Interest Grabber

A Trip Around the World

While on his voyage around the world aboard the H.M.S. Beagle, Charles Darwin spent about one month observing life on the Galápagos Islands. There, he encountered some unique animals, such as finches and tortoises.

Section 15-1

1. On a sheet of paper, list five animals that you have encountered in the past two days.

2. How do these animals differ from the finches and tortoises of the Galápagos Islands? (Examine Figures 15–3 and 15–4 in yourtextbook.)

3. Propose a hypothesis to account for the differences between the animals that you observed and the finches and tortoises of the Galápagos Islands.

Section Outline

15–1 The Puzzle of Life’s DiversityA. Voyage of the Beagle (1831)B. Darwin’s Observations

1. Patterns of Diversity2. Living Organisms and Fossils3. The Galápagos Islands

C. The Journey Home

Section 15-1

Words to Know

Evolution – change over time

Theory – well-supported testable explanation of natural phenomena

Fossils - preserved remains of ancient organisms

Hutton and Lyell – this geologic understanding influenced Darwin; recognized that Earth is millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present

Principles of Geology – Lyell’s book

Lamarck

Jean-Baptiste Lamarck•French naturalist•Selective use or disuse of organs (1809)•Inheritance of acquired traits•Theory is incorrect: he did not know that an organism’s behavior has no effect on its inheritable characteristics•Book-System of Invertebrate Animals

Thomas Malthus

Thomas Malthus (1798)•Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone•Proposed that war, famine, and disease limited the growth of human populations

Section 15-1

Figure 15–1 Darwin’s Voyage

Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shellHoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Giant Tortoises of the Galápagos Islands

Section 15-1

Interest Grabber

My, How You’ve Changed!

Prior to the 1800s, life scientists knew that living things changed over generations. They just didn’t know how these changes were brought about.

Section 15-2

1. Divide a sheet of paper into two columns and title the first one Inherited Characteristics. Title the second column Acquired Characteristics. In the first column, list the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.

2. In the second column, list your acquired characteristics. For example, you may have learned how to play a musical instrument.

3. Which of the items in your lists do you think you might pass on to your children? Explain your answer.

Section Outline

15–2 Ideas That Shaped Darwin’s ThinkingA. An Ancient, Changing Earth

1. Hutton’s Theory of Geological Change2. Lyell’s Principles of Geology

B. Lamarck’s Theory of Evolution1. Tendency Toward Perfection2. Use and Disuse3. Inheritance of Acquired Traits4. Evaluating Lamarck’s Theory

C. Population Growth

Section 15-2

Sea level

Sedimentary rocks form in horizontal layers.

When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.

As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.

New sediment is then deposited above the exposed older rock surface.

Movement of Earth’s Crust

Section 15-2

Sea level

Figure 15–7 Lamarck’s Theory of Evolution

Section 15-2

Interest Grabber

When Is a Flipper a Wing?

All living things are related. Some relationships are easy to see—your pet cat may not roar like a lion, but it clearly resembles one.Other relationships are less obvious.

Section 15-3

Interest Grabber continued

1. On a sheet of paper, construct a table that has five columns and six rows. In the columns, write the following heads: Animal Group, Example, Legs, Fins, and Tail. Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect.

2. Give one example for each group, and then fill in the informationfor that example. For Legs, write in the number of legs that eachanimal has. Do animals with fins have legs? Do animals with wingshave legs? If so, how many?

3. Can you tell from your table if a fish is more closely related to a birdor to an amphibian? Explain your answer.

Section 15-3

Section Outline

15–3 Darwin Presents His CaseA. Publication of On the Origin of SpeciesB. Natural Variation and Artificial SelectionC. Evolution by Natural Selection

1. The Struggle for Existence2. Survival of the Fittest3. Descent With Modification

D. Evidence of Evolution1. The Fossil Record2. Geographic Distribution of Living Species3. Homologous Body Structures4. Similarities in Early Development

E. Summary of Darwin’s Theory

Section 15-3

Words to know

Natural variation – differences among individuals of a species (physical strength, resistance to disease, vision, hearing, etc.)Artificial selection – selection by humans for breeding of useful traits from the natural variation among different organisms (breed largest hogs, fastest horses)Struggle for existence – members of each species compete regularly to obtain food, living space, and other necessities of lifeFitness – ability of an individual to survive and reproduce in its specific environment (a result of adaptation)

Adaptation – any inherited characteristic that increases an organism’s chance of survival (sharp quills, behavior in which some animals live and hunt in groups)

Survival of the fittest – individuals best suited to their environment survive and reproduce most successfully

Natural selection – survival of the fittest; over time, it results in changes in the inherited characteristics of a population (These changes increase a species’ fitness in its environment.)

Descent with Modification – each living species has descended, with changes, from other species over time; implies common descent (structures, niches, habitats)

Evidence of Evolution

1. Fossil record (fossils from sequential layers of rock)

2. Geographic distribution of living species – common mainland ancestors

3. Homologous body structures – structures that have different mature forms but develop from the same embryonic tissue; the greater the similarities among homologous structures, the more recently particular species last shared a common ancestor

Vestigial structures – traces of homologous structures that do not affect the organism’s ability to survive

4. Similarities in early development (Embryos)

In their early stages of development, embryos of

chickens, turtles, and rats look similar

Concept Map

Section 15-3

includes

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

which is composed of which indicates which implies which implies

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development

Beaver

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Coypu

Figure 15–14 Geographic Distributionof Living Species

Section 15-3

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Turtle Alligator Bird Mammals

Typical primitive fish

Figure 15–15 Homologous Body Structures

Section 15-3

Summary of Darwin’s Theory

•Struggle for existence•Survival of the fittest•Descent with modification•Natural selection•Common ancestry