Unit 2 - Similarities and Differences of Living Organisms
Review book Topic 1, page 1-16
It is not always easy to tell the difference between
living and non-living things.
Prior to the 1600's many people believed that
nonliving things could spontaneously turn into living
things. This is called …
For example, it was
believed that piles of straw could turn into mice.
That is obviously not the case.
Although scientists cannot agree on a single
definition, there are some very general rules to follow
when deciding if something is living or non-living.
A. Characteristics of Life
Listed here are six rules used by scientists:
Living things are organized structures, made of
one or more cells.
Living things obtain and use energy to carry out
activities or chemical reactions metabolism.
Living things grow and develop.
Living things reproduce.
Living things respond to their environments and
maintain a stable internal environment
Living things adapt to their environments.
Use GRACE to remember: Growth, reproduction,
adapt, cells and energy.
If something follows one or just a few of the rules listed
above, it does not necessarily mean that it is living.
To be considered alive, an object must exhibit all of the
characteristics of living things.
Ex. Sugar crystals growing on the bottom of a syrup bottle
Ex. Fingernails, toenails?
Living or non-living?
And the answer is: Non – living
Living (cuticle area only)
It depends (Hair shafts are dead, hair follicles are alive)
Can you think of some other examples of nonliving
objects displaying living characteristics?
Examples: machines, batteries, electric outlet, water
Remember, nonliving things have no functioning
cells and no metabolic activity; they do not reproduce
nor maintain homeostasis.
* Many scientists do not include viruses with living things because they
are not cells and they do not reproduce on their own
B. Classification of Living Things
Although living things share many characteristics,
there are also many differences.
Living things are classified into groups based on the
different ways they carry out life processes
There have been several attempts at classification
1. Aristotle used the following system:
- He divided organisms into 2 groups - plants and animals
- He divided animals into blood vs. bloodless
- He also divided animals into 3 groups according to how they
moved - walking, flying, or swimming (land, air, or water)
2. CAROLUS LINNAEUS – did things differently
18th century Swedish scientist
- He divided living things into one of two "kingdoms" - plant and animal
- He divided each of the kingdoms into smaller groups called "genera"
- He divided each genera into smaller groups called "species"
- He designed a system of naming organisms called binomial ("two
names") nomenclature ("system of naming")
- Genus is always capitalized while species is never capitalized.
- To be written correctly, the scientific name must be either underlined or
written in italics.
His classification system is still used today; however, we
use a 6-kingdom system (instead of 2).
C. Similarities of Living Things
Living Things share similar…
1. Life Processes
2. Chemical Composition
Life Processes – we will discuss 11 different processes
1. Metabolism – combination of all the chemical reactions
that occur in an organism
2. Homeostasis - maintaining a stable internal environment;
organisms must respond and adapt to both their internal
and external environments (also called steady state).
Ex. Body temp: too cold
3. Reproduction – process by which living things pass on
hereditary information and produce new individuals.
Species survival is dependent on reproduction.
Ex. A fish lays millions of eggs in a stream
4. Respiration – processes that provide energy to maintain
life functions. We obtain energy by releasing chemical
energy stored in nutrients (converting stored energy into
Ex: Sugar in barley is changed into alcohol and
5. Regulation – the control and coordination of the various
activities of an organism. Maintaining a stable internal
Ex: You breathe rapidly after running a mile.
A dog sheds its coat in the summer.
6. Growth/Development – an increase in the number of
cells, cell size, shape or form; this process utilizes
Ex: You are taller now than in first grade.
A seedling develops into a pine tree.
7. Synthesis – chemical activities that cause large molecules
to form from smaller ones; i.e. combining simple
substances chemically to form more complex substances
(building proteins or complex carbohydrates).
Ex: A green plant uses sunlight, water, and carbon
dioxide to make its own food
8. Nutrition – includes obtaining materials from the
environment and processing them for use; i.e. taking in
energy and converting it to a usable form
o Ingestion – to take food in
o Digestion – breaking down complex nutrients into a simpler
o Egestion – removal of indigestible material (solid waste)
Ex: A squirrel ingests a nut.
An owl regurgitates a pellet.
9. Excretion – the removal of cellular waste products
Ex: You urinate after consuming a liter of water.
10. Transport – the absorption and distribution of materials
within an organism. Usable materials are taken in
(absorbed) and distributed throughout the organism
Ex: An oxygen molecule travels from the lungs to a
11. Movement – change in position by a living thing
Ex. what happens when the bell rings???
All living things are made up of 4 main elements
1) Organic Molecules – contain both C & H
Ex: proteins, fats, DNA, carbohydrates such as
starch and sugar (glucose)
2) Inorganic molecules – do not contain both C & H
Ex: salts, minerals, CO2, O2, H2O
All living things are made of cells – can be either
one cell or billions of cells
Cells contain specialized structures called
In multi-cellular organisms, groups of cells group
together to form tissues
Ex. Muscle cells form muscle tissue
Tissues combine to form organs
Organs combine to form organ systems
This can be shown using a flow chart:
cells tissues organs organ systems organisms
D. Cells – Basic Structure of Life
In cells, there are structures know as organelles “little
Organelles are formed of many different molecules
They vary in size, shape, and function
ALL cells have –
1. Cell Membrane – also called a Plasma Membrane
a. A thin, flexible barrier around the cell
b. Made up of lipids and proteins
c. Separates the cell contents from the surrounding
d. Supports and protects the cell
e. Allows the cell to interact with its surroundings
f. Regulates transport of material into and out of
g. It is selectively permeable (semi permeable)
h. Helps maintain homeostasis (factors such as pH
and concentrations of all cell substances)
i. “Fluid Mosaic Model” (see overhead)
A. lipid molecules
B. protein molecules
C. phospholipids – glycerol, 2 fatty acids, and
a phosphate group
a. Watery, fluid or jelly-like material between the cell
membrane and the nucleus
b. Made primarily of water and organic compounds
c. Suspends the organelles that are within it
d. Transports materials though the cell
e. Site of many chemical reactions metabolism
a. Large spherical structure found in the center of
b. Surrounded by the nuclear membrane (double
c. Contains genetic information/material (DNA
d. Controls or directs the cell’s activities
e. Serves as the “control center” for cell metabolism
a. found within the nucleus
b. involved with synthesis of ribosomes (mRNA)
which manufacture proteins
5. Nuclear Envelope/Membrane
a. Double membrane structure
b. Dotted with thousand of pores
c. Allows material in and out of the nucleus – RNA
to the rest of the cell
6. Endoplasmic Reticulum (Smooth & Rough ER)
a. A series of interconnecting channels
b. Store, synthesize, and transport substances
c. Components of the cell are assembled and some
proteins are modified here
a. Tiny structures
b. Site of protein (enzyme) synthesis – very
c. Are either free bodies (float in cytoplasm) or
attached to membranes of the ER
a. Pod-shaped structures
b. Contain protein (enzymes) used to take energy
c. Called the cells “powerhouse” because they
release most of the cells energy
d. Use energy from food to make high-energy
compounds for cell functions
9. Golgi Complex, Golgi Bodies, Golgi Apparatus
a. Series of small membrane-bound sacs
b. Synthesize, package, and secrete cellular
a. Small organelles filled with digestive enzymes
b. Help with intracellular digestion when fused with
c. Break down lipids, carbohydrates, and proteins
from food to be used by the cell
d. Remove debris that might otherwise accumulate
and clutter up the cell
a. Storage sacs in the cytoplasm
b. Have a membrane around them
c. Contain either wastes or useful materials such as
food and water
d. Specialized vacuoles in unicellular organisms
A. Food vacuoles – are digestive organelles,
B. Contractile Vacuoles – help maintain
water balance, pump excess water out of
e. Plant cell vacuoles are much larger than animal
f. Plant vacuoles store water that help to support
heavy structures like leaves
a. Network of protein fibers and tubes extending
throughout the cytoplasm
b. Gives cell support and shape
a. Cylindrical structures in the cytoplasm
b. Function during cell division
c. Common in animal cells and rare in plant cells
a. A strong barrier that lies outside the cell
membrane in plant cells only
b. Made of cellulose and is nonliving
c. Provides shape, support, and protection
d. Allows cells to interact with surroundings
a. Primarily found in plant and algae cells
b. Green pigment containing structures
c. Serve as a site for photosynthesis
d. Capture light energy and then use it to produce
food for the plant
e. Animal cells do not contain chloroplasts!!!
Differences between Plant & Animal Cells
Prokaryotic vs. Eukaryotic Cells
Both have cytoplasm and a cell membrane
a. Lacking an organized nucleus and chromosomes
b. Smaller and simpler cells (less complex internal
c. Ex: bacteria (E. Coli)
a. Have an nucleus
b. Larger and more complex internal structures
c. Ex: plants and animals
Many scientists do not include viruses with living things
Are not composed of cells.
They are made of protein and genetic material.
Can only function within a host cell (ex: animal, human)
They can “take over” life activities in a host cell
No nucleus, are prokaryotes
Genetic material simply floats in the cytoplasm as a large
Some bacteria have smaller loops of DNA as well