Transcript Discover Biology

Anu Singh-Cundy • Gary Shin
Discover Biology
SIXTH EDITION
CHAPTER 1
The Nature of Science and the
Characteristics of Life
© 2015 W. W. Norton & Company, Inc.
CHAPTER 1
The Nature of Science and the
Characteristics of Life
EARTHBOUND EXTRATERRESTRIAL? OR JUST ANOTHER MICROBE IN
THE MUD?
1.1
The Nature of Science
People like you are contributing to the advance of science
Science is a body of knowledge and a process for generating that knowledge
Scientific hypotheses must be testable
The scientific method requires objectivity
1.2
The Process of Science
Observations are the wellspring of science
Scientific hypotheses make clear-cut predictions
Scientific hypotheses must be refutable, but cannot be proved beyond all doubt
Hypotheses can be tested with observational studies
Correlation is not causation
Experiments are the gold standard for establishing causation
© 2015 W. W. Norton & Company, Inc.
1.3
Scientific Facts and Theories
1.4
The Characteristics of Living Organisms
Living organisms are composed of cells
Living organisms reproduce themselves via DNA
Living organisms obtain energy from their environment
Living organisms sense their environment and respond to it
Living organisms actively maintain their internal conditions
Groups of living organisms can evolve
1.5
Biological Evolution and the Unity and Diversity of Life
Populations of a given species can evolve over the generations
Natural selection favors individuals with adaptive traits
Natural selection adapts a population to its habitat
Darwin and Wallace explained how natural selection produces new species
We can categorize all known species into three domains of life
1.6
The Biological Hierarchy
BIOLOGY MATTERS: SCIENCE AND THE CITIZEN
APPLYING WHAT WE LEARNED: RESEARCHERS WRANGLE OVER
BACTERIA
© 2015 W. W. Norton & Company, Inc.
Earthbound Extraterrestrial? Or Just
Another Microbe in the Mud?
• The claim: Mono Lake bacterium has arsenic instead
of phosphorus in its DNA!
• Are you convinced? How does science settle such
controversies?
We will return
to this story!
Biology Is the Scientific Study of Life
• This course is about us and how we connect with
other living beings and our surroundings.
• Many controversies facing society today require an
understanding of
the underlying
science, so we
can make
informed
decisions.
Is de-extinction
a good idea?
The Nature of Science
• The spirit of inquiry is the driving force behind science.
• Scientific thinking is objective and values evidence over
all other ways of discovering the truth.
Do you recall
any questions
about nature
that you
asked when
you were
little?
Citizen Scientists Are Contributing to the
Growth of Scientific Knowledge
Data collected by birders shows migratory birds aren’t going
as far south in the winter as they used to.
Some Examples of Citizen Science Projects
Science Is a Body of Knowledge and a
Process for Generating That Knowledge
The Process That Generates Scientific
Knowledge Is Called the Scientific Method
• The scientific method represents the core logic of how
science works.
• The scientific method is also known as the process of
science.
• It is central to scientific inquiry,
and is also applied in other
areas such as sociology
and law.
The Scientific Method: A Concept Map
The scientific method relies on observations, hypotheses, and hypothesis testing
through additional observations and/or experiments.
The Scientific Method Requires Objectivity
• Independent researchers should be able verify the
observations and experimental results.
• The process of peer review seeks to limit bias and
fraud in the scientific community.
• Peer review is assessment by experts who have no
direct involvement in the research under review.
A Deeper Look at the Scientific Method
Observations Are the Wellspring of Science
• The process of science
begins with observations
of the natural world.
• An observation is a
description,
measurement, or record
of any object or
phenomenon.
• An observation must be
reproducible.
A Hypothesis Is an Educated Guess
That Seeks to Explain the Observations
Scientific Hypotheses Must Be Testable
and Refutable
A Scientific Hypothesis Leads to
Testable Predictions
Hypotheses Can Be Tested with
Observations or Experiments or Both
• Observational studies can be descriptive (listing
what, where, when, how much) or analytical (asking
why; seeking to explain patterns in nature).
• Descriptive and analytical studies report information
(data) that can be used to build and then test a
hypothesis.
• Scientists use mathematical tools such as statistics to
estimate the reliability of data.
An Observational Study:
Higher Fish Consumption Is Correlated with
Lower Risk of Death from Heart Disease
• A variable is any aspect
of nature that is capable
of changing.
• Correlation means
two variables behave in
an interrelated manner:
the value of one variable
predicts the value of the
other variable.
Correlation Is Not Causation
• The correlation between fish consumption
and better heart health could be a
spurious correlation.
80
Percent high school grads
entering college
• Observational studies cannot demonstrate
that a change in one variable is the cause
of a change in the other variable.
70
60
50
40
30
20
Source: Department of
Labor Statistics
10
0
1960 1970 1980 1990 2000 2010
16.2
Temperature (0C)
• In a spurious correlation, a third
variable, such as higher income,
is the real cause of the observed
correlation.
Increase in average global temperature
16
15.8
15.6
15.4
15.2
15
1960
There is a correlation between global
warming and college enrollments!
1970
1980
1990
2000
2010
Is global warming driving young people to
college?
Experiments Are the Gold Standard for
Establishing Causality
• An experiment is a repeatable manipulation of one
or more aspects of the natural world by the
investigator.
Heart disease mortality
• In a controlled experiment, at least two groups are
compared, with the treatment group experiencing a
change in one variable, whereas that variable is
constant for the control group.
Control
Treatment
• Study subjects: 2,000 men
diagnosed with heart disease,
randomly assigned to control
or treatment group
• Control group: not directed to
alter diet in any way
• Treatment (experimental)
group: asked to take 900 mg of
fish oil daily
Conclusion: The experimental
data support the hypothesis
Heart disease mortality
A Controlled Experiment to Test the Health
Benefits of Fish Oil Supplements
In an Experiment, the Independent Variable Is
Manipulated in the Treatment Group
• The variable that the investigator manipulates in an experiment is called the
independent variable.
• Typically, there is only one independent variable in an experiment, and all other
variables are kept constant as much as possible.
• The independent variable is altered only for the treatment group (not for the
control group).
• The dependent variable is a variable that can potentially change when the
independent variable is altered.
• The goal in an experiment is to measure how a change in the independent variable
changes the value of the dependent variable; the dependent variable is not
expected to change in the control group.
A Double-Blind Study Reduces Experimenter Bias
and Estimates the Placebo Effect in Studies on Humans
Dependent
variable
This is the effect.
Independent
variable
This is the cause.
• In a double-blind study, neither the subjects nor the investigator knows who is
receiving the treatment and who is a control subject.
• The placebo effect is the (potentially false) feeling in a study participant that he or
she has benefited from the experimental treatment.
Testing Does Not Prove a Hypothesis
with Absolute Certainty
• A hypothesis can be
supported, but
never proven true.
• When a hypothesis
is refuted, it must
be reexamined and
then changed or
discarded.
A single black swan can refute
the hypothesis that all swans are white.
A Scientific Theory Is a Major Body of
Knowledge That Has Stood the Test of Time
• Scientific hypotheses becomes a scientific theory:
– After they have been repeatedly confirmed through
diverse methods of testing
– When they are accepted by experts as the best
explanation of the truth about the phenomenon
A Scientific Fact Is a Direct and Repeatable
Observation about the Natural World
Examples of Scientific Theories
Examples of Scientific Facts
Germ theory of disease: some diseases are
caused by infectious microbes.
The HIV-AIDS virus contains genetic material.
Cell theory: all living organisms are
composed of one or more cells.
Many different types of cells can be found in
the body of an adult human.
Evolution by natural selection: natural
variables may favor individuals with certain
inherited traits over individuals that lack
those traits, and as a result the favored traits
become more common in the succeeding
generations.
A population of E. coli bacteria can evolve
over time.
Anthropogenic climate change theory: global The average global temperature of Earth has
warming, caused at least in part by human
increased by at least 10C in the past 100
actions, has changed the climate of our
years.
planet.
The range of some species has shifted
northward in Europe and North America.
Because of Their Common Origin, All Living
Organisms Share Certain Key Characteristics
Living Organism Are Composed of Cells
• Cells are the foundation for
all living things.
• A cell is a self-contained unit
enclosed by a water-repellent
layer called the plasma
membrane.
• A bacterium is an example of
a single-celled organism.
• Multicellular organisms are
composed of many different
kinds of specialized cells
working together.
All Living Organisms Reproduce Via DNA
• DNA is genetic material that
contains all the instructions
for building, maintaining, and
growing a cell.
*
• In plant and animal cells,
DNA is stored within a
membrane-bound nucleus.
• A gene is a segment of DNA
that codes for a specific
genetic trait (inherited
characteristic).
*Nucleus: only in some
organisms; consists of
DNA enclosed within
membranes
Living Organisms Transmit Information to the Next
Generation (Offspring) in the Form of DNA
• In sexual reproduction,
DNA from two different
individuals is combined
in the offspring during
fertilization.
• Asexual reproduction
does not require
fertilization, and results
in offspring that are
genetically identical
to the one parent.
All Living Organisms Must Obtain Energy
from Their Environment
• Metabolism is the capture,
storage, and use of energy by
an organism.
• Producers obtain energy from
the nonliving part of their
environment.
• Consumers obtain energy from
the living part of their
environment (by consuming
producers or other
consumers).
Living Organisms Sense Their Environment
and Respond to It
Sharks are more sensitive to electrical fields than any other animal. Electroreceptors on the snout
enable sharks to detect minute electrical currents generated by their prey as a side effect of their
metabolic processes. Shark attacks destroyed a lot of undersea phone cables in the early years of
the telegraph.
Living Organisms Maintain Their
Internal Conditions
• Organisms maintain constant internal conditions through a
process called homeostasis, despite fluctuations in their
external environment.
Groups of Living Organisms Can Evolve
• Biological evolution is a
change in the overall
genetic characteristics in a
group of organisms over the
generations.
• Artificial selection is
evolutionary change caused
by humans; it occurs when
we select plants and
animals with preferred traits
for breeding.
Natural Selection Is an Evolutionary Mechanism That
Causes Adaptive Traits to Become More Common
over the Generations
An adaptive trait is genetic characteristics that enables an
individual to survive and reproduce better than its competitors
in the population.
Natural Selection Produces Adaptation, the
Good Match between Organisms and Their
Environment
All species known to
science are given a
two-part scientific
name, such as
Antilocapra americana
for the pronghorn.
A Population Evolves (Not an Individual)
A population of
pronghorn (Antilocapra americana)
in the sagebrush steppes
of Wyoming
• A population is a group of organisms within a species
that lives in a particular habitat.
• A species is a group of organisms that interbreed
under natural conditions to produce fertile offspring.
Over Time, Two Populations Can Evolve
into Separate Species
• Populations isolated from
one another for a long time may
evolve along different paths
to become distinctly different
Species.
• All the species on our planet
are grouped into three broad
categories called domains.
• Domain Eukarya is divided
into four main kingdoms.
• The tree of life depicts the
evolutionary relationship among
these domains and their descent
from a common ancestor.
The Biological
Hierarchy
Is a Concept Map
for Visualizing the
Breadth and
Scope of Life
The biological hierarchy shows
the many levels
at which biology can be studied.
• Atoms are the building
blocks of matter,
which compose the
universe.
• A molecule is created
when two or more
atoms are held
together by chemical
bonds.
• Biomolecules are
molecules found in all
living cells and
generally contain
carbon.
• The cell is the smallest
unit of life.
• Groups of cells that
perform a set of
unique tasks form a
tissue.
• Different types of
tissues make up an
organ, which performs
a broader range of
functions than any of
the individual tissue
types.
• Organs are networked into
organ systems that come
together to form an
individual organism.
• A population is
composed of
individuals of a single
species that interact
and interbreed in a
shared environment.
• Populations of
different species that
live in a shared
environment form a
biological community.
• A physical environment and all
the communities in it make up
an ecosystem.
• Biomes are large regions of
the world that have similar
physical characteristics and
therefore similar types of
organisms.
• At the highest level of the
biological hierarchy, all biomes
become part of the
biosphere, which is defined as
all the world’s living organisms
and the places where they
live.
BIOLOGY MATTERS: SCIENCE AND THE CITIZEN
• Public-funded research contributes to the advancements of science
--basic science
--technology
• Scientific literacy strengthens democracy
APPLYING WHAT WE LEARNED:
Researches Wrangle over Bacteria
• Previously, scientists had shown that DNA is made up of hydrogen,
oxygen, carbon, nitrogen, and phosphorus atoms
• The NASA-funded researchers claimed that in the Mono Lake
bacteria, arsenic replaces phosphorus in the DNA
• Evidence offered in support: in the lab, bacteria grow well in
‘phosphorus-free’ test tubes
• Critique of the hypothesis and tests: tubes not really free of
phosphorus; no phosphorus found in DNA purified from bacterium;
no adaptive value for using arsenic in DNA, since there’s plenty of
phosphorus in Mono Lake
• The claim is challenged because the tests
are not repeatable; alternative hypothesis
better explain the observations
Mono Lake at Sunset
List of Key Terms: Chapter 1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
adaptation (p. 19)
adaptive trait (p.19 )
Animalia (p. 20)
Archaea (p. 20)
asexual reproduction (p. 15)
atom (p. 20)
autotroph (p. 16)
behavior (p. 16)
biological evolution (p.18 )
biological hierarchy (p. 20)
biology (p. 4)
biome (p. 22)
biomolecule (p.20 )
biosphere (p. 22)
cell (p. 15)
community (p. 22)
consumer (p. 16)
control group (p. 12)
controlled experiment (p. 12)
correlation (p. 11)
data (p. 9)
dependent variable (p. 12)
development (p. 15)
DNA (p. 16)
domain (p.20)
double-blind experiment (p.13)
ecosystem (p. 22)
Eukarya (p.20)
experiment (p. 12)
fertilization (p. 15)
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Fungi (p. 20)
heterotroph (p. 16)
homeostasis (p. 16)
independent variable (p. 12)
individual (p. 22)
metabolism (p. 16)
microbe (p. 14)
molecule (p. 20)
multicellular organism (p. 15)
natural selection (p. 19)
nucleus (p. 16)
observation (p. 9)
organ (p. 20)
organ system (p. 22)
photosynthesis (p. 16)
placebo (p. 13)
placebo effect (p. 13)
Plantae (p. 20)
plasma membrane (p. 15)
population (p. 18)
producer (p. 16)
prokaryote (p. 20)
Protista (p. 20)
reproduction (p. 18)
science (p. 5)
scientific fact (p. 13)
scientific hypothesis (p. 6)
scientific method (p.5 )
•
•
•
•
•
•
•
•
•
scientific theory (p. 13)
sexual reproduction (p. 15)
single-blind experiment (p. 12)
species (p. 18)
statistics (p. 11)
technology (p. 4)
tissue (p. 20)
treatment group (p. 12)
variable (p. 11)
Class Quiz
Observations
?
Test
Revisions
Further tests
Hypothesis supported
Hypothesis rejected
Which word or phrase belongs in the box labeled with a question mark in
this concept map of the scientific method?
A.
B.
C.
D.
hypothesis
further observations
experiments
predictions
Class Quiz
A scientific hypothesis
A. must be testable repeatedly and independently.
B. cannot be used to generate a prediction because a
hypothesis is simply an educated guess.
C. is not testable in some disciplines such as
astronomy or evolutionary biology.
D. can be tested only through experiments, not
through observational studies.
Class Quiz
Reaction time was tested in sleepdeprived Navy Seals trainees. Cadets in
three treatment groups ate a snack bar
containing 100–300 milligrams of
caffeine. Those in the control group ate
a snack bar that tasted the same but
contained no caffeine. At the time of the
test, neither the trainees nor the
investigators knew whether a test taker
belonged to the treatment group or the
control group.
Which of the statements that follow is true?
A. This is an example of a descriptive observational study.
B. Cause and effect cannot be distinguished in such a study.
C. This is an example of a double-blind experiment.
D. The amount of caffeine consumed is the dependent variable in this study.
Class Quiz
To test the hypothesis that nitrogen fertilizer
improves corn production, agricultural
scientists applied different amounts of fertilizer
(0–250 kilograms per hectare) to separate corn
fields that were planted in exactly the same
way with exactly the same variety of corn. At
the end of the growing season, the researchers
measured the corn yield (kilograms of corn
cobs per hectare) and estimated the average
number of leaves per corn plant in each corn
field. Their data are plotted on this graph.
In this study
A. there were two variables that the scientist manipulated: corn yield and number of leaves.
B. the amount of nitrogen fertilizer added was the independent variable.
C. corn yield was the independent variable.
D. the control corn field gave the highest yield of corn cobs.
Class Quiz
Which of the following is a characteristic shared
by all living organisms?
A.
B.
C.
D.
Movement
Reproduction
Breathing
Having a nucleus
Relevant Art from Other
Chapters and Inside Back Cover
All art files from the book are available in
JPEG and PPT formats online and on the
Instructor Resource Disc
1.1 Concept Check
1. What characteristics of the process of
science set it apart from other ways of
knowing?
ANSWER: Scientific knowledge is acquired through evidence, and its
objectivity and accuracy are policed through peer review.
1.1 Concept Check
2. What mechanisms help bring objectivity to
the process of science?
ANSWER: Repeatability of observations and experiments, and the
requirement for peer-reviewed publication of scientific findings
1.2 Concept Check
1. Which type of test would you use to investigate a causal
link between two variables: an observational study or an
experiment?
ANSWER: A controlled experiment
1.2 Concept Check
2. How is a control group different from the
treatment (experimental) group?
ANSWER: The two groups are maintained under identical conditions,
except that the independent variable stays constant for the control group,
while changing for the treatment group.
1.3 Concept Check
1. How is a scientific hypothesis different from a scientific
theory?
ANSWER: A hypothesis is an educated guess that can be confirmed by
observation, experiments, or both. A scientific theory is a major
component of knowledge that has been confirmed through extensive
testing in many ways by independent researchers.
1.3 Concept Check
2. Is anthropogenic climate change an example of
a scientific hypothesis, fact, or theory?
ANSWER: Theory
1.4 Concept Check
1. What is the role of DNA in reproduction?
ANSWER: DNA stores information that can be passed from parent to
offspring through asexual or sexual reproduction.
1.4 Concept Check
2. Are humans producers or consumers in the
food web? Why?
ANSWER: We are consumers because we must obtain energy from the
living, rather than the nonliving, part of our environment.
1.5 Concept Check
1. Explain what is wrong with this statement: Over
time, a male white-tailed deer evolves larger antlers.
ANSWER: An individual deer does not evolve. A population of deer,
however, may evolve larger average antler size.
1.5 Concept Check
2. Which domain of life do humans belong to?
ANSWER: Eukarya
1.6 Concept Check
1. How is a population different from a
biological community?
ANSWER: A population is composed of members of the same species in
a shared habitat. A community refers to all members of all species that
share a common habitat.
1.6 Concept Check
2. Unscramble this scrambled biological hierarchy: community,
organ system, ecosystem, atom, tissue, individual, biosphere, organ,
cell, biome, population, molecule.
ANSWER: Atom, molecule, cell, tissue, organ, organ system, individual,
population, community, ecosystem, biome, biosphere