Themes of
Biology
Biology 1.1 Themes of Biology
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Everyday, you are surrounded by living
things that scientists call organisms.
Some organisms; such as people,
plants, animals, are obvious.
Others are so small that the human
eye can not see them, such as bacteria
and viruses.
When we try to determine what is
alive and what is not we look at
movement, response to environment
and creation and destruction.
While these characteristics may be
found in many objects in our world,
they do not always mean that
something is alive.
Biology 1.1 Themes of Biology
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Biology is the study of life
Biologists recognize that all living
things share certain characteristics;
properties that separate living
organisms from nonliving things.
7 unifying themes – properties of life
are shared by all things that are living
All things that are living are capable of doing the
following:
Every living organism
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is composed of one or more cells
is able to reproduce
can obtain and use energy to run life
processes
will maintain a constant internal
environment
can pass on traits to offspring
can respond and adjust to the environment
will grow and develop
Life is characterized by the presence of all
these properties at some stage in the
organism’s life
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Properties of Life
What does it mean to be alive?
The following properties help to define what is
life; what is living and what is not living.
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Cellular organization
Reproduction
Metabolism
Homeostasis
Heredity
Responsiveness
Growth and development
Unifying Themes of Biology
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In the study of biology, certain broad
themes emerge that both unify living
things and explain biology as a science.
 1: cellular structure and
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function
2: reproduction
3: metabolism
4: homeostasis
5: heredity
6: evolution
7: interdependence
Cellular structure and function
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All living things are made of one or
more cells
Cells are highly organized, tiny
structures tiny structures with thin
coverings called membranes
Organisms can range from a single
cell to trillions of cells
The basic structure of cells is the
same in all organisms although some
cells are more complex than others
Reproduction
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All living things can reproduce
Reproduction is the process by which
organisms make more of their own kind
from one generation to the next.
Some rapidly growing bacteria divide into
offspring cells approximately every 15
minutes while bristlecone pine trees that
are 5000 years old still produce seedlings.
Your body contains more than 100 trillion
cells which have grown from a single
original cell.
Metabolism
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Living organisms carry out many
different chemical reactions in order to
obtain and use energy to run their life
processes.
•All living things use energy to grow, to
move, and to develop
 Metabolism is the sum of all the chemical
reactions carried out in an organism
Metabolism
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Almost all energy used by living
organisms is originally captured by sunlight.
•Plants, algae, and some bacteria capture
this solar energy and use it to make
complex molecules in a process called
photosynthesis.
•These molecules than serve as the source
of energy, or food, for other organisms.
Metabolism
•Energy flows from sunlight to
plants, from these plants to plant
eating animals, from these animals
to meat eating animals, and so on
finally to humans.
• We extract our energy from
eating a variety of plant and animal
food sources.
Homeostasis
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All living organisms must maintain a stable
internal environment in order to function
properly.
Organisms respond to changes in their external
environment and their internal processes adjust
accordingly. Their bodies help them keep heat in
or let extra heat escape.
The maintaining of stable internal conditions in
spite of changes in the external environment is
called homeostasis.
Homeostasis
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An organism unable to balance it’s internal
conditions with it’s environmental conditions can
become ill and die.
Arctic seals are able to maintain a constant
body temperature in their cold environment
because of their body shape and thick layer of
body fat they posses.
In this way, they maintain their homeostasis or
even body temperature.
Heredity
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All living things are able to pass on traits to
their offspring through genes that are
passed from parent to offspring. Traits are
things like hair or eye color.
A gene is the basic unit of heredity.
The passing of traits from parent to
offspring is called heredity
Heredity is the reason you resemble your
parents. You inherit traits from them such
as your eye color, hair color and texture and
facial features.
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Somet imes d amag e caus es g en es t o
chan g e
A chan g e in t he DNA of a g en e is
called a mutation
Mutations:
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Most mutations are harmful, but
sometimes mutations can help an
organism survive.
Favorable mutations can aid an
organism in survival by making it a
better hunter or by making it better
at avoiding predators.
A fur seal’s white fur helps it blend
into it’s environment and avoid
hunters that may prey on it.
A leopard’s spotted fur is a favorable
mutation that helps it blend into the
dappled light of a jungle rainforest.
Evolution
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Mutations cause changes in the inherited
characteristics of species over
generations.
Change in the inherited characteristics of
species over generations is called
evolution.
A species is a group of genetically similar
organisms that can produce fertile
offspring. Individuals in a species are
capable of breeding with each other and
having young.
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A species is a group of
genetically similar organisms
that can produce fertile
offspring
Individuals in a species are
similar but not identical
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Individuals with genetic traits that better
enable them to meet nature’s challenges tend to
survive and reproduce in greater numbers
causing these traits to become more common.
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Charles Darwin, the 19th century British
naturalist, used the term naturalselection for the process in which
organisms with favorable traits are more
likely to survive and reproduce.
Darwin’s theory of evolution by
natural selection provides a
consistent explanation for
life’s diversity of organisms.
Most scientists believe that
the many different species of
animals, plants, and other
organisms on Earth today are
the result of a long process of
evolution.
Interdependence
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Organisms in any biological
community live and interact
with other organisms.
A biological community is a
group of interacting
organisms.
Ecology is the branch of
biology that studies the
interactions with one
another and with the
nonliving parts of their
environment
•Ecology is the branch of biology that
studies the interactions with one another
and with the nonliving parts of their
environment
•Organisms are dependant on one
another and on the nonliving parts of
their environment; they are
interdependent.
•Interdependence within biological
communities is the result of a long
history of evolutionary adjustments.
•The complex web of interactions in a
biological community depends on the
proper functioning of all it’s members,
even those organisms too small to be
seen without a microscope.