Transcript Selective Pressures

Selective Pressures
The making of a species
Selective Pressure
• Natural Selection
occurs over successive
generations
• Evolution works on a
species level by
describing how the
species attains the
genetic adaptations
that allow them to
survive in a changing
environment.
Special Note
• Without a changing
environment , neither
evolution nor natural
selection would occur.
Genotype Fitness
• Are the genes present
in a population best
suited to allow the
population to continue
to reproduce?
Types of Pressure
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Physiological Stress
Predation
Competition
Luck
Geologic Isolation
• Geologic isolation
creates a unique
situation that often
forces evolution to
occur through
speciation
• The Galapagos Islands
offer the best example
of this phenomenon
• Ring Species
• A modern example of
speciation through
geologic isolation.
Case Study
• Good Trait? Bad Trait?
• Congenital condition
known as myotonia
congenita
• Causes the goat's
muscles to tense up
when the animal is
startled and don't
immediately relax.
• The gene called CLCN1
(Chloride Channel 1).
Under normal conditions
• The animal's eyes and ears relay the perceived
threat to the brain, which then sends an
electrical signal to the skeletal muscles ,
causing a momentary tensing.
• This is often referred to as the fight or flight
response.
Fight or Flight
• Just think how it feels to be startled. You'll find
your voluntary muscles contract and tighten
for a second. This is your brain telling your
muscles that the time has come to possibly
confront or run away from an immediate
threat.
• Normally, this tensing is followed by an
immediate relaxing of the affected muscles,
allowing you to turn and run away from a
perceived threat.
The Biology of the Condition
• Positively charged sodium ions relay the
brain's message for the muscle cells to
contract.
• Negatively charged chloride ions, which
CLCN1 affects, tell the muscle cells to relax.
• Mytonia congenita results in an abnormal
channel of chloride ions, which throws this
relationship out of balance.
The Question?
• What is the Genotype
Fitness of the fainting
goat in the wild?
• Types of selective
pressure?
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Physiological Stress
Predation
Competition
Luck
Would these goats survive in the
wild?
• Artificial Selection
• In fact, they would not
survive in the wild.
• Bred as pets
• Used by goat herders as
bait animals for
predators.