Change Over TimeChange Over Time

Learning ObjectivesLearning Objectives Describe how Darwin’s observations helped him to

develop his hypothesis. Explain the process of natural selection and how it

contributes to evolution.

Who Was Charles Darwin?Who Was Charles Darwin?In 1839, Charles Darwin published his book The Voyage of the Beagle.

• Helped him develop one of the most important scientific theories of all time.

Scientific TheoryScientific Theory• A well tested concept that explains a wide range of

observations

Darwin’s HypothesisDarwin’s HypothesisDarwin was a naturalist—someone who observes and studies the natural world.

Modern-day sloth

Giant ground sloth

The Galápagos OrganismsThe Galápagos Organisms

Darwin became convinced that species do not always stay the same.

Galápagos Island iguana Mainland iguana

The Galápagos FinchesThe Galápagos FinchesThe structure of the Galápagos finch beaks is an adaptation to the type of food each bird eats.

Selective BreedingSelective Breeding• In Selective Breeding only the organisms with a

desired characteristic are bred.

Natural SelectionNatural SelectionThe process by which individuals that are better adapted to their environment are more likely to survive and reproduce

Three main points of natural selectionThree main points of natural selection• Overproduction

• Competition

• Variation

OverproductionOverproductionDarwin observed that most species produce far more offspring than can survive.

In many species there’s not enough resources, food, water, and living space.

CompetitionCompetition• Food , space, and other resources are limited, so

members of species must compete for survival

• Competition is not always physical, it is usually indirect.

• Ex. Some turtles are better at finding food then others

• A slower turtles may be caught by a predator while a faster one can escape.

VariationVariation• Any difference between individuals of the same

species.

Ex. Sea turtles may differ in color, size, the ability to swim quickly, and shell hardness

Natural SelectionNatural Selection

Overproduction Competition Variation

• Examine the sequence below that shows how natural selection could affect a group of sea turtles over time.

SpeciesSpecies• A group of similar organisms that can mate with

each other and produce offspring.

AdaptationAdaptationAdaptation – an inherited behavior or physical characteristic that helps an organism survive and reproduce in its environment

Change Over Time OverviewChange Over Time Overview1. An adaptation is a trait that increases an organism’s ability

to and .

2. The different shapes of bird beaks are examples of .

survive reproduce

adaptation

survive natural selection evolution competitionreproduce adaptation