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Chapter 1
Introduction: Themes in the Study of
Life
Lecture Presented By
Shilla Chakrabarty, Ph.D.
Objectives
• Explain fundamental concepts of biological sciences and
how these concepts are connected within various areas of
the biological sciences at the survey level (SLO#1)
• Understand that evolution is the core theme of biology, and
accounts for the unity and diversity of life
• Learn how to design and conduct a scientific experiment by
stating a hypothesis, recording and analyzing data, and
writing conclusions (SLO#2)
• Appreciate that science benefits from a cooperative
approach and diverse viewpoints
© 2011 Pearson Education, Inc.
Overview: Inquiring About Life
• Evolution is the process of change that
has transformed life on Earth
• Evolution accounts for the unity and
diversity of life
• As a result of evolution an organism can
adapt to its environment
Example: The mother-of-pearl plant or
ghost plant can survive in the crevices
of rock walls because it is adapted to
conserving water
© 2011 Pearson Education, Inc.
What is Biology?
• Biology is the scientific study of life (Bios – life;
logy – study)
• Biologists ask questions such as
– How does a single cell develop into an organism?
– How does the human mind work?
– How do living things interact in communities?
• Life defies a simple, one-sentence definition
• Life is recognized by what living things do
© 2011 Pearson Education, Inc.
Properties And Processes Associated With Life
Order
Response to
the environment
Evolutionary adaptation
Reproduction
Regulation
Energy processing
Growth and
development
Themes In Biology
• Themes help to organize biological information
• There are at least 8 unifying themes that pervade all of
biology:
1.
2.
3.
4.
5.
6.
7.
8.
New properties emerge at each level in the biological hierarchy
Organisms interact with other organisms and the physical
environment
Life requires energy transfer and transformation
Structure and function are correlated at all levels of biological
organization
The cell is an organism’s basic unit of structure and function
Continuity of life is based on heritable information in the form of DNA
Feedback mechanisms regulate biological systems
Evolution is the core theme that accounts for the unity and diversity of
life
© 2011 Pearson Education, Inc.
Theme 1: New properties emerge at each level in the biological hierarchy
The biosphere
Tissues
Ecosystems
Organs and
organ systems
Communities
Organelles
Organisms
Populations
Cells
Atoms
Molecules
Emergent Properties
Emergent properties:
• Properties that emerge at each step and are not present at the
preceding level
• Arise from the arrangement and interaction of parts as
complexity increases
Example: Photosynthesis does not occur in a disorganized testtube mixture of chlorophyll and chloroplast molecules.
Photosynthesis requires a specific organization of these
molecules in the chloroplast.
• Characterize non-biological entities as well
Example: A functioning bicycle can only emerge when all the
necessary parts are connected properly
© 2011 Pearson Education, Inc.
Biology Balances Reductionism With Study Of Emergent
Properties
Reductionism: Reduction of complex systems to simpler
components that are more manageable to study
Example: By studying the molecular structure of DNA,
Watson and Crick (1953) inferred how this molecule could
serve as the chemical basis of inheritance
The central role of DNA in cells and organisms could
however, only be derived from studies of emergent
properties involving the interactions of DNA with other
molecules
© 2011 Pearson Education, Inc.
Systems Biology
• System: Combination of components that function together
– Can be studied at any level of organization
• Systems biology: Constructs models for the dynamic behavior of
whole biological systems
– Successful models enable biologists to predict how a change in
one or more variables will affect other components and the
whole system
Example:
– How does a drug for blood pressure affect other organs?
– How does increasing CO2 alter the biosphere?
© 2011 Pearson Education, Inc.
Theme 2: Organisms Interact with Other Organisms and the Physical
Environment
Sunlight
Leaves absorb
light energy from
the sun.
CO2
Leaves take in
carbon dioxide
from the air
and release
oxygen.
O2
Cycling
of
chemical
nutrients
Leaves fall to
the ground and
are decomposed
by organisms
that return
minerals to the
soil.
Water and
minerals in
the soil are
taken up by
the tree
through
its roots.
Animals eat
leaves and fruit
from the tree.
Drastic Consequences Of Human
Interactions With The Environment
• About half the human-generated CO2 stays in the atmosphere
and contributes to global warming
• Global warming, a major aspect of global climate change, has
dire effects on life-forms and habitats all over the Earth
• There is an urgent need to find ways of reducing humangenerated CO2 in order to save the environment and protect lifeforms and habitats of the Earth
© 2011 Pearson Education, Inc.
Theme 3: Life Requires Energy Transfer and Transformation
•
•
•
•
A fundamental characteristic of living organisms is their use of energy to carry out life’s
activities
Work, including moving, growing, and reproducing, requires a source of energy
Living organisms transform energy from one form to another
Example: Light energy is converted to chemical energy, then kinetic energy
Energy flows through an ecosystem, usually entering as light and exiting as heat
Sunlight
Heat
When energy is used
to do work, some
energy is converted to
thermal energy, which
is lost as heat.
Producers absorb light
energy and transform it into
chemical energy.
An animal’s muscle
cells convert
chemical energy
from food to kinetic
energy, the energy
of motion.
Chemical
energy
Chemical energy in
food is transferred
from plants to
consumers.
(a) Energy flow from sunlight to
producers to consumers
(b) Using energy to do work
A plant’s cells use
chemical energy to do
work such as growing
new leaves.
Theme 4: Structure and Function are Correlated at all Levels of Biological
Organization
(a) Wings
(b) Bones
Infoldings of
membrane
Mitochondrion
100 µm
(c) Neurons
0.5 µm
(d) Mitochondria
Theme 5: The Cell Is an Organism’s Basic Unit of Structure and
Function
• The cell is the lowest level of organization that can perform all
activities required for life
• All cells
– Are enclosed by a membrane
– Use DNA as their genetic information
• Cells may be:
– Eukaryotic: has membrane-enclosed organelles, the largest of which is
usually the nucleus
– Prokaryotic: simpler and usually smaller than eukaryotic cell; does not
contain a nucleus or other membrane-enclosed organelles
© 2011 Pearson Education, Inc.
Theme 5: The Cell Is an Organism’s Basic Unit of Structure and Function
Eukaryotic
Cell
Membrane
DNA
(no nucleus)
Membrane
Prokaryotic
Cell
Cytoplasm
Nucleus
(membraneenclosed)
Membraneenclosed organelles
DNA (throughout
nucleus)
1 m
Theme 6: The Continuity of Life Is Based on Heritable Information in
the Form of DNA
• Chromosomes contain most of a cell’s genetic material in the
form of DNA (deoxyribonucleic acid)
• Each DNA molecule is made up of two long chains of nucleotides
arranged in a double helix
• DNA is the substance of genes
• Genes are the units of inheritance that transmit information from
parents to offspring
• The ability of cells to divide is the basis of all reproduction,
growth, and repair of multicellular organisms
© 2011 Pearson Education, Inc.
DNA: The Genetic Material
Nucleus
DNA
Nucleotide
Cell
(a) DNA double helix
(b) Single strand of DNA
DNA Structure and Function
•
•
•
Each chromosome has one long DNA molecule with hundreds or thousands of genes
DNA is inherited by offspring from their parents
DNA controls the development and maintenance of organisms
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
Functions of DNA
• Genes encode the information necessary to build
other molecules, such as proteins in the cell
• DNA of genes provide blueprints for making proteins
necessary for the cell
• DNA is first transcribed into RNA and then translated
into a protein
• Gene expression is the process of converting
information from gene to cellular product
© 2011 Pearson Education, Inc.
Genomics: Large-Scale Analysis of DNA
Sequences
• Genome: An organism’s entire set of genetic instructions
– The human genome and those of many other organisms have been
sequenced using DNA-sequencing machines
• Genomics is the study of sets of genes within and between
species
– The genomics approach depends on
• “High-throughput” technology, which yields enormous amounts of
data
• Bioinformatics, which is the use of computational tools to process
a large volume of data
• Interdisciplinary research teams
© 2011 Pearson Education, Inc.
Biology As An Information Science
Theme 7: Feedback Mechanisms Regulate Biological Systems
• Feedback mechanisms allow biological processes to selfregulate
– Negative feedback: As more of a product accumulates, the
process that creates it slows down and less of the product is
produced
– Positive feedback: As more of a product accumulates, the
process that creates it speeds up and more of the product is
produced
© 2011 Pearson Education, Inc.
Theme 7: Feedback Mechanisms Regulate Biological Systems
A
Negative
feedback
Enzyme 1
B
Excess D
blocks a step.
D
D
Enzyme 2
D
C
Enzyme 3
D
(a) Negative feedback
W
Enzyme 4
Positive
feedback
Excess Z
stimulates a
step.
Z
X

Enzyme 5
Y
Z
Z
Enzyme 6
Z
(b) Positive feedback
Theme 8: Evolution, the Overarching Theme of
Biology
• Evolution makes sense of everything we know about biology
• Organisms are modified descendants of common ancestors
• Evolution explains patterns of unity and diversity in living
organisms
• Similar traits among organisms are explained by descent from
common ancestors
• Differences among organisms are explained by the accumulation of
heritable changes
© 2011 Pearson Education, Inc.
Evolution: The Core Theme of Biology
• The history of life is a saga of a restless
Earth billions of years old, inhabited by a
changing cast of living forms
– This cast is revealed through fossils and
other evidence.
• Evolution unifies biology at different scales
of size, and accounts for the unity and
diversity of life
– Each species is one twig on a branching
tree of life extending back through
ancestral species.
“Nothing in biology makes sense except in
the light of evolution”
Theodosius Dobzhansky
© 2011 Pearson Education, Inc.
Classifying the Diversity of Life
• Approximately 1.8 million species already identified and
named to date; thousands more identified each year
• Total number of species that actually exist is estimated to
range from 10 million to over 100 million
• Taxonomy: The branch of biology that names and classifies
species into groups of increasing breadth
• Domains, followed by kingdoms, are the broadest units of
classification
© 2011 Pearson Education, Inc.
Species
Genus
Family
Order
Class
Phylum
Ursus americanus
(American black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Classifying Life
Eukarya
Kingdom
Domain
The Three Domains of Life
• Organisms are divided into three domains
• Domain Bacteria and domain Archaea compose the prokaryotes
– Most prokaryotes are single-celled and microscopic
• Domain Eukarya includes all eukaryotic organisms that are
classified into three multicellular kingdoms
– Plantae, which produce their own food by photosynthesis
– Fungi, which absorb nutrients
– Animalia, which ingest their food
NOTE: Other eukaryotic organisms were formerly grouped into the Protist kingdom,
though these are now often grouped into many separate groups
© 2011 Pearson Education, Inc.
The Three Domains Of Life
2 m
(b) Domain Archaea
2 m
(a) Domain Bacteria
(c) Domain Eukarya
Kingdom Animalia
100 m
Kingdom Plantae
Protists
Kingdom Fungi
Unity in the Diversity of Life
A striking unity underlies the diversity of life
Example:
• DNA is the universal genetic language common to all organisms
• Unity is evident in many features of cell structure
15 m
5 m
Cilia of
Paramecium
Cilia of
windpipe
cells
0.1 m
Cross section of a cilium, as viewed
with an electron microscope
Charles Darwin and the Theory of Natural Selection
•
•
•
•
Charles Darwin published
On the Origin of Species by
Means of Natural Selection
in 1859
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Darwin observed that
– Individuals in a population vary in their traits, many
of which are heritable
– More offspring are produced than survive, and
competition is inevitable
– Species generally suit their environment
Darwin inferred that
– Individuals that are best suited to their environment
are more likely to survive and reproduce
– Over time, more individuals in a population will have
the advantageous traits
Evolution occurs as the unequal reproductive success of
individuals. Thus, the environment “selects” for the
propagation of beneficial traits
Darwin called this process Natural Selection
Unity And Diversity In The Orchid Family
Charles Darwin And The Theory of Natural Selection
Darwin made two main points :
– Species showed evidence
of “descent with
modification” from
common ancestors
– Natural selection is the
mechanism behind
“descent with
modification”
Darwin’s theory explained the
duality of unity and diversity
Population
of organisms
Hereditary
variations
Overproduction
and competition
Environmental
factors
Differences in
reproductive success
of individuals
Evolution of adaptations
in the population
Darwin’s Theory of Natural Selection
Population
of organisms
Hereditary
variations
Overproduction of offspring and competition
Environmental
factors
Differences in
reproductive success
of individuals
Evolution of adaptations
in the population
Natural Selection:
1 Population with
varied inherited
traits
2 Elimination of
individuals with
certain traits
3 Reproduction of
survivors
4 Increasing
frequency of
traits that
enhance
survival and
reproductive
success
Natural Selection and Adaptation
• Natural selection is often evident in adaptations of
organisms to their way of life and environment
• Bat wings are an example of adaptation
The Tree of Life
• “Unity in diversity” arises from “descent with
modification”
Example:
The forelimb of the bat, human, and horse and the
whale flipper all share a common skeletal architecture
• Fossils provide additional evidence of anatomical
unity from descent with modification
© 2011 Pearson Education, Inc.
Evolution of Adaptations In The
Population
Darwin proposed that natural selection can, by its
cumulative effects over vast spans of time, produce
new species from ancestral species.
Example:
A population may be fragmented into several isolated
populations in different environments.
• What began as one species could gradually diversify into
many species.
• Each isolated population would adapt over many
generations to different environmental problems
NOTE: Evolutionary relationships are often illustrated with treelike diagrams
that show ancestors and their descendants
© 2011 Pearson Education, Inc.
Insect-eaters
Warbler finches
Gray warbler finch
Certhidea fusca
Bud-eater
Seed-eater
COMMON
ANCESTOR
Green warbler finch
Certhidea olivacea
Sharp-beaked
ground finch
Geospiza difficilis
Vegetarian finch
Platyspiza crassirostris
Mangrove finch
Cactospiza heliobates
Insect-eaters
Tree finches
Woodpecker finch
Cactospiza pallida
Medium tree finch
Camarhynchus pauper
Large tree finch
Camarhynchus psittacula
Small tree finch
Camarhynchus parvulus
Cactus-flowereaters
Seed-eaters
Ground finches
Descent With Modification:
Adaptive Radiation Of Finches
On The Galapagos Islands
Large cactus
ground finch
Geospiza conirostris
Cactus ground finch
Geospiza scandens
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza
magnirostris
The Process of Studying Science:
• The word science is derived from Latin and means
“to know”
• Inquiry is the search for information and explanation
• Scientists study science by making observations,
forming logical hypotheses and testing them
© 2011 Pearson Education, Inc.
The Scientific Process
• Making observations
– Biologists describe natural structures and processes
– This approach is based on observation and data analysis
Collecting data
 Data or recorded observations or items of information fall into two
categories:
– Qualitative data, or descriptions rather than measurements
Example: Jane Goodall’s observations of chimpanzee behavior
– Quantitative data, or recorded measurements, which are sometimes organized
into tables and graphs
© 2011 Pearson Education, Inc.
Jane Goodall collecting qualitative data on chimpanzee behavior
The Scientific Process
• Forming and Testing Hypotheses
– Observations and inductive reasoning can lead us to ask
questions and propose hypothetical explanations called
hypotheses
What is Inductive reasoning?
– Inductive reasoning draws conclusions through the logical process of
induction
– Repeating specific observations can lead to important generalizations
Example: “The sun always rises in the east”
© 2011 Pearson Education, Inc.
Hypothesis-Based Science
• The observations of discovery
science lead to further questions
and proposal of hypothetical
explanations called hypotheses
• A hypothesis is a tentative answer
to a well-framed question
• A scientific hypothesis leads to
predictions that can be tested by
observation or experimentation
© 2011 Pearson Education, Inc.
Observations
A Campground Example Of
Hypothesis-based Inquiry
Question
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test of prediction
Test of prediction
Test falsifies hypothesis
Test does not falsify hypothesis
Alternative Hypotheses in Hypothesisbased Inquiry
• Hypothesis-based science often makes use of two or
more alternative hypotheses
• Failure to falsify a hypothesis does not prove that
hypothesis
Example: You replace your flashlight bulb, and it now
works; this supports the hypothesis that your bulb
was burnt out, but does not prove it (perhaps the first
bulb was inserted incorrectly)
© 2011 Pearson Education, Inc.
Inductive Versus Deductive Reasoning
• Inductive reasoning draws conclusions through the
logical process of induction
– Repeating specific observations can lead to
important generalizations
Example: “The sun always rises in the east”
• Deductive reasoning uses the “if….then” logic of
hypothesis-based science to make specific predictions
Example: If organisms are made of cells (premise 1), and
humans are organisms (premise 2), then humans are
composed of cells (deductive prediction)
© 2011 Pearson Education, Inc.
Questions That Can and Cannot Be
Addressed by Science
• A scientific hypothesis must be testable and falsifiable
Example: A hypothesis that ghosts fooled with the flashlight
cannot be tested
• Supernatural and religious explanations are outside
the bounds of science
© 2011 Pearson Education, Inc.
The Flexibility of the Scientific Method
• The scientific method is an idealized process of inquiry
• Hypothesis-based science is based on the “textbook”
scientific method but rarely follows all the ordered
steps
© 2011 Pearson Education, Inc.
A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations
Scarlet kingsnake (nonvenomous)
Key
Range of scarlet
kingsnake only
Overlapping ranges of
scarlet kingsnake and
eastern coral snake
North
Carolina
South
Carolina
Eastern coral snake
(venomous)
Experiment to test Henry
Bates’ Hypothesis
Scarlet kingsnake (nonvenomous)
Field Experiments with
Artificial Snakes
• To further test Henry Bates’ mimicry
hypothesis, researchers made
hundreds of artificial snakes:
– An experimental group
resembling king snakes
– A control group resembling
plain brown snakes
• Equal numbers of both types were
placed at field sites, including areas
without poisonous coral snakes
(a) Artificial kingsnake
(b) Brown artificial snake that has been attacked
© 2011 Pearson Education, Inc.
RESULTS NOTED AFTER 4 WEEKS
100
84%
Percent of total attacks
on artificial snakes
83%
Brown
artificial
snakes
80
60
40
20
Artificial
kingsnakes
17%
16%
0
Coral snakes
absent
Coral snakes
present
Conclusion From The Data Obtained
• The data fit the predictions of the mimicry hypothesis:
The ringed snakes were attacked less frequently in
the geographic region where coral snakes were
found
© 2011 Pearson Education, Inc.
Experimental Controls and Repeatability
• A controlled experiment compares an experimental group (the
artificial king snakes) with a control group (the artificial brown
snakes)
• Ideally, only the variable of interest (the effect of coloration on
the behavior of predators) differs between the control and
experimental groups
• A controlled experiment means that control groups are used to
cancel the effects of unwanted variables
• A controlled experiment does not mean that all unwanted
variables are kept constant
• In science, observations and experimental results must be
repeatable
© 2011 Pearson Education, Inc.
Theories in Science
• In the context of science, a theory is
– Broader in scope than a hypothesis
– General, and can lead to new testable hypotheses
– Supported by a large body of evidence in comparison to
a hypothesis
Example: The Theory of Natural Selection
© 2011 Pearson Education, Inc.
Science benefits from a cooperative approach and
diverse viewpoints
• Most scientists work in teams, which often include graduate and
undergraduate students
• Good communication is important in order to share results
through seminars, publications, and websites
• Scientists check each others’ claims by performing similar
experiments, and often build upon the work of others to advance
the field
• It is not unusual for different scientists to work on the same
research question
• Scientists cooperate by sharing data about model organisms
(e.g., the fruit fly Drosophila melanogaster)
© 2011 Pearson Education, Inc.
Science As A Social Process
Science, Technology, and Society
• The goal of science is to understand natural phenomena
• The goal of technology is to apply scientific knowledge for some specific
purpose
• Science and technology are interdependent
• Biology is marked by “discoveries,” while technology is marked by
“inventions”
• The combination of science and technology has dramatic effects on
society
Example: The discovery of DNA by James Watson and Francis Crick
allowed for advances in DNA technology such as testing for hereditary
diseases
• Ethical issues can arise from new technology, but have as much to do with
politics, economics, and cultural values as with science and technology
© 2011 Pearson Education, Inc.
DNA Technology And Crime Scene Investigation
The Value of Diverse Viewpoints in
Science
• Many important inventions have occurred where
different cultures and ideas mix
Example: The printing press relied on innovations
from China (paper and ink) and Europe (mass
production in mills)
• Science benefits from diverse views from different
racial and ethnic groups, and from both women
and men
© 2011 Pearson Education, Inc.
Key Concepts
1.
2.
3.
4.
5.
6.
A number of unifying themes characterize the biological
sciences
Evolution is the core theme in Biology, and accounts for the
unity and diversity of life
All organisms can be classified into three domains of life
The theory of natural selection explains the unity and
diversity in life
In studying nature, scientists make observations, form and
test hypotheses
Science benefits from a co-operative approach and diverse
viewpoints
© 2011 Pearson Education, Inc.