Chapter 1Chapter 1
Exploring Life
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Biology - the scientific study of life
The phenomenon we call life
– We recognize life by what living things do
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HIGHLY ORDERED
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EVOLUTIONARY ADAPTATION
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RESPOND TO ENVIRONMENT
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REGULATIONLiving things adjust and control cell processesto maintain conditionssuitable for life
HOMEOSTASIS
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ENERGY PROCESSING
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GROWTH & DEVELOPMENT
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REPRODUCTION
Ecosystems
Communities
Organisms
Populations
Biosphere
A Hierarchy of Biological Organization
8 Cells
6 Organs and organ systems
7 Tissues
10 Molecules
9 Organelles
50 µm
10 µm
1 µm
Atoms
New properties emerge with each step up in hierarchy of biological
orderStructural arrangement and interaction
of parts is important to function!
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EMERGENT PROPERTIES~ the sum is greater than the parts
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Individual amino acids don’t catalyze chemical reactions… but proteins do!
11 MAJOR THEMES
that unify
biology
Connect concepts and provide aframework forunderstanding
Unifying Themes in Biologyconnect concepts & provide framework for understanding
•Evolution ~ biology’s core theme; differential reproductive success
•Emergent Properties ~ the sum is greater than the parts
•The Cell ~ basic structure of all organisms
•Heritable Information ~ DNA
•Structure & Function ~ form follows function
•Environmental Interaction ~ organisms are open systems
•Energy and life ~ work requires energy that flows from sunlight to producers to consumers
•Regulation ~ feedback mechanisms
•Unity & Diversity ~ universal genetic code
•Scientific Inquiry ~ observation; testing; repeatability
•Science, Technology & Society ~ functions of our world
Evolution – Evolution, biology’s core theme, explains both the unity and diversity of life. The Darwinian theory of natural selection accounts for adaptation of populations to their environment through the differential reproductive success of varying individuals.
11 MAJOR THEMES that unify biology
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EVOLUTION is the CORE THEME
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11 MAJOR THEMES that unify biology
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Energy and Life – All organisms must perform work, which requires energy. Energy flows from sunlight to producers to consumers.
Producers
(plants and other
photosyntheticorganisms)
Consumers(including animals)
Sunlight
Chemical
energy
Heat
Heat
Ecosystem
11 MAJOR THEMES that unify biology
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Continuity and Change (Unity & Diversity) – All species tend to maintain themselves from generation to generation using the same genetic code. However, there are genetic mechanisms that lead to change over time, or evolution.
•Diversity is a hallmark of life BUT . . .
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. . . as diverse as life is, there is also evidence of remarkable unity
Cilia of Paramecium.The cilia of Parameciumpropel the cell throughpond water.
Cross section of cilium, as viewedwith an electron microscope
15 µm
1.0 µm
5 µm
Cilia of windpipe cells. The cells that line the human windpipe are equipped with cilia that help keep the lungs clean by moving a film of debris-trapping mucus upward.
11 MAJOR THEMES that unify biology
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Structure and Function – Form and function are correlated at all levels of biological organization
11 MAJOR THEMES that unify biology
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Regulation - Everything from cells to organisms to ecosystems is in a state of dynamic balance that must be controlled by positive or negative feedback mechanisms.
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In feedback regulation
– The output, or product, of a process regulates that very process
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• In negative feedback
– An accumulation of an end product slows the process that produces that product
B
A
C
D
Enzyme 1
Enzyme 1
Enzyme 2
Enzyme 3
DD D D
D
D
DD
DD
C
B
A Negative feedback
Example: sugar breakdown generates ATP; excess ATP inhibits an enzyme near the beginning of the pathway
• In positive feedback (less common)
– The end product speeds up production WW
X
Y
Z
ZZ
ZZ
Z
Z Z Z
Z Z Z Z
Z
ZZ Z
ZZ
Y
X
Enzyme 4
Enzyme 5
Enzyme 6
Enzyme 4
Enzyme 5
Enzyme 6
Positivefeedback
EXAMPLE: Chemicals released by platelets that accumulate at injury site, attract MORE platelets to the site.
11 MAJOR THEMES that unify biology
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Interdependence in Nature – No organism
“is an island”.
Organisms are open systems that exchange materials and energy with their surroundings.
11 MAJOR THEMES that unify biology
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Science as a Process - Science is a way of knowing. It can involve a discovery process using inductive reasoning, or it can be a process of hypothesis testing.
11 MAJOR THEMES that unify biology
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Science, Technology, and Society – Scientific research often leads to technological advances that can have a positive and/or negative impacts on society as a whole.
11 MAJOR THEMES that unify biology
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Cells are every organism’s basic units of structure and function.
The TWO main types of cells are: PROKARYOTES (bacteria & archaea) EUKARYOTES
(protists, fungi, plants & animals)
11 MAJOR THEMES that unify biology
HERITABLE INFORMATION-The continuity of life depends on the inheritance of biological information in the form of DNA molecules. This genetic information in encoded in the nucleotide sequences of the DNA
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11 MAJOR THEMES that unify biology
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EMERGENT PROPERTIES-The living world has a hierarchical organization, extending from molecules to the biosphere. With each step upward in level, system properties emerge as a result of interactions among components at the lower levels.
How can we understand biological systems?
DILEMMA:
Because of EMERGENT PROPERTIESwe can’t fully explain a higher level of order by breaking it into parts, but . . . organisms are too complex to analyze without taking them apart!
TWO STRATEGIES :
REDUCTIONISM SYSTEMS BIOLOGY
REDUCTIONISM
Reducing complex systems to simpler components that are more manageable to study
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EXAMPLE:By studying the molecular structure of DNA, James Watson & Francis Crick were able to infer how this
molecule could serve as thechemical basis of inheritance
The study of DNA structure has led tofurther study of heredity, such as the Human Genome Project
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SYSTEMS BIOLOGY tries to understand how all parts are functionally integrated
Systems biology
• Seeks to create models
– Diagrams
– Graphs
– 3-D objects
– Computer programs
– Mathematical equations
• models of ideas, structures, and processes help us understand scientific phenomena and make predictions
To lungs To body
Rightartium
Rightartium
Rightventricle
Right ventricle
Fromlungs
Frombody
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Concept 1.5: Biologists use various forms of inquiry to explore life
• At the heart of science is inquiry
– A search for information and explanation, often focusing on specific questions
• Biology blends two main processes of scientific inquiry
– Discovery science
– Hypothesis-based science
Discovery science
– Describes natural structures and processes as accurately as possible through careful observation and analysis of data
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Types of Data
• DATA are recorded observations
Can be:
– Quantitative involves analysis of numerical data(measure, count, etc)
– Qualitative involves analysis of data such as words (e.g., from interviews), pictures (e.g., video), or objects (e.g., an artifact).
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Induction in Discovery Science• In inductive reasoning
– Scientists derive generalizations based on a large number of specific observations
EX: “The sun always rises in the East.”
“All living things are made of cells.”
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Hypothesis-Based Science (Deductive reasoning)
• Inquiry that asks specific questions
– Usually involves the proposing and testing of hypothetical explanations, or hypotheses
• Hypothesis
– Is a tentative answer to a well-framed question, an explanation on trial
– Makes predictions that can be tested
– Usually expressed as an:
If…., then …. statement
Deduction: The “If…then” Logic of Hypothesis-Based Science
• In deductive reasoning
– The logic flows from the general to the specific
• If a hypothesis is correct
– Then we can expect a particular outcome
• We all use hypotheses in solving everyday problems
Observations
Questions
Hypothesis # 1:Dead batteries
Hypothesis # 2:Burnt-out bulb
Prediction:Replacing batterieswill fix problem
Prediction:Replacing bulbwill fix problem
Test prediction
Test does not falsify hypothesis
Test prediction
Test falsifies hypothesis
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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
An hypothesis can only be proven to be FALSE, never proven to be TRUE!
The Myth of the Scientific Method• The scientific method
– is an idealized process of inquiry
• There is not “ONE” methodMay design experiment, then backtrack when realize need more observations
May redirect research if realize been“barking up wrong tree”
Hind sight is 20/20
EXPERIMENTAL DESIGN• A CONTROLLED experiment must see the
effect of ONE VARIABLE at a time
• Hard to do in field/lab
• Don’t eliminate unwanted variables…. cancel their effects by using a CONTROL GROUP
• Must be repeated (at least 3 X)
• Can’t ignore or rule out data which do not support the hypothesis
VARIABLESA variable is any factor, trait, or condition that
can exist in differing amounts or types.
– independent variable is the one that is changed by the scientist.
– dependent variable is observed to see how it responds to the change made to the independent variable. The new value of the dependent variable is caused by and depends on the value of the independent variable.
– controlled variables. are quantities that a scientist wants to remain constant, and must be observed as carefully as the dependent variables.
HYPOTHESIS
Independent variable(What I change)
Dependent variable(What I observe)
Controlled variables(What I keep the same)
If fertilizer is added, then a plant will grow bigger.
Measure amount of fertilizer (grams)
•Growth of the plant measured by its height
•Growth of the plant measured by the number of leaves
•There are other ways to measure growth
•Same size pot
•Same type of plant
•Same type and amount of soil
•Same amount of water and light
•Make measurements of growth for each plant at the same time
The many variables above can each change how fast a plant grows, so to insure a fair test of the fertilizer, each of them must be kept the same for every pot.
“IT’S JUST A THEORY”In every day conversation, a theory often implies an untested guess.
In science, the word “theory” means something different than in common usage.
• Broader than a hypothesis• General enough to spin off more hypotheses• Supported by a massive body of evidence
“IT’S JUST A THEORY”
A theory is a well supported, testable explanation of natural phenomena.
EX: Cell Theory, Gravitational theory, or Atomic theory
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TECHNOLOGY applies scientific knowledge for a specific purpose
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