Characteristics of Life
Intro to Biology
Composition of Life
Let’s think about what living things are made out of.
All organisms, no matter how strange they look, are
built from the same building blocks:
Proteins
Lipids
Carbohydrates
Nucleic Acids
Proteins
Lipids
Carbohydrates
Nucleic Acids
• Muscle fibers
• Enzymes
• Antibodies
• Fats and oils
• Cholesterols
• Cell membranes
• Sugars
• Starches
• Cellulose
• DNA
• RNA
What do each of those molecules have in
common?
• They each contain atoms of carbon
We are carbon based life forms
• All living things on Earth contain carbon
Why carbon?
• Carbon is like the really cool lego in the
building set. You can attach so many things to
it! Carbon can make really big complex
molecules necessary for living things.
Characteristics of Living Things
All living things have a similar compositions.
What else do they have in common?
Characteristic #1
complex organization, made of cells containing
DNA
HAVE CELLS AND DNA
• Multi-cellular: cells differentiate from a single
fertilized egg cell, and they just “know” to
become a heart, leg etc.
• Uni-cellular : one celled organism (amoeba or
bacteria)
• Both above have DNA ( the genetic code:
which is why we look like our parents)
Characteristic #2
• have motility and can respond to the
environment
• Stimulus- signal to which an organism
responds
– Response- (what they do because of the signal)
• Internal stimulus- ex.) sugar levels drop?
…then you feel hungry
• External: ex.) flower leans toward the window
in a classroom
Characteristic #3
reproduce
Reproduce
• There are 2 types of reproduction:
• Asexual : 1 parent (budding) - identical
– bacteria
• Sexual: 2 parents
– cats
– people
Characteristic #4
Living things grow and develop
Growth and Development
• Bacteria- grow, they just increase in size
• People – develop … they increase in size and
their bodily functions change over time….until
they become an adult
• ex) puberty…
Characteristic #5
• Populations of
organisms can mutate
and evolve from one
generation to the next
• 100,000’s of millions of
years…changes can be
dramatic within a
species…
• ex) pre-historic horse
was the size of a Barbie
doll horse
Characteristic #6
• Living Things Need and Use Energy
Living things use energy to
grow/develop/reproduce… or just stay alive
• Where do we get energy from?
• Metabolism: combination of chemical
reactions through which an organism builds
up and breaks down materials (will release
energy) as it carries out life processes
– Fast metabolism- break down
– Slow metabolism – store for later
Where are they getting energy from?
How obtain energy?
• Plants: From the sun’s energy
“photosynthesis”
• Lion: From eating other organisms “herbivore,
carnivore”
• Mushroom: From the remains of dead
organisms (decomposers)
7. Maintain Homeostasis
7. Maintain Homeostasis
• External: conditions may vary widely
• But internal…. Should be kept constant.. This
is homeostasis
• Ex) temperature 98.6 F, water content, etc
• Ex of how it happens?
– Shivering/sweating
– Thirst/feeling of fullness
Complex organization
based on DNA-one or
more cells
Response to
environment
Reproduction
Growth and
development
Mutations and
evolution
Need and Use Energy
Maintain Homeostasis
Homework
Due: Thursday, September, 3
• You will create a product to summarize what you
have learned about the 7 Characteristics of Living
Things
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Personal Choice
Must Include lots of color if doing anything visual
Must have approval from Teacher
Possible Products:
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Poem or song
Book mark
Children’s book
Poster
Case #1: Journey to Europa
Journey to Europa
It is 2113. You are a xenobiologist traveling with
a crew of astronauts to Europa. It has long
been thought that Europa could support
living organisms. Your mission is to gather
samples and analyze them for the presence of
alien life.
Arrival
Your shuttle arrives on the Galilean moon’s
surface, a cold and barren place. It is -370⁰F,
and the radiation that burns through the
moon’s thin atmosphere makes it terribly
dangerous to step outside.
As the shuttle sets down, you and the crew look
out through the view ports. It is the only close
up view you will have of the moon’s surface.
No one is allowed out. All of your work will be
done under the protective hull of the ship.
Drilling
Once the shuttle has secured itself to the
surface, its drill is activated. Europa’s ice crust
is thin, and it only takes
..a few hours before the first
.samples are brought up.
Water!
Under the ice is an ocean! Finally, after over a
century of speculation, we now know that the
tidal forces from Jupiter have kept the moon’s
core warm enough for liquid water.
Samples
Before cameras and submersibles can be
deployed, the first set of samples are brought
up for analysis, and there is no time to lose.
Sample #1
The first water sample reveals tiny particles.
After analysis, these particles appear to have
the following characteristics:
•
•
•
•
•
•
Complex boron based molecules, but no DNA or RNA
Mobility
Response to light and temperature stimuli
No observable reproduction after 2 days
Uptake of sulfur and boron “nutrients”
Production of nitrogenous secretions
Sample #2
The second sample shows a filmy substance that
collects at the surface of the water. Further
analysis shows the following characteristics:
• A lipid bi-layer membrane similar to our own cells
• Organic molecules such as carbs and amino
acids inside the membrane bubbles
• No observed reproduction after 2 days
• No DNA or RNA
• No response to external stimuli
• No gas exchange or nutrient uptake
Case #2: A Mysterious Plant Illness
A Diseased Tobacco Crop
You are a botanist studying the spread of
disease among tobacco plants. Crops have
been failing extensively, and tobacco farmers
are desperate for a cure. Nothing seems to be
working!
What Could it be?
You obtain some infected plants for further
analysis and head back to your lab.
Where is the Pathogen?
You crush up the leaves and examine the fluids
under a microscope. There are several
different types of bacteria, but all of the ones
you see are common and not known to cause
disease.
The Chamberland Filter
• You decide to pass the fluids through a
Chamberland filter, a special apparatus with
holes that are tinier than bacteria. The fluid
should pass and leave all bacteria behind.
A Tiny Disease
The fluid no longer has any bacteria. You take a
closer look. The microscope reveals that the
fluid is perfectly clear. However, when you
drop the fluid onto healthy tobacco leaves,
they become sick. There is something in that
fluid!
An Even Closer Look
You decide to send the samples to be analyzed
by a more powerful microscope. You only have
a light microscope, and you need an electron
microscope to get a closer look.
The Results Are In!
An electrograph is sent back to you. In the
image, you see strange, rod-like particles.
Structure of the Mystery Particles
These particles are highly organized. They are
composed of proteins, and each have a strand
of their own hereditary information in the
form of RNA.
How Strange!
The particles do not appear to be able to
reproduce on their own. Yet, when they are
placed on living plant cells, they inject their
RNA into the plant and force it to make new
mystery particles! In this way, they are literally
hijacking the tobacco cells and causing them
to die while the particles reproduce and
spread.
Are they alive?
What are these strange things?
You decide to probe further. In your studies you
learn:
• they do not respond to outside stimuli.
• they do no appear to grow or develop once they
are assembled by the tobacco plants.
• they do not need nutrients or oxygen or carbon
dioxide.
• but, after trying various treatments you notice
that resistant particles evolve. The genes in the
RNA must be mutating!
So what is it?
It’s a type of virus!
Viruses are not considered living things, but they
share a lot of characteristics with life.