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Principles of Life
Chapter 1 Principles of Life
Key Concepts
• 1.1 Living Organisms Share Common
Aspects of Structure, Function, and Energy
Flow
• 1.2 Genetic Systems Control the Flow,
Exchange, Storage, and Use of Information
• 1.3 Organisms Interact with and Affect Their
Environments
Chapter 1 Principles of Life
• 1.4 Evolution Explains Both the Unity and
Diversity of Life
• 1.5 Science Is Based on Quantifiable
Observations and Experiments
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Biology—the scientific study of living things
“Living things”—All the diverse organisms
descended from a single-celled ancestor (a
single common ancestor)
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Characteristics shared by all living organisms:
• Composed of a common set of chemical
components and similar structures
• Contain genetic information that uses a nearly
universal code
• Convert molecules obtained from their
environment into new biological molecules
• Extract energy from the environment and use it
to do biological work
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
• Regulate their internal environment
• Replicate their genetic information in the same
manner when reproducing
• Share sequence similarities among a
fundamental set of genes
• Evolve through gradual changes in genetic
information
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Earth formed between 4.6 and 4.5 billion years
ago.
It was some 600 million years or more before the
earliest life evolved.
Figure 1.1 Life’s Calendar
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Complex biological molecules possibly arose
from random associations of chemicals in the
early environment.
Experiments that simulate conditions on early
Earth show that this was possible.
Critical step for evolution of life—formation of
nucleic acids
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Biological molecules were enclosed in
membranes, to form the first cells.
Fatty acids were important in forming
membranes.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
For 2 billion years, organisms were unicellular
prokaryotes.
Early prokaryotes were confined to oceans,
where they were protected from UV light.
There was little or no O2 in the atmosphere, and
hence no protective ozone (O3) layer.
Figure 1.2 The Basic Unit of Life is the Cell
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Photosynthesis evolved about 2.7 billion years
ago.
The energy of sunlight is transformed into the
energy of biological molecules.
Earliest photosynthetic cells were probably
similar to cyanobacteria.
O2 was a byproduct of photosynthesis, and it
began to accumulate in the atmosphere.
Figure 1.3 Photosynthetic Organisms Changed Earth’s Atmosphere (Part 1)
Figure 1.3 Photosynthetic Organisms Changed Earth’s Atmosphere (Part 2)
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
O2 was poisonous to many early prokaryotes.
Organisms that could tolerate O2 evolved
aerobic metabolism (energy production using
O2), which is more efficient than anaerobic
metabolism.
Organisms were able to grow larger. Aerobic
metabolism is used by most living organisms
today.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
O2 also produced a layer of ozone (O3) in the
upper atmosphere.
This layer absorbs UV light, and its formation
allowed organisms to move from the ocean to
land.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Some cells evolved membrane-enclosed
compartments called organelles.
Example: The nucleus contains the genetic
information.
These cells are eukaryotes.
Prokaryotes lack nuclei and other internal
compartments.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Some organelles may have originated by
endosymbiosis, when larger cells engulfed
smaller ones.
Mitochondria (site of energy generation)
probably evolved from engulfed prokaryotic
organisms.
Chloroplasts (site of photosynthesis) probably
evolved from photosynthetic prokaryotes.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Multicellular organisms arose about 1 billion
years ago.
Cellular specialization—cells became
specialized to perform certain functions.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Evolution of species:
Mutations are introduced when a genome is
replicated.
Some mutations give rise to structural and
functional changes in organisms, and new
species arise.
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Each species has a distinct scientific name, a
binomial:
• Genus name
• Species name
Example: Homo sapiens
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Evolutionary relationships of species can be
determined by comparing genomes.
A phylogenetic tree documents and diagrams
evolutionary relationships.
Figure 1.4 The Tree of Life
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Relationships in the tree of life are determined
by fossil evidence, structures, metabolic
processes, behavior, and molecular analyses
of genomes.
Three domains of life:
• Bacteria (prokaryotes)
• Archaea (prokaryotes)
• Eukarya (eukaryotes)
Concept 1.1 Living Organisms Share Common Aspects of
Structure, Function, and Energy Flow
Because all life is related, discoveries made
using one type of organism can be extended to
other types.
Biologists use model systems for research,
such as the green alga Chlorella to study
photosynthesis.
Concept 1.2 Genetic Systems Control the Flow, Exchange,
Storage, and Use of Information
Genome—the sum total of all the information
encoded by an organism’s genes
DNA consists of repeating subunits called
nucleotides.
Gene—a specific segment of DNA that contains
information for making a protein
Proteins govern chemical reactions in cells and
form much of an organism’s structure.
Figure 1.5 DNA Is Life’s Blueprint
Concept 1.2 Genetic Systems Control the Flow, Exchange,
Storage, and Use of Information
Mutations alter nucleotide sequences of a gene,
and the protein is often altered as well.
Mutations may occur during replication, or be
caused by chemicals and radiation.
Most are harmful or have no effect, but some
may improve the functioning of the organism.
Mutations are the raw material of evolution.
Concept 1.2 Genetic Systems Control the Flow, Exchange,
Storage, and Use of Information
Complete genome sequences have been
determined for many organisms.
Genome sequences are used to study the
genetic basis of everything from physical
structure to inherited diseases, and
evolutionary relationships.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Biological systems are organized in a hierarchy.
Traditionally, biologists concentrated on one
level of the hierarchy, but today much biology
involves integrating investigations across many
levels.
Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 1)
Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 2)
Concept 1.3 Organisms Interact with and Affect Their
Environments
Living organisms acquire nutrients from their
environments.
Nutrients supply energy and materials for
biochemical reactions.
Some reactions break nutrient molecules into
smaller units, releasing energy for work.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Examples of cellular work:
• Synthesis—building new complex molecules
from smaller chemical units
• Movement of molecules, or the whole organism
• Electrical work of information processing in
nervous systems
Concept 1.3 Organisms Interact with and Affect Their
Environments
Metabolism is the sum total of all chemical
transformations and other work done in all cells
of an organism.
The reactions are integrally linked—the products
of one are the raw materials of the next.
Concept 1.3 Organisms Interact with and Affect Their
Environments
In multicellular organisms, cells are specialized,
or differentiated.
Differentiated cells are organized into tissues.
Tissue types are organized into organs, and
organ systems are groups of organs with
interrelated functions.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Multicellular organisms have an internal
environment that is acellular—an extracellular
environment of fluids.
Homeostasis—maintenance of a narrow range
of conditions in this internal environment
Regulatory systems maintain homeostasis in
both multicellular organisms and in individual
cells.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Organisms interact:
Population—group of individuals of the same
species that interact with one another
A community—populations of all the species that
live in the same area and interact
Communities plus their abiotic environment
constitute an ecosystem.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Individuals may compete with each other for
resources, or they may cooperate (e.g., in a
termite colony).
Plants also compete for light and water, and
many form complex partnerships with fungi,
bacteria, and animals.
Concept 1.3 Organisms Interact with and Affect Their
Environments
Interactions of plants and animals are major
evolutionary forces that produce specialized
adaptations.
Species interaction with one another and with
their environment is the subject of ecology.
Concept 1.4 Evolution Explains Both the Unity and Diversity of
Life
Evolution is a change in genetic makeup of
biological populations through time—a major
unifying principle of biology.
Charles Darwin proposed that all living
organisms are descended from a common
ancestor by the mechanism of natural
selection.
Concept 1.4 Evolution Explains Both the Unity and Diversity of
Life
Natural selection leads to adaptations—
structural, physiological, or behavioral traits
that enhance an organism’s chances of survival
and reproduction
Figure 1.7 Adaptations to the Environment (Part 1)
Figure 1.7 Adaptations to the Environment (Part 2)
Figure 1.7 Adaptations to the Environment (Part 3)
Figure 1.7 Adaptations to the Environment (Part 4)
Concept 1.4 Evolution Explains Both the Unity and Diversity of
Life
In science, a theory is a body of scientific work
in which rigorously tested and well-established
facts and principles are used to make
predictions about the natural world.
Evolutionary theory is:
(1) a body of knowledge supported by facts
(2) the resulting understanding of mechanisms
by which populations have changed and
diversified over time, and continue to evolve
Concept 1.4 Evolution Explains Both the Unity and Diversity of
Life
Evolution can be observed and measured by:
• Changes in genetic composition of populations
over short time frames
• The fossil record—population changes over
very long time frames
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Scientific investigations are based on
observation and experimentation.
Understanding the natural history of
organisms—how they get food, reproduce,
behave, regulate internal environments, and
interact with other organisms—facilitates
observation and leads to questions.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Observation is enhanced by technology:
microscopes, imaging, genome sequencing,
and satellites.
Observations must be quantified by
measurement and mathematical and statistical
calculations.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
The scientific method (hypothesis–prediction
(H–P) method):
• Observations
• Questions
• Hypotheses
• Predictions
• Testing
Figure 1.8 Scientific Methodology
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Inductive logic leads to tentative explanations
called hypotheses.
Deductive logic is used to make predictions.
Experiments are designed to test these
predictions.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Controlled experiments manipulate the
variable that is predicted to cause differences
between groups.
Independent variable—the variable being
manipulated
Dependent variable—the response that is
measured
Figure 1.9 Controlled Experiments Manipulate a Variable (Part 1)
Figure 1.9 Controlled Experiments Manipulate a Variable (Part 2)
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Comparative experiments look for differences
between samples or groups.
The variables cannot be controlled; data are
gathered from different sample groups and
compared.
Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 1)
Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 2)
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Statistical methods help scientists determine if
differences between groups are significant.
Statistical tests start with a null hypothesis—
that no differences exists.
Statistical methods eliminate the possibility that
results are due to random variation.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Not all forms of inquiry into nature are scientific.
Scientific hypotheses must be testable, and have
the potential of being rejected.
Science depends on evidence that comes from
reproducible and quantifiable observations.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Religious or spiritual explanations of natural
phenomena are not testable and therefore are
not science.
Science and religion are nonoverlapping
approaches to inquiry.
Concept 1.5 Science Is Based on Quantifiable Observations and
Experiments
Scientific advances that may contribute to
human welfare may also raise ethical
questions.
Science describes how the world works; it is
silent on the question of how the world “ought
to be.”
Contributions from other forms of human inquiry
may help us come to grips with such questions.