Biology in the 21st Century
I. Biology - the study of life
A. Earth is home to an incredible diversity of life
1. Biosphere - every part of Earth where life
might be found
2. Biodiversity - the variety of living things
a. biodiversity generally increases from the
poles to the equator
b. species - a particular type of living thing
that can reproduce by interbreeding among
themselves
B. Characteristics of Life – all living things share
certain characteristics
1. All living things are made up of cells. A cell is
the basic unit of life
2. Need for energy – all organisms need a source
of energy
a. plants capture the energy of the sun
b. animals get their energy by eating other
organisms
c. metabolism – all the chemical processes
that build up or break down material
3. Response to environment
a. stimuli – factors that cause a response in an
organism
4. Reproduction and Development
a. reproduction – ability to produce new
individuals
b. development – change in an organism
c. DNA (deoxyribonucleic acid) – genetic
material passed from one generation to the
next
II. Unifying Themes of Biology
A. All levels of life have systems of related parts
1. system – organized group of related parts
2. cellàtissueàorganàorgan systemàorganism
example:
3. speciesàcommunityàecosystemàbiosphereà
universe
4. ecosystem – physical environment with
different species that interact with one another
and with nonliving things
B. Structure and function are related in biology
1. teeth have different structures and perform
different functions (front teeth cut and back
teeth grind)
2. heart muscle has different structure than arm
muscle
C. Organisms must maintain homeostasis to survive
in diverse environments
1. Homeostasis – the maintenance of constant
internal conditions in an organism
2. examples:
D. Evolution explains the unity and diversity of life
1. Evolution – the change in living things over
time
2. adaptation – an inherited trait that gives an
advantage to individual organisms and is
passed to future generations
3. All living things show both unity and diversity
a. unity – all living things use the same DNA
code
b. no two living things have identical DNA
III. Scientific Thinking and Processes
A. Scientific Method
1. Observation – scientist make observations and
examine previous research
2. Forming hypothesis – try to explain
observations
hypothesis – proposed answer for a scientific
question
3. Testing hypothesis – collect data to support or
reject a hypothesis
4. Analyze data – look at data and draw
conclusions
5. Evaluate Results
B. Scientific Experiments – testing hypothesis
1. Independent variables – the condition that is
manipulated
2. Dependent variables – what is observed and
measured during an experiment. Dependent
variables change in response to changes in the
independent variables
3. Constants – conditions that do not change
during an experiment
4. experiments must change only one variable
C. Theory – a proposed explanation for a wide range
of observations
1. Examples – theory of evolution, germ theory
2. Law – a known truth, no exceptions, always
correct
IV. Biologist Tools and Technology
A. Imaging provides new views of Life
1. Microscopes
a. light microscope
b. Scanning electron microscope (SEM)
c. transmission electron microscope (TEM)
2. Medical Imaging
a. CAT scan
b. MRI Magnetic resonance imaging
c. X-ray
3. Computers allow us to model complex systems
V. Biology and Your Future
A. Health Care
B. Environmental Studies
C. Biotechnology
D. Ethics