2The Puzzle of Life’s Diversity 15-1 In 1831, at age 22, Charles Darwin joined the crew of the H.M.S. Beagle as a naturalist for a 5 year voyage around the world.
3Darwin went ashore and collected plant and animal specimens for his collection. He studied the specimens, read the latest scientific books, and filled many notebooks with his observations and thoughts.This led him to propose a revolutionary hypothesis about the way life changes.EVOLUTION!
4What is Evolution?Any change in the heritable traits within a population across generationsResults in new species
5Darwin’s Observations Life is Diverse:Darwin observed many different kinds of plants and animalsAll were well suited to the environments they inhabitedHe was impressed by the ways in which organisms survived and produced offspring
6Fossils: The preserved remains of once living organisms Some of those fossils resembled organisms that were still aliveOthers looked completely unlike any creature he had ever seen
73. The Galapagos Islands: The islands are very close together but have very different climates.Some are hot and dry with little vegetation while others are rich in rainfall and vegetationEach island had its own unique assortment of plant and animal species.
8Giant Tortoises of the Galápagos Islands and on Pinta Island, tortoise neckswere somewhere in betweenPintaTowerPinta Island Intermediate shellMarchenaJamesFernandinaSanta CruzIsabelaSanta FeHood IslandSaddle-backed shellFloreanaHoodOn the desert-like Hood Island,tortoises had long necks…Isabela IslandDome-shaped shell…while on the lush rainforest of Isabela Island,tortoises had short necks…
9After his voyage, Darwin spent a great deal of time thinking about his findings. Had animals living on different islands once been members of the same ancestral species that developed different characteristics after becoming isolated from one another in different habitats?
10Ideas that Shaped Darwin’s Thinking 15-2 James Hutton1785Proposes that the earth was shaped by geological forces which occurred over very long periods of time and is millions of years old.
11Charles Lyell1833Proposes that the geological process that shaped the earth are still occurring now.How did Hutton and Lyell’s work influence Darwin’s theory of evolution?
12This understanding of geology led Darwin to conclude… If the earth could change over time, so could life.The earth must be older that was previously thought
13Thomas Malthus 1798 Observed that birth rate far surpassed death rate. Proposed that famine, disease, and war were necessary and unavoidable population controls.Darwin is influenced because he sees that there will be a struggle for existence within species.
14Jean-Bapiste Lamarck1809First to propose a scientific theory for the way life changed over timeFirst to suggest that all life descended from a common ancestorFirst to realize that species were specially adapted to their environments
15Lamarck’s TheoryLamarck proposed that through selective use and disuse of organs, organisms could gain or loose traits.Further, he believed that those acquired characteristics could be inherited by offspring.He says that this is how species changed over time
16The male fiddler crab uses its front claw to attract mates and fight off predators. Through repeated use, the front claw becomes larger.The fiddler passes on this acquired characteristic to its offspring
17What’s RIGHT about Lamarck’s theory? First to develop a scientific hypothesis about evolution and recognize that organisms are adapted to their environments.What’s WRONG about Lamarck’s theory?Didn’t know about genes and how traits are inheritedAcquired traits CAN NOT be passed on!Ex) if you lifted weights your whole adult life, and then had children, your children would not be born more muscular!
18Darwin Presents his Case 15-3 After Darwin returned to England in 1836 he filled notebooks with his ideas and the process that he would later call evolution.He did not rush to publish his ideas because they disagreed with the fundamental religious and scientific ideas of the day.He asked his wife to publish his ideas after he died.
191858—Alfred Russel Wallace, another naturalist, publishes an essay describing his work in Malaysia and outlining the same ideas that Darwin had for 25 years!This provided the incentive that Darwin needed to publish his own ideas.
201859—Darwin publishes On the Origin of Species Presented his evidence for evolutionDarwin proposes a mechanism for evolution called NATURAL SELECTION
21Inherited Variation & Artificial Selection Darwin noticed that plant and animal breeders would breed only the largest hogs, fastest horses, or the cows that produced the most milkHe called this, Artificial Selection Selection by humans for breeding of useful traits from the natural variation among different organisms.
22Breeds of Dogs Chihuahua – bred from Techichi of Mexico by Mayans, had religious significanceSaint Bernard – bred by monks around 1050 A.D.to rescue travelers of mountain passes in theSwiss Alps between Italy and SwitzerlandIrish Wolfhound – bred in Ireland tohunt wolves and elkDachshund – bred in Germany as earlyas the 15th century to hunt badgers
23Evolution by Natural Selection Darwin compared processes in nature to artificial selection. He thought that nature could “select” organisms based on their fitness.
24Natural SelectionGenetic variation is found naturally in all populationsThe environment presents certain challengesStruggle for existence: members of each species must compete for food, space, and other resources.Some variation is more favorable; some is not favorable
25Natural Selection (cont.) 4. Individuals with the favorable traits (adaptations) will survive and reproduce more than those individuals without the favorable trait.= Survival of the fittestAbility to survive and reproduce = fitnessAny inherited characteristic that increases an organisms chance of survival = adaptation5. The favorable variation will become more common in the population.
26Descent with Modification Suggests that each species has descended with changes from other species over time.Further suggests that all living things are related to each other and that all species, living and extinct, share a common ancestor.
27Evidence for Evolution The Fossil RecordFossils = the remains of ancient organisms found in layers of rockFossils are thought to be the same age as the rock they are found inRock tells the history of earth while fossils tell the history of life.
28Transitional Fossils TIKTAALIK! FishTetrapod Shows the transition between 2 species
29Evidence (cont.) 2. Geographic Distribution Darwin thought that the Galápagos finches could have descended with modification from a common mainland ancestor
30Evidence (cont.) 3. Homologous Body Structures these are structures that have different mature forms, but develop from the same embryonic tissuesimilarities and differences help biologists group animals according to how recently they shared a common ancestor
31Homologous Body Structures TurtleAlligatorBirdMammalAncient lobe-finned fish
32Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species.These organs are called vestigial organs.
33Evidence (cont.) 4. Embryology The early stages, or embryos, of many animals with backbones are very similar.Similarities of embryos provides evidence of a common ancestor.
34Patterns of Evolution 17-4 Macroevolution—refers to large scale evolutionary patterns and processes that occur over long periods of timeFive important topics in macroevolution are:extinctionadaptive radiationconvergent evolutioncoevolutiongradualism & punctuated equilibrium
35ExtinctionMore than 99% of all species that have ever lived are now extinct!Mass Extinction = when large numbers of species disappearResult is the remaining species now have new niches (jobs) to fill, and may then thrive causing bursts of evolution that produces many new species.
36Adaptive RadiationProcess by which a single species or a small group of species evolves into several different forms that live in different waysEx) Darwin’s Finches—more than a dozen species evolved (due to different habitats) from a single speciesCan also happen on a much larger scaleExtinction of dinosaurs = adaptive radiation of mammals
37Convergent EvolutionProcess by which unrelated organisms come to resemble one another, due to living in similar environments.They develop structures that look and function similarly, but are made up of different parts = analogous structuresEX: A bat’s wing (mammal) and a bird’s wing are analogous structures
38CoevolutionWhen organisms that are closely connected to one another by ecological interactions evolve together.The two species evolve in response to changes in each other over time.
39Gradualism vs. Punctuated Equilibrium Evolution has often proceeded at different rates for different organisms at different times during the history of life on Earth.Gradualism:Darwin felt that biological change was slow and steady, an idea known as gradualism.
40Gradualism vs. Punctuated Equilibrium Punctuated equilibrium: a pattern of evolution in which long stable periods are interrupted by brief periods of rapid change.