What is Life?
I. Spontaneous Generation
a. the theory that life could evolve
from non-living matter
b. disproved by Francesco Redi in
1668
• 
Redi s Experiment
II. Characteristics of Living Things
a. All living things:
1. are made of cells
2. contain DNA
3. grow and develop
4. respond to their environment
5. use energy
6. reproduce
1. Living Things have Cells
a. the basic building blocks of
living things
b. unicilluar- single celled
organism
ex. Bacteria
c. multi-cellular- many celled
organism
ex. flowers, plants, animals
Bacteria = single cell
2. Living Things Contain DNA
a. DNA (deoxyribonucleic acid)
-- genetic material that carries
traits and directs cells activities
DNA
3. Living Things Grow and Develop
a. increase in size and complexity
b. life span- the maximum length of
time a particular organism can be
expected to live
4. Responsd to Environment
a. living things can move
b. stimulus- signal to which an
organism reacts; a change in
the environment
c. response- reaction, movement or
change in behavior---- a
stimulus causes a response
d. homeostasis- the maintenance
of stable internal conditions
1. outside environment may
change, but conditions in the body
must stay the same
ex. body temperature
a. ectotherms- cold-blooded animals—
temperature changes with the
temp. of the environment.
ex. reptiles
b. endotherms- warm-blooded animals—
maintain a constant body
temperature
ex. mammals
Endotherm
Ectotherm
5. Living Things use Energy
a. use energy to carry out the
chemical activities of life
b. Metabolism the sum of all the
activities that the organism
performs--ex. digestion
Metabolism= body using energy
6. Living Things Reproduce
a. sexual reproduction- two
parents
b. asexual reproduction- single
parent
ex. bacteria
Asexual Reproduction in Hydra
Asexual Reproduction in Bacteria
III. Living Things Need:
1. energy (food)
a. primary source of energy for
all organisms is the sun
b. autotrophs- produce own
food
ex. plants
c. heterotophs- must consume
food.
2. water
a. about 70% of body is
water
3. air
a. most organisms need
oxygen
4. living space
IV. Terms to Know
a. organism- a living thing
b. organic compound
a. living things
b. contain carbon
c. animals, plants, humans
c. inorganic compound
a. non-living things
b. most don t have carbon
c. water, salt, metal, etc.
V. Origin of Life
a. The Earth is about 4.6 billion years
old
b. scientists think life began about 3.6
billion years ago
-bacteria first organisms to
appear
c. Life formed gradually over time
d. The first cells did not need oxygen
to survive