Chapter 1
Introduction: Themes in the Study of Life
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Lectures by Chris Romero
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• Overview: What is Biology?
• Biology is the scientific study of life
• People who study it are "biologists“
• Biologists are moving closer to understanding:
– How a single cell develops into an organism
– How plants convert sunlight to chemical energy
– How the human mind works
– How living things interact in communities
– How life’s diversity evolved from the first microbes
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• Life’s basic characteristic is a high degree of order
• Each level of biological organization has emergent
properties
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Characteristics of life
1. The ordinate structures
All organisms consist of the basic unit:
cell
– Basic life unit: Cell, (organelles and biological
macromolecules)
– Biosphere: cell, tissue, organ, organ system,
organism (individual), population, community
and ecosystem
– Without such ordinate structures, there is no
life
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Characteristics of life
– Unicellular (Prokaryotic) organisms
• Single cell
– Multicellular (Eukaryotic) organisms
• Many cells organized to form tissues, organs,
and organ systems
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Characteristics of life
2. Metabolism processes
Living organisms carry out metabolism in which they
use and transform energy.
–
Chemical reactions and energy transformations
–
Growth and repair of cells, and conversion of energy
–
Regulation of metabolic processes maintains
homeostasis
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Characteristics of life
3. All living things maintain stable internal
conditions, or homeostasis.
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Characteristics of life
4. Growth
– Increase in the size of cells, the number of
cells, or both
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Characteristics of life
5. Living organisms reproduce
– Reproduction in plants and animals takes place
sexually, resulting in the production of offspring.
– Reproduction can also occur via asexual
propagation
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Characteristics of life
6. Heredity:
• All living things possess a genetic system
based on DNA and transmit characteristics
from parent to offspring in a process called
heredity
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Characteristics of life
7. Adaptation (Response to the environment)
– Organisms evolve to better survive
– Adaptations to the environment
• Characteristics that enhance an organism’s
ability to survive in a particular environment
• May be structural, physiological, behavioral,
or a combination
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Figure 1.3
Order
Response to
the environment
Evolutionary adaptation
Reproduction
Regulation
Energy processing
Growth and
development
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Figure 1.3g
Order
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A Hierarchy of Biological Organization
1. Biosphere: all environments on Earth
2. Ecosystem: all living and nonliving things
in a particular area
3. Community: all organisms in an ecosystem
4. Population: all individuals of a species
in a particular area
5. Organism: an individual living thing
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A Hierarchy of Biological Organization (continued)
6. Organ and organ systems: specialized body
parts made up of tissues
7. Tissue: a group of similar cells
8. Cell: life’s fundamental unit of structure and
function
9. Organelle: a structural component of a cell
10. Molecule: a chemical structure consisting of
atoms
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The biosphere
Ecosystems
Organelles
1 µm
Cell
Cells
Atoms
10 µm
Communities
Molecules
Tissues
50 µm
Populations
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Organisms
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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Organs and organ systems
Figure 1.4a
The biosphere
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Figure 1.4b
Ecosystems
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Figure 1.4c
Communities
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Figure 1.4d
Populations
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Figure 1.4e
Organisms
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Figure 1.4f
Organs and
organ systems
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Figure 1.4g
50 m
Tissues
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Figure 1.4h
Cell
Cells
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10 m
Figure 1.4i
Chloroplast
1 m
Organelles
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Figure 1.4j
Atoms
Chlorophyll
molecule
Molecules
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Concept 1.1: Biologists explore life from the microscopic to
the global scale
• The study of life extends from molecules and cells
to the entire living planet
• Biological organization is based on a hierarchy of
structural levels
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A Hierarchy of Biological Organization
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Populational level
Organism
Population
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Community Ecosystem
29
A Closer Look at Ecosystems
• Each organism interacts with its environment
• Both organism and environment affect each other
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Ecosystem Dynamics
• The dynamics of an ecosystem include two major
processes (functions):
– Cycling of nutrients, in which materials
acquired by plants eventually return to the soil
– The flow of energy from sunlight to producers
to consumers
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Figure 1.5
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.
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Animals eat
leaves and fruit
from the tree.
Cycling of nutrients: (Nitrogen cycle)
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The phosphorus cycle
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The functions of Ecosystem
•Energy flow
•Ecosystems depend
on continuous input
of energy
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Ecosystem
• Organisms can neither create energy nor use it with complete
efficiency
• During every energy transition, some is lost to the
environment as heat
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Energy Conversion
• Activities of life require work
• Work depends on sources of energy
• Energy exchange between an organism and
environment often involves energy transformations
• In transformations, some energy is lost as heat
• Energy flows through an ecosystem, usually
entering as light and exiting as heat
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LE 1-4
Sunlight
Ecosystem
Producers
(plants and other
photosynthetic
organisms)
Heat
Chemical
energy
Consumers
(including animals)
Heat
A Closer Look at Cells
• The cell is the lowest level of organization that can
perform all activities of life
• The ability of cells to divide is the basis of all
reproduction, growth, and repair of multicellular
organisms
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Theme: The Cell Is an Organism’s Basic Unit of
Structure and Function
• All cells
– Are enclosed by a membrane
– Use DNA as their genetic information
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Two Main Forms of Cells
• Characteristics shared by all cells:
– Enclosed by a membrane
– Use DNA as genetic information
• Two main forms of cells:
– Eukaryotic: divided into organelles; DNA in
nucleus
– Prokaryotic: lack organelles; DNA not
separated in a nucleus
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• A eukaryotic cell has membrane-enclosed
organelles, the largest of which is usually the
nucleus
• By comparison, a prokaryotic cell is simpler and
usually smaller, and does not contain a nucleus or
other membrane-enclosed organelles
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© 2011 Pearson Education, Inc.
Figure 1.8
Prokaryotic cell
Eukaryotic cell
Membrane
DNA
(no nucleus)
Membrane
Cytoplasm
Nucleus
(membraneenclosed)
Membraneenclosed organelles
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DNA (throughout
nucleus) 1 m
Structure
of a plant
cell
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Structure
of an
animal
cell
Cells
Basic unit of organismal organization;
compartmentalize macromolecules and organelles
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• Prokaryotes have a very simple architecture
– They lack a nucleus and organelles
Pilus
Found in all
prokaryotes
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The Cell’s Heritable Information
• Cells contain DNA, the heritable information that
directs the cell’s activities
• DNA is the substance of genes
• Genes are the units of inheritance that transmit
information from parents to offspring
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LE 1-6
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
Figure 1.11
Nucleus
A
C
DNA
Nucleotide
T
A
T
Cell
A
C
C
G
T
A
G
T
A
(a) DNA double helix (b) Single strand of DNA
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• Each DNA molecule is made up of two long chains
arranged in a double helix
• Each link of a chain is one of four kinds of
chemical building blocks called nucleotides and
nicknamed A, G, C, and T
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DNA molecule
The DNA double
helix
• Each DNA molecule is made up of
two long chains arranged in a double
helix
• Each link of a chain is one of four
kinds of chemical building blocks
called nucleotides
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Concept 1.2: Biological systems are much more
than the sum of their parts
• A system is a combination of components that
form a more complex organization
• System = a network of relationships among a
group of parts, elements, or components that
interact with and influence one another through
the exchange of energy, matter, and/or
information
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The Emergent Properties of Systems
• Emergent properties result from arrangements
and interactions within systems
• New properties emerge with each step upward in
the hierarchy of biological order
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Emergent properties
Properties of a
whole system
not evident in
the system’s
components
“The whole is
more than the sum
of its parts.”
A tree is an
element of a forest,
a sink for CO2, and
habitat for birds.
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Systems show several defining properties
• Systems receive input, process it, and produce
output.
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Feedback loops: Negative feedback
Feedback loop = a circular process whereby a
system’s output serves as input to that same
system
•In a negative feedback loop, output acts as input that moves
the system in the opposite direction.
This compensation stabilizes the system
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Feedback loops: Positive feedback
• In a positive
feedback loop,
output acts as input
that moves the
system further in
the same direction.
• This magnification
of effects
destabilizes the
system.
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Positive feedback
• In a positive feedback loop, the output drives the
system further toward one extreme.
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• In negative feedback, the accumulation of a
product slows down the process itself
• In positive feedback (less common), the product
speeds up its own production
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• Concept 1.3: Biologists explore life across its
great diversity of species
• Biologists have named about 1.8 million species
• Estimates of total species range from 10 million to
over 200 million
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Grouping Species: The Basic Idea
• Taxonomy is the branch of biology that names and
classifies species into a hierarchical order
• Kingdoms and domains are the broadest units of
classification
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The Three Domains of Life
• At the highest level, life is classified into three
domains:
– Bacteria (prokaryotes)
– Archaea (prokaryotes)
– Eukarya (eukaryotes)
Eukaryotes include protists and the kingdoms
Plantae, Fungi, and Animalia
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Three-Domain Classification
• Archaea
– Prokaryotesin cell walls
• Bacteria
– Prokaryotesin cell walls
• Eukarya
– all eukaryotes: protists, fungi, plants, animals
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Three-Domain Classification
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Protists Plants Fungi Animals
First eukaryote
Bacteria
Archaea
Stepped Art
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Fig. 23-4b, p. 489
Figure 1.15
2 m
(b) Domain Archaea
2 m
(a) Domain Bacteria
(c) Domain Eukarya
Kingdom Animalia
100 m
Kingdom Plantae
Protists
Kingdom Fungi
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LE 1-15
Bacteria
Archaea
4 µm
0.5 µm
Protists
Kingdom Fungi
100 µm
Kingdom Plantae
Kingdom Animalia
Charles Darwin
• The evolutionary view of life came into sharp focus
in 1859, when Charles Darwin published On the
Origin of Species by Natural Selection
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• The Origin of Species articulated two main points:
– Descent with modification (the view that
contemporary species arose from a
succession of ancestors)
– Natural selection (a proposed mechanism for
descent with modification)
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Natural Selection
• Darwin inferred natural selection by connecting
two observations:
– Observation: Individual variation in heritable
traits
– Observation: Overpopulation and competition
– Inference: Unequal reproductive success
– Inference: Evolutionary adaptation
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LE 1-20
Population
of organisms
Overproduction
and competition
Hereditary
variations
Differences in
reproductive success
Evolution of adaptations
in the population
Darwin’s theory: variation is inherited
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The Tree of Life
• Many related organisms have similar features
adapted for specific ways of life
• Such kinships connect life’s unity and diversity to
descent with modification
• Natural selection eventually produces new species
from ancestral species
• Biologists often show evolutionary relationships in
a treelike diagram
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Tree of Life
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Results of Cladistic Analyses Sometimes Run Counter to Classical
Classification Schemes
Which pair is more closely related? A lizard/crocodile or bird/crocodile?
Cladistic analysis indicates that the bird/crocodile pair is more closely related.
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The Classification of Living Things
• Taxomony is the science of identifying and
classifying organisms according to specific
criteria using these categories:
Kingdom
Phylum (Division)
Class
Order
Family
Genus
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Species
Taxa
• Hierarchical system of classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Higher Categories
• Taxonomists use a hierarchical system to classify organisms
Information
gets more
and more
general
– Species
spaghetti
– Genus
green
– Family
for
– Order
– Class
– Phylum
– Kingdom
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over
came
Philip
King
• Concept 1.5: Biologists use various forms of
inquiry to explore life
• Inquiry is a search for information and explanation,
often focusing on specific questions
• The process of science blends two main
processes of scientific inquiry:
– Discovery science: describing nature
– Hypothesis-based science: explaining nature
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Discovery Science
• Discovery science describes nature through
careful observation and data analysis
• Examples of discovery science:
– understanding cell structure
– expanding databases of genomes
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Types of Data
• Data are recorded observations
• Two types of data:
– Quantitative data: numerical measurements
– Qualitative data: recorded descriptions
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Induction in Discovery Science
• Inductive reasoning involves generalizing based
on many specific observations
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A Closer Look at Hypotheses in Scientific Inquiry
• A scientific hypothesis must have two important
qualities:
– It must be testable
– It must be falsifiable
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Scientific method
• The scientific method involves systematic
thought
– Deductive reasoning draws conclusions from
premises
– Inductive reasoning begins with observations
and draws conclusions or extrapolates
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Stage of a scientific method
The scientific method involves 6
steps:
1. Observation: Find a question
2. Hypothesis
3. Predictions
4. testing: experiment
5. Control
6. Results and Conclusion
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1. Observation
• You might observe something unusual or
something very common.
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2. Hypothesis
• A hypothesis attempts to explain an observation. It is an
educated guess
• As questions are asked, scientist attempt to answer
those questions by proposed explanations that answer
the questions.
• Those proposed explanations are called hypothesis.
• Alternative hypotheses: If they have more than one
guess about what they observe.
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Hypothesis-Based Science
• In science, inquiry usually involves proposing and
testing hypotheses
• Hypotheses are hypothetical explanations
– Educated guess
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The Role of Hypotheses in Inquiry
• In science, a hypothesis is a tentative answer to a
well-framed question
• A hypothesis is an explanation on trial, making a
prediction that can be tested
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Prediction: The “If…then” Logic of Hypothesis-Based Science
• In deductive reasoning, the logic flows from the
general to the specific
• In inductive reasoning begins with observations
and draws conclusions or extrapolates
1. Observation: Find a question
– 2. Hypothesis
– 3. Predictions
– 4. testing: experiment
– 5. Control
– 6. Results and Conclusion
• If a hypothesis is correct, then we can expect a
particular outcome
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LE 1-25a
Observations
Question
PowerPoint Lectures for
Biology, Seventh Edition
Hypothesis #1:
Neil Campbell and Jane Reece
Dead batteries
Lectures by Chris Romero
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Hypothesis #2:
Burnt-out bulb
LE 1-25b
Hypothesis #1:
Dead batteries
Hypothesis #2:
Burnt-out bulb
Prediction:
Replacing batteries
will fix problem
Prediction:
Replacing bulb
will fix problem
Test prediction
Test prediction
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Test
falsifies
hypothesis
Lectures
by Chris
Romero
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Test does not falsify hypothesis
3. Prediction
• The prediction states the expected results of
the experiments based on the hypothesis.
Predictions often take the form of an
“if…then…” statement: “IF the hypothesis is
correct, then the results of the experiment will
be…”
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4. Testing
• Test the hypothesis by attempting to verify
some of its predictions
• We called the test of a hypothesis an
experiment (Procedure, process)
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How to perform the testing
• Set up the variables
– Independent variables
– Dependent variables
– Control variables
• Control treatments (standard, or zero)
• Levels of treatment
• Replications
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Variables
• The independent variable is what the investigator
varies during the experiment.
 It is what the investigator thinks will affect the
dependent variable.
• The dependent variable is what the investigator
measures (or counts or records).
 It is what the investigator thinks will be affected during
the experiment.
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5. Controls: Designing Controlled Experiments
• Controlled variables: we test one independent variable
and keep the other factors are constant
– Scientists do not control the experimental environment by
keeping all variables constant
• Control treatment: A control is a treatment in which the
independent variable is either eliminated or set at a
standard value.
– Researchers usually “control” unwanted variables by using
control groups to cancel their effects
• Zero test
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Results:
Figure 1. Relationship between plant weight and fertilizer content
12
Expected curve
Actual curve
Average weight of plants (kg)
10
8
6
4
2
0
0
1
2
3
4
Conentration of fertilizer (%)
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5
6
7
Other graphs: Bar Chart, Pie chart
-1
Mean FCO2 (mol m-2 s )
10
9
Gap
Non-gap
8
7
**
6
**
**
5
4
3
2
0
2
4
6
8
Years after harvesting
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10
1
2
3
4
6. Conclusion
• The results either support or do not support the
hypothesis.
• As long as the experiment is good, whatever
the results is same or different with the
hypothesis, the results is valid
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Experimental design
Completely randomized
design (CRD)
Tree diameters in
response to
Fertilization
experiment
Treatment:
Concentration of
Fertilization
F50kg/ha
F100kg/ha
(year6)
Total 4*5*=20
Tree diameters
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F150kg/ha
C0
In the fertilizer example
• the control would be treatment in which no
fertilizer is applied or some standard amount
of fertilizer is applied.
• This allows the scientist to be sure that the
effect on the dependent variable is in fact
due to the independent variable.
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings