life

1. Is It Alive?
Characteristics of
Living Things
&
Necessities of
Life

2. Characteristics of Living
Things
 What makes something
living or nonliving?
 Is a rock living? What
about a piece of grass?
Or an icicle?
 There are 6
characteristics of
living things

3. #1: Living Things Have Cells
 All living things are
composed of one or
more cells
 What is a cell? A cell
is a membrane-
covered structure that
contains all the
material necessary for
life
 Unicellular = one cell;
multicellular = more
than one cell

4. #2: Living Things Sense and
Respond to Change
 A stimulus is a change that affects the activity of an
organism.
-Examples: chemicals, gravity, light, sound,
hunger, or anything else that activates a
response
 Homeostasis is the maintenance of a stable internal
environment
 Allows us to keep our internal environment in check when
external environment is changing
 Example: When it gets cold outside, our internal temp still
stay 98.6 degrees

5. Homeostasis is kind of like a see-saw, which your body wants to keep
balanced.
-Outside temp is cold, but our bodies don’t plunge into a low
body temp—it works hard to balance our temp at 98.6 degrees, no
matter what the outside weather!

6. #3: Living Things Reproduce
 Sexual reproduction:
two parents produce
offspring that is similar
to both parents
 Asexual reproduction:
single parent produces
offspring that is identical
to the parent

7. #4: Living Things Have DNA
 The cells of ALL living
things contain the
molecule
“deoxyribonucleic acid,
or DNA
 DNA controls structure
and function of the
cells
 Heredity: passing
copies of DNA from
parent to offspring

8. #5: Living Things Use Energy
 Organisms need and use energy to carry out
activities in life
 Metabolism: the total of all the chemical
activities that the organism performs

9. #6: Living Things Grow and
Develop
 We all GROW! It doesn’t
matter if you are a multicellular
or unicellular organism
 We all develop! As we grow,
we go through different stages
in our lives.
 Example: US! Baby->child->teen-
>adult
 Acorn  seedling  sapling 
tree

10. Those 6 things
define us as
living…But what 4
things do we need
in order to live??

11. Necessities of Life

Organisms need 4things to live:
1. Water
Your body is made up of 70 %
water
Most of the chemical reactions
involved in metabolism require
water

12. 2. Air
A mixture of gases (oxygen and
carbon dioxide)
Organisms on land get oxygen from
the air
Marine animals get dissolved oxygen
from the water or by coming up for
air
Green plants, algae, and some
bacteria need carbon dioxide in
addition to oxygen to undergo their
food making process called
photosynthesis

13. 3. Food
 Gives us energy and raw materials
needed to carry on life processes such
as replacing cells
 Producers: make their own food
 Consumers: get food by eating other
organisms
 Decomposers: break down nutrients of
dead organisms or animal wastes

14. 4. Shelter
(a place to live)
 All living
things need a
place to live
that has all of
the
necessities
of life (enough
space, food,
water, etc.)

15. 5 Building Blocks of Cells
 1) Proteins:
Molecule made up
of amino acids;
helps build and
repair body
structures.
Example: protein
hemoglobin is in red
blood cells and
binds to oxygen to
deliver it throughout
the body

16.  2) Carbohydrates:
molecules made up of
sugar
 A) Simple
carbohydrates: one
sugar molecule, like
table sugar
 B) Complex
carbohydrates:
hundreds of sugar
molecules, such as
plants (potato, whole
wheat)

17.  3) Lipids: do not
dissolve in water;
include fats and
steroids
 A) phospholipids are
the molecules that
form much of the cell
membrane; the head
is attracted to water
but the tail is not—the
tails attract to form
two layers

18.  4) ATP:
“Adenosine
Triphosphate”;
major energy-
carrying molecule
in the cell; provides
energy for the cell

19. 5) Nucleic
Acids: have all
the information a
cell needs to
make proteins;
DNA is a nucleic
acid