WHAT IS LIFE?
Characteristics of Life
THINK ABOUT IT:
What drives the diversity and unity of life?
What characteristics do all living things share?
ALL LIVING THINGS…
In groups of 2 or 3, brainstorm some ways to finish this
sentence:
“All living things…”
CARD SORTING
Based on the criteria set by the class, divide into two
groups (Living or Non-living) based on the cards you
were given
DISCUSSION
Were there some cards that were difficult to place based on the
criteria we used?
Do any of the non-living cards have at least one characteristics of
living things?
Should we add, remove, or change any of our criteria?
ANALYSIS
Do you think that all scientists agree on what defines life?
Why might viruses, fire, or alien life be difficult to
categorize?
DEFINITION ADOPTED BY NASA:
Life is a self-sustained chemical system
capable of undergoing Darwinian
evolution. --Joyce (1995)
CHARACTERISTICS OF LIVING ORGANISMS:
…All
living things
Are made of one or more CELLS
Obtain and use energy (METABOLISM)
Maintain balance (HOMEOSTASIS)
Have the ability to GROW
Have the ability to REPRODUCE
RESPOND to STIMULI
ADAPT and EVOLVE
CELLS
All living things are made of cells
Different parts of a cell serve different
functions
Two types of cells
Prokaryotic
eukaryotic
METABOLISM
All living things need to obtain and use some form of
energy
Plants use sunlight (photosynthesis)
Plants AND Animals covert sugars into ATP (cellular respiration)
Some bacteria can even use chemicals as an energy source
directly (chemosynthesis)
HOMEOSTASIS
Cells (and organisms) must maintain stable internal
environments
temperature
pH levels
concentrations of water and solutes
and much more
All of the processes that regulate this balance and create
a stable state are part of homeostasis
GROWTH
Every cell grows larger
Multicellular organisms grow by making more cells
REPRODUCTION
•The ability to create new organisms
•HEREDITY- Living things transmit their genetic material (DNA)
to their offspring
Sexually (two parents)
Asexually (cell division, natural clones)
RESPONSE TO STIMULI
Living things react to changes in their environment
A stimulus triggers a response
predators chase prey
Plants roots grow down and stems grow up in response to gravity
Leaves change color in response to light, water, and temperature
variations in the fall
ADAPTATIONS AND EVOLUTION
Adaptations
traits that make an organism better suited to its environment
Adaptations arise through evolution
Evolution
Genetic change in populations over generations
LEVELS OF BIOLOGICAL
ORGANIZATION
Atoms
ORGANIC VS. INORGANIC
ORGANIC
INORGANIC
MUST Contain Carbon
Almost never contain carbon
Found in Living Organisms
 (except for a few like CO2 or
carbonates)
 Lipids
 Proteins
 carbohydrates
Never a part of a living organism
THINK ABOUT IT:
What drives the diversity and unity of life?
What characteristics do all living things share?