A Closer Look At Darwin’s Idea of Natural Selection Jarod Raithel Mary Carroll High School Honors Biology I Spring 2007

Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

Natural Selection Rests on 4 Premises: 2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t

Natural Selection Rests on 4 Premises: 3) Traits have a genetic basis, or are inherited from parents

Natural Selection Rests on 4 Premises: 3) Traits have a genetic basis, or are inherited from parents

Natural Selection Rests on 4 Premises: 4) Advantageous traits, which allows organisms to have more offspring, will become more common in the population over time.

Examples of Natural Selection: The Evolution of The Polar Bear Our story begins with the Polar Bear’s closest living relative – the Brown Bear

The Evolution of The Polar Bear Around 300,000 years ago a small group of Brown Bears became reproductively isolated from the rest of the population

The Evolution of The Polar Bear This small founding population of Brown Bears were able to survive and reproduce living in the Arctic Tundra. After MANY generations, a random genetic mutation occurred...

The Evolution of The Polar Bear Because of the genetic mutation, a litter of Brown Bears exhibited WHITE coloration

The Evolution of The Polar Bear How do you think the white fur color affected these bears chances of surviving long enough to have cubs of their own?

REMEMBER: Natural Selection Rests on 4 Premises: 1) There is variation in the traits of individuals within a population

2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t REMEMBER: Natural Selection Rests on 4 Premises:

2) There is differential survival and reproduction, i.e., some individuals survive and reproduce, some don’t REMEMBER: Natural Selection Rests on 4 Premises: X X X X

3) Traits have a genetic basis, or are inherited from parents REMEMBER: Natural Selection Rests on 4 Premises:

4) Advantageous traits, which allows organisms to have more offspring, will become more common in the population over time. REMEMBER: Natural Selection Rests on 4 Premises: X X X X

XX X X X

X X X X X

X X X X X

X X X X X

X X X X X

What Happened?

Through Reproductive Isolation and Natural Selection... One Species Evolved Into Another New Species By Adapting To Its New Environment

We see this trend again and again in the Animal Kingdom... Speciation by means of Reproductive Isolation & Natural Selection!