UNIT 1: Science, Chemistry, and Cells
Chapter 1
The Scientific
Study of Life
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Biology is the scientific study of life
Life is everywhere, but it can be difficult to
define.
Biologists study all forms of life.
Each living individual is an organism.
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All organisms are made of cells
Cells are the basic units of life.
Every organism consists of one or more cells.
• Simple single-celled organisms are unicellular.
• More complex organisms are multicellular.
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left image: ©Melba/age fotostock; right image: ©Jeff Gynane/Getty Images RF
All organisms have DNA
DNA is the molecule that
carries genetic information.
It is what is passed on to the
next generation.
All cells use DNA to produce
proteins, which carry out the
work that cells do.
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©SMC Images/The Image Bank/Getty Images
Life is defined by its characteristics
How do we know the trees are alive and the
rocks are not alive?
All forms of life share a common set of
characteristics.
If something possesses all of the characteristics,
it is considered alive.
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What are the characteristics of life? (1)
Organization
Energy
Internal constancy
Reproduction, growth, and
development
Evolution
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©SMC Images/The Image Bank/Getty Images
The characteristics of life:
Life is organized
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Photos: (population): ©Gregory G. Dimijian, M.D./Science Source; (community): ©Daryl Balfour/Gallo Images/Getty Images; (ecosystem): ©Bas Vermolen/Getty Images; (biosphere): ©StockTrek/Getty Images
Life is organized
Tissues are organized into organs
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Life is organized
Organs are organized into organ systems
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Life is organized
Life is organized into individual organisms
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Life is organized
Individual organisms are organized into populations
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Life is organized
Populations are organized into communities
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Life is organized
Communities are organized into ecosystems
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Life is organized
Ecosystems are organized into a biosphere
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Organization leads to emergent
properties
Emergent properties arise
at each level of biological
organization.
The components interact,
and the whole is greater
than the sum of the parts.
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All organisms obtain energy
Energy is needed for:
• Keeping organized.
• Carrying out chemical reactions.
• Transporting molecules inside and among cells.
• Maintaining internal constancy.
• Reproducing, growing, and developing.
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All organisms obtain energy—Producers
Producers
include
plants, some
protists, and
many
prokaryotes.
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All organisms obtain energy—Consumers
Consumers
are generally
animals;
some are
protists and
others are
prokaryotes.
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All organisms obtain energy—Decomposers
Decomposers include fungi,
some animals, some
protists, many prokaryotes.
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All organisms maintain internal
constancy
Homeostasis is the process by which a cell or
organism maintains internal constancy.
Humans have an internal
thermostat that helps
maintain temperature
homeostasis.
This woman shivers when
she feels cold and puts on
a jacket.
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(a): ©Design Pics/Kristy-Anne Glubish RF; (b): ©John Rowley/Getty Images RF
Homeostasis is the optimal balance
Homeostasis involves many aspects of internal
constancy.
For example, organisms also fluctuate around
their optimal balance of nutrients, sugar, salt,
and water.
This means they must be able to sense and
respond to stimuli in their environment.
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Organisms reproduce, grow & develop:
Reproduction can be asexual
In asexual reproduction only one parent is involved,
and the offspring are genetically identical to the parent.
Asexual reproduction is a successful strategy in
unchanging environments.
Strawberry plants sometimes
reproduce asexually. Each of
these plantlets is identical to
the parent plant.
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©Dorling Kindersley/Getty Images
Organisms reproduce, grow & develop:
Reproduction can be sexual
In sexual reproduction two parents are involved, and
the offspring are genetically different from the parent.
Sexual reproduction is a successful strategy in changing
environments since offspring are unlike either parent.
Most plants and animals
reproduce sexually.
These young swans
received genetic material
from two parents.
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©Jadranko Markoc/flickr/Getty Images RF
All organisms evolve
EVOLUTION is genetic change over time in a
population
The genes in this population of bacteria have changed over time. A
new gene, conferring antibiotic resistance, appears in the red bacteria.
There are more bacteria with this new gene when antibiotics are
present.
Long description on Slide 37.
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All organisms evolve
Different organisms have different genes
How is it that so many
organisms seem perfectly
suited to their environment?
This pigmy seahorse blends
into the coral habitat where it
lives, because of its genes.
Other seahorses, with different
genes, do not blend in as well.
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©Mark Webster Wwwphoteccouk/Getty Images
All organisms evolve
Some organisms survive and reproduce
How is it that so many
organisms seem perfectly
suited to their environment?
This pigmy seahorse is well
hidden from predators.
It survives, reproduces, and
passes along its genes.
The offspring have genes that
allow them to blend into the
environment.
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©Mark Webster Wwwphoteccouk/Getty Images
All organisms evolve
Example: antibiotic resistance in bacteria
Bacteria reproduce and
evolve quickly.
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©Mark Webster Wwwphoteccouk/Getty Images
All organisms evolve
Beneficial adaptations develop at random
This population has
genetic variation.
Some cells have a different
gene than other cells, making
them resistant to the effects of
antibiotics.
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©Mark Webster Wwwphoteccouk/Getty Images
All organisms evolve
The environment “selects” beneficial adaptations
Antibiotics kill off most of the
bacteria. The resistant bacteria
survive (red cells).
Antibiotic-resistant bacteria are
most successful when antibiotics are
present.
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©Mark Webster Wwwphoteccouk/Getty Images
Scientists use taxonomy to name and
classify organisms
Organisms are
grouped by their
features,
including
structure,
chemistry, and
the sequence of
their DNA.
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Taxonomy reveals evolutionary
relationships
Classifying
organisms helps
show how closely
related they are
to each other.
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All organisms share common
ancestors
Humans are more
closely related to a
kangaroo than to a
platypus because we
share a more recent
common ancestor with
the kangaroo.
Long description on Slide 48
and 49.
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There are 8 levels of taxonomic
hierarchy
All living organisms are
organized into these
eight levels.
The most inclusive is
domain, and the least
inclusive is species.
Each species has an
exclusive two-part
species name.
Long description on Slide 51.
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The tree of life includes three main
branches
Species are
broadly
categorized into
one of three
domains.
Long description on Slide 53.
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Domains are divided into kingdoms
All 3 domains
include one or
more kingdoms
that represent
thousands to
millions of
different species.
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Life’s three domains:
Bacteria and Archaea
Domain Bacteria and domain Archaea
are prokaryotic and unicellular.
Prokaryotic means their cells lack nuclei
and other compartments.
DOMAIN BACTERIA
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DOMAIN ARCHAEA
(Bacteria): ©Heather Davies/SPL/Getty Images RF; (Archaea): ©Eye of Science/Science Source
Life’s three domains:
Eukarya, kingdom Protista
Protists are the most diverse group of
Eukaryotes.
Protista (multiple kingdoms)
• Unicellular or multicellular
• Autotrophs or heterotrophs
Organisms in domain
Eukarya have larger,
more complex cells
with nuclei.
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©Melba/age fotostock
Life’s three domains:
Eukarya, kingdom Animalia
Animals are a familiar group of
Eukaryotes, including vertebrates such
as fish, frogs, and humans.
Kingdom Animalia
• Multicellular
• Heterotrophs (by ingestion)
Organisms in domain
Eukarya have larger,
more complex cells
with nuclei.
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USDA/ARS/Scott Bauer
Life’s three domains:
Eukarya, kingdom Fungi
Fungi are nature’s decomposers.
Kingdom Fungi
• Most are multicellular
• Heterotrophs (by external digestion)
Organisms in domain
Eukarya have larger,
more complex cells
with nuclei.
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©Corbis RF
Life’s three domains:
Eukarya, kingdom Plantae
Plants are producers that capture light
energy from the sun.
Kingdom Plantae
• Multicellular
• Autotrophs
Organisms in domain
Eukarya have larger,
more complex cells
with nuclei.
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USDA/Keith Weller
Scientists use the scientific method
In general, all scientific inquiry follows a
standard process to study the natural world.
The process is known as the scientific method.
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The scientific method has multiple
interrelated parts
Long description on Slide 65.
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The scientific method has multiple
interrelated parts
Long Description
The cycle of the scientific method starts with
observations, for example, a baby is sick. The step is
followed by asking a question, consulting prior
knowledge, forming a hypothesis, and making
predictions. All of this allows scientists to design an
experiment, collect and interpret the data, and consult
prior knowledge again before forming a conclusion.
Peer review and publishing can occur at this point, and
then the cycle repeats.
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An experimental design is a careful
plan
Well-designed experiments include
• Sample size: number of subjects in a
group
• Independent variable: what is
manipulated
• Dependent variable: what is
measured
• Standardized variable: held constant
for all subjects
• Control: untreated group used for
comparison
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©Corbis/age fotostock RF
An experimental design includes clear
variables
Independent variable: A variable that an investigator
manipulates to determine whether it influences the dependent
variable (Example: Dose of vaccine)
Dependent variable: A variable that an investigator measures to
determine whether it is affected by the independent variable
(Example: Number of children with illness caused by rotavirus)
Standardized variable: Any variable that an investigator
intentionally holds constant for all subjects in an experiment,
including the control group (Example: Age and health of children
in study)
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An experimental design includes clear
controls
Control: Basis for comparison to treatment group(s);
control subjects may remain untreated or receive a
placebo (Example: Placebo lacking active ingredient in
vaccine)
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Data are interpreted using statistical
analysis
Analyses test the
data for statistical
significance: the
probability that the
results arose purely
by chance.
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©Corbis/age fotostock RF
Theories are comprehensive
explanations
Scientific theories differ from the use of
“theory” outside of science.
Scientific theories include:
• Germ theory
• Theory of evolution
• Gravitational theory
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Theories are potentially falsifiable
In science, a theory is an explanation for a
natural phenomenon and broader in scope than
hypotheses.
Scientific theories are supported by a
tremendous amount of research.
(Facts are repeatable observations that
everyone agrees on.)
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Scientific inquiry has limitations
Limitations to scientific inquiry include:
• Multiple interpretations
• Misinterpretations of observations or results
• Slow acceptance of unexpected conclusions
• Limited to existing phenomena of the natural
world
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