11-2 Darwin’s Theory Essential Question: How do Life Forms Change over time?

1. 7th Grade Ms. De Los Rios 11-2 Darwin’s Theory Essential Question: How do Life Forms Change over time? What was Darwin’s Hypothesis? What Natural Selection? Darwin’s Theory Pgs. 384-393

2. Vocabulary • Adaptation – An inherited behavior or physical characteristic that helps an organism survive and reproduce in its environment. • Scientific theory - A well-tested explanation for a wide range of observations or experimental results. • Trait - A specific characteristic that an organism can pass to its offspring through its genes. • Natural selection - The process by which organisms that are best adapted to their environment are most likely to survive and reproduce. • Variation – Any difference between individuals of the same species.

3. My Planet Diary pg. 384 • In 1839, Charles Darwin published his book The Voyage of the Beagle. Read the following excerpt about an animal Darwin encountered while in the Galápagos Islands. • The inhabitants believe that these animals are absolutely • deaf; certainly they do not overhear a person walking • close behind them. I was always amused when overtaking • one of these great monsters, as it was quietly pacing along, • to see how suddenly, the instant I passed, it would draw • in its head and legs, and uttering a deep hiss fall to the • ground with a heavy sound, as if struck dead. I frequently • got on their backs, and then giving a few raps on the • hinder part of their shells, they would rise up and walk • away;—but I found it very difficult to keep my balance. • What kind of animal do you think Darwin was describing? • Describe your reaction to an unusual animal that you may have seen at a zoo, or at an aquarium, or in a pet store. What was your first impression of the animal?

4. Charles Darwin Darwin was a British scientist who laid the foundations of the theory of evolution and transformed the way we think about the natural world. Charles Robert Darwin was born on 12 February 1809 in Shrewsbury, Shropshire into a wealthy and well-connected family. His maternal grandfather was china manufacturer Josiah Wedgwood, while his paternal grandfather was Erasmus Darwin, one of the leading intellectuals of 18th century England. Darwin himself initially planned to follow a medical career, and studied at Edinburgh University but later switched to divinity at Cambridge. In 1831, he joined a five year scientific expedition on the survey ship HMS Beagle.

5. Online Resources • Discovery Video Evolution Theory • Brainpop Charles Darwin • Brainpop Natural Selection

6. Diversity and Fossils Pg. 385 • In 1831, The British ship HMS Beagle set sail from England on a five year trip around the world. Charles Darwin was on board. Darwin was a naturalist--- a person who observes and studies the natural world. • During his five-year voyage around the world, Charles Darwin observed great diversity among living things, often within the same species. • Darwin also observed fossils that shared some, but not all, traits with living animals. • A trait is a specific characteristic that an organism can pass to its offspring. • Darwin also observed differences in plants and animals that lived in South America and the Galápagos Islands, which are off the coast of South America. • He attributed these differences to examples of adaptations - a trait that increases an organism’s ability to survive and reproduce.

7. Darwin’s Theory • Galápagos Finches • The structure of each bird’s beak is an adaptation to the type of food the bird eats. • Match each finch to the type of food you think it eats.

8. Darwin’s Hypothesis pg. 388 • Darwin thought about what he had seen during his voyage on theBeagle. By this time, Darwin was convinced that organisms change over time. He wanted to know how organisms change. Over the next 20 years he consulted with other scientists and gathered more information. Based on his observations,Darwin reasoned that plants or animals that arrived on the Galapagos Islands faces conditions that were different from those on the nearby mainland. • The iguanas on the Galapagos Islands have large claws that allow them to grip slippery rocks so they can feed on seaweed. The Iguanas on the mainland have smaller claws that allow them to climb trees so they can eat leaves.

9. What Was Darwin’s Hypothesis? Pg. 388 • Darwin hypothesized that species gradually change over many generations and become better adapted to new conditions. • Because the gradual change in a species over time is called evolution, Darwin’s ideas are often referred to as the theory of evolution. • What is a scientific theory? • A scientific theory is a well-tested • concept that explains a wide range of • observations. .

10. Did You Know? Galapagos Penguin • The Galápagos penguin is the northernmost penguin in the world! • It lives on the equator and is kept cool by ocean currents. The Galápagos penguin is the rarest penguin species and is endangered. Galápagos penguin

11. Assess Your Understanding pg. 389 • 1a. Make of list of three observations that Darwin made during the Beagle’s voyage. • b. An adaptation is a trait that increases an organism’s ability to • ____________________and ___________________. • c. How does artificial selection support Darwin’s hypothesis? • I get it! Now I know that Darwin’s hypothesis was____________ • ___________________________________________________

12. What is Natural Selection? Pg. 390 • In 1858, Darwin and Alfred Russel Wallace proposed the same explanation— natural selection —for how evolution occurs. • Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce more than other members of the same species. • Darwin proposed that, over a long time, natural selection can lead to change. • Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear. • Without variations, all the members of a species would have the same traits and equal chances of surviving and reproducing.

13. Overproduction pg. 390 • Darwin knew that most species • produce far more offspring than • can possibly survive. • In many species, so many offspring are produced that there are not enough resources – food, water, and living space – for all of them.

14. Variation pg. 391 • Members of a species differ from • one another in many of their • traits. • Variation is any difference • between Individuals of the same • species. • For Example, • sea turtles may differ in color, size, the ability to swim quickly, and shell hardness • .

15. Competition pg. 391 • Since food, space, and other resources are limited, the members of a species must compete with one another to survive. • Competition doesn’t always involve physical fights between members of a species. Instead, competition is usually indirect. • For example, • some turtles may not find enough to eat. • A slower turtle may be caught by a predator, while a faster turtle may escape. • Only a few turtles will survive to reproduce.

16. Selectionpg. 391 • Darwin observed that some variations make individuals better adapted to environment. • Those individuals are more likely to survive and reproduce and their offspring may inherit the helpful characteristic. • The offspring, in turn, will be more likely to survive and reproduce, and pass the characteristic to their offspring. • After many generations, more • members of the species will • have the helpful characteristic.

17. Factors That Affect Natural Selection pgs. 130-131 • What are the factors of natural selection that affect a group of sea turtles over time? • Examine the sequence below that shows how natural selection could affect a group of sea turtles over time. • Label Each Factor In The Illustration and write a brief caption explaining what is occurring.

18. Darwin’s Theory Relate Cause and Effect Identify the factors that cause natural selection.

19. Environmental Change pg. 392 • A change in the environment can affect an organism’s ability to survive and therefore lead to natural selection. For example, monkey flowers are plants that do not normally grow in soil that has a high concentration of copper. However, because of genetic variation, some varieties of monkey flower now grow near copper mines. Environmental Change When copper contaminated the soil surrounding the monkey flowers, the environment changed. Draw what you think the area will look like in ten years in the last circle.

20. Genes and Natural Selection pg. 392 • Darwin could not explain what caused variations or how they were passed on, but scientists later learned that variations can result from changes in genes and the shuffling of different forms of genes when egg and sperm join. Only traits that are inherited, or controlled by genes, can be acted upon by natural selection. Other factors, such as competition and environmental change, • can affect an organism’s • survival.

21. Do The Math! Pg. 392 Loggerhead Sea Turtle Data Do you think clutch size influences the survival rate of offspring? 1.Which measure of central tendency would you use to find the average clutch size? Calculate It! _____________________ 2. Do you think clutch size influences the survival rates of the offspring? Use the data to support your answer. ________________________________________ 3. Hypothesize why Site F had the largest number of returning turtles. ______________________________________________________________________

22. Assess Your Understanding pg. 393 • 2a. A variation is any (similarity / difference) between individuals of the same species. • b. How do life forms change over time? • ______________________________________________________________________________________________________ • c. How does genetic variation contribute to the diversity of organisms? _________________________________________ • ___________________________________________________