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BIOLOGY 101
• Scientific Study of Life
• Introduction to Biology
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Life in the Trees
• The lives of gray-headed flying foxes are closely
entwined with the lives of the eucalyptus trees
that form their habitat
– Eucalyptus trees
provide food and
roosting sites for
the flying foxes
– Flying foxes aid in
eucalyptus pollination
and help disperse
the resulting seeds
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• Flying foxes are becoming an endangered
species, partly because of habitat destruction
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THE SCOPE OF BIOLOGY
• Biology is the scientific study of life
• Interactions between different kinds of
organisms affect the lives of all
– Recall the example of flying foxes and eucalyptus
trees
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1.1 Life’s levels of organization define the scope of
biology
• A structural hierarchy of life, from molecules to
ecosystems, defines the scope of biology
• An ecosystem consists of:
– all organisms living in a particular area
– all nonliving physical components of the
environment that affect the organisms
(soil, water)
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• At the top of life’s
hierarchy is the
ecosystem
ECOSYSTEM LEVEL
Eucalyptus forest
• Ecosystems include:
– all the organisms
in an area, which
make up a
community
– interbreeding
organisms of the
same species, a
population
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COMMUNITY LEVEL
All organisms in
eucalyptus forest
POPULATION LEVEL
Group of flying foxes
ORGANISM LEVEL
Flying fox
Brain
ORGAN SYSTEM LEVEL
Nervous system
ORGAN LEVEL
Brain
Spinal cord
Nerve
TISSUE LEVEL
Nervous
tissue
CELLULAR LEVEL
Nerve cell
MOLECULAR LEVEL
Molecule of DNA
Figure 1.1
• Organisms are
made up of:
– organ systems
ECOSYSTEM LEVEL
Eucalyptus forest
– organs
– tissues
– cells
– molecules
COMMUNITY LEVEL
All organisms in
eucalyptus forest
POPULATION LEVEL
Group of flying foxes
ORGANISM LEVEL
Flying fox
Brain
ORGAN SYSTEM LEVEL
Nervous system
ORGAN LEVEL
Brain
Spinal cord
Nerve
TISSUE LEVEL
Nervous
tissue
CELLULAR LEVEL
Nerve cell
MOLECULAR LEVEL
Molecule of DNA
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Figure 1.1
THE PROCESS OF SCIENCE
1.2 Scientists use two main approaches to learn
about nature
• In discovery science, scientists describe some
aspect of the world and use inductive reasoning
to draw general conclusions
– Example: scientists have
described how newborn
flying foxes cling to their
mother’s chest for the
first weeks of life
Figure 1.2
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• In hypothesis-driven science, scientists use the
“scientific method”
– They propose a hypothesis
– They make deductions leading to predictions
– They then test the hypothesis by seeing if the
predictions come true
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1.3 With the scientific method, we pose and test
hypotheses
Observation
• The main
steps of the
scientific
method
Question
Hypothesis
Prediction
Test does not
support hypothesis;
revise hypothesis or
pose new one
Figure 1.3A
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Test:
Experiment or
additional
observation
Test supports
hypothesis; make
additional predictions
and test them
• Deductive reasoning is used in testing
hypotheses
– starts with a general
explanation which leads
to predictions for
specific observations
supporting it
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• Experiments designed to test hypotheses must
be controlled experiments
• Control groups must be tested along with
experimental groups for the meaning of the
results to be clear.
– Controls are used to filter out other
explanations. A control is a replica of the
experiment with the independent variable
omitted. The dependent variable is what is
measured (like how much a plant grows from
day to day). The control in human drug tests is
generally a sugar pill called a placebo.
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The scientific method
• In order to eliminate human bias most drug tests are
conducted in a double blind fashion. In a double blind
experiment researchers and patients do not know
whether the pill given is the drug or the placebo until
the trial is over.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Case study: spider mimicry
Pounce rate (% of trials in
which spider jumped on fly)
Figure 1.3C
Control group
(untreated flies)
Figure 1.3D
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Experimental group
(wing markings masked)
Number of stalk and
attack responses
by spiders
• Another test of the spider mimic hypothesis:
wing transplants
Wing
markings
Wing
waving
Normal
spider
mimic
Figure 1.3E
Mimic with
mimic wing
transplant
Controls
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Mimic with
housefly
wing
transplant
Housefly
with
mimic wing
transplant
Experimentals
Normal
housefly
Modern Biology is based on;
• The Cell Theory
• The Theory of Evolution by Natural
Selection
• Gene Theory
• Homeostasis
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The Cell Theory:
• All cells come from
pre-existing cells
• All organisms are
composed of one or
more cells.
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EVOLUTION, UNITY, AND DIVERSITY
1.4 The diversity of life can be arranged into three
domains
• Grouping organisms by fundamental features
helps make the vast diversity of life manageable
for study
• Scientists classify organisms into a hierarchy of
broader and broader groups
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Figure 1.8 Evolution
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Tree of Life
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• Most classification schemes group organisms
into three domains:
– Domain Bacteria
– Domain Archaea
Figure 1.4A, B
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– Domain Eukarya
Figure 1.4C-F
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Cells
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Cells and Organelles
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Macromolecules
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1.5 Unity in diversity: All forms of life have
common features
• All organisms share a set of common features,
signs of unity in life’s vast diversity
– All are made of cells
– All have DNA as
their genetic
blueprint
• These orchids show
the variety possible
within one species
Figure 1.5A
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• DNA is made of chemical units called
nucleotides
• Each species has its own nucleotide sequence
Figure 1.5B
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DNA
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Central Dogma
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Chromosomes
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Cell Cycle
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Mitosis
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• The genetic information in DNA underlies all of
the features that distinguish life from nonlife
– Order and regulation
– Growth and development
– Use of energy from the environment
– Response to environmental stimuli
– Ability to reproduce
– Evolutionary change
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Molecular Basis of Inheritance
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Scale
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Cells and Tissues
• In human body, there are more than 200
different kinds of cells.
• These cells make up five main type of
tissue
• Epithelial tissue
• Connective tissue
• Blood
• Nervous tissue
• Muscle
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Connective Tissue
Fibroblasts
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Epithelial tissue
Bile duct
mouth
From The Cell 2nd ednASM & Sinauer
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Blood
Granulocyte
Lymphocyte
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Monocyte
Nervous tissue
from http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Nervous/Nervous.htm
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Muscle
Smooth muscle
Skeletal muscle
Cardiac muscle
From http://www.meddean.luc.edu/lumen/MedEd/Histo/frames/h_frame7.html
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
1.6 Evolution explains the unity and diversity of
life
• Charles Darwin is a central figure in biology
• He synthesized the theory of evolution by
natural selection
– A theory in science is a
comprehensive idea with
broad explanatory power
• Evolution is the core theme
of biology
Figure 1.6A
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• The theory of
natural selection
explains the
main mechanism
whereby all
species of
organisms
change, or evolve
Figure 1.6B
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(1) Population with varied inherited traits
(2) Elimination of individuals with certain traits
(3) Reproduction of survivors
Model Organisms: E. coli
• Uses medium containing glucose, aa, salts,
vitamins; Divide every 20 mins
• Genome contains 4.6 million base pairs; about
4000 genes
• Clonal populations can be selected; those
resistant to penicillin
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Figure 1.14 Bacterial Colonies
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Yeast: S. cerevisiae
• Eukaryotic
• Genome contains 12 million base pairs of DNA;
6000 genes; 16 linear chromosomes
• Can be grown in the lab; replicate every 2 hours
grown in colonies
• Can be used to understand DNA replication,
transcription, RNA processing, protein sorting,
regulation of cell division
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Figure 1.15 Electron Micrograph of
Saccharomyces cerevisiae
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Worm: C. elegans
• Multicellular
• Understanding development
• Genome contains 100 million bps of DNA;
19000 genes
• Contain 959 cells (somatic); 1000-2000 germ
cells
• Lineage tracing; genes of development and
differentiation
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Figure 1.17 Caenorhabditis elegans
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Plant: Arabidopsis
• Plant molecular biology and development
• Genome contains 120 million bp of DNA,
15000 genes.
• Can be grown in pots; mutants are available
• Comparisons of cellular mechanisms between
plants and animals
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Figure 1.19 Arabidopsis thaliana
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Vertebrates
• Xenopus laevis: frog
• Danio rerio: fish
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Figure 1.20 Eggs of the Frog Xenopus laevis
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Figure 1.21 Zebrafish
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Model Organisms and Applications
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Model Organisms and Applications
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Model Organisms and Applications
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Model Organisms and Applications
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Model Organisms and Applications
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Model Organisms and Applications
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Model Organisms and Applications
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Model Organisms and Applications
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Figure 1.22 Defects in pigmentation (piebaldism)
due to mutations in a gene regulate migration of
melanocytes
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Humans and Flies Alike (Pax6 gene)
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Table 1.1 Prokaryotic and Eukaryotic Cells
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Table 1.2 DNA Content of Cells
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