Evolution

1.Individuals differ, and some of the differences can be passed on to their offspring. 2.More offspring are produced than can survive and reproduce. 3.There is competition for limited resources, or a struggle for existence. 4.Individuals best suited to their environment survive and reproduce most successfully. In other words, there is survival of the fittest. Darwin’s Theory Evolution by Means of Natural Selection

Section Outline 15–1The Puzzle of Life’s Diversity 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 Section 15-1

Charles Darwin Proposed the theory of evolution by means of natural selection. (note: Darwin did not originate the idea of evolution, he was the first to scientifically explain how it happens)

Alfred Russell Wallace Independently arrived at the same hypothesis of evolution by means of natural selection. Darwin and Wallace presented their papers together.

Section 15-1 Darwin’s Voyage

Pinta Island Intermediate shell Pinta Isabela Island Dome-shaped shell Hood Island Saddle-backed shell Hood Floreana Santa Fe Santa Cruz James Marchena Fernandina Isabela Tower Giant Tortoises of the Galápagos Islands – different neck length and shell shape, corresponding to different conditions on each island. Section 15-1

Galapagos Finches – different beaks corresponding to different diets on different islands.

Section Outline 15–2Ideas That Shaped Darwin’s Thinking A.An Ancient, Changing Earth 1.Hutton and Geological Change 2.Lyell’s Principles of Geology B.Lamarck’s Evolution Hypotheses 1.Tendency Toward Perfection 2.Use and Disuse 3.Inheritance of Acquired Traits 4.Evaluating Lamarck’s Hypotheses C.Population Growth

James Hutton Hutton published a detailed hypothesis explaining geologic processes (formation of sedimentary rocks, etc.) Since most processes work very slowly, Hutton believed the Earth must be millions of years old.

Charles Lyell Published Principles of Geology text, in which he explained Earth’s history in terms of present processes. Lyell also found that the Earth was very, very old.

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

Lamarck’s Hypothesis 1809 (same year Darwin was born) Lamarck proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time, this process led to change in a species.

Lamarck’s Theory of Evolution Section 15-2

Lamarck’s hypothesis, though plausible at the time, was not supported by data, and was ultimately rejected.

Malthus and Population Growth Reverend, economist, In 1798, first published essays on population growth. Malthus noted that populations tend to grow exponentially, whereas resources do not, thus creating a struggle for survival.

Section Outline 15–3Darwin Presents His Case A.Publication of On the Origin of Species –Darwin is prompted to publish in 1859, after receiving a letter from Wallace, outlining basically the same concepts.

Section Outline 15–3Darwin Presents His Case B.Inherited Variation and Artificial Selection

Wild Mustard

Figure 13.2 Brussels sprouts Lateral buds Terminal bud Flowers and stems Cabbage Broccoli Stem Kohlrabi Wild mustard Leaves Kale

Artificial Selection Applied to Wild Mustard

Section Outline 15–3Darwin Presents His Case C.Evolution by Natural Selection 1.The Struggle for Existence 2.Survival of the Fittest 3.Descent With Modification

1. Struggle for Existence Organisms reproduce many more individuals than can actually survive.

2. Survival of the Fittest In any population, there are heritable variations between individuals.

2. Survival of the Fittest Some variations will give individuals a survival advantage.

3. Descent With Modification Individuals with favorable traits tend to leave more descendents, changing allele frequency (and phenotype) in the population over time.

Section Outline D.Evidence of Evolution 1.The Fossil Record 2.Geographic Distribution of Living Species 3.Homologous Body Structures 4.Similarities in Embryology

Concept Map Section 15-3 includes Evidence of Evolution Physical remains of organisms Common ancestral species Similar genes which is composed ofwhich indicateswhich implies The fossil record Geographic distribution of living species Homologous body structures Similarities in early development

The Fossil Record Fossils indicate that organisms have changed over time.

Geographic Distribution & Homologous Structures are best explained by Common Ancestry

Beaver NORTH AMERICA Muskrat Capybara SOUTH AMERICA Coypu Geographic Distribution of Living Species Section 15-3 Beaver Muskrat Beaver and Muskrat Coypu Capybara Coypu and Capybara

Modern Lobe-Finned Fish

TurtleAlligatorBirdMammal Ancient lobe-finned fish Homologous Body Structures Section 15-3

Homologous Structures (cont) Homologous Cellular Structures

A CLUSTALW alignment of SEC35 promoter sequences of sensu stricto species reveals conserved elements that could function as regulatory elements. Cliften P F et al. Genome Res. 2001;11: ©2001 by Cold Spring Harbor Laboratory Press Homologous DNA Sequences

Example of an alignment. Kumar S, and Filipski A Genome Res. 2007;17: Copyright © 2007, Cold Spring Harbor Laboratory Press

E.Summary of Darwin’s Theory There is variation within populations. Some adaptations are better suited for survival than others. More young are produced in a generation than can survive AND there is a struggle for existence. Those that have favorable variations survive Descent with modification occurs (small changes over large periods of time result in organisms changing through time).

F.Evolutionary Theory Since Darwin Modern Synthesis – Modern knowledge of genetics aids our understanding of the mechanisms of evolution.