Chapter 1 – The Study of Life
Biology – The study of life and living
organisms
Organism – Anything capable of carrying on
all of the processes of life
Branches of biology –
•There are many subtopics within biology –
a few examples we’ll hit upon this year:
•Biochemistry – Chemical substances and
processes in organisms
•Genetics – Inheritance – passing of traits
from one generation to next
Evolution – Change in organisms over time
Cell biology/cytology – Cell structure and
function
Zoology – Animals
Anatomy – Structures of organisms
Physiology – Functions, activities, and
processes of organisms
Ecology – Interactions of organisms and
environment
Characteristics of Life – Life is diverse
yet all organisms share a set of
characteristics:
1. Living things are organized –
levels of organization vary
In general: atoms  molecules 
cells tissues  organs  organ
systems  organisms
(Cells grouped based upon roles)
2. Living things are made of one or more
cells
Multicellular organisms (more than 1 cell)
will have the above system based on jobs
cells perform (although some organisms
may not have complex organs or systems –
more primitive, ex: sponge)
Cells in these organisms are
considered specialized (have certain
jobs)
Examples: some fungus, plants, and
animals
Unicellular organisms (one cell) will
be organized up to the cellular level
1 cell does all jobs for organism
Examples: bacteria, protists, and
some fungus
3. Living things requires energy
 Metabolism – all the chemical
reactions in cell
 Heterotrophs are organisms that
obtain nutrients from food eaten
Ex: some bacteria and
protists, fungus, & animals
Autotrophs are organisms that
make their own food through
photosynthesis
Take CO2, H2O, and solar
energy to make glucose, a simple
sugar that can be used as a
source of energy
Ex: plants, some protists, and
some bacteria
4. Living things reproduce
 Reproduction – production of
offspring
 Prevents extinction of species
(group of organisms that can breed
and produce fertile offspring)
 Uses DNA (hereditary information) –
which can be copied
 Can be sexual or asexual
•Asexual reproduction – used by
unicellular and some multicellular
organisms; only 1 parent; offspring
has DNA identical to parent
•Sexual reproduction – used by
multicellular organisms; 2 parents,
each parent contributes ½ genetic
information to offspring; offspring
has mixed traits from parents
5. Living things respond to stimuli
• Stimuli is external, and causes a
reaction
• May be seen as movement, such as
movement away from danger, or
reactions to other organisms.
• Response – observable, coordinated
reaction to environmental stimuli
• Examples: plant growing toward light,
hair raising on back of cat’s neck,
pupils dilating in response to light
6. Living things are homeostatic
 Homeostasis – maintaining
(relatively) constant internal
conditions (such as body
temperature, pH, blood pressure,
water balance) regardless of
external changes
 Examples of homeostatic behavior:
sweating or shivering to maintain
body temperature; urinary system
ridding body of wastes
7. Living things grow and develop
 Growth – an increase in the number of
cells/ increase in the size
 Occurs through cell division and
enlargement; part of development
 Example – getting taller
 Development – Changes an organism
undergoes between conception and
death
 Example – going through puberty
8. Adaptations - evolve over time
 Adaptations – modifications that
make an organism suited to its way
of life
 Examples – hollow bones of birds
for flight, gills for fish to breathe in
water
Adaptations come about through
evolution – a process through which
a species changes over time
This is the source of the diversity
of life
Organisms do not develop
adaptations during the course of
their lives
Classification
•Systematics - the study of biological
diversity with an emphasis on
evolutionary history
•Taxonomy – The study of identifying
and classifying organisms according
to specific criteria
•Taxa –the categories into which
organisms are classified
Why do we need scientific names?
•Common names don’t tell you enough
information
•What kind of frog? Is it poisonous???
•Common names are misleading
•Jellyfish – you mean it’s not a fish?
•Ringworm – what do mean it’s not a
worm?
•Common names vary from country to
country
•Mountain lion, cougar and puma all
refer to the same animal
Earliest classification system
•Designed by Aristotle (384-332 b.c.)
•Everything was classified as either a
plant or an animal
•Animals divided according to
presence of blood, then habitats and
morphology (form and structure)
•Plants divided by size and structure
as trees, shrubs, or herbs
•Limitations of Aristotle’s system:
•Failed to include bacteria, fungus and
protists
•Did not take evolution into account (he
saw species as distinct, separate and
unchanging)
•Failed to show evolutionary relationships
between organisms
•Some organisms didn’t fit (ex: birds that
don’t fly, frogs living on both land and
water)
Linnaeus’s classification system
Developed by Carolus (Carl) Linnaeus
in the 18th century
Grouped according morphology and
behavior
First formalized means of classifying
organisms
Binomial nomenclature – each
organism has a two-part name
Modern system of classification:
•Grouped according to their presumed
evolutionary relationship as well as
morphological and behavioral characteristics
• Those placed in the same genus will be
most closely related, those in different
domains most distantly related
Ex: Those in genus Felis are more
closely related to each other than
organisms in the domains Eukarya and
Archaea are to each other.
The taxa:
Domain
Kingdom
Phylum (Division for plants)
Class
Order
Family
Genus
Species
Did King Phillip Come Over For Good
Spaghetti????
Domain Archaea –
Unicellular prokaryotes
May have been first cells
Live in aquatic
environments that
lack oxygen or
are too salty, too
hot, or too acidic
for most other
organisms – like
primitive Earth(?)
Domain Bacteria
Unicellular prokaryotes
Found almost
anywhere – in
soil, water,
atmosphere,
on and inside
living
organisms
Domain Eukarya
Cells contain membrane-bound
nucleus
Four Kingdoms within –
Protists (Protista)
Fungus (Fungi)
Plants (Plantae)
Animals (Animalia)
Writing scientific names:
Ex: Homo sapiens or Homo sapiens
Can be abbreviated H. sapiens
If typed – should be italicized.
If handwritten – should be underlined.
First word is genus – capitalized
Second word is specific epithet of species
within a genus – lower case