 F)
10 Celsius = cool (50 F)
20 Celsius = comfortably warm (68 F)
30 Celsius = hot (86 F)
40 Celsius = very hot (104 F)
What would you wear outside in tempsf:
10C, 0C, 10C, 20C, 30C?