Characteristics of Life
Regents Biology Unit 1
“The Living Environment”
• The living environment is essentially a biology
course
• Biology- the study of all living things
– Biologists use the scientific method to study life
and it’s processes
• What is Life?
To be alive…
• Nearly all living things share several
characteristics
• Living things…
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are made up of units called cells
reproduce
are based on a universal genetic code
grow and develop
obtain and use materials and energy
respond to their environment
maintain a stable internal environment
change over time
1) Made up of Cells
• Cells are the basic units of structure and
function of all life
• Cells are the smallest unit of life, but are quite
complex
• Organisms may exist as single cells
(unicellular) or many cells (multicellular)
– Examples:
• Unicellular= bacteria, protozoa (amoeba, paramecia),
and algae
• Multicellular= complex plants, animals, and fungi
2) Reproduction
• All organisms produce new organisms (offspring)
– Reproduction is necessary for the survival of a
species, but is not necessary for the survival of an
individual organism
• Species- a group of organisms that are genetically distinct
from other groups
– 2 types
• Asexual reproduction- one parent produce genetically
identical offspring
• Sexual reproduction- two parents combine genetic
information to produce genetically different offspring
• Forms of repro
3) Based on a Universal Genetic Code
• All known organisms store all the information
necessary for their life processes within a
genetic code, written in a molecule of DNA
– The DNA of all organisms is made of the same 4
bases• Adenine, Thymine, Cytosine, Guanine
4) Grow and Develop
• All organisms undergo some form of growth
and development
– Growth can be accomplished in 2 ways:
• Individual cells increase in size, like a balloon
• The number of cells in the organism increases
– During Development, cells often change or
differentiate into different structures
5) Obtain and use Materials and
Energy
• All organisms must take in materials (nutrients)
and energy to grow, develop, reproduce, and stay
alive.
– Nutrition- how an organism obtains raw materials
(water, carbohydrates, fats, proteins, vitamins, and
minerals) from the environment.
– Metabolism- chemical reactions through which
organisms make and use energy
• Synthesis- building molecules (storing energy)
• Respiration- breaking down molecules to make energy (ATP)
6) Respond to Their Environment
• Organisms detect and respond to stimuli from
their environment.
– Stimuli- signal to which an organism responds
• Ex. Light, water, temperature, seasons
• Phototropism
• Behavioral reg.
7) Maintain a Stable Internal Environment
• Maintaining the conditions inside an organism in
a stable manner is called homeostasis.
– Balance of:
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Body temperature
Sugar levels
Hormone levels
pH
Ion concentrations or electrolytes
Water Concentrations
• Homeostasis is constantly being threatened by
changes in the environment
8) Change Over Time
• Organisms must change or adapt to survive in
a variable world.
• Taken as a whole (think species level)
organisms change/evolve over time
– Changes are not noticeable over individual
lifetimes, but the small change become dramatic
over many generations
• Fossil record
Essential Processes
• While all life fulfills by the characteristics we just
talked about, there are also several very
important processes that are essential to the
survival of an organism or its species.
• Processes:
1. Obtaining nutrients from the environment and
breaking them down for transport
2. Transporting materials through the organisms
Essential Processes
3. Respiration- Breaking down nutrients (sugar)
into smaller units to release chemical energy
(ATP)
4. Synthesis- combining simple substances into
complex substances
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Ex. Glucose in plants, proteins in cells
5. Growth- increase in size or number of cells
Essential Processes
6. Excretion- the removal of any type of waste
product from the organism
7. Reproduction- the creation of new organism
from the parent
8. Regulation and Response- responding to various
internal and external stimuli