Chapter 9, Lesson 1

Darwin's Theory

Chapter 9, Lesson 1

Pages 336-345

• What was Darwin's hypothesis?

• What is natural selection​?

What was Darwin's Hypothesis?​

• Charles Darwin was a naturalist - a person who observes and studies the natural world

• Da​rwin began witnessing the diversity of living things during his voyage on the HMS Beagle

• Scientists have identified more than 1.6 million species of organisms on ​Earth

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

What was Darwin's Hypothesis?​

• On the voyage, Darwin also saw fossils of animals that had died long ago

• A fossil is the preserved remains or traces of an organism that lived in the past

• For example, he saw fossils that resembled organisms that he was familiar with, but still different - giant sloth

What was Darwin's Hypothesis?​

• Darwin studied organisms on the Galapagos Islands

  • Islands are good places to study how organisms change over time

  • The Galapagos Islands are isolated from the mainland

• He compared the organisms on the islands to organisms elsewhere

• He also compared organisms on the different islands​

Multiple Choice

The preserved remains of an organism that lived long ago is a(n) ___________.

• adaptation

• Galapagos

• fossil

• Beagle

Comparisons

• Many of the birds on the Galapagos Islands resembled the ones on the mainland

• There were also many differences like those in the iguanas

• He began to think the species could change and maybe even create a new species over time​

• There were many differences between organisms on each island

Adaptations

• Each island had "different" birds, however, Darwin later learned that all of the birds are finches

• Over time, different finches developed different beak shapes and sizes based on the food they ate

• The beak shapes are all adaptations - a trait that increases an organism's ability to survive and reproduce

Darwin's Hypothesis

• Evolution - the process of change over time

• Darwin's research and collaboration with other scientists led him to believe that plants and animals on the islands faced different conditions from those on the mainland and that is why they evolved over time

• Darwin hypothesized that species change over many generations and become better adapted to new conditions

• Scientific Theory - well-tested concept that explains a wide range of observations

Darwin's Hypothesis - Artificial Selection

• Darwin studied the offspring of domesticated animals that were produced by artificial selection

• In artificial selection, only the organisms with the desired characteristics are bred

• Darwin thought that a process similar to artificial selection might happen in nature

Multiple Choice

A trait that helps an organism to survive and reproduce is called a(n) _________.

• variation

• adaptation

• species

• selection

Multiple Choice

Only the organisms with a desired characteristic are bred in _________.

• artificial selection

• natural selection

• England

• South America

Fill in the Blanks

A variation is any

between individuals of the same species.

What is natural selection?

• Darwin and another biologist - Alfred Russel Wallace - proposed the same explanation for evolution

• Natural Selection - the process by which organisms that are best adapted to their environment are most likely to survive and reproduce

• Darwin identified 3 factors that affect natural selection:

  • overproduction

  • variation

  • competition

What is natural selection?

• Overproduction

  • most species produce more offspring than can survive

  • there are not enough resources - food, water, and living space

• Variation - the differences between individuals of the same species

• Competition

  • not always physical fights - usually indirect

  • ​one turtle can swim faster than others so it has a better chance to survive and reproduce

What is natural selection?

​

• Some variations make individuals better adapted to their environment

• After many generations, more members of the species will have the helpful characteristics

• Darwin proposed that, over a long time, natural selection can lead to change. Helpful variations may accumulate in a species, while unfavorable ones may disappear

What is natural selection?

• Environmental Changes - Changes in the environment can affect an organism's ability to survive

• Only genes that are inherited can be affected by natural selection

Multiple Choice

A(n) ___________ is a group of similar organisms that can mate with each other and produce fertile offspring.

• adaptation

• natural selection

• species

• theory

• variation

Multiple Choice

A(n) ___________ is a trait that helps an organism survive and reproduce.

• adaptation

• natural selection

• species

• theory

• variation

Multiple Choice

A scientific ___________ is a well-tested concept that explains a wide range of observations.

• adaptation

• natural selection

• species

• theory

• variation

Multiple Choice

The process by which individuals that are better adapted to their environment are more likely to survive and reproduce is called ___________.

• adaptation

• natural selection

• species

• theory

• variation

Multiple Choice

That some newly hatched turtles can swim faster than others of the same species is evidence of ________ within a species.

• adaptation

• natural selection

• species

• theory

• variation

Multiple Choice

Members of a species can mate with each other and produce __________.

• gene pools

• fertile offspring

• variations

• adaptations

Multiple Choice

The different shapes of bird beaks are examples of __________-.

• fossils

• adaptations

• evolution

• naturalism

Fill in the Blanks

Two organisms that can mate and produce fertile offspring are members of the same

.

Multiple Choice

The 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 is called _________.

• natural selection

• evolution

• competition

• overproduction

Multiple Choice

Which of the following is the best example of an adaptation that helps organisms survive in their environment?

• green coloring in lizards living on gray rocks

• a thick coat of fur on animals that live in the desert

• an extensive root system in desert plants

• thin, delicate leaves on plants in a cold climate

Multiple Choice

Which of the following sets of factors did Darwin identify as affecting natural selection?

• adaptations, gradualism, and evolution

• overproduction, variation, competition

• adaptations, traits, and variations

• predation, competition, and mutualism