Transcript Ch01_lecture student

Chapter 1
An Introduction to
Life on Earth
Lectures by
Gregory Ahearn
University of North Florida
Copyright © 2009 Pearson Education, Inc..
1.1 Why Study Biology?
 Biology helps you understand your
_____________.
 Biology helps you become an
_____________ ____________.
 Biology can open ____________
opportunities.
 Biology can enrich your appreciation of the
___________.
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1.2 How Do Biologists Study Life?
 THE SCIENTIFIC METHOD
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1.2 How Do Biologists Study Life?
Observation
Question
Hypothesis
Prediction
Experiment or
Observation
Hypothesis
not supported:
pose new
hypothesis
Conclusion
Hypothesis
supported:
make more
predictions
Fig. 1-2
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1.2 How Do Biologists Study Life?
 The scientific method in everyday life
Observation
Question
Hypothesis
Prediction
Experiment or
Observation
Conclusion
Fig. 1-3
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Observation: Flies swarm around meat left in the open; maggots appear on the meat.
Question:
Why do maggots appear on the meat?
Hypothesis: Flies produce the maggots.
Prediction:
If flies are kept away from the meat, then no maggots will appear.
Experiment
Obtain identical pieces of
meat and two identical jars
Place meat
in each jar
Leave jar
uncovered
Experimental variable:
gauze prevents
entry of flies
Cover jar
with gauze
Leave exposed
for several days
Controlled variables:
time, temperature,
place
Leave covered
for several days
Flies swarm around
and maggots appear
Results
Flies kept from meat;
no maggots appear
Control situation
Experimental situation
Conclusion: Spontaneous generation of maggots from meat does not occur; flies
are probably the source of maggots.
Fig. E1-1
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1.2 How Do Biologists Study Life?
 *A well-designed experiment tests a single variable and
controls all other variables.*
• Question: Have all other variables been eliminated?
• Example: loose battery cables
• Example: broken electrical wires
• Solution: Control for other variables
• Make sure cables are tight.
• Make sure electrical wires are in good condition.
 A _________ ________ is a general explanation of natural
phenomena supported by extensive, reproducible tests and
observations.
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1.2 How Do Biologists Study Life?
 LIFE CAN BE STUDIED AT DIFFERENT LEVELS OF
ORGANIZATION
cell
nerve cell
tissue
nervous tissue
organ
brain
organism
pronghorn antelope
population
herd of pronghorn antelope
community
snakes, antelope, hawks, bushes, grass
Fig. 1-5
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1.2 How Do Biologists Study Life?
 SCIENCE IS A HUMAN ENDEAVOR
• Scientists are real people and sometimes make
mistakes.
• One of the greatest medical advances in history was
made by mistake, by Alexander Fleming.
• The mold _______________, which kills bacteria, was
discovered by chance by Fleming.
• This led to the discovery of penicillin, an important
antibiotic that has saved millions
of lives.
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1.2 How Do Biologists Study Life?
 Penicillin kills bacteria.
A petri dish
contains solid
growth medium
Bacteria grow in
a pattern created
by streaking
A substance from
the mold diffuses
outward and inhibits
the growth of
nearby bacteria
A colony of the
mold Penicillium
Fig. 1-7
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1.3 What Is Life?
 LIVING THINGS ARE BOTH ____________ AND
________________
Fig. 1-8
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1.3 What Is Life?
 LIVING THINGS CAN __________ AND ______________
 LIVING THINGS RESPOND TO ___________
• Light, Sound, Chemicals, Hunger, Pain, Touch, Heat,
Cold, Motion, Gravity
Fig. 1-9
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1.3 What Is Life?
 LIVING THINGS ACQUIRE AND USE
_______________ AND ______________
Fig. 1-10
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1.3 What Is Life?
 LIVING THINGS USE _______ TO STORE
INFORMATION
• Each segment of DNA that contains a set of instructions is
called a ______.
• ___________: offspring inheriting their parents’
characteristics/genes.
Fig. 1-11
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1.4 Why Is Life So Diverse?
 DNA: THE UNIVERSAL MOLECULE OF LIFE
• DNA is found in the bodies of all organisms
• Its universal presence suggests that all organisms have
descended from a common ancestor having the same
molecule.
• DNA is passed from generation to generation during
periods of reproduction.
• Organism diversity results from small changes in DNA
over billions of years of evolution.
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1.4 Why Is Life So Diverse?
 LIFE’S UNITY AND DIVERSITY ARE A RESULT OF
EVOLUTION
• An organism changes over long periods of time.
• Groups of organisms change from generation to generation.
• The changes that accumulate in populations of organisms
over time is called evolution.
• Life’s unity arises from the fact that diverse descendants
arise from single ancestors.
• The unifying principle of biology is that all of life’s features in
today’s organisms arose through evolution.
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1.4 Why Is Life So Diverse?
 NATURAL SELECTION IS THE BASIS OF
EVOLUTIONARY CHANGE
• Characteristics of individuals in a group vary.
• Some characteristics help individuals survive and
reproduce.
• Those that reproduce pass on these traits to future
generations.
• The favored traits are accumulated in populations over
time, changing the individuals within the group.
• Example: Big teeth in beavers favor survival and are
passed on to future generations.
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1.4 Why Is Life So Diverse?
 BIODIVERSITY IS THREATENED BY HUMAN
ACTIVITY
• Biodiversity is the wealth of species in the world and the
interrelationships that sustain them.
• Human expansion in the world has severely reduced
habitats for these interrelationships to flourish.
• Extinction of many organisms have followed from the
growth of human populations on all the world’s
continents.
• Pollution and chemical wastes kill organisms.
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