SPECIES VARIATION
CHANGES OVER TIME
YOU ALREADY KNOW:
SPECIES - A GROUP OF SIMILAR ORGANISMS THAT CAN
MATE WITH EACH OTHER AND PRODUCE FERTILE OFFSPRING
Members of a species have a shared “gene pool”.
GENE POOLall of the alleles
of all individuals
in a population
VARIATION- ANY DIFFERENCE BETWEEN
INDIVIDUALS OF THE SAME SPECIES
CHANGES IN GENE
POOLS CAN BE
CAUSED BY :
• Climate changes
• Landforms
• Interactions between
species
• Mutations
DEFINITIONS ARE IMPORTANT –
QUICK LAB
• Take 1 minute and write on the back of your notes the
definition of “home”.
• Swap your definition with the person sitting closest to you.
• Are your definitions exactly the same?
• Why do you think it’s important for us to make sure we all
have the same understanding of the words we are using?
WHAT CHANGE ARE WE TALKING ABOUT?
Change
over time
Evolution
Microevolution
Evolution
Macroevolution
MICROEVOLUTION
Changes occur in
gene pool
Causing more
variation in
individuals
Causing more
variations in
individuals
Causing more
changes in the
gene pool
MICROEVOLUTION
the process that occurs
over time where changes
in gene pools causing
more variation in
individuals, causing more
changes in the gene pool
and so forth.
QUICK REVIEW:
1. True/False: The word “evolution” always means the same thing to everybody.
False
1. A gene pool is all of the ____________ of all the individuals in a population.
Alleles
1. Changes in gene pools can be caused by what 4 things:
1. Climate changes
2. Landforms
3.Interactions between species
4.Mutations
QUICK REVIEW 2
1.The process of small changes taking place in gene
pools over time is known as: ____________
Microevolution
2.Can individuals evolve?
No. Only populations can evolve.
CHANGES IN GENE POOLS
CAUSED BY
CLIMATE CHANGES
A change in the
climate can affect
an organism’s
ability to survive.
Ex: Wood frogs in shady
ponds vs. sunny ponds
CHANGES IN GENE
POOLS CAUSED BY
LANDFORMS
Landforms
are features on the
Earth's surface like
mountains and plains
CHANGES IN GENE POOLS
CAUSED BY
INTERACTIONS
BETWEEN SPECIES
The changes caused
by interactions of
species in the same
community.
Example: Asian shore crabs &
blue mussels
CHANGES IN GENE
POOLS CAUSED BY
MUTATIONS
Mutations are random
changes in the DNA
DDT resistance in
insects
ANOTHER QUICK REVIEW
Name the 4 factors that can cause changes in a gene pool:
• Climate changes
• Landforms
• Interactions between species
• Mutations
ANOTHER QUICK REVIEW 2
1. Turn to your classmate closest to you and take 1-minute
turns explaining how climate change might cause species
change. Jot down any questions you have as you discuss
it.
2. Turn to a different classmate and take 1-minute turns
explaining how landforms might cause species variation.
REVIEW 3
1. Turn to a person you have not shared with and take turns
explaining to each other how species interacting with
each other might cause species variation.
2. Turn to a person you have not shared with yet (3rd
person of the day) and take 1 minute each to explain
how mutations might cause species variation.
SO WHAT IS
CONSIDERED
EVIDENCE OF SPECIES
VARIATION?
1. The fossil record over
geologic time
2. Rapid bacterial
mutations due to
environmental
pressures
FOSSILS
Preserved remains
of once-living
organisms
HOW DO FOSSILS
FORM?
• Water
• Sediments
• Pressure
• Time
FOSSIL RECORD
The sum total of all
fossils collected by
scientists and the
information they give.
THE GEOLOGIC TIME
SCALE
A “calendar” of Earth’s
history based on
information interpreted
from the study of fossils.
The lower a fossil is found in
the layers of earth, the
older it is believed to be.
BUT THAT’S THE PAST,
WHAT IS CONSIDERED
EVIDENCE OF SPECIES
VARIATION TODAY?
Rapid bacterial mutations due
to environmental pressures
In other words, bacteria
changing quickly because of
factors in their environment
threatening to destroy them.
BACTERIAL MUTATION: HOW FAST IS IT?!
HOW BACTERIA BECOME RESISTANT TO
ANTIBIOTICS
SO WHAT DOES THIS
HAVE TO DO WITH
SPECIES VARIATION?
SCIENTISTS BELIEVE THIS
MODERN BEHAVIOR OF
BACTERIA SHOWS THAT
SPECIES VARIATION MAY
HAVE OCCURRED THE SAME
WAY IN THE PAST.
THE LAST QUICK REVIEW
1. What are the 2 pieces of “evidence” of species
variation?
• The fossil record over geologic time
• Rapid bacterial mutations due to environmental pressure
2. What are the characteristics of bacteria?
• Unicellular (one-celled)
• Prokaryotes
• Live everywhere
THE LAST QUICK REVIEW 2
1. Antibiotics kill bacteria not viruses.
2. Mutations help bacteria to survive.
3. Only the strongest bacteria survive an antibiotic and the
strong bacteria multiply rapidly passing on those
antibiotic-resistant genes.