The Unifying Themes of Biology
Intro
• Life has many
levels of
organization, and
great diversity
▫ There are several
themes that help
to unify the
different aspects
of biology
Target #19- I can describe how the
living world is a hierarchical system
• The living world is a hierarchical system
▫ System: A combination of parts that make up a
more complex whole
▫ Exists on all scales
 Microscopic to biosphere
▫ Scientists can work within one system
 Ex: studying predator-prey relationships in ecology
▫ Scientists can also study “across systems”
 Ex: study how chemicals in the brain affect social
interactions
• Systems also apply to
classification/organizati
on of organisms
▫ Classification
 Identificationtaxonomy
 Evolutionary
relationshipsphylogeny
 Ecological organization
▫ Illustrates close
relationships between
organisms
 Shows shared
characteristics
Target #20- I can describe the cellular basis of life
• Cells
▫ The basic unit of
structure and function in
all organisms
▫ Two main types
 Prokaryote
 Bacteria
 Archaea
 Eukaryote
 Protists
 Plants
 Fungi
 Animals
• In multicellular organisms,
cells are organized
▫
▫
▫
▫
Cell specific types
Tissues made of many cells
Organ made of tissues
Organ system made of several
organs with similar functions
• Multicellular organization is a
part of the hierarchical system
found in biology
• Heritable Information
▫ The continuity of life
depends on the
inheritance of biological
information in the form of
DNA
 Encoded in a nucleotide
sequence of the DNA
▫ Must be able to be passed
down from parent to
offspring
Target #21- I can state why
genetic information must be
heritable
Target #22- I can give an example of
how structure is related to function
• Structure & Function are related
▫ What something does in an organism is
directly related to its shape or form
▫ Related at many different levels
micro & macro
 Ex: different types of proteins that play
separate roles in cellular function
 Ex: different types of cells have very
different functions and structures
 Nerve cell vs. skin cell
Target #23- I can explain the role of
negative feed back loops
• Regulation
▫ Feedback mechanisms
regulate biological systems
 Helps to maintain
homeostasis
 regulated through
negative feedback loops
▫ a change in a system
causes a response that
tends to return that
system to its original
state.
• Evolution
▫ The core, and most
significant, unifying theme
 Explains both the unity and
diversity of life
▫ Evolution is the change in
the genetic make-up of a
sub-group, or population, of
a species
 Occurs through the process of
natural selection of adaptations,
or traits, found in different
organisms
 Those that are more successful
than their peers at reproducing
will be able to pass down their
genetic information more
frequently than their peers.
Target #24- I can
state how
evolution
explains both
the diversity &
unity of life
• As you study biology,
you will see time
after time that
organisms are
related to one
another
▫ Ex: Organisms have
similar cell structures
and chemical
processes
▫ Shared characteristics
result from a common
evolutionary descent
- Ex: humans and
bacteria