Change Over Time Chapter 6 Lesson 1 Darwin’s Theory

Describe how Darwin’s observations helped him to develop his hypothesis. Explain the process of natural selection and how it contributes to evolution. Learning objectives

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

Charles Darwin Naturalist – studied nature 5 year voyage around the world Made observations that helped him create a theory of how evolution happens Galapagos Islands

CREATION, The movie (2009) EXTRA CREDIT Watch movie Write 20 facts you learned about Darwin and his life Have your parent/guardian/grandparent, etc., sign it Turn in by March 7 ENJOY the movie 2 points Extra Credit in test category

Read: My Planet Diary pg 166

Darwin’s Hypothesis In 1831, the HMS Beagle set sail from England on a 5 year trip. Charles Darwin was on board.

5 year trip – many, many stops

Darwin’s Hypothesis Darwin was a naturalist—someone who observes and studies the natural world. Diversity Darwin was amazed by the diversity of organisms. Wondered why organisms were so different from those in England Saw insects that looked like flowers, sloths hanging from trees Scientists have identified more than 1.6 million species of organisms on Earth. Species – a group of similar organisms that can mate with each other and produce fertile offspring

Darwin’s Hypothesis Fossils A fossil is the preserved remains of traces of an organism that lived in the past. Puzzling for Darwin – he saw fossils that resembled the bones of living sloths but were much larger. What happened?

Darwin’s Hypothesis Darwin was a naturalist—someone who observes and studies the natural world. Modern-day sloth Giant ground sloth What are two similarities that you notice between the sloths? (see figure 1)

The Galápagos Organisms Comparisons to South American Organisms Discovered many similarities Ex: birds and plants resembled those on mainland. Also noted differences between organisms Ex: iguanas

The Galápagos Organisms Darwin became convinced that species do not always stay the same. Galápagos Island iguana Mainland iguana Were they related? Did they change over time? Darwin thought so…

The Galápagos Organisms Comparisons Among the Islands Discovered many differences among organisms on the different Galápagos islands. Ex: tortoises on one island had dome-shaped shells – on another they were saddle shaped.

Galápagos Organisms Adaptations Birds were different from one island to the next. Ex: finches - all related to one ancestor species from the mainland. Over time they developed different beak shapes and sizes based on the food they ate. Beak shape is an example of an adaptation ADAPTATION – a trait that increases an organism’s ability to survive and reproduce.

The Galápagos Finches The structure of the Galápagos finch beaks is an adaptation to the type of food each bird eats. What does each finch eat?

Darwin’s Hypothesis Darwin was convinced that organisms change over time. Made observations that helped him create a theory of how evolution happens. Evolution – The process of change over time. Darwin hypothesized that species change over many generations and become better adapted to new conditions.

Artificial Selection Let’s read about it – pg What animal did Darwin work with? Pigeons, but also, not in the book…horses, dogs, cows, monkeys, etc.

What is Natural Selection? Natural Selection – the process where individuals that are better adapted to their environment are more likely to survive and reproduce more than other members of the same species.

Can you relate this to our Monster Lab?

Factors affecting Natural Selection Overproduction – each species produces more offspring that will survive Variation – individuals within a population have slightly different traits Competition – since food, space, and other resources are limited, members of a species must compete with each other. Selection - individuals within a population have a particular characteristic that helps them survive and reproduce.

Explore the Big Q How do life forms change over time? What are the four main points of Darwin’s theory of natural selection? Overproduction, variation, competition, selection What does overproduction mean? More individuals are produced than can survive. What is variation? Any difference between members of the same species. How does overproduction lead to competition? There are more individuals in a population than there is food to consume. There are more individuals than there are places for plants to grow or animals to nest and hide.

Explore the Big Q How do life forms change over time? How does competition lead to selection? Individuals whose variations make them better at competing for food and shelter or better able to escape predators are more likely to survive and reproduce. How might natural selection have led sea turtles to develop flippers instead of feet? Some turtles had feet that were flatter or had more skin between the toes, making them flipper-like. Those turtles could swim faster and dive deeper and had a better chance of surviving and passing on their genes. Over many generations, as the species evolved, legs became more flipper-like.

Natural Selection Overproduction CompetitionVariation

Natural Selection Overproduction: Turtles lay many eggs. Not all of the young will survive. Competition: Turtles compete with one another. A faster turtle may escape form a shark. Variation: Each turtle has slightly different traits. Some may be protected by harder shells.

Explore the Big Q How do life forms change over time? What does overproduction not lead to overpopulation? Because there are predators that catch and eat the turtles, especially the baby turtles. What are the hatchlings especially vulnerable? They are very small and easy for predators to grab. They hatch on the beach and have to cross the sand to get to the water. Birds and crabs can catch then before they get to the water. Which hatchlings are most likely to survive? The ones that can move the fastest As the turtles grow up, which are most likely to survive? The ones that can swim fast and get away from predators; the ones that can find food.

Explore the Big Q How do life forms change over time? How is this an example of natural selection? The turtles that are better adapted to escape predators and get food are most likely to survive and eventually reproduce. In addition to survival, what else must happen for natural selection to affect the evolution of the species? The individuals that survive must reproduce and pass on their adaptions to their offspring.

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.

Environmental Change A change in the environment can affect an organism’s ability to survive and therefore lead to natural selection. Read pg 174 – environmental change

Environmental Change When copper contaminated the soil surrounding the monkey flowers, the environment changed. Due to a genetic variation, some varieties of monkey are now able to survive in the soil. In the last circle, draw what you think the area will look like in ten years time. Write a caption describing what has taken place. Many monkey flowers can now grow in the soil.

Genes and Natural Selection Darwin could not explain what caused variations or how they were passed on. (work in genetics came later) Scientists later learned, variations can result from changes in genes and shuffling of different forms of genes. Only traits that are inherited (controlled by genes) can be acted upon by natural selection.

Darwin’s Hypothesis

Galápagos Finches Match each finch to the type of food you think it eats.

Read: My Planet Diary pg 166

Charles Darwin Chapter 6-1 Darwin’s Theory In 1859, following 30 years of study and travels, Darwin published a book called The Origin of Species by Means of Natural Selection Started a scientific revolution: it showed that life on Earth is constantly changing and only the fittest organisms survive Picture of Charles Darwin Courtesy of The Bettmann Archive

Darwin’s cruise on the BEAGLE British ship: the HMS Beagle Sailed for 5 years from England Darwin was 22 years old He became known as the ship’s naturalist – his job: learn as much as he could about the organisms he saw

How did birds differ among the islands of the Galapagos? Each island had its own types of birds that were clearly different from other islands

Darwin noticed wide variations – in beak shape and size from island to island These differences made the finches better adapted to get the food in their environment

VARIATION Any difference between individuals of the same species Example: The color of a few insects may be different from that of most other insects in the same species

ADAPTATION A trait that helps an organism survive and reproduce EXAMPLE: Milkweed is poisonous and has a nasty taste. ANOTHER ONE: Bright colors of flowers attract insects which helps to pollinate it. NEXT: Back to the finches….