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 PropertiesReductionism - 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) byGustave 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!

AtomsMolecules

Macromolecules

Cell

Tissue

OrganOrgan System

PopulationOrganism

Community

BiomeEcosystem

Organelle

Biosphere

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.com/stories/2006/04/03/ap/health/mainD8GOQ9C83.shtml

Lab Grown Organs – Beating rat heart

• New hope may lie in lab-created heartJanuary 14, 2008.

• See link at: http://www.cnn.com/2008/HEALTH/01/14/rebuilt.heart/index.html