We all have these in common.
8 Characteristics of Life
Living things share 8 characteristics:
1. Living things are made up of units called
cells.
a. Every organism is composed of at least one
cell.
1.) single-celled or unicellular
2.) many-celled or multicellular
b. There are two broad categories of cells:
1) prokaryotic—no organized nucleus nor membrane
bound organelles; found in bacteria and cyanobacteria
2) eukaryotic—do have an organized nucleus and
membrane-bound organelles such as Golgi apparatus
and mitochondria. All other organisms such as plants
and animals have this kind of cell.
2. Living things reproduce.
There are two basic kinds of reproduction:
a) Asexual—only one parent and all offspring are
identical; for example, binary fission of bacteria or
amoebas.
b) Sexual—two cells from different parents unite to
produce the first cell of a new organism.
3. Living things are based on a universal genetic
code (DNA).
a) The directions for inheritance are found in
deoxyribonucleic acid or DNA.
b) The genetic code is basically the same for all
organisms on Earth.
4. Living things grow and develop.
a) For single-celled organisms, growth is mostly
an increase in size.
b) Multicellular organisms go through a process
called development, where cells divide and
differentiate into different kinds of cells.
5. Living things obtain and use materials and energy.
a) The combination of chemical reactions through which
an organism builds up or breaks down materials as it
carries out its life processes is called metabolism.
b) Autotrophs (also called producers)—plants, most
algae, and some bacteria obtain their energy directly
from the sun through photosynthesis.
c) Heterotrophs (also called consumers)—most other
organisms, rely on the energy stored during
photosynthesis.
1. Herbivores—eat plants and other photosynthesizing
organisms
2. Carnivores—eat the herbivores or other carnivores
3. Omnivores—eat both plants and animals
4. Decomposers—such as bacteria and fungi; obtain
energy from the remains of organisms that have died
6. Living things respond to
their environment.
a) Organisms detect and
respond to stimuli from
their environment.
b) A stimulus is a signal to
which an organism
responds.
c) External stimuli include
temperature and light.
d) Internal stimuli come from
within, such as blood sugar
level or feeling thirsty.
8. Taken as a group, living things change over
time (living things evolve).
a) Plants have adapted to living in dry and hot
deserts.
b) Fossils of ancient organisms can be used to
show how organisms have changed over time.
8. Taken as a group, living things change over
time (living things evolve).
a) Plants have adapted to living in dry and hot
deserts.
b) Fossils of ancient organisms can be used to
show how organisms have changed over time.
1. Organism
2. Organ
System
3. Organ
4. Tissue
5. Cell
Cell Structure and Function
Notes
Discovery of the Cell:
•Mid 1600’s scientists began using
microscopes to observe living things
•Robert Hooke used microscope to
observe thin slice of cork—dead plant
material
Cork seemed to be made of boxlike chambers—Hooke called cells
•Anton van Leeuwenhoek discovered
living cells in pond water
Cell Theory:
•All living things composed of cells
•Cells are the basic unit of structure
and function in living things
•New cells are produced from existing
cells
Cell and its Environment:
•Organisms made of one cell—
unicellular organisms
Ex: bacteria
•Organisms made of many cells—
multicellular organisms
Ex: plants, animals
• Each cell must be in “balance” with its environment, exchange
food, waste, H2O, CO2, O2 etc.
• Process by which organisms maintain a relatively stable
internal environment—homeostasis
Cell:
•Organisms that do not have a distinct nucleus—
prokaryotic (PRO = NO)
Ex: bacteria
•Organisms with cells that have true nucleus and
organelles—eukaryotic (EU = TRUE)
Ex: plants, animals, fungi
Cell Parts and Their Functions:
Specialized cell parts called organelles—
“little organs”
1. Cell membrane—determines what goes
in and out of the cell
2. Cytoplasm—gel-like medium that holds the
organelles in position
3. Nucleus—control center of the cell
•
Double membrane that surrounds the nucleus—
nuclear membrane
•
Hereditary information inside the nucleus—
chromatin (DNA)
4. Ribosomes—makes proteins
5. Rough Endoplasmic Reticulum (rough ER)—
makes and transports proteins within the cell
•Called rough ER because of the ribosomes
found on its surface
6. Smooth Endoplasmic Reticulum
(smooth ER)—makes and transport
lipids and other materials within the cell
•
Called smooth ER because no ribosomes
found on its surface
7. Cytoskeleton—network of protein
filaments that helps cell maintain its
shape
8. Golgi apparatus—processes and
packages proteins and other substances
produced in the ER
9. Mitochondria—energy source of the cell
(powerhouse)
10. Vacuoles—sac-like structures for storage
•
Plant cells usually contain a large vacuole
that fills most of the cell—pressure from this
large vacuole helps plants support
themselves
Found in animal cells only:
11.Lysosomes—cleans up the cell and
digests unwanted materials
Found in plant cells only:
12.Cell wall—provides support and
protection for cell
•Composed mainly of cellulose (plant starch)—fiber for
our diet
13.Chloroplast—makes glucose using the energy
from the sun (photosynthesis)
Specialized Parts for movement:
1. Cilia (like little hairs)
2. Flagella (like a tail)
Specialized Cells:
Different cells in your body do different jobs. The
structure (how it’s built) of cells matches the
function (what it does).
• Plant Examples:
1.Leaf cell—contains many
chloroplasts to maximize
photosynthesis
2.Root cell (potato)—
contains many vacuoles to
maximize water and starch
storage
• Animal Examples:
1.Epithelial cells—have villi to increase
nutrient absorption; found in the intestines
2. Muscle cells—contain many mitochondria
to produce more energy for movement
3.
Nerve cells—have fibers called dendrites
that allow nerve cells to communicate
with each other