Life- How do we define life?
What do each of these
things have in common?
6 Characteristics of Life
1.Living things have cells
 A cell is a membrane covered
structure that contains all the
materials necessary for life.
 Unicellular organisms have one cell
 Multicellular organisms have more
than one cell.

Cells perform specialized functions
2- Living Things
Sense and Respond
to Change
 All organisms have the ability to sense
change in their environment (stimulus)
and to respond to that change.
 Stimuli can be chemicals, gravity,
darkness, light, sound, smell, taste,
temperature…..
 Ex.) Sweating (yuck!) is your body’s
response to high temperatures (stimulus).
What is the stimulus and
response in these pictures?
How do living things manage
stimuli?
 Even though an organism’s external
environment may change, the organism
must maintain a stable internal
environment in order to survive,
called homeostasis
 Your body maintains an average
temperature of about 98.6º F, (37ºC)
 How does it accomplish this?
3- Living Things Reproduce
 There are two main
branches of
reproduction
 Asexual reproduction
involves a single parent
(mostly unicellular),
producing offspring
which are identical to
that parent.
Living Things Reproduce
 Sexual reproduction
almost always
requires two parents
to produce offspring
that will share
characteristics of
both parents.
 Most plants and
animals reproduce in
this way.
Sperm cells on an egg
4- Living Things Have DNA
 DNA (deoxyribonucleic acid) is a
special molecule which provides
instructions for making proteins.
 These proteins take part in almost all
of the organism’s characteristics.
 When organisms reproduce, they pass
on copies of DNA to their offspring.
DNA is responsible for heredity
 Heredity is the transmission of
characteristics from one generation
to the next.
5- Living Things
Use Energy
 Organisms use energy to carry
out activities, such as, making food,
breaking down food, building cells, and
moving materials in and out of cells.
 An organism’s metabolism is the total of
all of the chemical activities that it
performs.
Describe some energy/organism
relationships.
6- Living Things Grow and Develop
 Whether unicellular or
multicellular, living things grow
throughout their lives.
 Unicellular organisms increase
their cell size, while multicellular
animals increase their cell number.
Life keeps growing!!
In your journal, answer the following
questions using your notes
1. What characteristics of living things
does a river have? Is it alive?
2. What does the fur coat of a bear
have to do with homeostasis?
3. How is reproduction related to
heredity?
4. What are some stimuli in your
environment? How do you respond to
these stimuli?
Answers
1. A river has energy (it moves) and can grow
larger (after rain, or when snow melts).
But, it is not alive because it not is made
of cells, cannot respond to stimuli, has no
DNA, and cannot reproduce.
2.Homeostasis is the maintenance of a
stable internal environment. The fur coat
of bear helps it keep a stable
temperature.
Answers
3.Heredity is the passing of characteristics
from parents to offspring. When organisms
reproduce, offspring inherit copies of their
parents’ DNA
4.One example of a stimulus is thirst. I was
really thirsty the other day, so I got a
drink of water as soon as I could to replace
the fluids in my body.
Characteristics of Life
Review Questions
1. Name four living and non-living things
that you interact with daily.
2. What do you do when you go outside
and it is cold?
3. How do people use technology to
improve their ability to respond to
environmental stimuli?
4. Is your alarm clock a stimulus?
Explain.
5. Why is it important to respond to
stimuli?