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Lecture 1: Understanding Life
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Please Read Biology 9 Edition By Sylvia Mader Page 317-340
Lecture Outline
I.
II.
What is Biology?
A.
Biology is the study of life.
B.
Biology reveals the themes and characteristics of life.
o Living things display organizational complexity (molecules 
cells  tissues  organs  organ systems  organism)
What are the themes and characteristics of life?
A.
Organisms have a cellular and hierarchical organization.
 A cell is the smallest living structural unit of organisms
 Organisms are either unicellular or multicellular
 Cells are grouped together into functional tissues (example = muscle
tissue)
 Tissues form an organ (example = the heart)
 An organ system is a group of organs that function together (example
= the circulatory system)
 Interactions occur among all of the levels of organization within an
organism (example = the circulatory system carries nourishment from
the digestive system to the muscular system
B.
Organisms interact with one another.
C.
Organisms are more than the sum of their parts
D.
Organisms reproduce, passing on biological information.
E.
Organisms use and transform energy.
F.
The structures of organisms fit their functions.
G.
Organisms exhibit diversity and unity.
 Biologists estimate that from 5 million to 30 million different species
exist on Earth
 Amid this great diversity, there is unity in the patterns of life (see the
five Domains listed later)
H.
Organisms alive today are descended from those that lived long ago.
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III.
How do scientists organize the diversity of life?
A.
Scientists use classification systems to organize the living world.
 Scientists use a naming system, called binomial nomenclature, to name
living organisms (Homo sapiens = humans)
o The Swedish botanist Carolus Linnaeus invented binomial
nomenclature in the mid-1700s
o The first name identifies a genus, which comprises a group of
closely related species
 Today, we use a classification system that employs the following
inclusive categories: domain, kingdom, phylum, class, order, family,
genus, and species
B.
Scientists classify organisms based on common ancestry
 Taxonomy is the science of classifying and naming organisms
 Systematics is the study of the diversity of organisms by focusing on
their evolutionary relationships
C.
An increasingly accepted classification scheme includes three domains
 Today, most biologists recognize three domains of living things
 The Domain Archaea includes single-celled organisms usually found
in extreme habitats, such as hot springs, acid lakes, the Antarctic,
ocean depths, swamp bottoms, and volcanic areas
 The Domain Bacteria includes many single-celled organisms that
cause common diseases
 Both archaeans and bacteria lack a nucleus and membrane-bound
organelles, and are referred to as prokaryotes
 The Domain Eukarya may be unicellular or multicellular
o Eukaryote cells have a nucleus and membrane-bound organelles
o The Kingdom Protista includes single-celled organisms such as
the bloblike ameba and the oval-shaped paramecium
o The Kingdom Fungi includes molds, mushrooms, and certain
parasites, such as those that cause athlete’s foot and ringworms
o The Kingdom Plantae includes multicellular plants that make their
own food, and are called autotrophs
o The Kingdom Animalia includes the worms, insects, vertebrates,
and other organisms that belong to this diverse group
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