Our last week! Agenda. Ch 13: A brief history of evolution. A brief history of evolution, continued. Lamarck: Inheritance of acquired characteristics

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1 Agenda Overview of the next four days Chapter 13 Linking the Film: Apes to Man, to Chapter 13 Our last week! Monday: Chapter 13, Film notes Tuesday: Chapter 14 (macroevolution and taxonomy) and Chapter 15 (prokaryotes and protists) Wednesday: Quiz (Chp 9, 19, 13, 14,15) Chapter 16 (plants and fungi) Thursday: Chapter 17 (animals) Next Monday: Review Session! Ch 13: A brief history of evolution Ancient Greeks: Aristotle at it again, species are fixed and permanent This idea solidified by Judeo-Christian beliefs and the literal interpretation of Genesis, ie. Earth ~ 6000 years old s, Buffon studied fossils (remnants of extinct,ancient species) and saw similarities between extinct and living animals Oh, the horror! A brief history of evolution, continued 1700 s Buffon looking at fossils 1800: Jean Baptiste Lamarck, studying fossils suggested an explanation as to why fossils of ancient species resembled present day species Life evolves through a process of adaptation Lamarck hypothesized incorrectly about HOW this evolution occurs: Use and disuse-individuals lose characteristics they do not require (or use) and develop characteristics that are useful. And these are passed down to offspring Late 1800 s: Charles Darwin, the father of evolution Lamarck: Inheritance of acquired characteristics If an organism changes during its lifetime in order to adapt to its environment, those changes are passed on to its offspring. The idea that an organism can acquire characteristics during its lifetime and pass them on to its offspring Lamarck said that change is made by what the organisms want or need A giraffe stretching its necks to reach leaves high in trees strengthen and gradually lengthens its neck. This giraffe will have offspring with slightly longer necks. Because this giraffe is stretching his neck, this will affect his neck length, and this NEW, longer neck length will be passed to offspring 1

2 Lamarck also said that body parts that are not being used, such as the human appendix and little toes are gradually disappearing. Eventually, people will be born without these parts.? Analysis of Lamarck s Hypothesis Do somatic (body) cells, like a stretched neck muscle, or a lazy little toe have any effect on what genes are passed down to offspring? What type of cells in the parent are important for passing down genetic info to offspring? What is the major flaw in Lamarck s idea? Charles Darwin While most of the crew studied uncharted shoreline, Darwin wandered ashore and collected 1000 s of specimens Where did he go? What did he see? Darwin Darwin Observed adaptations of organisms in diverse habitats (jungle, islands, mountains) Although he saw differences in the organisms he encountered, all of the organisms were quite different from those in Europe. They had a South American stamp. He wondered if current species owed their South American features to descent from a common (South American) ancestor As the voyage continued, Darwin apparently read a lot. He read and was influenced by the work of Charles Lyell, a geologist, who presented a case for an ancient Earth, one that was formed slowly by geological events (and is still forming) Darwin experiences his first earthquake 2

3 Darwin and the Galapagos Islands Young, volcanic islands, 540 miles from South America Most of the animals inhabitants are unique to the Galapagos These species, though, resembled South American mainland species Darwin wondered if these islands could have been colonized by plants and animals that strayed from the mainland.and then diversified as they adapted to their new environment. Did one ancestral, South American Finch population colonize these islands? A vivid example of resource partitioning and adaptive evolution Establishment of different ecological niches (a) Large ground finch (b) Small tree finch (c) Woodpecker finch Darwin Medium ground finch Cactus ground finch Small Medium Woodpecker tree finch tree finch finch Origin of Species Large Large Small cactus Vegetarian Large ground ground ground finch tree finch Mangrove finch finch finch finch Sharp-beaked ground finch Seed-eaters Cactus-flower Bud-eater Insect-eaters -eaters Green Gray warbler warbler finch finch What were the major points in Darwin s essay? What ideas were new? Why did Darwin wait over 15 years to publish his ideas? Ground finches Tree finches Warbler finches Common ancestor from South American mainland Origin of Species Descent with modification Point #1: Point #2: 3

4 Descent with modification =Evolution Natural Selection is the mechanism for evolution What is Natural Selection? The concept of Natural Selection relies on two key observations Observation #1: Overproduction All species tend to produce excessive numbers of offspring This leads to a struggle for existence Observation #2: Individual variation Variation exists among individuals of a population Much of this variation is heritable (can be inherited) What did Darwin infer, (conclude) from these two observations? Those individuals with traits best suited for the local environment are more likely than less fit individuals to survive and reproduce (leave behind more offspring). The environment screens a populations inherent variability. Differential reproductive success causes favored traits to accumulate in a population. This Natural Selection by the environment, on individuals, causes a population to evolve, undergo adaptive evolution. Evolution Biology s core theme explains both the unity and the diversity of life Natural Selection is always occuring Natural Selection is always occuring Notice that the ENVIRONMENT does the selecting!! Notice, that we are comparing the gene pool over time! It is sometimes tempting to say that, Trait X was beneficial so the population got trait X," than to say Trait X was beneficial, individuals without trait X were less likely to survive and reproduce, resulting in the population having mostly individuals with trait X." 4

5 Evidence for Evolution 1. Fossil record 2. Biogeography 3. Comparative anatomy 4. Comparative embryology 5. Molecular biology 1. Fossils Are preserved remnants or impressions left by organisms that lived in the past Are often found in sedimentary rocks 1 Rivers bring sediment to the ocean. Sedimentary rocks containing fossils form on the ocean floor. 2 Over time, additional strata are added, containing fossils from each time period. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion by rivers reveals strata; deeper strata contain older fossils. Younger stratum with more recent fossils Older stratum with older fossils The fossil record Is the chronology of fossil appearances in rock layers Testifies that organisms have appeared in a historical sequence The Fossil Record evidence of evolution: -oldest fossils are 3.5 billion years old -prokartyotes believed to be the ancestors to all life youngest oldest 2. Biogeography Is the study of the geographic distribution of species and the process that resulted in such patterns. First suggested to Darwin that today s organisms evolved from ancestral forms Why are volcanic islands worth studying? 2. Biogeography Australia might be the ultimate experiment in biogeography In the film, Apes to Man, what geological processes may have contributed to the distribution of ancestral primate species? Biogeography: the study of the geographic distribution of species and the process that resulted in such patterns. 5

6 The lee side of a mountain Western slopes of mountain ranges tend to receive more moisture than the corresponding eastern slope As western winds rise up the mountain side, the air cools and precipitation is often dropped When the air reaches the other side of the range (the eastern or lee side) the air contains less moisture Consequently, the eastern slope is drier What phenotypes might be favored in each habitat? Why? Rain forest Savannah Rain forest Western slope Savannah Eastern slope 3. Comparative anatomy Comparative Anatomy The forelimbs of mammals all consist of the same skeletal elements Is the comparison of body structures between different species When structures are similar due to common ancestry, the structures are called homologous structures Human Cat Whale Bat Figure Ancestral structures that originally functioned in one capacity become modified as they take on new functions-descent with modification! What examples of comparative anatomy were explored in the film? Anatomical structures studied How change in structure complemented new function 6

7 4. Comparative Embryology Vertebrates (animals with backbones) all have an embryonic stage in which gill pouches appear The comparison of structures that appear during the development of different organisms Gill pouches Comparative embryology of vertebrates supports evolutionary theory (a) Chick embryo Post-anal tail (b) Human embryo Shared embryology points to a common ancestor 5. Molecular Biology Gibbon Human -Can be used to study the evolutionary relationships among species Old World monkey Orangutan Gorilla Chimpanzee Leave signs in DNA, RNA, and proteins Can be determined by comparing sequence of DNA, RNA, and proteins of different organisms Depending on the technique used, human and chimp DNA is between 95-99% identical Figure