Transcript Natural selection lecture 12-12

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 Harmful
 Adaptive
 No Value
 Whether or not a trait is Adaptive, Harmful, or No Value is
Time and Locationspecific
Harmful – These types of mutations are detrimental to the
organism
• Either causing it to be less well adapted for its environment, or
by causing a basic life function of the animal to function
deficiently or not at all
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http://www.ridacritter.com/albino%20sqhttp://www.moosefoundation.org/pictures/albino.jpgrrel%20005.jpg
• Write a brief list of how the albino organisms color mutation is
detrimental to that organism’s survival in the wild.
Adaptive – These types of mutations cause the organism to gain
some advantage that increases its ability to survive and
reproduce successfully
Adaptive
Examples:
 The ability to utilize another food source
 Disease immunity or resistance
 Makes the organism more competitive
 More successful at passing on genes
Examples:
• Disease immunity or resistance
http://evolution.berkeley.edu/evosite/evo101/images/sicklecell.jpg
• Sickle cell anemia (uh-NEE-me-uh) is the most common form of sickle cell
disease (SCD). SCD is a serious disorder in which the body makes sickleshaped red blood cells. “Sickle-shaped” means that the red blood cells are
shaped like a crescent.
• Normal red blood cells are disc-shaped and look like doughnuts without
holes in the center. They move easily through your blood vessels. Red blood
cells contain an iron-rich protein called hemoglobin (HEE-muh-glow-bin). This
protein carries oxygen from the lungs to the rest of the body.
• Sickle cells contain abnormal hemoglobin called sickle hemoglobin or
hemoglobin S. Sickle hemoglobin causes the cells to develop a sickle, or
crescent, shape.
• Sickle cells are stiff and sticky. They tend to block blood flow in the blood
vessels of the limbs and organs. Blocked blood flow can cause pain and
organ damage. It can also raise the risk for infection.
Examples:
The ability to utilize
another food source
http://fig.cox.miami.edu/~cmallery/150/unity/c1x17b-finches.jpg
• “ The relative contribution an individual makes to the gene pool
to the next generation”
•
Cambell, Biology
Makes the organism more
competitive
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• Write down a list of at least 7 adaptations that the Giraffe
posses that increase its fitness within its environments
• 1. Survive
• 2. Reproduce
• Species are members of populations that interbreed in nature,
and whose offspring are fertile; not according to similarity of
appearance
No Value – These types of mutations do nothing to either harm
the organism or to make them more fit
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Mutations assist a species because they cause a variety of
variations to exist within that species. Adaptive mutations
increase the fitness of a species by providing increased
variation
• Recurrent mutation – a mutation for a trait that is genetically
different from either parent, but is already present in the
population
• Novel Mutation – a mutation that results in a trait
that is not already present in the population
Conflict that arises between individuals or groups in the process of
acquiring limited resources
Limiting Resource
• Any factor (usually a nutrient) within an ecosystem
that is in finite quantity and that is required by
individuals in that ecosystem for survival
• “Two species with similar needs for the
same limiting resources cannot coexist in
the same place” –Campbell, Biology
2 types
 Fundamental niche – the resources (biotic and
abiotic) that are theoretically available to an
organism
Realized niche – the resources (biotic and abiotic) that
are actually utilized by a given population
(Campbell,
Biology)
A niche is what the animal does in its community, its
habitat is where it lives
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• Interspecific - competition between different
species
• Intraspecific – competition within the same species
1. If all offspring were able to reproduce successfully
populations size would exponentially increase over a
few generations
2. In natures populations sizes are relatively stable
3. Limited resources exist in all environments
4. Individuals within the same species have a variety of
unique and distinct traits (every individual is different)
5.
Many of these variations can be passed on to
successive generations

Competition results when more offspring are
produced then can survive because resources
are limited
Offspring that posses more beneficial
characteristics are more likely to survive and
pass on their genes
Because more fit individuals survive most often
populations will shift over time to accumulate
more beneficial characteristics
• This is called….
• Adaptations are not static as environments change
so do the characteristics of a population. The best
combination of traits changes over time
• Note: species do not develop a trait to cope
with an element in their environment rather a
pool of traits (range of variation) exist within a
given population and those that are best
adapted survive more frequently and reproduce
more successfully.
• Artificial selection – human modification of species (ex.
Selective breeding)
•
•
•
•
•
•
•
Food
Habitat
Mates
Predation
Disease
Climate
Competition for resources ( invasive species)
Stabilizing Selection
• This type of selection encourages the average or
status quo combination of traits.
• It happens in environments where there is little
change occurring
• Many human characteristics are a result of stabilizing selection.
Human birth weight is not only a polygenic trait, but it is also
controlled by environmental factors. Infants with average birth
weight are more likely to survive than a baby that is too small
or too large. The bell curve peaks at a birth weight that has the
minimum death rate.
• Directional Selection
This type of selection favors a specific combination
of traits that were relatively rare in the original
population
It happens in environments where there is great
change occurring or is a species is moving into a
new environment
• Charles Darwin studied what was
to become known as directional
selection while he was in the
Galapagos Islands. The beak
length of the Galapagos finches
changed over time due to
available food sources. When
there was a lack of insects to eat,
finches with larger and deeper
beaks survived because they
could crack seeds. Over time, as
insects became more plentiful,
directional selection favored
finches with smaller and longer
beaks.
• Diversifying (disruptive) Selection
This type of selection favors traits on either end of
the spectrum but not the middle
It happens in environments where there is change but
the new factors favor multiple variations, this often
happens in a divergence of species
• One of the most studied examples of disruptive selection is the
case of London's peppered moths. In rural areas, the peppered
moths were almost all a very light color. However, these same
moths were very dark in color in industrial areas. Very few
medium colored moths were seen in either location. It seems that
the darker colored moths survived predators in the industrial
areas by blending in to the polluted surroundings. The lighter
moths were seen easily by predators in industrial areas and
were eaten. The opposite happened in the rural areas. The
medium colored moths were easily seen in both locations and
were therefore very few of them left after disruptive selection.
• Only traits that already
exist in a population can be
selected for
• Every adaptation is also a
compromise
• Every adaptation has to be
based on a preexisting
element of the organism
• There cannot be a
permanently perfect
organism
Sexual
Reproduce
(Often Intraspecific)
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• A feature possessed by a single sex that increases
reproductive fitness (generally in vertebrates)…
• Reproductive fitness can (but doesn’t have to)
detract significantly from the environmental
fitness of an individual ie.
The Peacock …
Important
Please
EAT ME!!
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Sexual secondary characteristic can assist the animal
in survival such as a elk’s antlers, but it is often the
females that determine the fitness of a Sexual
dimorphism