Chapter 1
Biology is the scientific study of life
Exploring Life
• Life is investigated from the microscopic
(microbiology) to the global scale (global warming)
• Biological organization is based on a hierarchy of
structural levels
A Hierarchy (levels) of Biological
Organization
 Biosphere: all environments on Earth (the part of the
earth, including air, land, surface rocks, and water,
within which life occurs, and which biotic processes in
turn alter or transform their envirnment).
 Ecosystem: all living and nonliving things
in a particular area.
 Community: all organisms in an ecosystem
 Population: all individuals of a species
in a particular area.
 Organism: an individual living thing.
A Hierarchy of Biological Organization
(continued)
 Organ and organ systems: specialized body parts
made up of tissues.
 Tissue: a group of similar cells.
 Cell: life’s fundamental unit of structure and function.
 Organelle: a structural component of a cell.

Molecule: a chemical structure consisting of atoms.
The biosphere
Ecosystems
Organelles
1 µm
Cell
Cells
Atoms
10 µm
Communities
Molecules
Tissues
50 µm
Populations
Organs and organ systems
Organisms
Life, a lot going on
Ecosystem Dynamics
 Each organism interacts with its environment
 Both organism and environment affect each
other
 The dynamics of an ecosystem include two
major processes:
 Cycling of nutrients, in which materials
acquired by plants eventually return to the soil
 The flow of energy from sunlight to producers
to consumers
Energy Conversion
 Activities of life require work.
 Work depends on sources of energy.
 Energy exchange between an organism and environment
often involves energy transformations.
 In transformations, some energy is lost as heat.
 Energy flows through an ecosystem, usually entering as
light and exiting as heat.
LE 1-4
Sunlight
Ecosystem
Producers
(plants and other
photosynthetic
organisms)
Heat
Chemical
energy
Consumers
(including animals)
Heat
A Closer Look at Cells
The cell is the lowest level of organization
that can perform all activities of life
The ability of cells to divide is the basis of all
reproduction, growth, and repair of
multicellular organisms
Cells contain DNA, the heritable information that directs the cell’s activities
DNA is the substance of genes. Genes are the units of inheritance that transmit
25
information from parents to offspring
µm
Sperm cell
Nuclei
containing
DNA
Egg cell
Fertilized egg
with DNA from
both parents
Embryo’s cells
With copies of
inherited DNA
Offspring with traits
inherited from both parents
Nucleus
DNA
Nucleotide
Cell
DNA double helix
Single strand of DNA
Eukaryotic and Prokaryotic Cells
 Characteristics shared by all cells:
 Enclosed by a membrane
 Use DNA as genetic information
 Two main forms of cells:
 Eukaryotic: divided into organelles; DNA in
nucleus
 Prokaryotic: lack organelles; DNA not separated
in a nucleus
EUKARYOTIC CELL
PROKARYOTIC CELL
DNA
(no nucleus)
Membrane
Membrane
Cytoplasm
Organelles
Nucleus (contains DNA)
1 µm
Taxonomy (naming species)
 Biologists explore life across a great diversity of
species (1.8 million named)
 Estimates of total species range from 10 million to
over 200 million
 Taxonomy is the branch of biology that names and
classifies species into a hierarchical order
 Kingdoms and domains are the broadest units of
classification
Species Genus Family
Order
Class Phylum Kingdom Domain
Ursus
americanus
(American
black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
The Three Domains of Life
Bacteria (Most of the Known Prokaryotes )
Archaea (Prokaryotes of Extreme Environments )
Eukarya (eukaryotes)
 Eukaryotes include protists and the kingdoms
Plantae, Fungi, and Animalia
LE 1-15
Bacteria
Archaea
4 µm
0.5 µm
Protists
Kingdom Fungi
100 µm
Kingdom Plantae
Kingdom Animalia
How did we get where we are?
Evolution accounts for life’s unity and
diversity
The history of life is a continuing saga of a
changing Earth billions of years old
Evolution
The evolutionary view of life came into sharp
focus in 1859, when Charles Darwin
published On the Origin of Species by
Natural Selection
“Darwinism” became almost synonymous
with the concept of evolution
Gregor Johann Mendel 1822 - 1884
The Origin of Species articulated two main
points:
 Descent with modification (the view that
contemporary species arose from a
succession of ancestors)
 Natural selection (a proposed mechanism
for descent with modification)
Some examples of descent with modification
are unity and diversity in the orchid family
Natural Selection
 Darwin inferred natural selection by connecting
two observations:
 Observation: Individual variation in heritable
traits
 Observation: Overpopulation and competition
 Inference: Unequal reproductive success
 Inference: Evolutionary adaptation
Natural Selection (continued)
 Natural selection can “edit” a population’s
heritable variations
 An example is the effect of birds preying on a
beetle population
Population with varied inherited traits
Elimination of individuals with certain traits
Reproduction of survivors
Increasing frequency of traits that enhance
survival and reproductive success
The Tree of Life
 Many related organisms have similar features
adapted for specific ways of life.
 Such kinships connect life’s unity and diversity
to descent with modification.
 Natural selection eventually produces new
species from ancestral species.
 Biologists often show evolutionary relationships
in a treelike diagram.
Large
ground finch
Large cactus
ground finch
Geospiza
magnirostris
Sharp-beaked
ground finch Geospiza
conirostris
Large
tree finch
Small
ground
finch
Geospiza
fuliginosa
Medium
ground
finch
Camarhynchus
psittacula
Woodpecker
finch
Geospiza
difficilis Cactus
ground finch
Mangrove
finch
Geospiza
fortis
Geospiza
scandens
Seed eater
Cactospiza
pallida
Medium
tree finch
Camarhynchus
pauper
Small
tree finch
Gray
warbler
finch
Certhidea
olivacea
Certhidea
fusca
Camarhynchus
parvulus
Cactospiza
heliobates
Cactus flower
eaters
Green
warbler
finch
Vegetarian
finch
Seed eaters
Platyspiza
crassirostris
Insect eaters
Ground finches
Tree finches
Bud eater
Warbler finches
Common ancestor from
South American mainland
Biologists use various forms of inquiry to
explore life.
Inquiry is a search for information and
explanation, often focusing on specific
questions.
The process of science blends two main
processes of scientific inquiry:
 Discovery science (natural history):
describing nature
 Hypothesis-based science: explaining
nature
Discovery Science (natural
history)
 Discovery science describes nature through
careful observation and data analysis
 Examples of discovery science:
 understanding cell structure
 expanding databases of genomes
Types of Data
 Data are recorded observations
 Two types of data:
 Quantitative data: numerical measurements
 Qualitative data: recorded descriptions
Induction in Discovery Science
 Inductive reasoning involves generalizing based
on many specific observations
 The premises of an argument are believed to
support the conclusion but do not ensure it.
• The stove top is hot: all stove tops are hot
• A bird flies: all birds fly
Deduction: If the premises are true then the
conclusion must be true
Hypothesis-Based Science
In science, inquiry usually involves
proposing and testing hypotheses.
Hypotheses are hypothetical explanations.
In science, a hypothesis is a tentative
answer to a well-framed question.
A hypothesis is an explanation on trial,
making a prediction that can be tested.
Observation: Flashlight does not work
Observations
Question
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test prediction
Test prediction
Test falsifies hypothesis
Test does not falsify hypothesis
Deduction: The “If…then”
Deductive reasoning, the logic flows from
the general to the specific; thus, If a
hypothesis is correct, then we can expect
a particular outcome.
A scientific hypothesis must have two
important qualities:
 It must be testable
 It must be falsifiable
The Myth of the Scientific
Method
The scientific method is an idealized
process of inquiry
Very few scientific inquiries adhere rigidly
to the “textbook” scientific method –
probably more true in biology than physics
or chemistry.
A Case Study in Scientific Inquiry:
Investigating Mimicry in Snake
Populations
In mimicry, a harmless species resembles a
harmful species
An example of mimicry is a stinging
honeybee and a nonstinging mimic, a flower
fly
LE 1-26
Flower fly (nonstinging)
Honeybee (stinging)
This case study examines king snakes’
mimicry of poisonous coral snakes
The hypothesis states that mimics benefit
when predators mistake them for harmful
species
The mimicry hypothesis predicts that
predators in non–coral snake areas will
attack king snakes more frequently than will
predators that live where coral snakes are
present
LE 1-27
Scarlet king snake
Key
Range of scarlet
king snake
Range of eastern
coral snake
North
Carolina
Eastern coral
snake
South
Carolina
Scarlet king snake
Field Experiments with Artificial
Snakes
Artificial snakes:
 An experimental group resembling king
snakes
 A control group resembling plain brown
snakes
LE 1-28
(a) Artificial king snake
(b) Artificial brown snake that has been attacked
Field Experiments with Artificial
Snakes (continued)
Equal numbers of both types were placed
at field sites, including areas without coral
snakes
After four weeks the artificial snakes were
retrieved and bite/claw marks recordered
The data fit the predictions of the mimicry
hypothesis
LE 1-29
17%
In areas where coral snakes
were absent, most attacks
were on artificial king snakes.
83%
Key
North
Carolina
% of attacks on
artificial king snakes
% of attacks on
brown artificial snakes
Field site with
artificial snakes
South
Carolina
16%
84%
In areas where coral
snakes were present,
most attacks were on
brown artificial snakes.
• QUESTION: How will the amount of fertilizer used affect plant
growth?
• HYPOTHESIS: Increased dosages of fertilized will cause greater
growth in tomato plants.
• TEST VARIABLE: The amount of fertilizer used.
• TEST CONSTANTS:
• The seeds must all come from the same package.
• All seeds must be planted in the same sized pots with similar soil.
• All plants must receive exactly the same amount of water and light.
• The temperature should be the same for all test plants.
• More than one plant should be used in each test group (in case one
type of seed grows better at this time of year than another).
• More than one seed should be placed in each container (in case one
seed is damaged).
• Set one group as the CONTROL GROUP. This group is not given
fertilizer.
• Set up two other test groups. Once receives a certain amount of
fertilizer and the other receives twice as much.