Biology 1
Chapter 1
• An Introduction to Life on Earth
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Chapter 1 Outline
• 1.1 How Do Scientists Study Life? p. 2
• 1.2 Evolution: The Unifying Theory of Biology,
p. 9
• 1.3 What Are the Characteristics of Living
Things? p. 10
• 1.4 How Do Scientists Categorize the Diversity
of Life? p. 14
• 1.5 How Does Knowledge of Biology Illuminate
Everyday Life? p. 15
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How Do Scientists Study Life?
Life Can Be Studied at Different Levels of
Organization
1. The living and nonliving world is
hierarchically organized at many levels:
• All matter is formed of elements
• An atom is the smallest particle of an
element retaining the properties of an
element
• Atoms combine to form molecules
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Characteristics of Living
Things:
• Molecules provide the building blocks
for cells, the smallest unit of life
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The smallest unit of life is the:
• CELL
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Levels of Organization
• Some forms of life
consist of single
cells
• In multicellular
forms cells combine
to form tissues
• Tissues combine to
form organs, which
can be united as
organ systems
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Levels of Organization
• Multicellular
organisms are
composed of
multiple organ
systems
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Levels of Organization
• Organisms of the
same type that are
capable of
interbreeding are
called a species
• A group of organisms
of the same species
living in a given area
is a population
• Interacting populations
make up a
community
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Levels of Organization
• A community and its nonliving
environment is an ecosystem
• The entire surface of the Earth, including
living and nonliving components is the
biosphere
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Levels of Organization
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Atom  molecule
Molecules  organelle
Organelles  cell
Cells  tissue
Tissues  organ
Organs  organ system
Organ systems  organism
Organisms  population
Populations  species
Group species  community
Communities  ecosystem
Ecosystems  Biosphere
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Scientific Principles
• Biology is a scientific discipline
• All scientific inquiry is based on a small
set of assumptions or principles
– Natural causality
– Uniformity in space and time
– Similar perception
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Natural Causality
• Historical approaches to studying life
1. Belief that some events happen through
supernatural forces (e.g. the actions of Greek
gods)
2. Belief that all events can be traced to natural
causes that we can comprehend (natural
causality)
• Corollary: Evidence gathered from nature has not
been deliberately distorted to fool us
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Natural Laws Apply
Everywhere
• Natural laws are uniform in space and
time
• This principle is key understanding
biological events (e.g. evolution) that
occurred before humans recorded them
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Natural Laws Apply
Everywhere
• Creationism is contrary to the principle of
uniformity-in-time and natural causality
– Creationists hold that different species were
created one at a time by the direct intervention
of a supernatural being, contrary to events we
see happening today
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Similar Perceptions
• Assumption that all human beings
perceive natural events in fundamentally
the same way
• Common perception allows us to accept
observations of other humans as reliable
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Similar Perceptions
• Common perception is
usually not found in
appreciation of art,
poetry, and music, nor
between cultures or
religious beliefs
– Value systems are
subjective
– Science requires
objectively gathered data
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The Scientific Method
• Scientific inquiry is a rigorous method for
making observations
• The Scientific Method for inquiry follows
4 steps…
• (= LAB REPORTS!)
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OBSERVATION
HYPOTHESIS
EXPERIMENTS
CONCLUSION
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Examples of Lab Reports
(TYPED!)
• ..\..\..\final projects\Human
Survivorship1.ppt
• ..\..\..\final projects\HUMAN
GENOME.ppt
• ..\..\..\final projects\Biology (final
copy).ppt
• ..\..\..\final projects\Photosynthesis
powerpoint.ppt
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The Scientific Method
1. Observation of a
phenomenon
– Subsequent development
of questions
2. Formulation of a
hypothesis
– A supposition that
explains an observed
phenomenon, leading to
testable predictions
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The Scientific Method
3. Testing through
experimentation
– Additional
controlled
observations
4. Development of a
conclusion
– Evaluation of
hypothesis in light
of experimental
data
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The Scientific Method
• Scientific experimentation tests the
assertion that a single variable causes a
particular observation (experimental
variable)
• The experiment must rule out the
influence of other possible variables on
the recorded observations (controlled
variables)
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The Scientific Method
• Controls are incorporated into
experiments
• Controls keep untested variables constant
• Scientific method is illustrated by
Francesco Redi’s experiment
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Flies swarm around meat left in the open;
maggots appear on meat.
Flies produce the maggots; keeping flies away
from meat will prevent the appearance of maggots.
Obtain identical pieces of
meat and two identical jars.
Place meat
in each jar.
Leave jar
uncovered.
Experimental variable: Cover jar
gauze prevents
with gauze.
entry of flies
Leave exposed Controlled variables: Leave covered
for several days. time, temperature, for several days.
place
Flies swarm around
and maggots appear.
Control situation
Results
Flies kept from meat;
no maggots appear.
Experimental situation
Spontaneous generation of maggots
from meat does not occur; flies are
probably the source of maggots.
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Application to Everyday
Problems
• Assume you are late for an appointment
and hurriedly try to start your car
1. Observation: The car won’t start
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Application to Everyday
Problems
2. Hypothesis: the battery is dead
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Application to Everyday
Problems
3. Experimental design: Replace your
battery with another and restart the car
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Application to Everyday
Problems
4. Premature conclusion:
• The problem was a dead battery because
the car starts when replaced with a
different one
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Application to Everyday
Problems
5. Recognition of inadequate controls
• Did you attempt to start the car more than
once?
• Was the battery cable on my original
battery loose?
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Application to Everyday
Problems
6. Establishing a control
a. Reinstall your old battery, check for tight
cables, now try to start the car
b. If car still fails to start on old battery, the
only variable in this investigation now is
the effectiveness of the battery
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Application to Everyday
Problems
7. Making a better conclusion, based on
controlled experiments
• Your battery was probably dead
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Limitations of the Scientific
Method
• Can never be sure all untested variables
are controlled
• Conclusions based on the experimental
data must remain tentative
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Limitations of the Scientific
Method
• Results of experimentation must be
communicated thoroughly and accurately
to other scientists for repetition
• Repetition by other scientists add
verification that findings can be used as
the basis for further studies
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Science Is a Human
Endeavor
• Human personality traits are part of “real
science”
• Scientists, like other people may be driven
by pride, ambition, or fear
• Scientists sometimes make mistakes
• Accidents, lucky guesses, intellectual
powers, and controversies with others
contribute strongly to scientific advances
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Science Is a Human
Endeavor
1.In the 1920s, bacteriologist Alexander
Fleming grew bacteria in cultures
2.One of the bacterial cultures became
contaminated with a mold
3.Fleming nearly destroyed the culture
when he noticed the mold (Penicillium)
inhibited bacterial growth in the culture
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Science is a Human
Endeavor
4. Fleming hypothesized that the mold
produced an antibacterial substance
5. Further tests using broth from pure
Penicillium cultures lead to the discovery
of the first antibiotic, penicillin
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Science is a Human
Endeavor
6. Fleming continued beyond a lucky
“accident” with further scientific
investigation to a great discovery
7. “Chance favors the prepared mind”
(Louis Pasteur)
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Scientific Theory
• A scientific theory differs in definition
from that of everyday usage
– Many people use the word theory to mean
hypothesis, and “educated guess”
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Scientific Theory
• A scientific theory is a general explanation
for important natural phenomena
– It is extensively and reproducibly tested
– It is more like a principle or natural law (e.g.
the atomic, gravitational, and cell theories)
– If compelling evidence arises, a theory may be
modified
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Scientific Theory
• New scientific evidence may prompt
radical revision of existing theory
• Example: the discovery of prions…
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Scientific Theory
• Before 1980, all known infectious
diseases contained DNA or RNA
• In 1982, Stanley Prusiner showed that the
infectious sheep disease scrapie is
caused by a protein (a “protein infectious
particle” or prion)
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Scientific Theory
• Prions have since been shown to cause
“mad cow disease” and diseases in
humans
• The willingness of scientists to revise
accepted belief in light of new data was
critical to understanding and expanding
the study of prions
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Science Is Based on
Reasoning
• Inductive Reasoning
– Used in the development of scientific theories
– A generalization is created from many
observations
– e.g., the cell theory (all living things are made
of one or more cells) arises from many
observations that all indicate a cellular basis
for life
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Science Is Based on
Reasoning
• Deductive Reasoning
– Generating hypotheses based on a wellsupported generalization (such as a theory)
– e.g., based on the cell theory, any newly
discovered organism would be expected to be
composed of cells
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Section 1.2 Outline
• 1.2 Evolution: The Unifying Theory of
Biology
– Three natural processes underlie evolution
– Much of organism variability is inherited
– Natural selection preserves survival and
reproductive genes
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Unifying Theory of Biology
• Abundant evidence has been found to
support evolutionary theory since Darwin
and Wallace proposed it in the mid-1800s
• Those who see evolution as “just a theory”
don’t understand the scientific definition of a
theory
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Unifying Theory of Biology
• Evolution explains how diverse forms of life
originated through changes in their genetic
makeup
– Modern organisms descended with modification
from pre-existing life forms
– “Nothing in biology makes sense, except in the
light of evolution” (Theodosius Dobzhansky)
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Three Natural Processes Underlie
Evolution
• Charles Darwin and Alfred Russel Wallace
formulated the basis of our modern
understanding of evolution
• Evolution arises as a consequence of three
natural processes…
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Three Natural Processes Underlie
Evolution
1.Genetic variation among members of a
population
2.Inheritance of those variations by
offspring of parents carrying the variation
3.Natural selection of individuals whose
survival and enhanced reproduction are
due to the favorable variations they carry
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Genetic Variability
• Genetic variation arises from
segments of DNA (genes)
• Changes in genes (mutation)
alter the informational content
• Mutations arise from a
number of sources
– Mutations can occur from
irradiation
– Mutations occasionally arise
from copying mistakes in DNA
during cellular reproduction
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Genetic Variability
• Effects of mutation
– No effect (harmless)
– A decrease in organism’s ability to function
– Death of the organism
– An increase in an organism’s ability to survive
and reproduce (rare)
• Mutations occurring over millions of years
and passed through many generations
cause members of a species to be slightly
different
Copyright
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Natural Selection
• Organisms that best meet environmental
challenges leave the most offspring
• Natural selection preserves genes that
help organisms flourish
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Natural Selection
• Adaptations are structures, physiological
process, or behaviors that aid in survival
and reproduction
• Adaptations that are good for one
environment may be poor in another
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Natural Selection
• Species that cannot adapt to
environmental change go extinct (e.g. the
dinosaurs, illustrated by the Triceratops
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Natural Selection
• The many different habitats
(environments) in an area coupled with
evolutionary adaptive processes produce
species variety or biodiversity
• Humans are responsible for accelerating
the rate of environmental change (and
therefore the rate of extinction of species)
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Section 1.3 Outline
• 1.3 What Are the Characteristics of
Living Things?
– Living Things Are Both Complex, Organized,
and Composed of Cells
– Living Things Respond to Stimuli
– Living Things Maintain Relatively Constant
Internal Conditions Through Homeostasis
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Characteristics of Living
Things:
• 1. Living Things Are Complex,
Organized, and Composed of Cells
• Table salt  ocean wave  water flea
(Daphnia longispina)
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The smallest unit of life is the:
• CELL
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Characteristics of Living
Things:
Living Things Maintain Relatively Constant
Internal Conditions 
homeostasis
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Characteristics of Living
Things:
• Organisms sense and respond to internal
and external environmental stimuli
Excitability
– Sensory organs in animals can detect and
respond to external stimuli like light, sound,
chemicals, etc.
– Internal stimuli in animals are perceived by
stretch, temperature, pain, and chemical receptors
– Plants and bacteria respond to stimuli as well (e.g.
plants to light, bacteria to available nutrients in the
medium)
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Characteristics of Living
Things:
Living Things Acquire and Use Material and Energy;
its sum in a cell is called 
METABOLISM
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Characteristics of Living
Things:
• Increase in size 
GROWTH
• Add continuity to live
of a species through
REPRODUCTION
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Characteristics of Living
Things:
• Living things, Collectively, have the
Capacity to change over many
generations; 
EVOLUTION
– The most important force in evolution is
NATURAL SELECTION
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1.4. Diversity of Life
• There are 3 domains of life
– Archae (prokaryotes)
– Bacteria (prokaryote)
– Eukarya (eukaryote)
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Diversity of Life
• Domain Eukarya is divided into 4
kingdoms:
– Protista
– Fungi
– Plantae
– Animalia
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(a) The domain Bacteria
(b) The domain Archaea
cell wall
plasma
membrane
genetic
material
(DNA)
1 micrometer
A color-enhanced electron micrograph of a dividing
bacterium. Bacteria are unicellular and prokaryotic;
most are surrounded by a thick cell wall. Some bacteria
photosynthesize, but most absorb food from their
surroundings.
(c) A protist (domain Eukarya)
oral groove (“mouth”)
Food
vacuoles
contractile
vacuole
A color-enhanced electron micrograph of an archaean. The
cell wall appears red, and DNA is scattered inside. Many
archaeans can survive extreme conditions. This Antarctic
species lives at temperatures as low as –2.5°C.
(d) The kingdom Fungi (domain Eukarya)
10 micrometers
This light micrograph of a Paramecium illustrates the
complexity of these large, normally single, eukaryotic
cells. Some protists photosynthesize, but others ingest
or absorb their food. Many, including, Paramecium are
mobile, moving with cilia or flagella.
(e) The kingdom Plantae (domain Eukarya)
An exotic mushroom found in Peru. Most fungi are
multicellular. Fungi generally absorb their food, which is
usually the dead bodies or wastes of plants and animals. The
food is digested by enzymes secreted outside the fungal
body. Most fungi cannot move.
(f) The kingdom Animalia (domain Eukarya)
This butterfly weed represents the flowering plants, the
dominant members of the kingdom Plantae. Flowering
plants owe much of their success to mutually beneficial
relationships with animals, such as these pearl crescent
butterflies, in which the flower provides food and the
insect carries pollen from flower to flower, fertilizing
them. Plants are multicellular, nonmotile eukaryotes that
acquire nutrients by photosynthesis.
A wrasse rests on a soft coral. Animals are multicellular;
animal bodies consist of a wide assortment of tissues and
organs composed of specialized cell types. Most animals can
move and respond rapidly to stimuli. The coral is a member
of the largest group of animals: the invertebrates, which lack
a backbone. This group also includes insects and mollusks.
The wrasse is a vertebrate; like humans, it has a backbone.
So What?
• Financial level: Job explosion
• Personal level:
– Daily interaction improves with
knowledge.
• Complex adaptations help
ensure pollination
– Respect, open mindedness, more
accurate perspective of things
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Lake Belton