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Evolution and Natural Selection

How species change over time

Evolution and Natural Selection

Genetic variations are passed on through reproduction

Evidence for evolution illustrates how organisms are related

Natural selection leads to evolution

Our understanding of evolution has changed over time

Evolution

The theory that organisms today developed from more simple life forms and have changed (evolved) over time.

Natural Selection

The theory that states that those organisms best adapted to their environment have a better chance of surviving and reproducing.

What was Darwin’s hypothesis?

Darwin hypothesized that organisms had a common ancestor, but had adapted to their particular environments and changed over time.

Darwin published his

research in 1859

Natural Selection For natural selection to

occur, there must be at least two varieties of a species.

For example: the peppered moth

Peppered Moths

At the beginning of the Industrial Revolution in England, coal burning produced soot that covered the countryside in many areas

What do you think happened?

Evolution/Natural Selection White moths became

easier to see, while the black moths became harder to see. The black moths were more likely to survive and pass on the gene for dark color to their offspring.

Over time, the black moths

have become more common.

Evidence for Evolution:Common Ancestry

Common Ancestry: If species evolved from a common ancestor, then they should share common anatomical traits

Hawaiian Honeycreeper: family of

birds in Hawaii that have similar

skeletons and muscles, indicating

they are closely related.

Over time, their common ancestor evolved

into several species, each with a specialized bill for eating certain foods. Just like Darwin’s finches on the Galapagos!

Evidence for Evolution:Homologous Structures

If animals evolved from a common ancestor, then they should share common structures – and they do!

These are called

homologous structures

Evidence for EvolutionEmbryo Development

What do you notice? List 2 observations

Evidence for Evolution:Vestigial Organs

Some organisms have structures or organs that no longer have a useful function.

These structures or organs may have been useful to the ancestors of a species, but over time have evolved into what we term vestigial organs.

Examples of Vestigial Organs

Kiwi (flightless bird)

Whales (hind leg bones)

Humans (tailbone, appendix)

Evidence for EvolutionFossils

Fossils provide a look

into the past

Scientists can trace how

a species has evolved

by studying fossils

Wrap Up the Evidence

Common Ancestry

Homologous Structures

Vestigial Organs

Embryonic Development

Fossils

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 BearOur story begins with the Polar

Bear’s closest living relative – the Brown Bear

The Evolution of The Polar BearAround 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 BearBecause of the genetic mutation,

a litter of Brown Bears exhibited WHITE coloration

The Evolution of The Polar BearHow 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

X X

X

XX

XX

X

X

X

X

X

X

X

X

XX

X

X

X

X

X

X

XX

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!

Discussion Topic

Echidna and Platypus belong in the animal kingdom and in the Phylum Mammalia, though both Echidna and Platypus have characteristics that can be categorized in the mammal, reptile or avian phylum. If you were the scientist to change the taxonomy, would you change their classification or keep it the same? Give evidence and logical response. 

Activity

Go to the following website and answer the worksheet.

http://phet.colorado.edu/en/simulation/natural-selection

You will need to download Java to play this.