Transcript Natural Selection

NATURAL SELECTION
Natural Selection…………
 In a nutshell, organisms with favorable
phenotypes that allow for adaptation in a
particular environment will survive, reproduce,
pass their alleles along to their off spring
 Environment DOES NOT NECESSARILY MEAN
THE WEATHER!!!! It simply indicates those that
can withstand selective pressures such as:
 Selective pressures from competition for mates, for
food, for shelter, escaping predators, acclimation to
climate. Others may include physical features such as
variation in beak size (must adapt to other food
sources!)
Natural Selection
 First of all, it does NOT produce the perfect
organism!! There are still fish that swim too
slow and get eaten, not to mention the
human genetic diseases out there!!
 However, there is genetic variation in
populations of organisms (Remember genetic
recombination in Meiosis? Mutations?
 Natural selection LEADS to evolution!
Example of Natural Selection
• In this fish population, individuals have
variations. For example, they may differ in
color, size, and speed.
• *Individuals with
certain useful
variations, (in this
case speed) survive in
their environment,
passing those
variations to the next
generation.
* Over time, offspring
with certain
variations make up
most of the
population and may
look entirely different
from their ancestors.
Peppered Moth Video
 You Tube Title:
 Peppered Moth
 by Mark Drollinger
 http://www.youtube.com/watch?v=sVVldxxb
Wig
 (2 minutes!!)
Fitness??
**The word fitness describes how well a particular
phenotype is at leaving offspring in the next generation
relative to how good others. This does NOT mean the
organism is the strongest…just the “best” suited
**For example, if brown beetles consistently leave more
offspring than green beetles because of their color (possibly
less noticeable to predators) you’d say that the brown beetles
had a higher fitness. Se say the brown phenotype is selected
for.
The brown beetles have a greater fitness relative to the green beetles.
Darwin’s Finches, Natural
Selection and Fitness
Darwin and the Galapagos
Finches Video
 YouTube Title:
 Galapagos: the finches (4/7)
 http://www.youtube.com/watch?v=l25MBq8T
77w
 (2 minutes long!!)
What’s Up
With The
Finches? What
do You Notice
About Their
Beaks? How
Would You
Explain This
Observation?
A subspecies of this species is also known as
the vampire finch as it will occasionally drink
the blood of blue-footed booby nestlings
Natural selection
not only affects finches,
but insects, bacteria and
viruses as well!!
In Bacteria!!
~~Remember they multiply like
crazy (exponentially!! ).
Remember when we grew some
yucky stuff overnight??
~~Mutations occur quickly as
well!!
~~ Along with overuse, and
misuse, of antibiotics many
strains have developed immunity
Antibiotics Are Medications Used to
Kill, or at Least Slow Down,
Bacterial Infections, Like Strep
Throat
Antibiotic Resistance
Pesticide Resistance
Immunity  Your Ability to
Fight Off Infections and
Diseases
 Diseases can be caused by bacteria, viruses,
some protists and some fungi
 These are called pathogens
 Two basic types of acquired immunity
 Active
 Passive
Vaccines and Anti-Virals
Viruses
 Although viruses aren’t living, they have a single nucleic
acid chain (either DNA or RNA) surrounded by a protein
coat and capable of replication but only within the cells
of living organisms
More About Viruses!!
 Virus that enter your body will attach themselves to a
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cell and insert its DNA, or RNA, into your cell that
carries the instructions to make more viruses
New viruses leave the cell to invade other cells
However, your immune system can learn from these
encounters and develop strategies to prevent
reinfection.
The next time the same virus comes to a host cell, it
may find that it is no longer able to attach to the cell's
surface membrane.
So to survive, viruses must adapt or evolve, changing
its surface proteins enough to trick the host cell into
allowing it to attach.
Vaccines Help Guard Against
Antiviral Medications
 Antiviral resistance means that a virus has
changed in such a way that the antiviral drug
is less effective in treating or preventing
illnesses caused by viruses, such as the flu
 The drug Tamiflu shortens the duration and
severity of the flu
 Nucleic acids of the virus may change in a
way that results in the virus becoming
resistant to antiviral drugs
Mass Production of Tamiflu – The
Antiviral Drug for Influenza