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Chapter 1
General Biology I
1
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The Science of Life
• Biology unifies much of natural science
• Life defies simple definition
– Living systems are the most complex chemical
systems on Earth
– Life is constrained by the properties of
chemistry and physics
• Science is becoming more interdisciplinary
– Combining multiple fields
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The Science of Life
7 characteristics of all living organisms
1.
2.
3.
4.
5.
6.
7.
Cellular organization
Ordered complexity
Sensitivity
Growth, development, and reproduction
Energy utilization
Homeostasis
Evolutionary adaptation
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The Science of Life
• Living systems show hierarchical organization
– Cellular level
– Organismal level
– Populational level
– Ecosystem level
– Biosphere
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The Science of Life
• Living systems show hierarchical organization
– Cellular level
• Atoms, molecules, organelles, cells
• Cell is the basic unit of life
– Organismal level
• Tissues, organs, organ systems
– Populational level
• Population, community
– Ecosystem level
– Biosphere
• All the livable space on the planet
• 99% of it is in the ocean!!!
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Populational Level
POPULATIONAL LEVEL
Population
Species
Community
Ecosystem
Biosphere
(population): © George Ostertag/agefotostock; (species): © PhotoDisc/Volume 44 RF; (community): © Ryan McGinnis/Alamy;
(ecosystem): © Robert and Jean Pollock; (biosphere): NASA
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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The Science of Life
• As you move up the hierarchy, novel
properties emerge
– Result from interaction of components
– Cannot be deduced by looking at parts
themselves
– “Life” is an emergent property
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The Nature of Science
• Science aims to understand the natural
world through observation and reasoning
• Science begins with observations,
therefore, much of science is purely
descriptive
– Classification of all life on Earth
– Human genome sequencing
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The Nature of Science
• Science uses both deductive and inductive reasoning
• Deductive reasoning uses general principles to make specific
predictions
• If all mammals have hair and you find an animal that
doesn’t, you might say that the animal you are looking at is
not a mammal
• Used to test the validity of general ideas in all branches
of knowledge
• Inductive reasoning uses specific observations to develop
general conclusions
• If poodles have hair and terriers have hair, then you
might generalize that all dogs have hair
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The Nature of Science
• Scientists use a systematic approach to
gain understanding of the natural world
= Scientific Method
– Observation
– Hypothesis formation
– Prediction
– Experimentation
– Conclusion
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The Nature of Science
• A hypothesis is a possible explanation
for an observation
• Not just an “educated guess”
• A hypothesis
– Must be tested to determine its validity
– Is often tested in many different ways
– Allows for predictions to be made
• Iterative
– Hypotheses can be changed and refined
with new data
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The Nature of Science
• Experiment
– Tests the hypothesis
– Must be carefully designed to test only one
variable at a time
– Consists of a test experiment and a
control experiment
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The Nature of Science
• Predictions
– Hypotheses should make predictions
– Predictions provide a way to test the
validity of hypotheses
– Hypothesis must be rejected if the
experiment produces results inconsistent
with the predictions
– The more experimentally supported
predictions a hypothesis makes, the more
valid the hypothesis
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The Nature of Science
• Philosophical approaches to science
– Reductionism
• To break a complex process down to its simpler parts
• For example
• Cellular metabolism is very complex, reductionism is
looking at one pathway and the function of that
enzyme
• However, that enzyme may work differently when not
isolated from other enzymes and molecules within the
cell
– Systems biology
• Focus on emergent properties that can’t be understood by
looking at simpler parts
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The Nature of Science
• Models in science
– Way to organize thought
– Parts provided by reductionist approach
– Model shows how they fit together
– Suggest experiments to test the model
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The Nature of Science
• Scientific theory
– Is a body of interconnected concepts
– Is supported by much experimental evidence and
scientific reasoning
– Expresses ideas of which we are most certain
– When you say “theory” in science, it is as close to
fact that you will get to with the information and
technology we have available to us at the time
• Compare to general meaning of theory
– Different in everyday language, implies a lack of
knowledge or a guess
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Darwin and Evolution
• Example of how a scientist
develops a hypothesis and a theory
gains acceptance
• Charles Darwin served as
naturalist on mapping expedition
around coastal South America
• 30 years of observation and study
before publishing On the Origin of
Species by Means of Natural
Selection
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Voyage of the HMS Beagle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
British Isles
NORTH
PACIFIC
OCEAN
NORTH
AMERICA
Galápagos
Islands
Western
Isles
NORTH
ATLANTIC
OCEAN
Valparaiso
Society
Islands
ASIA
NORTH
PACIFIC
OCEAN
Canary
Islands
Cape Verde
Islands
SOUTH
AMERICA
Bahia
Marquesas
EUROPE
Philippine
Islands
AFRICA
INDIAN
OCEAN
Ascension
Madagascar
St. Helena
Rio de Janeiro
Keeling
Islands
Mauritius
Bourbon Island
Equator
AUSTRALIA
Friendly
Islands
Sydney
Montevideo
Buenos Aires
Port Desire
Straits of Magellan
Falkland
Islands
Cape Horn Tierra del Fuego
Cape of
Good Hope
SOUTH
ATLANTIC
OCEAN
King George’s
Sound
Hobart
New
Zealand
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Darwin and Evolution
• Darwin was not the first to propose
evolution
– Living things have changed over time
• Darwin’s contribution was a mechanism
for evolution
– He proposed Natural selection
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Darwin and Evolution
• On the Beagle, Darwin saw that
characteristics of similar species varied
from place to place
• Galápagos Finches
– 14 related species differ only slightly
– “Descent with modification” or evolution
Woodpecker Finch (Cactospiza pallida)
Large Ground Finch (Geospiza magnirostris)
Cactus Finch (Geospiza scandens)
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Darwin and Evolution
• Darwin studied Thomas Malthus’s An Essay on the
Principle of Population
– Populations of plants and animals increase
geometrically (multiplicative, example x3)
– Humans can only increase their food supply
arithmetically (additive, example +2)
– Populations of species remain constant because
death limits population numbers
– There are individuals that possess physical,
behavioral or other attributes that give
them an advantage
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Darwin and Evolution
Darwin saw that:
• Every organism
has the potential
to produce more
offspring
• But, only a
limited number
survive and
reproduce
themselves
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geometric progression
arithmetic progression
54
Human Growth is
Geometric
Human food
production is
Arithmetic
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6
2
4
8
6
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Darwin and Evolution
Darwin made an important association:
• Individuals with attributes that give them
an advantage in their environment are more
likely to survive and reproduce
• Pass these characteristics on to their
offspring
• The population will gradually change over
time
• Darwin called this selection
Darwin and Evolution
• Evidence supporting Darwin’s theory has
only grown
– Fossil record
– Earth’s age
– Mechanism for heredity
– Comparative anatomy
– Molecular Evidence
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Darwin and Evolution
– Fossil record
• Transitional forms have been found at predicted
positions in time
– Earth’s age
• Earth is very old – 4.5 billion years old
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Darwin and Evolution
– Mechanism for heredity
• Mendel’s laws of inheritance were unknown to
Darwin
• At time of Darwin there was no concept of
“genes” or how heredity worked
• Darwin could not completely explain how
evolution worked
• Now have detailed understanding of heredity
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Darwin and Evolution
– Comparative anatomy
• Vertebrate forelimbs all share the same basic
array of bones
• Homologous – same evolutionary origin but now
differ in structure and function
• Analogous – structures of different origin used
for the same purpose (butterfly and bird wings)
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Unifying Themes in Biology
• Cell theory
– All organisms composed of cells
– Cells are life’s basic units
– All cells come from preexisting cells
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a.
60 µm
b.
500 µm
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a: © Dennis Kunkel/Phototake; b: © Karl E. Deckart/Phototake
Unifying Themes in Biology
• Molecular basis of inheritance
– Deoxyribonucleic acid (DNA)
– Sequence of 4 nucleotides encode all of a
cell’s information – A, T, C, G
– Gene – discrete unit of information
– Genome – entire set of DNA instructions
– Continuity of life depends on faithful
copying of DNA into daughter cells
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Unifying Themes in Biology
• Structure and function
– Study structure to learn function
– Know a function – look for that structure in
other organisms
– Example
• Receptor on human cell for insulin known
• Find similar molecule in a worm
• Might conclude this molecule functions the same
in the worm
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Unifying Themes in Biology
• Diversity of life arises by evolution
– Underlying unity of biochemistry and genetics
argues for life from the same origin event
– Diversity due to evolutionary change over time
– 3 domains
• Bacteria – single-celled prokaryote, bacteria
• Archaea – single-celled prokaryote, includes
extremophile bacteria
• Eukarya – single-celled or multicellular eukaryote;
includes protists, fungi, plants, and animals.
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Plantae
Fungi
Eukarya
Animalia
Protista
(plantae middle): © David M. Dennis/Animals Animals; (plantae right): © Corbis/Volume 46 RF; (fungi left): © Royalty Free/Corbis; (fungi middle):
© Mediscan/Corbis; (fungi right): © PhotoDisc BS/Volume 15 RF; (animalia left): © Royalty-Free/Corbis; (animalia middle): © Tom Brakefield/Corbis;
(animalia right): © PhotoDisc/Volume 44 RF; (protista left): © Corbis/Volume 64 RF; (protista middle): © Tom Adams/Visuals Unlimited;
(protista right): © Douglas P. Wilson/Frank Lane Picture Agency/Corbis
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Unifying Themes in Biology
• Evolutionary conservation
– All organisms today descended from a simple
creature 3.5 BYA
– Some characteristics preserved
– Our DNA encodes everything
– For example, you need certain enzymes for
cellular respiration, those are encoded in
your DNA; those same enzymes are used by
other organisms for the same process
– Conservation reflects that they have a
fundamental role
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Unifying Themes in Biology
• Cells are information-processing
systems
– Information in DNA used to direct
synthesis of cellular components
• Control of gene expression leads to different
cells/ tissue types
– Cells process environmental information
• Glucose levels, presence of hormones
– Cells in multicellular organisms must
coordinate with each other
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Unifying Themes in Biology
• Nonequilibrium state
– Living systems are open systems
– Constant supply of energy needed
– Self-organizing properties at different
levels
– Emergent properties from collections of
molecules, cells, and individuals
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