17–1 The Fossil Record A. Fossils and Ancient Life The fossil record provides evidence about the history of life on earth. It also shows how different groups of organisms have changed over time

17–1 The Fossil Record How Fossils Form Most fossils form in sedimentary rock. It is formed when exposure to rain, heat, wind and cold breaks down clay As layers of sediment build up over time, dead organisms may also sink to the bottom and become buried Conditions are right, the remains may be kept intact

17–1 The Fossil Record C. Interpreting Fossil Evidence 1. Relative Dating- the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock (estimate age of fossils) 2. Radioactive Dating- scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains

17–1 The Fossil Record D. Geologic Time Scale Eras 2. Periods

Comparing Relative and Absolute Dating of Fossils Section 17-1 Compare/Contrast Table Comparing Relative and Absolute Dating of Fossils Can determine Is performed by Drawbacks Relative Dating Absolute Dating Age of fossil with respect to another rock or fossil (that is, older or younger) Age of a fossil in years Comparing depth of a fossil’s source stratum to the position of a reference fossil or rock Determining the relative amounts of a radioactive isotope and nonradioactive isotope in a specimen Imprecision and limitations of age data Difficulty of radio assay laboratory methods Go to Section:

Figure 17-2 Formation of a Fossil Section 17-1 Figure 17-2 Formation of a Fossil Water carries small rock particles to lakes and seas. Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied. Go to Section:

Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) Era Period Time (millions of years ago) Era Period Time (millions of years ago) Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 363–290 410–363 440–410 505–440 544–505 Quarternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544 Go to Section:

Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) Era Period Time (millions of years ago) Era Period Time (millions of years ago) Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 363–290 410–363 440–410 505–440 544–505 Quarternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544

Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) Era Period Time (millions of years ago) Era Period Time (millions of years ago) Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 363–290 410–363 440–410 505–440 544–505 Quarternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544

17–2 Earth’s Early History A. Formation of Earth Earth’s early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide, and water

17–2 Earth’s Early History The First Organic Molecules Organic molecules would have been able to be constructed but the oxygen in atmosphere was to reactive and would destroy any organic molecules that formed

17–2 Earth’s Early History C. How Did Life Begin? 1. Formation of Microspheres- protection that allowed for the growth of organic molecules 2. Evolution of RNA and DNA- still unanswered but scientists are searching

17–2 Earth’s Early History Free Oxygen The rise of oxygen in the atmosphere drove some life forms to extinction, while other life forms evolved new, more efficient metabolic pathways that used oxygen for respiration

17–2 Earth’s Early History Origin of Eukaryotic Cells The endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms

Figure 17-12 Endosymbiotic Theory Chloroplast Plants and plantlike protists Aerobic bacteria Ancient Prokaryotes Nuclear envelope evolving Photosynthetic bacteria Mitochondrion Primitive Photosynthetic Eukaryote Animals, fungi, and non-plantlike protists Ancient Anaerobic Prokaryote Primitive Aerobic Eukaryote Go to Section:

17–2 Earth’s Early History F. Sexual Reproduction and Multicellularity A few hundred million years after the evolution of sexual reproduction, evolving life forms crossed to developing multicellular organisms from single celled (unicellular) organisms

17–3 Evolution of Multicellular Life Precambrian Time- life existed only in the sea B. Paleozoic Era- rich with evidence of many types of marine life Mesozoic Era- increasing dominance of dinosaurs, appearance of flowering plants D. Cenozoic Era- mammals evolved adaptations that allowed them to live in various environments, on land, water and air

Geologic Time Scale with Key Events Section 17-3 Era Period Time (millions of years ago) Key Events Cenozoic Mesozoic Paleozoic Precambrian Time Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian 1.8–present 65–1.8 145–65 208–145 245–208 290–245 363–290 410–363 440–410 505–440 544–505 650–544 Glaciations; mammals increased; humans Mammals diversified; grasses Aquatic reptiles diversified; flowering plants; mass extinction Dinosaurs diversified; birds Dinosaurs; small mammals; cone-bearing plants Reptiles diversified; seed plants; mass extinction Reptiles; winged insects diversified; coal swamps Fishes diversified; land vertebrates (primitive amphibians) Land plants; land animals (arthropods) Aquatic arthropods; mollusks; vertebrates (jawless fishes) Marine invertebrates diversified; most animal phyla evolved Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life

17–4 Patterns of Evolution A. Mass Extinctions- dinosaurs B. Adaptive Radiation- species evolved into several different forms that live in different ways C. Convergent Evolution- unrelated organisms come to resemble one another

17–4 Patterns of Evolution D. Coevolution- process by which two species evolve in response to changes in each other over time E. Punctuated Equilibrium- patterns of long, stable periods interrupted by brief periods of more rapid change Gradualism- patterns of slow, gradual change

17–4 Patterns of Evolution F. Developmental Genes and Body Plans- changes in developmental genes, revealing major news about evolution of life

Flowchart Species Go to Section: that are Unrelated Related form in under under in in Inter-relationshiops Similar environments Intense environmental pressure Small populations Different environments can undergo can undergo can undergo can undergo can undergo Coevolution Convergent evolution Extinction Punctuated equilibrium Adaptive radiation Go to Section:

Section 15-1 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.

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

B. Darwin’s Observations 1. Patterns of Diversity 15–1 The Puzzle of Life’s Diversity Section 15-1 A. Voyage of the Beagle B. Darwin’s Observations 1. Patterns of Diversity 2. Living Organisms and Fossils 3. The Galápagos Islands C. The Journey Home

Giant Tortoises of the Galápagos Islands Pinta Island Intermediate shell Hood Island Saddle-backed shell Pinta Island Intermediate shell

Figure 15–1 Darwin’s Voyage

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.

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 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

A. An Ancient, Changing Earth 1. Hutton’s Theory of Geological Change 15–2 Ideas That Shaped Darwin’s Thinking A. An Ancient, Changing Earth 1. Hutton’s Theory of Geological Change 2. Lyell’s Principles of Geology

15–2 Ideas That Shaped Darwin’s Thinking B.Lamarck’s Theory of Evolution 1. Tendency Toward Perfection 2. Use and Disuse 3. Inheritance of Acquired Traits 4. Evaluating Lamarck’s Theory C.Population Growth

Hutton’s Theory of Geological Change In 1975, geologist James Hutton proposed that layers of rock form very slowly. Some rocks are moved up by forces beneath the Earth’s surface, others are buried. Resulting rocks, mountains, and valleys are then shaped by a variety of natural forces-including rain, heat and cold temperatures

Lyell’s Principles of Geology Lyell’s work explained how awesome geological features could be built up or torn down over long periods of time. His work influenced Darwin in two ways: If the earth could change overtime, might life change as well? He realized that it must have taken many, many years, earth must be very old

Movement of Earth’s Crust As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed. When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers. New sediment is then deposited above the exposed older rock surface. Sedimentary rocks form in horizontal layers

Lamarck’s Theory of Evolution 1. Tendency Toward Perfection He proposed that all organisms are continually changing and acquiring features that help them live more successfully in their environment

2. Use and Disuse He proposed that organisms could alter the size or shape of particular organs by using their bodies in new ways. Conversely, if a winged animal did not use its wings (ex. of disuse) the wings would decrease in size over generations and finally disappear

3. Inheritance of Acquired Traits Lamarck thought that acquired characteristics could be inherited By this reasoning, if you spent much of your life lifting weights to build muscles, your children would inherit big muscles, too.

4. Evaluating Lamarck’s Theory He was incorrect in many ways Lamarck, like Darwin, did not know how traits are inherited or that behavior has no effect on its inheritable characteristics One of first to develop scientific theory of evolution and realize that organisms are adapted to their environment

Figure 15–7 Lamarck’s Theory of Evolution

15–3 Darwin Presents His Case A. Publication of On the Origin of Species Darwin(1859)proposed a mechanism for evolution called natural selection Continuous for millions of years and continues in all living things Others strongly opposed

15–3 Darwin Presents His Case B. Natural Variation and Artificial Selection Natural variation is the differences among individuals of a species, is found in all types of organisms Artificial Selection occurs through a technique called selective breeding, that would determine which individuals to use for breeding based on the natural variation that was found

15–3 Darwin Presents His Case C.Evolution by Natural Selection The Struggle for Existence- means that members of each species compete regularly to obtain food, living space, an other necessities of life

15–3 Darwin Presents His Case C. Evolution by Natural Selection 2. Survival of the Fittest Fitness- the ability of an individual to survive and reproduce in its specific environment Adaptation- is any inherited characteristics that increase an organism’s chance of survival

15–3 Darwin Presents His Case C. Evolution by Natural Selection 2. Survival of the Fittest Individuals that are better suited to their environment-that is, with high levels of fitness-survive and reproduce most successfully

15–3 Darwin Presents His Case C. Evolution by Natural Selection 2. Survival of the Fittest Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in it’s environment

15–3 Darwin Presents His Case C. Evolution by Natural Selection Descent With Modification Each living species has descended, with changes, from other species over time

15–3 Darwin Presents His Case D. Evidence of Evolution 1. The Fossil Record provided evidence that living things have been evolving for millions of years. Sometimes fossil records includes similar, intermediate forms of a group of organisms that together suggest gradual modification over time

Evidence of Evolution includes The fossil record Geographic distribution of living species Homologous body structures Similarities in early development which is composed of which indicates which implies which implies Physical remains of organisms Common ancestral species Similar genes

D. Evidence of Evolution 2. Geographic Distribution of Living Species Animals living under similar ecological conditions, were exposed to similar pressures of natural selection Because of these similar selection pressures, different animals ended up evolving certain striking features in common

Figure 15–14 Geographic Distribution of Living Species Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara

D. Evidence of Evolution 3. Homologous Body Structures structures that have different mature forms and functions but develop from the same embryonic tissues

Figure 15–15 Homologous Body Structures Turtle Alligator Bird Mammals Typical primitive fish

D. Evidence of Evolution 4. Similarities in Early Development early stages, or embryos, of many animals with backbones are so similar that they can be hard to tell apart

E. Summary of Darwin’s Theory Organisms in nature differ, some variation is inherited Survival of the fittest Natural Selection Variation

1. Make a list of physical traits that you think are influenced by genes. Then, write next to each trait whether you have the trait or not (e.g., a widow’s peak) or whether there are many variations of the trait (e.g., hair color).

2. Are most of the traits you listed clear-cut or are they mostly traits that have many variations? Which traits in your list are difficult to categorize?

3. Compare your list with that of another student 3. Compare your list with that of another student. Did he or she think of any traits that you missed? Why do you think some traits are clear-cut, while others are not?

16–1 Genes and Variation A. Darwin’s Ideas Revisited Without an understanding of heredity, Darwin was unable to explain two important factors. First, he did not know the source of the variation that was so central to his theory. Second, he could not explain how inheritable traits were passed from one generation to the next.

16–1 Genes and Variation B. Gene Pools is the combined genetic information of all the members of a particular population

16–1 Genes and Variation C. Sources of Genetic Variation Mutations- is any change in a sequence of DNA Gene Shuffling- occurs during the production of gametes (23 chromosomes in sperm and 23 in egg=46 Zygote) Crossing over- exchange of genetic material between chromosomes

16–2 Evolution as Genetic Change C. Genetic Drift In small, populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences of this type can cause an allele to become common in a population

16–2 Evolution as Genetic Change D. Evolution Versus Genetic Equilibrium Random Mating Ensures that each individual has an equal chance of passing on it’s alleles

16–2 Evolution as Genetic Change D. Evolution Versus Genetic Equilibrium Large Population Important in maintaining genetic equilibrium Genetic drift has less effect on large populations

16–2 Evolution as Genetic Change D. Evolution Versus Genetic Equilibrium No Movement Into or Out of the Population Keep gene pool together and separate of other populations

16–2 Evolution as Genetic Change D. Evolution Versus Genetic Equilibrium No Mutations

16–2 Evolution as Genetic Change D. Evolution Versus Genetic Equilibrium 5. No Natural Selection

Sample of Original Population

Sample of Original Population Founding Population A Founding Population B

Sample of Original Population Descendants Founding Population A Founding Population B

Country Cousin/City Cousin What happens when a population or group of living things is divided into two separate groups in two separate environments? To understand what goes on, think about someone who lives in another part of the United States or in another country.

1. Make a list of everyday things that this person encounters that you don’t. For example, does he or she eat different kinds of food? Does he or she live in a climate different from yours? 2. All humans are the same species. What might happen if groups of humans were separated for millions of years in very different environments, such as those you have just described?

16–3 The Process of Speciation A. Isolating Mechanisms As new species evolve, populations become reproductively isolated from each other 1. Behavioral Isolation- two populations are capable of interbreeding, but differences in courtship rituals

2. Geographic Isolation- two populations are separated by geographic barriers such as rivers, mountains, or bodies of water 3. Temporal Isolation- two or more species reproduce at different times (orchid in the rainforest)

16–3 The Process of Speciation B. Testing Natural Selection in Nature 1. Variation- Grant’s concluded that there is a great deal of variation of inheritable traits among the Galopagos finches 2. Natural Selection- when food for finches was scarce, individuals with the largest beaks were more likely to survive 3. Rapid Evolution- changes in beaks occurred over decades instead of thousands of years

16–3 The Process of Speciation C. Speciation of Darwin’s Finches 1. Founders Arrive 2. Separation of Populations 3. Changes in the Gene Pool 4. Reproductive Isolation 5. Ecological Competition 6. Continued Evolution

16–3 The Process of Speciation C. Speciation of Darwin’s Finches 1. Founders Arrive Once they arrived on one of the island, they managed to survive and reproduce

16–3 The Process of Speciation C. Speciation of Darwin’s Finches 2. Separation of Populations Species crossed islands

16–3 The Process of Speciation C. Speciation of Darwin’s Finches Changes in the Gene Pool Over time natural selection would have caused that population to evolve larger beaks, forming a separate population

16–3 The Process of Speciation C. Speciation of Darwin’s Finches Reproductive Isolation Gene pools of the two bird populations remain isolated from each other

16–3 The Process of Speciation C. Speciation of Darwin’s Finches Ecological Competition Overtime, species evolve in a way that increases the differences between them

16–3 The Process of Speciation C. Speciation of Darwin’s Finches Continued Evolution Over many generations, it produced the 13 finch species found there today

Reproductive Isolation results from Isolating mechanisms which include Behavioral isolation Temporal isolation Geographic isolation produced by produced by produced by Behavioral differences Different mating times Physical separation which result in Independently evolving populations which result in Formation of new species

The End