Chapter 1:
Exploring Life
Unifying Themes in Biology
 Evolution~ biology’s core theme;
differential reproductive success
(sex!)
 Emergent Properties~ hierarchy of life
 The Cell~ all organism’s basic
structure
 Heritable Information~ DNA
 Structure & Function~ form and
function
 Environmental Interaction~ organisms
are open systems
 Regulation~ feedback mechanisms
 Unity & Diversity~ universal genetic
code
 Scientific Inquiry~ observation;
testing; repeatability
 Science, Technology & Society~
functions of our world
Hierarchy of Organization
Molecule
Organelle
Cells
Tissues
Organ
Organism
Feedback Regulation: Negative
Accumulation of an
end product of a
process slows that
process
Example: sugar
breakdown generates
ATP; excess ATP
inhibits an enzyme
near the beginning of
the pathway
Feedback Regulation: Positive
An end product
speeds up its
production
Example: blood
clotting in response to
injury
The Process of Science
The Scientific Method
Deductive reasoning
“If….then” Logic
Hypothesis vs.
Theory
Properties of Living things
Early Views of life
Vitalism: The insistence that there
is some big, mysterious extra
ingredient in all living things
 Led to idea of spontaneous
generation
Flies came from dead animals
Mice came from Hay
The Redi Experiment
Idea was challenged by scientist
Francesco Redi in 1698.
Designed an experiment where 3
jars contained meat.
Setup 1
One Jar contained meat and had an
open top which would allow the
passage of flies.
(maggots would appear on the meat)
Setup 2
The second jar was covered with an
airtight lid not allowing the passage
of flies.
(no maggots would appear on the meat)
Setup 3
The third was covered by a screen
allowing passage of eggs, but not
flies.
(few maggots would appear on meat)
Conclusion
Since the third setup would
theoretically allow the passage of
“ethers”, but no maggots appeared, it
was implied that flies were the source
of the maggots.
Led to the theory of Biogenesis
All life comes from preexisting life
PROPERTIES of LIFE
Be made of Cells.
The Cell is the basic unit of life
Is self contained and possesses a
barrier (membrane) which separates
itself from the environment.
Two types of organisms.
Unicellular - One celled organism
(Uni=1)
Multicellular - Many cells
(Multi=”many”)
PROPERTIES of LIFE
Living Things must Reproduce.
Must be able to create more of it’s own
kind
Two types of reproduction:
Sexual - Two parent organisms combine
genetic material to produce the offspring.
Asexual - When a single organism can divide
or “bud” to create it’s offspring without
another of it’s species.
PROPERTIES of LIFE
Living things must Have DNA.
(Universal Genetic Code?)
PROPERTIES of LIFE
Living things must Grow & Develop.
Growth refers to two processes.
Increase in the number of cells.
Increase in the size of cells.
Development refers to changes in the
organism which occur through it’s lifespan.
Includes cell differentiation.
Includes organ development
Includes aging & death.
PROPERTIES of LIFE
Living things obtain & use energy.
Energy is used by all living things for
growth, development & reproduction.
Life processes which result in
“building” the organism ia known as
Anabolism.
Life process where energy is
extracted by “breaking-down”
substances is called Catabolism.
PROPERTIES of LIFE
 Living things must Respond (or react) to their
environment in some way.
 Something which causes an organism to react is
known as a Stimulus (stimuli).
 The ability of an organism to react is called
Irritability.
 Most responses are geared for maintaining
Homeostasis.
 Homeostasis is a process where an organism maintains a
stable internal environment so life can continue.
 Some examples include temperature, pH, and water content
of the cell.