DARWIN’S THEORYof

NATURAL

SELECTION

(Survival of the Fittest)

HOW DID DARWIN EXPLAIN THE DIFFERENCES BETWEEN SPECIES ON THE GALAPAGOS ISLANDS AND ON MAINLAND SOUTH AMERICA?

HOW DOES NATURAL SELECTION LEAD TO EVOLUTION?

HOW DO NEW SPECIES FORM?

In this section you will want to find the answers for:

In 1831, Charles Darwin set sail on the HMS Beagle for a 5 year trip around the world

Darwin collected and studied numerous marine organisms during this famous voyage...

Observations he made on the Beagle expedition also provided him with the ideas that he later used to formulate his theory of evolution and natural selection.

Group of similar organisms that can mate and produce offspring

VOCABULARY

a well tested concept (idea) that explains a wide range of observations

SCIENTIFIC THEORY:

SPECIES:

What is the difference between an idea, theory and fact?

DARWIN’S THEORY:

Species gradually change over many generations and become

better adapted to new conditions

THE GALAPOGOS ISALNDS ARE A GROUP OF VOLCANIC ISLANDS

HOW DID DARWIN THINK PLANTS...

...AND ANIMALS ORIGINALLY CAME TO GALAPAGOS ISLAND?

Ancestors of today’s plants & animals on the islands were brought from the mainland by wind, currents, or on floating debris...

ONCE THEY REACHED ILSANDS, THEY REPRODUCED & OFFSPRING BECAME DIFFERENT

FROM MAINLAND RELATIVES DUE TO RESOURCES AVAILABLE.

Mainland TurtleIsland Turtles

THIS BRINGS US TO DARWIN’S THEORY OF NATURAL SELECTION

Natural SelectionIndividuals that are better adapted to their environment are more likely to survive.

WHAT ARE FACTORS THAT AFFECT SURVIVAL?

•Differences in species (variations)

SURVIVAL OF THE FITTEST

•Competition for resources

•Over production of same species

SO….

HOW DOES THIS APPLY TO THE

GALAPAGOS ISLANDS?

Organisms that were on the Islands first had NO competition for resources (food, shelter, H2O) because no other species was there.

Darwin studied finches found on these islands. This played an important role in his recognition of the evolutionary process.

by studying the finches - Darwinshowed how species are related to other species

...And

over long periods of

time natural selection can

lead to evolution.

HOW?

VARIATIONS IN ORGANISMS GRADUALLY ACCUMULATE WHILE UNFAVORABLE ONES DISAPPEAR.

As you can see in the next photos,

Darwin's finches share similar size color, and habits -

the difference is size and shape of their

beak.

The

FINCHES

WARBLER FINCHES

Lava Finch Galapagos Volcanoes

WHAT ARE SOME OTHER WAYS NEW SPECIES COULD HAVE FORMED?

CONTINENTAL

DRIFT

SEPARATION by:

RIVERS

SURVIVAL of the FITTEST

How is each organism suited to play a certain role in a certain habitat?ADAPTATIONS:inherited features that let organisms survive & produce young

Camouflage:

Adaptations that allow organisms to blend in w/environment.

What’s right w/these pics?

What’s the problem here?

What’s wrong w/this pic?

MIMICRY

ANOTHER ADAPTATION SEEN IN ANIMALS AND PLANTS:

KING SNAKE

CORAL SNAKE

WHICH IS WHICH?

CORAL KING

CRITICAL THINKING

•WHAT MAKES AN IDEA A THEORY?

•HOW IS A THEORY DIFFERENT FROM A FACT?

•UPON WHAT FACTS DID DARWIN BASE HIS THEORY OF EVOLUTION?