Transcript Natural Selection

Natural Selection vs.
Artificial Selection
Natural Selection
• The process in
which the fittest
organisms survive
to produce
offspring.
Natural Selection
3 Factors that cause natural selection
to take place
1. Overpopulation
• Many more offspring are
produced than actually
survive
2. Survival of the Fittest
• Struggle for existence
• Organisms compete for
food, water and shelter
Natural Selection
3. Variation – variety within a species
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Organisms of the same species have different
traits
Some traits give an organism a better chance
to survive
Organisms that lose
the struggle:
1. Leave less offspring
2. Do not pass on traits
3. Die out
Artificial Selection
• A technique in which a
breeder selects particular
traits
• Can cause divergent
evolution to occur.
• Divergent evolution is when
related populations or
species become more and
more dissimilar.
Example: All domestic
dogs are the same species
Canis familiaris, but
because of breeders
breeding them for select
traits results in different
breeds.
European rabbits were introduced to Australia in 1859. The
rabbits reproduced rapidly in their new environment, displaced
other animals and overgrazed vegetation. In an attempt to
reduce the rabbit population, a virus deadly to Europeans
rabbits was introduced in 1951.
When the virus was first introduced, the rabbits died in large
numbers, but the death rate decreased over time.
What statement best explains the decrease in the rabbit
death rate?
A. Natural selection favored rabbits that were resistant to
the virus.
B. Young rabbits learned to avoid being infected by the
virus.
C. The virus had a short life span and died out with the
rabbits.
D. The rabbits died of natural causes and the introduced
virus did not work.
European rabbits were introduced to Australia in 1859. The
rabbits reproduced rapidly in their new environment, displaced
other animals and overgrazed vegetation. In an attempt to
reduce the rabbit population, a virus deadly to Europeans
rabbits was introduced in 1951.
When the virus was first introduced, the rabbits died in large
numbers, but the death rate decreased over time.
What statement best explains the decrease in the rabbit
death rate?
A. Natural selection favored rabbits that were resistant to
the virus.
B. Young rabbits learned to avoid being infected by the
virus.
C. The virus had a short life span and died out with the
rabbits.
D. The rabbits died of natural causes and the introduced
virus did not work.
In a mouse population inhabiting a grassland area, a
mutation occurs that results in a new allele for coat
color.
Which of the following factors has the greatest
effect on whether the new coat color allele will
become more common in the mouse population?
A. Whether abundant food is available in the
grassland
B. Whether the new coat color allele is dominant or
recessive
C. Whether the rate of reproduction in the mouse
population is stable
D. Whether the new coat color allele increases the
survival of mice in their environment
In a mouse population inhabiting a grassland area, a
mutation occurs that results in a new allele for coat
color.
Which of the following factors has the greatest
effect on whether the new coat color allele will
become more common in the mouse population?
A. Whether abundant food is available in the
grassland
B. Whether the new coat color allele is dominant or
recessive
C. Whether the rate of reproduction in the mouse
population is stable
D. Whether the new coat color allele increases the
survival of mice in their environment
An individual in a population that is considered
the most fit would
A. produce the most viable offspring.
B. live the longest.
C. consume the most food.
D. be the strongest and the fastest.
An individual in a population that is considered
the most fit would
A. produce the most viable offspring.
B. live the longest.
C. consume the most food.
D. be the strongest and the fastest.