Transcript Biology - Introductory Remarks

What Do Biologists
Study?
Biology: the study of life
Classification of Organisms
• Three domains:
– Archaea
– Eubacteria
– Eukarya, has 4 kingdoms
•
•
•
•
Plantae
Animalia
Fungi
Protista
Archaea
• Bacteria that live in
extreme
environments — hot
springs, salt ponds
Eubacteria
• Bacteria that live and
grow in common
environments — our gut
and skin, fresh and salt
water, and almost every
other environment on
Earth
Eukarya - Protista
• Single celled
eukaryotes; live
mostly in water
• Amoebas, algae,
water molds, slime
mold
Eukarya - Plantae
• Multicellular plants,
from mosses to
redwood trees
• Have cellulose cell
walls, perform
photosynthesis
Eukarya - Fungi
• Multicellular, with
cell walls
containing chitin;
obtain food by
absorption
• Mushrooms, yeast
Eukarya - Animalia
• Multicellular
animals
• Sponges,worms,
insects, birds, fish,
mammals
• Have no cell walls;
obtain energy from
other organisms
Diversity
• There are about 1.4 million (about ¾ of million of
these are insects) described species, but there
may be as many as 100 million living species;
this is only about 1% of the species that have
ever lived — most are extinct
• This diversity has arisen by evolution; all living
organisms are related and are descended from
one or several common ancestors
The Kingdoms of Life
Living Organisms
•
What is life? What characteristics do all these organisms share? All living
organisms share certain characteristics or activities that separate them from
non-living matter. What are some of these?
– Structure/organization, which arise from the basic properties of matter
and energy.
– Metabolism - "energy transfers".
– Homeostasis – Ability to maintain a livable internal environment.
– Reproduction
– Response to stimuli (e.g., temperature, injury, light, gravity, etc...).
– Movement
– Mutations or changes in form are possible.
– Adaptation to the environment.
– Interdependence with other organisms
– Blueprint of life is coded by nucleic acid
– Growth and development
•
Fundamental unit of all life is the cell
– The cell is the fundamental unit that possesses all of these
characteristics of life is found in the cell. We recognize the cell as
being alive!
How Do Biologists
Study Life?
What is Science?
• Asking questions about the world around
us
• Biology is asking about life: How does it
work? How can we modify it? — curing
diseases
• Use scientific method to answer questions
Scientific Method
• The scientific method is the way scientists approach a
study of the natural world and physical universe
• Focus on a single answerable question — reductionism
– Observation, either with our senses or instruments
– A question or problem is posed by the scientist
– Create a hypothesis or model — a proposed answer to the
question or proposed solution to the problem that is testable in
some conceivable fashion
– Construct an experiment that makes a prediction of the outcome
based on the hypothesis
– Conclusion
Experiments
• Procedure carried out under controlled
conditions
– Controls: a version of the experiment that is
the same except for the variable being tested
— minus drug, for example
– Replicates, because each organism is unique;
Then compare averages with statistics
Theory
• A group of related hypotheses that have
withstood rigorous experimental testing.
• How does this differ from the idea of
“theory” held by the general public?
Reductionism and Emergent Properties
Reductionism - assumes that if you know the parts,
you'll know the whole.
To a major extent this is an extremely useful way to
learn about the living world. Insight gained by knowing
the internal workings of an organism and its cells do tell
us a lot about the whole.
Reductionism does not take into account emergent
properties.
Emergent properties are characteristics that arise from
higher levels of organization.
As one moves from simple to more complex systems,
some characteristics invariably arise that are not readily
obvious or easily predicted simply by examining the parts
and seeing how these interact with one another.
Reductionism and Emergent
Properties
A landscape emerges from a
series of seemingly random
colored dots of paint.
Reductionism Examines the Parts
but can not always anticipate the
“big picture”
Rainy Day in Paris (1877) by
Gustave Caillebotte
On Becoming a Biologist (1985)
by John Janovy, Jr.
• The philosophical problem faced by a modern biologist is this:
Although analytical techniques, including formal mental ones,
have given us a highly detailed knowledge, down to the
biochemical level, of a number of organisms (Escherichia coli,
Paramecium species, strains of inbred mice), it has yet to be
demonstrated that this knowledge logically explains all aspects
of the organisms’ lives. For example, let us ask a question: If
we knew the entire DNA sequence of a sandpiper, had an
inventory of its chemical compounds, knew how the expression
of its every gene was regulated, could describe its enzymatic
reactions, and knew the structure of all its proteins, could we
then logically explain, from that information, the bird’s annual
migration from Canada to Argentina, or nesting behavior so
tender it brings tears to the eyes of a seasoned field man? If
your answer is yes, you are operating mentally in the
philosophical tradition of a committed reductionist. If the
answer is no, you have one foot in the camp of the vitalists.
LEVELS OF ORGANIZATION
• ATOMS ===> MOLECULES ===> CELLULAR
COMPONENTS ===> CELLS ===> TISSUES ===>
ORGANS ===> ORGAN SYSTEM ===> ORGANISM
===> POPULATION (SAME SPECIES IN SAME AREA)
===> COMMUNITY (DIFFERENT SPECIES IN SAME
AREA) ===> ECOSYSTEM (ORGANISMS
INTERACTING IN THE SAME ENVIRONMENT) ===>
BIOME (ORGANISMS IN THE SAME CLIMATE ZONE)
===> BIOSPHERE (ALL LIFE ON EARTH)
• Keep in mind that the fundamental unit or level of organization
that possesses all of the characteristics of life is found in the
cell. Biologists recognize the cell as being alive!
Macromolecules
Atoms
Organelle
Molecules
Cell
Biosphere
Biome
Ecosystem
Tissue
Organism
Community
Population
Organ
System
Organ
The Scale of Things
• http://www.cellsalive.com/howbig.htm
The Biosphere - Earth as viewed from the moon!
What’s new in cell biology?
From cells to organs!
Lab Grown Organs – Human
Bladder
• Scientists Rebuild
Bladder in 7
Patients
BOSTON, Apr. 3,
2006
• See link at:
http://www.cbsnews.c
om/stories/2006/04/0
3/ap/health/mainD8G
OQ9C83.shtml
Lab Grown Organs – Beating rat
heart
• New hope
may lie in labcreated heart
January 14,
2008.
• See link at:
http://www.cnn
.com/2008/HE
ALTH/01/14/re
built.heart/inde
x.html