Transcript Characteristics of Living Things and Cell Structure and

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.
7. Living things maintain a
stable internal
environment.
a) Even though external
environmental conditions may
vary widely, most organisms
must keep internal conditions,
such as temperature and
water content, fairly constant.
b) Maintaining a stable internal
environment is called
homeostasis (Greek, same
condition).
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 box-like
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