What is Evolution? What is Evolution?. EVOLUTION: the process of change over time Evolution is the idea that new species develop from earlier species.

What is Evolution?

EVOLUTION: the process of change over time

Evolution is the idea that new species develop from earlier species by accumulated changes. This is also referred to as “descent with modification”.

Evolution is NOT…

It is NOT a fact...it's a theory:

a well supported testable explanation of something that occurred in the natural world.

Lamarck's Hypothesis: Inheritance of Acquired Characteristics

1. “Acquired Characteristics”: Through use and/or non-use, those features needed for survival are developed in each

individual.

2. Inheritance: Those characteristics developed (“acquired”) by individuals are

passed on to their offspring, who can continue that development.

3. New Species: Eventually, over many generations, enough differences have developed that we can say we have a new species.

Darwin's Hypothesis: Natural Selection

1. Overproduction: There are more offspring produced than will survive and reproduce

2. “Survival of the fittest” (not necessarily the strongest): Those with more adaptive traits tend to survive longer and/or produce the most offspring; these are the “naturally selected”.

Natural selection is based on 4 facts:

1.Organisms produce more offspring than can survive.

2.There is variation among offspring.

3.There are limited resources

(not enough food, water, space,

etc. for everyone).

4.The organisms best fit to their environment will survive and the others will not.

Organisms produce more offspring than can survive.

Example: A frog can lay 200 eggs, yet not all eggs will survive to become adult frogs.

Results of Evolution -- Speciation!!

Speciation is the process that creates new species!A species is a group of organisms that can naturally

interbreed and produce fertile offspring.

The Liger--the offspring of a tiger and a lion. Tigers and lions are still considered separate species, because

although they can produce

offspring, the offspring

is not fertile.

Evidence of Evolution -- Fossils!!

Fossils are preserved remnants or impressions left by an organism that lived in the past.

Usually, the deeper down the fossil is, the older it is.

Evidence of Evolution -- Embryology!

It is believed that all vertebrates evolved from a common ancestor. The genetic information that guides their development is nearly the same.

That's why scientists can learn about human development by studying other organisms--including zebrafish.

Evidence of Evolution --Anatomical/Physiological SimilaritiesNotice how there are similar bones and similar

structures in humans, birds and whales!

Can you tell which is the bird and which is the whale?

Vestigial Organsorgan that serves no useful functionover generations, they reduce in size

Adaptations!Inherited characteristic that increase an organism’s chance of survival

Why are most animals in the artic white? So they blend in with the snow and avoid being seen!

Why do sharks have such sharp teeth?

It allows them to catch their prey!

Why do elephants have such big ears? To let heat escape their bodies so they can stay cool!

Extinction!

Extinction occurs when there are no members of a species left alive.

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What do these pictures represent?

What is a vestigial structure? How do vestigial structures support the

theory of evolution?Give an example of a vestigial structure.

How do fossils serve as evidence of evolution?

What can we learn about evolution by looking at amino acid sequences (DNA)?

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Definition Examples

Homologous structures

Analogous structures

Vestigial structures