Transcript Activity 97 Power Point

ACTIVITY 97: ORIGIN OF
THE SPECIES
97: ORIGIN OF THE SPECIES
• Challenge
What role do mutations play in natural
selection?
Useful Vocabulary:
Mutations
Speciation
Speciation – The divergence, or
branching, of one species into 2 distinct
species.
When the DNA within a species
becomes SO different (mutations)
that it can no longer reproduce
successfully, speciation is said to
occur.
EXAMPLE OF SPECIATION:
• The scene: a population of wild fruit flies minding its
own business on several bunches of rotting
bananas, cheerfully laying their eggs in the mushy
fruit...
• Disaster strikes: A hurricane washes the bananas and the
immature fruit flies they contain out to sea. The banana bunch
eventually washes up on an island off the coast of the
mainland. The fruit flies mature and emerge from their slimy
nursery onto the lonely island. The two portions of the
population, mainland and island, are now too far apart for
gene flow to unite them. At this point, speciation has not
occurred — any fruit flies that got back to the mainland could
mate and produce healthy offspring with the mainland flies.
The populations diverge: Ecological
conditions are slightly different on the island,
and the island population evolves under
different selective pressures and experiences
different random events than the mainland
population does. Morphology, food
preferences, and courtship displays change
over the course of many generations of
natural selection.
So we meet again: When another storm
reintroduces the island flies to the mainland, they
will not readily mate with the mainland flies since
they've evolved different courtship behaviors. The
few that do mate with the mainland flies, produce
inviable eggs because of other genetic differences
between the two populations. The lineage has split
now that genes cannot flow between the
populations.
ANTICIPATION GUIDE
1)Complete the before column in the anticipation
guide as best as you can.
2)Tape or Glue the anticipation guide into your
Science Journals.
PROCEDURE
• While you read the information,
be sure to complete each
Stopping to Think Question in
your notebooks (In complete
sentences)
STOPPING TO THINK 1
Physical Features likely
to be a result of
genetic differences
Physical features that
may not be a result of
genetics, but as a
result of some other
factor from birth to
adulthood
Physical features that
might be a result of
both genetic and other
factors
Hair color
Eye color
Skin color
Height
Amputations
Burns
Tattoos
Piercings
Scars
Skin tone
Intelligence
Personality
Weight
Muscles
STOPPING TO THINK 2
a. A mutation in a puppy that would be
neither helpful or harmful would be
different colored eyes
b. A mutation in a puppy that could be
harmful could be missing a leg.
STOPPING TO THINK 3
• You can NOT choose your traits. Your genes
are passed to you by your parents at
conception. These traits are INHERITED and
not Acquired.
STOPPING TO THINK 4
I would disagree with my friend.
The Total number of mutations in the
Galapagos Finches would have exceeded
14.
It is also unlikely that one mutation will prevent
2 populations from interbreeding, or change
their breeding habits enough that they no
longer try.
ANALYSIS #1
• Mutations are not always helpful
• Since mutation occur randomly, many or most
of them are either harmful or neither helpful OR
harmful.
• In addition, whether a mutation is helpful is
relative to the particular environment.
• In general, if a mutation becomes common in a
population, it must have been helpful, or
advantageous, for that population.
ANALYSIS #2
• Originally there was just one species of cichlid.
• A cichlid was born with a mutation that allowed it to
withstand colder water.
• When there was a shortage of food, this cichlid could
survive on different food that then other cichlids
because it could go deeper in the lake
• It survived, reproduced, and passed on its traits to its
offspring.
• Over time, there were 2 types of cichlids. One spent
most time in deeper levels.
• The two types interbreed less and less.
• Eventually as a result of accumulated mutations, the 2
types of species could no longer interbreed.
• At this point they become 2 different species.
ANALYSIS #3
• Bacteria must evolve faster, since their populations
go through so many more cycles of reproduction
within equivalent time periods
• In fact, bacteria are far more capable of surviving
sudden environmental changes than slower
reproducing species such as humans and other
complex species
• This helps to explain Antibiotic Resistance!