Natural Selection vs. Artificial Selection

Natural Selection

• The process in which the fittest organisms survive to produce offspring.

Natural Selection3 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 Selection3. Variation – variety within a species

• 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 offspring2. Do not pass on traits3. 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.