1.1 The Diversity of Life

The Living WorldFourth Edition

GEORGE B. JOHNSON

Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display

PowerPoint® Lectures prepared by Johnny El-Rady

1 The Science of Biology


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


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



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



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


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


Fig. 1.4


Fig. 1.4


Fig. 1.4


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


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



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



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



5. HomeostasisAll living organisms act to maintain a relatively stable internal environment

Maintaining homeostasis requires a lot of signaling back-and-forth between cells


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


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


Fig. 1.5


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


Fig. 1.6 How CFCs attack and destroy ozone


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


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


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


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


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



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



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



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


1.9 Four Theories Unify Biology

1. The Cell Theory

2. The Gene Theory

3. The Theory of Heredity

4. The Theory of Evolution


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


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


Fig. 1.12 The gene theory


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


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


Fig. 1.15 The tree of life

Crocodiles are more closely-

related to birds than to other

reptiles


The Theory of Evolution: Diversity of Life

Biologists divide all living organisms into three great groups, termed domains

Bacteria

Archaea

Eukarya


Fig. 1.16

Prokaryotes

Simplest and most diverse;Gave rise to the other three eukaryotic

kingdoms

1.1 The Diversity of Life

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