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What is Biology?
Bio = Life
ology = the study of
Biology= the study of life
OBJECTIVES
• 1. Relate the relevance of Biology to a person’s
daily life.
• 2. List the characteristics of living things.
• 3. Summarize the hierarchy of organization
within complex multicellular organisms.
• 4. Distinguish between homeostasis and
metabolism and between growth,
development, and reproduction.
Characteristics of Life
• The world is full of familiar things:
What criteria do we use to
determine what is living or once
alive?
Living things share 7 characteristics of
Life:
• 1. Organization and the presence of one or
more cells.
• 2. Response to stimuli
• 3. Homeostasis
• 4. Metabolism
• 5. Growth/ Development
• 6. Reproduction
• 7. Change through time
1. Organization and Cells
• Organization is the highest degree of order
within organisms.
• CELL: smallest unit that can perform life’s
processes.
• Cells can be UNICELLULAR: one cell. Ex.
Bacteria
• Cells can be MULTICELLULAR: more than 1
cell.
• Cell  tissue  Organ 
Organ system  Organism
2. Response to Stimuli
• This means that living organisms have physical
or chemical changes in the internal or external
environment. CAUSE AND EFFECT.
• Ex. When you flash a pen light into your pupil,
your pupil constricts
• Ex. Increase the temp of water will make fish
more active
• Ex. A rabbit gets scared so it runs away.
• Ex. You get cold so you put on a jacket.
Another example is plant stem growth. It has a positive
response to light. You can see this in the picture below.
The process of the
plant growing to
the sun is:
PHOTOTROPISM
If you touch your hand to a hot pan, you will have a
negative response. (If you don't, you should have some
serious concerns.)
• For example, if I put chocolate chip cookies
out on the lab stations tomorrow during class
(dream on) most of you would have a positive
response. You would get up and move
towards the stimulus.
3. Homeostasis
• This is a mechanism that allows organisms to
maintain stable internal conditions.
• Ex. Cells can only take in or release certain
amounts of water or the cell will burst or
shrivel up and die. This mechanism keeps the
cell from doing this.
• Organisms have regulatory systems that do
this
When our body gets too hot, what is
our bodies response?
Why?
• Ex. Our body response is to sweat. This is a
homeostatic mechanism to maintain an ideal
body temperature.
• Ex. When we get really cold, what is our
homeostatic response?
– We shiver. This is a similar mechanism to maintain
body temperature.
Can you think of other
homeostatic mechanisms?
4. Metabolism
• Metabolism is the sum of all chemical processes
that our bodies use. It is all the processes that
take in and use energy for cellular processes.
• Our bodies get the energy they need from food
through metabolism, the chemical reactions in
the body's cells that convert the fuel from food
into the energy needed to do everything from
moving to thinking to growing.
• Metabolism is a complicated chemical
process, so it's not surprising that many
people think of it in its simplest sense: as
something that influences how easily our
bodies gain or lose weight.
5. Growth and Development
• These concepts are different.
• All living things GROW and increase in size.
• Ex. The growth of living cells is a process called: Cell
Division.
• Development is when an organism becomes a mature
adult.
• Ex. The human body develops from one single,
fertilized egg.
• Ex. Tadpoles develop into a frog.
6. Reproduction
• All organisms produce new organisms like
themselves in a process called Reproduction.
• During reproduction, organisms pass on
hereditary information .
• Hereditary info is encoded segments of DNA
(deoxyribonucleic acid).
– 2 types of reproduction:
• Sexual and Asexual
7. Change through Time
• Organisms change during the lifetime of lifecycle, but
genetic info doesn’t change.
• However, populations of living organisms evolve or change
over time.
• Evolution of animals is essential to the survival of species.
• Ex. Peppered Moth- changes over the last 200 years. Were
lighter colored, but with pollution, moths have evolved a
darker color to help camouflage themselves against
predation.
• Ex. Darwin’s Finches- Differences in beaks due to what was
prevalent to eat.
• Ex. Bacteria evolve and become resistant to
antibiotics. This is a change over time.
Themes in Biology
• With the vast array of animal species on Earth,
how can one understand so many different
types?
• Scientists use unifying themes to help explain
the world and biology.
• The themes are: Diversity and Unity of Life,
Interdependence or Organisms, and the
Evolution of Life
DIVERSITY and UNITY OF LIFE
• What is diversity?
–It refers to the variety of
organisms.
• If life is diverse, how can we also explain
it as UNIFIED?
• All Organisms have specific things in
common.
– Genetic code: rules of how cells use
hereditary info in DNA
– Presence of organelles that carry out
cellular activities
• The “Tree of Life” is a representation
showing the relationships by
ancestry among organisms.
• While organisms share certain genes,
no 2 types of organisms have the
same full set of genes.
This shows that there are 3 main
lineages of life: THREE DOMAINS OF
LIFE
• 1. Bacteria
• 2. Archaea
• 3. Eukarya
INTERDEPENDENCE of ORGANISMS
• Organisms interact with each other
throughout the living world.
• ECOLOGY is a branch of biology that deals
with organisms interacting with each other
and with the environment.
• Interdependence is defined as:
– is a dynamic of being mutually responsible to and
sharing a common set of principles with others.
– Animals are interdependent because they often
rely on others for survival and stability.
– Ex. Panther eats a bird which eats a nut from a
tree. Tree needs CO2 and water, CO2 is waste
product of all animals.
EVOLUTION of LIFE
• Evolution is “descent with modification”. This
means = change over time.
• Natural selection- organisms that have
certain favorable traits are better able to
survive and reproduce.
• Adaptation: traits that improve an individual’s
ability to survive and reproduce.