Download AP Biology Chapter 22: Descent with Modification Chapter Notes I

AP Biology Chapter 22: Descent with Modification Chapter Notes I. Overview: Darwin Introduces a Revolutionary Theory: A. Darwin publishes “On the Origin of Species” on November 24, 1859 1. Darwin makes two points: i. many species of organisms presently inhabiting the Earth are descendants of ancestral species that were different from the modern species a. it was previously believed that all organisms on the Earth were always present b. the Earth was only a few thousand years old ii. natural selection is the mechanism for this evolutionary process a. populations can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals. 2. Natural Selection is driven by evolutionary adaptation which is an accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments i. evolution: a change over time in the genetic composition of a population. a. evolution eventually will lead to a new species do to the accumulation of enough change b. on a grand scale – evolution means the gradual appearance of all of biological diversity, from the earliest microbes to the enormous variety of organisms alive today. II. Chapter 22.1-­‐ The Darwinian revolution challenged traditional views of a your Earth inhabited by unchanging species. A. Resistance to the Idea of Evolution: 1. it was previously believed that all organisms on the Earth were always present (they were created at the beginning of time) and that the Earth was only a few thousand years old B. The Scale of Nature and Classification of Species: 1. Aristotle: species were fixed-­‐ unchanging i. Scala Naturae (scale of nature)-­‐ life forms could be arranged on a ladder or scale of increasing complexity a. living things had a certain affinity b. each life form had its allotted rung on the ladder and was permanent and perfect. ii. ideas coincided with the Old Testaments account of creation where all species were individually created and designed by God for a particular purpose 2. Carolus Linnaeus: Swedish scientist-­‐ founder of taxonomy or a classification system i. developed a two part (binomial) system of naming organisms according to genus and species ii. physical likeness did not imply evolutionary kinship iii. he grouped similar species into increasing general categories (species, genus, family, order, class, phylum , kingdom-­‐ highlighted terms came after him)??? iv. Linnaeus did not imply evolution but a pattern of creation v. his system played a role in Darwin’s argument for evolution C. Fossils, Cuvier, and Catastrophism: 3. Georges Cuvier: French scientist – developed the field of Paleontology or the study of fossils i. three types of rock a. igneous-­‐ no fossils b. metamorphic-­‐ no fossils c. sedimentary-­‐ fossils-­‐ eutrophication of a lake ii. older strata contained more dissimilar fossils a. if you want to look for a particular fossil, your look in a particular stratum i. example: if you want to find the link between fish and amphibians(sea vs. land animals) you would want to search in rock that is about 375 million years old (tiktaalik-­‐ link between fish and amphibians-­‐ flat head w/ eyes on top, owens pattern in the limbs). ii. if you want to find the origin of mammals, you want to search in rock that is about 210 million years old b. zoo analogy-­‐ the organization of a zoo is analogous to the strata of rock i. example: if you wanted to see a lion, you would not go to the reptile house iii. new species seemed to appear and old species disappeared from one stratum to the next iv. catastrophism-­‐ each boundary between layers of rock represents a catastrophic event-­‐ opposed gradual evolutionary change D. Theories of Gradualism: 4. James Hutton: Scottish geologist proposed gradualism i. gradualism-­‐ profound change can take place through the cumulative effect of slow but continuous processes-­‐ in contrast to catastrophism a. Earth’s geological features could be explained by gradual mechanisms currently operating in the world 5. Thomas Malthus: 1798-­‐ “Essay on the Principle of Population” i. increases in population would eventually lead to a diminished capacity for the world to feed itself a. he collected information on birth, death, age of marriage and childbearing and economic factors contributing to longevity b. food increases more slowly than population i. populations grow geometrically where food grows arithmetically c. because humans have not starved must mean there are economic choices in play i. a rise in population would mean a rise in death rate ii. those that did not apply preventative checks (birth control) would out grow their food supply and fall in status ii. analysis of populations influenced Darwins theory of natural selection 6. Charles Lyell: used Hutton’s thinking to develop uniformitariansism i. uniformitarianism-­‐ the geological processes shaping the world today have been operating over the history of the planet E. Lamarck’s Theory of Evolution: 7. Jean Baptiste de Lamarck-­‐ 1809-­‐ compared current species with fossil forms and from this developed several “lines of descent” i. philosopher-­‐ not a scientist who reported the current theories of evolution a. is unfairly credited with the inherited acquired characteristic theory of evolution b. environmental factors are now thought to affect the inheritance of traits in the offspring-­‐ epigenetics c. epigenetics is a field that studies the environmental affects on DNA i. the process of methylation can turn on or turn off genes ii. the phenotype is changed but no the genotypes i. lines of descent are chronological series of older to younger fossils leading to a living species ii. explained with two principles: a. use/disuse-­‐ parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate-­‐ giraffe’s neck b. inheritance of acquired characteristics-­‐ an organism could pass these modifications to its offspring-­‐ again the giraffe’s neck c. evolution happens because organisms have an innate drive to become more complex iii. Darwin rejected this hypothesis for natural selection and also thought that variation was introduced as a result of inheritance of acquired characteristics iv. Lamarck incorrectly hypothesized about evolution-­‐ there is no evidence that acquired characteristics can be inherited v. Cuvier denied that species ever evolved. III. Chapter 22.2: In The Origin of Species, Darwin proposed that species change through natural selection. A. Darwin’s Research: 1. Darwin was a protégé’ of the Reverend John Henslow, a professor of botany who recommended he work as a naturalist on the HMS Beagle B. The Voyage of the Beagle: 1. 1831-­‐ Darwin boards the HMS Beagle-­‐ primary mission to chart poorly know stretches of the South American coastline i. Darwin spent most of his time on the shore, observing collecting thousands of plants and animals ii. observed various adaptation of plants and animals that inhabited the Brazilian jungles, grasslands of the Argentine pampas, Tierra del Fuego and the Andes mountains iii. noticed that plants and animals of the temperate regions of SA, more closely resembled species living in the tropic regions of SA versus the temperate regions of Europe. iv. he found fossils that were clearly different from living species but most closely resembled SA species v. Influenced by Lyell’s “Principles of Geology” he also observed geologic change vi. he found fossils of ocean organisms high in the Andes mountains, which must have been raised long time ago-­‐ reinforced what he learned from Lyell 2. Galapagos Islands: Darwin found unusual organisms on these islands i. collected several different species of finches a. some were unique to the individual island, others were found on multiple islands-­‐ did not realize the significance of this until he was back in England ii. most animals of the Galapagos are not found anywhere else a. he hypothesized that animals of the Galapagos had strayed from SA and then diversified on the various islands C. Darwin’s Focus on Adaptation: 1. all the evidence observed from his voyage he began to perceive adaptation to the environment and origins of a new species as related processes i. new species could arise from an ancestral species through a gradual accumulation of adaptations to a different environment a. the finches beaks are adapted to the specific foods available on their home islands 2. 1840-­‐ Darwin theorized that natural selection was the mechanism of evolution 3. 1844-­‐ Darwin writes a long essay on the origin of species and natural selection but does not publish it 4. 1858-­‐ Alfred Wallace developed and published a theory of natural selection very similar to Darwin’s i. Wallace worked in the East Indies ii. Darwin reviewed Wallace’s publication before it was submitted then forward it to Lyell-­‐who submitted the publication along with some of Darwin’s essays 5. November 24, 1859-­‐ Darwin publishes “The Origin of Species” i. Wallace, who was an admirer of Darwin’s agreed that Darwin’s theory of natural selection was much more extensive than his own and determined that Darwin should be known as its main architect D. The Origin of Species: Descent with Modification 1. Evolution was referred to as Descent with Modification-­‐ which summarized Darwin’s way of life i. Darwin perceived unity in life, all organisms related through descent from an ancestor that lived in the remote past ii. modifications, or adaptations accumulated over millions of years iii. history of life is like a tree with multiple branches E. Natural Selection and Adaptation: 1. Five observations as explained by evolutionary biologist Ernest Mayr: i. For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully (exponential fertility) ii. nonetheless, populations tend to remain stable in size, except for seasonal fluctuations iii. Resources are limited iv. Members of a population vary extensively in their characteristics; no two individuals are exactly alike v. Much of the variation is inheritable 2. Three inferences as explained by evolutionary biologist Ernest Mayr: i. Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving each generation ii. Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have higher fitness and are likely to leave more offspring than less fit individuals iii. This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulation over generations 3. Darwin’s connection between natural selection and overpopulation came from an essay written by Thomas Malthus in 1798. i.Thomas Malthus: essay on population growth-­‐Contended that much of human suffering, disease, famine, homelessness and war was the inescapable consequence of the human population’s potential to increase faster than food and other resource ii. all species have the capacity to over reproduce iii. in each generation, environmental factors filters heritable variations, favoring some over others. iv. differential productive success= favored traits being disproportionately represented in the next generation 4. Artificial Selection: modification of plants and animals by selective breeding i. Darwin derived part of his theory from the selective breeding of plants and animals ii. results are a crop of plants and animals bred as livestock or pets often bear little resemblance to their wild ancestors iii. considering what artificial selection has accomplished over a short period of time, the results of hundreds of thousands of years of natural selection should be capable of much more 5. Summary of Natural Selection: i. natural selection is the differential success in reproduction among individuals that vary in their heritable traits a. differences emerge as individuals interact with its environment ii. over time, natural selection can increase the adaptation of organisms to their environment iii. if an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process 6. Three points about evolution and natural selection: i. individuals do not evolve, natural selection occurs between and individual organism and its environment a. a population is the smallest unit that can evolve b. evolution can be measured only as changes in relative proportions of heritable variations in a population over a succession of generations ii. natural selection can amplify or diminish only heritable traits-­‐ traits that are passed from organisms to offspring a. acquired characteristics are not inherited by offspring iii. a trait that is favorable in one location may be detrimental in another a. natural selection always operates, but the favorability of traits depends on the environment 7. Ultimately, Darwin views life as evolving through this gradual accumulation of small changes. IV. Chapter 22.3: Darwin’s Theory Explains a Wide Range of Observations A. Natural Selection: Two Examples: 1. Differential Predation and Guppy Population: i. researchers observed significant differences between populations in the average age and size at which the guppies reached sexual maturity a. these variations correlated with the type of predator most active on the population ii. two main types of predators: a. killifish-­‐ preys on juvenile guppies b. pike-­‐cichlid which preys on mature fish-­‐ these guppies tend to reach sexual maturity at a younger age and smaller size iii. researchers introduced guppies from the “pike-­‐cichlid” pool into pools that contained killifish but no guppies a. results: after 30-­‐ 60 generations the transplanted guppies were an average of 14% heavier at maturity, and average age to maturity had also risen b. natural selection caused the difference 2. The Evolution of Drug-­‐ Resistant HIV: a variation of a bacteria or virus that makes individuals resistant to a particular drug can increase in frequency very quickly in a population i. researchers have developed numerous drugs to counter the HIV virus ii. these drugs have selected for viruses resistant to the drugs iii. there may be by chance, drug resistant viruses in a given population a. those that survive the drugs early on will pass on the genes that make them resistant, then rapidly increase iv. example: drug 3TC-­‐ developed to combat the HIV virus by interfering with reverse transcriptase(enzyme used by HIV to copy its RNA into DNA) a. 3TC-­‐ is very similar to cytosine-­‐ virus picks it up, in place of cytosine and the error terminates elongation of the DNA and blocks reproduction of HIV b. 3TC resistant HIV carry slightly different versions of reverse transcriptase and are able to discriminate between the 3TC and cytosine c. this becomes a powerful selecting force 3. Two key points of natural selection: i. natural selection is more a process of editing than a creative mechanism a. the HIV drug did not create a resistance, rather it selected individuals that were already resistant ii. natural selection depends on time and place a. it favors those characteristics in a population that increase fitness in the current population B. Homology, Biogeography and the Fossil Record: 1. Homology: underlying similarities in related species resulting from common ancestry i. anatomical homologies: the arms, forelegs, flippers and wings of different mammals are homologous structures that represent variation on a structural theme a. vestigial organs-­‐ have marginal if any importance to the organism-­‐ remnants of ancestral structures that once served a purpose ii. molecular homologies: all forms of life use the same genetic machinery (DNA and RNA) iii. homologies and the tree of life: homologies result in a nested pattern with all life sharing the deepest layer and each smaller group adding homologies to those they share with larger groups a. different kinds of homologies in a group of organisms will all tend to v show the same branching pattern through their evolutionary history 2. biogeography: geographic distribution of species i. closely related species tend to occupy similar geographic regions ii. the same ecological niches in distant regions are occupied by very different though similar looking species iii. endemic species are those that are found nowhere else in the world iv. Darwin noticed that most island species are closely related to species from the nearest mainland or neighboring island 3. Fossil Records: fossil records often support and come to the same conclusion as biochemistry, molecular biology and cell biology i. Darwin believed that evolutionary transitions should leave fossil evidence ii. Darwin’s theory explains so many different kinds of observations: anatomical and molecular homologies that match patterns in space and time 4. Modern examples of evolution: i. drug resistance in bacteria and viruses: a. Staphalococcus aurea-­‐ with the development of penicillin in the 1950’s, the Staphalococcus bacteria became penicillin resistant, so scientist synthesized methicillin. Within a few years MRSA proliferated, so science adapted with the formation of venecillin and again within a few years VRSA became proliferated in the populations. ii. Evolution and sickness: a. hemochromatosis-­‐ a widely spread disease in the European population came about as a result of the black plague. Individuals who had hemochromatosis had a natural resistance to the plague and there for were more likely to survive and pass on their genetic information. b. Diabetes-­‐ a condition that may have resulted as and adaptation to could weather. As humans started to populate colder regions, blood sugar levels may have increased as a means to prevent freezing of the blood-­‐ freezing point depression-­‐ cold diuretics, or the urge to urinate when cold, may have been the physiological response to this process. iii. Fore peoples of Papua New Guinea-­‐ this small tribe would practice cannibalism-­‐ they would honor their dead relatives by eating them after they passed away-­‐ this practice caused an outbreak of CJV disease and eventually lead to the ban of the practice in 1955 by the government. What resulted was a natural resistance to the development of the prion protein that caused the disease. iv. Domestication of the wolf-­‐ the very diverse dog population seen today is a direct result of the domestication of the wolf. Most of the behaviors observed in the wolf are still found in different dog populations. Although this is artificial selection, the mechanism by which the wolf was domesticated over the past 5000 years is the same mechanism by which natural selection works. a. Dimitri Belyaev-­‐ domesticated the red fox in just forty years. Over this time there have been physical changes to the fox such as a more rounded skull, drooping ears and decrease in coat color (became less vibrate). v. Pizzlies-­‐ shift from cold to warm climate has lead to an expansion of the polar bear range (south) and the grizzly bear range (north) and lead to interbreeding and the formation of the pizzly bear. Good example of a breakdown of the post-­‐ zygotic barrier, which allows two like species to interact and breed. vi. Coydogs-­‐ the elimination of the wolf in the Eastern part of the US has lead to a change coyote, which have become larger and more aggressive vii. Stick insects: The creosote bush, originally from Argentina has taken over certain areas of the Southwest US. Its thick resin, found on its leaves, allow it to be adapted to the dry, harsh desert environment. Over the past 10,000 years insects have evolved to exist with the creosote bush. A certain species of stick insect has evolved to mimic the twigs of the creosote bush, and a species of grasshopper has developed silvery patches to mimic the shine of the plants resin on the leaves. Both of these insects are genetically related to insects of North America with no South American ancestors. C. What is Theoretical About the Darwinian View of Life? 1. Darwin’s theory of evolution accounts for many observations and data and attempts to explain and integrate a great variety of phenomena i. many scientists now believe that natural selection is not the only mechanism behind evolution