1.1 the diversity of life
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Animalia. Bacteria. Protista. Fungi. Archaea. Plantae. 1.1 The Diversity of Life. Biology is the study of living things Living things can be divided into six kingdoms. Fig. 1.1. 1.2 Properties of Life. Biology is the study of life But what does it mean to be alive? - PowerPoint PPT PresentationTRANSCRIPT
The Living WorldFourth Edition
GEORGE B. JOHNSON
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PowerPoint® Lectures prepared by Johnny El-Rady
1 The Science of Biology
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1.1 The Diversity of Life
Biology is the study of living things
Living things can be divided into six kingdoms
Fig. 1.1
Archaea Bacteria Protista
Fungi Plantae Animalia
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1.2 Properties of Life
Biology is the study of life
But what does it mean to be alive?
Living organisms and many non-living things share three properties
Complexity
Movement
Response to stimulation
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1.2 Properties of Life
All living organisms share five basic properties
1. Cellular OrganizationAll living organisms are composed of at least one cell
2. MetabolismAll living organisms use energy
3. HomeostasisAll living organisms maintain stable internal conditions
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1.2 Properties of Life
All living organisms share five basic properties
4. Growth and reproductionAll living organisms grow and reproduce
5. HeredityAll living organisms possess a genetic system that is based on DNA
Deoxyribonucleic acid
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1.3 The Organization of Life
Living organisms function and interact with each other at many levels
These levels are organized in a hierarchy of increasing complexity
Cellular Level
Organismal Level
Populational Level
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Fig. 1.4
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Fig. 1.4
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Fig. 1.4
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1.3 The Organization of Life
Each higher level contains novel properties not present at the simpler level of organization
These properties are termed emergent properties
They are a consequence of the structural organization that is the hallmark of life
They characterize many aspects of the living world
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1.4 Biological Themes
The living world is organized by major themes
Indeed, five general themes unify and explain biology as a science
Refer to Table 1.1
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1.4 Biological Themes
1. EvolutionThe genetic change in a species over time
It is a result of a process termed natural selection
Variation may also be caused by artificial selection
2. The Flow of EnergyAll living organisms require energy
The sun is the source of energy for ecosystems
Plants capture energy via photosynthesisThey then act as an energy source for other organisms
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1.4 Biological Themes
3. CooperationCooperation between organisms is critical for evolution
Symbiosis occurs when two organisms of different species live in direct contact
4. Structure Determines FunctionBiological structures are well suited to their function
This is true at every level of organization
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1.4 Biological Themes
5. HomeostasisAll living organisms act to maintain a relatively stable internal environment
Maintaining homeostasis requires a lot of signaling back-and-forth between cells
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1.5 How Scientists Think
Deductive ReasoningUsing accepted general principles as a “guide” to explain specific observations
It is the reasoning ofMathematics
Philosophy
Politics
Ethics
It is also how a computer works
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1.5 How Scientists Think
Inductive ReasoningDiscovering general principles through examination of specific cases
It is used by scientists to develop hypotheses about how the world works
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Fig. 1.5
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1.6 Science in Action: A Case Study
In 1985, a scientist discovered low levels of ozone in the upper Antarctic atmosphere
The culprit was later revealed to be chlorofluorocarbons (CFCs)
Coolants in air conditions; propellants in aerosols
CFCs condense into tiny ice crystalsWarmed by the sun, they attack and destroy ozone
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Fig. 1.6 How CFCs attack and destroy ozone
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1.6 Science in Action: A Case Study
The ozone layer protects us from the sun’s ultraviolet (UV) rays
1% drop in ozone 6% increase in skin cancers
Its depletion is a serious world problemSo governments have rushed to correct the situation
There is now a worldwide reduction in CFC production
The ozone layer will recover by mid-21st century
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1.7 Stages of a Scientific Investigation
The scientific process can be divided into six stages
1. Observation Careful observation of a process or phenomenon
2. Hypothesis Guess regarding the observation
If more than one guess, alternative hypotheses are formed
3. Prediction Expected consequences based on the correct hypothesis
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1.7 Stages of a Scientific Investigation
The scientific process can be divided into six stages
4. Testing The hypothesis is tested through an experiment
5. Controls A factor that influences a process is called a variable
In a control experiment, all variables are held constant
6. Conclusion Based on the results of the experiment, a hypothesis is either accepted or rejected
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Observation
Fig. 1.7
Question
Hypothesis 1Hypothesis 2Hypothesis 3Hypothesis 4Hypothesis 5
Potentialhypotheses
ExperimentRejecthypotheses1 and 4
Hypothesis 5Hypothesis 3Hypothesis 2
Remainingpossiblehypotheses
ExperimentRejecthypotheses2 and 3
Last remainingpossible hypothesisHypothesis 5
Predictions
Experiment 1 Experiment 2 Experiment 3 Experiment 4
Predictionsconfirmed
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1.8 Theory and Certainty
A theory is a set of hypotheses that have been tested many times and not rejected
It indicates a higher degree of certainty
However, there is no absolute truth in science
So the acceptance of a theory is provisional
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1.8 Theory and Certainty
Note:
To scientists, a theory represents that of which they are most certain
To the general public, a theory represents lack of knowledge or a guess
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1.8 Theory and Certainty
The scientific “method”
A series of logical “either/or” predictions tested by experiments to reject alternative hypotheses
This trial-and-error testing was once viewed as the way scientific progress is made
However, science is not done this way!
Insight and imagination are necessary to good scientific examination
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1.8 Theory and Certainty
The limitations of science
It is limited to organisms and processes that can be observed and measured
Supernatural and religious phenomena are beyond the scope of science
There are also practical limits Science cannot be relied upon to solve all problems
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1.9 Four Theories Unify Biology
1. The Cell Theory
2. The Gene Theory
3. The Theory of Heredity
4. The Theory of Evolution
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The Cell Theory: Organization of Life
Robert Hooke, 1665Discovered cells
Anton van Leeuwenhoek, 1670sDiscovered single-celled life
Matthias Schleiden & Theodor Schwann, 1839All living organisms are composed of cells
Cells are the basic units of life
Rudolf Virchow, 1866All cells come from other cells
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The Gene Theory: Molecular Basis of Inheritance
The information that determines what an organism is like is encoded in its genes
Genes are located along DNA moleculesRefer to Fig. 1.11
The entire set of DNA instructions that specifies a cell is termed its genome
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Fig. 1.12 The gene theory
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The Theory of Heredity: Unity of Life
This theory was first advanced by Gregor Mendel in 1865
It basically states that genes of an organism are inherited as discrete units
Later, other biologists proposed the chromosomal theory of inheritance
Genes are physically located on chromosomes
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The Theory of Evolution: Diversity of Life
This theory was first advanced by Charles Darwin in 1859
It attributes the diversity of the living world to natural selection
An essential component of this theory is that evolution involves “descent by modification”
All living organisms are related to one another in a common tree of life
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Fig. 1.15 The tree of life
Crocodiles are more closely-
related to birds than to other
reptiles
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The Theory of Evolution: Diversity of Life
Biologists divide all living organisms into three great groups, termed domains
Bacteria
Archaea
Eukarya
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Fig. 1.16
Prokaryotes
Simplest and most diverse;Gave rise to the other three eukaryotic
kingdoms