Natural Selection

Which mouse is the fittest? Why? Fur color Brown Tan Black White Age at death 6 months 8 months 4 months 2 months # of pups 6 12 2 Running speed 8 m/ min 6 m/ min 9 m/ min 7 m/ min Other Bit 5 birds that tried to attack her pups. Chases off 2 snakes that wanted to eat her pups. Relocated her pups after her den was flooded during high tide. Had the deepest and most well hidden den on the beach.

The organisms best suited to their environment have more chance of survival if the species falls upon hard times.

This idea is known as survival of the fittest.

Natural selection is the process by which these “fit” individuals survive & reproduce to pass on the advantageous traits to their offspring.

Darwin studied finches and how their beak adaptations have allowed them to adapt to take advantage of food sources in different ecological niches.

His studies led him to come up with a theory based on the process of natural selection.

Charles Darwin’s Theory of Natural Selection:

Organisms produce more offspring than can survive.

There is competition among offspring for food, space & other resources.

There are variations among the offspring of an organism caused by genetic differences.

Individuals with certain traits are better suited to survive in their environment than those without the traits

Organisms that survive & reproduce pass the genes for their useful traits to the next generation.

Adaptations can only happen if there is variety within the offspring of a species.

This variety is caused by genetic variation, the normal differences that exist among individuals of the same species.

Selective breeding is the process of breeding plants and animals for particular genetic traits.

Selective breeding is most often seen with domestic animals like cats and dogs which are bred for specific traits such as size, health, looks, fur type, or their specialized job.

Selective breeding is also common in organisms used for consumption such as cattle, chickens, pigs, fruits and vegetables.

Traits that are favorable in these organisms include growth rate, survival rate, disease resistance, and meat/ egg/ flesh quality.