DO NOW

• When people think “EVOLUTION,” they often think of the phrases “Only the strong survive” or “survival of the fittest.” – Based on your reading for homework,

what do these phrases mean to you?– How do you think it applies to other

species of animals besides humans?

Evolution

Changes Through

Time

DARWIN’S VOYAGE• Charles Darwin –

naturalist aboard a ship from England that sailed around the world.– his job was to learn about

all the living things that he saw on the journey.

– His ship, the HMS Beagle, spent a lot of time on a chain of islands called the Galapagos Islands.

• His observations of living things, fossils, and the characteristics of all the organisms he saw on the Galapagos islands led to some of the most basic theories about evolution

DARWIN’S OBSERVATIONS

• While on the voyage Darwin was amazed by the variety of living things he saw.

• Today scientists have identified more than 1.7 million species of organisms and not all living things have been identified.

• A species is a group of similar organisms that can mate with each other and produce fertile offspring.

•Magnifying glass

•Glass bottom bucket

•Notebook and pencil

•He observed organisms living on the island as well as studied fossils that were left behind from long ago.

•Fossil: Preserved remains or traces of organisms that lived in the past

•Darwin found fossils that were similar to the bones of sloths living on the island now, except they were much larger. He wondered what happened to these giant animals.

Darwin’s Tools Were Simple

DARWIN’S OBSERVATIONS

• On the Galapagos Islands Darwin saw the largest amount of diversity. He saw: giant tortoises, sally light-foot crab, blue footed boobies, seals covered with fur, and lizards that only ate cacti.

Many of the plants and animals on the islands were similar to organisms Darwin saw on the mainland of South America.

• EXAMPLES: Birds and plants.

HOW DID THEY GET THERE?

• Darwin inferred that some species came to the islands from the mainland.

• Maybe they were taken there by the ocean

• Once on the islands they reproduced.

There were also important differences between organisms on the islands and those on the

mainland.

• Cormorants on the mainland could fly, those on the islands could not.

• Iguanas on the islands had large claws and iguanas on the mainland had small ones.

Observe the Claws

Galapagos Islands

Mainland

There were even differences between the islands!

• The tortoises on one island had dome-shaped shells, while on another island they were saddle-shaped shells.

DO NOW - Discussion

• Some insects look just like sticks. How could this be an advantage to the insects? How could this trait have evolved through natural selection?

ADAPTATIONS• Darwin also noticed

differences in finches on the islands.

• There beaks were suited towards their diet. – Which two do you

think were adapted to eat seeds?

– Which two do you think were adapted to eat insects?

Adaptation – a trait that helps an organism survive and reproduce.

ADAPTATIONS

• Beak shape is an example of an adaptation.

Based on these two pictures, what adaptations do you see?

• Darwin studied his observations for many years. He thought that the organisms arrived on the islands and faced conditions that were different from those on the mainland.

• He concluded that the species must have gradually changed over generations and became better adapted to their new conditions

EVOLUTION

• The gradual change in a species over time.

How does the environment select

organisms to survive• Individuals with helpful variations will allow them to survive and reproduce possibly passing that helpful allele to their offspring.

• Nature selects the ones with better variations while unfavorable variations disappear.

Natural Selection

• Process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

Darwin Hypothesized That There are THREE Factors that Can Effect Natural Selection

OverproductionCompetitionVariations in the species

There are many factors that affect natural selection

• Overproduction – Most species produce more offspring than could possibly survive.– Not enough food,

water, or living space.

There are many factors that affect natural selection

• Competition – The offspring must battle indirectly with each other to survive.

There are many factors that affect natural selection

• Variations – Differences between individuals of the same species.

• HOW do variations and natural selection work to change a species over time?

Variations acted on by Natural Selection

• Suppose the climate in an area becomes much drier than it was before. What kinds of variations in the area’s plants might be acted on by natural selection.

Can a change in the environment effect survival of

an organism?• YES!• An organism more suited for the

environment is “selected” by nature to survive, reproduce, and pass on its helpful variation.

Discussion

• When people think “EVOLUTION,” they often think of the phrases, “Only the strong survive” or, “Survival of the fittest”. How do these phrases describe the concept of natural selection?

Discussion

• Imagine that Conackamack is one of the islands that Darwin is observing. What are some selected traits that would benefit a student and help them to survive and make it to the high school and beyond? In other words, what species of student would be “strong enough to survive” our educational system?