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You are responsible for reading these chapters…we will be discussing these slides in class, however, we will not be going slow enough for students to copy word-for-word This PowerPoint combines Darwin information from both texts It provides a lot of background information that should better help you understand the development of Darwin’s theories as well as give you a more thorough foundation of the history of Earth. Complete the Chapter 15 WebQuest: ContinentalDriftQuest (located on the Biology: Exploring Life site Try to explain how Plate Tectonics and Continental Drift influenced evolution and biodiversity You will need to read "On the Move...Continental Drift and Plate Tectonics." –this is linked on that site = VERY USEFUL! Fossils/Their Dating Fossil Record/Geologic Time Scale Continental Drift/Macroevolution Mass Extinctions Formed from remains of organisms buried by sediments, dust, or volcanic ash Soft body parts – usually decay rapidly Hard body parts (shells, bones, or teeth) – may become preserved; long-lasting Hard body parts are hardened more Minerals dissolve in groundwater Seep into tissues of dead organisms and replace its organic material Plant/animal becomes petrified Some rare fossils contain organic material Found as thin films Pressed between layers of sand stone or shale Ex. Idaho – plant leaves millions of years old that are still green with chlorophyll Other Fossils: footprints, animal burrows, sediment impressions Sometimes an organism happens to die in a place where bacteria and fungi cannot decompose the corpse Ice Plant sap Fossil record is a “rich storehouse of information” about macroevolution Geologic Time Scale Precambrian Paleozoic Mesozoic Cenozoic Periods are divided into epochs Boundaries between eras are marked by a major change in forms of life and possibly mass extinctions Know age of fossils based on location in sediment Relative Ages = reflect the order in which groups of species existed compared to one another Absolute Ages = Actual ages in years Measurement of certain radioactive isotopes in objects Every isotope has a fixed rate of decay Number of years for 50% of original sample to decay = half-life Unaffected by temperature, pressure and other environmental conditions Used to date rocks Fossils can sometimes be dated as well Could contain isotopes of elements that accumulated in the organisms when they were alive When organism dies, intake of isotopes stops, but radioactive decay continues Dinner and a movie usually works! Just kidding. Can only be used to find the age of recent fossils due to half-life of C-14 = 5,600 yrs Any fossil older than 50,000 must be estimated using the surrounding rocks that contain Uranium-238 and other radioactive isotopes that have longer half-lives Continents aren’t locked into place Landmasses on different plates change position relative to each other as a result of continental drift Solution to many biological puzzles Matching fossils in totally different locations Differing plants in locations that became isolated 1. 250 million years ago, near end of Paleozoic Era Plates moved = 1 supercontinent = Pangea Variety of changes Shoreline reduced Sea levels dropped Shallow coastal seas were drained, destroying shallow water environments and inhabiting species Continental interiors influenced as well Isolated, evolving species came together and competed = cause mass extinctions 2. 180 Million years ago = Continental Drift Pangea broke up Each continent became isolated Species on each continent diverged in their evolution and adapted and diversified based on new, separate continents Long periods of relative stability broken by brief periods of great species loss Extinction of dinosaurs (end of Cretaceous Period – 65 million years ago) Climate was cooling Shallow seas receding Large meteor hit Yucatan Peninsula in Mexico during same time, sending dust into the atmosphere Blocked sunlight Reduced food production by photosynthesis Adaptive radiation of survivors In aftermath, biological diversity increased again Gives surviving organisms new opportunities Rise of mammals may have resulted from the void left by the extinction of dinosaurs Identification, naming, and classification of species Common names cause confusion Common name can refer to many different species Doesn’t reflect organism Universal scientific name needed for all scientists to clearly communicate Binomial Nomenclature = two-part Latin naming system for naming each species Also a hierarchy of species into broader and broader groups Genus + species (Ex. Panthera pardus) Closely related species are grouped into same genus Phylogenetic Tree reflects the hypotheses of evolutionary relationships Homologous structures Basic underlying similarities if evolved from single structure in a common ancestor Greater number of homologous structures = more closely the species are thought to be related Not all structures are inherited from common ancestor Unrelated species from similar environments have adaptations that seem very similar = analogous structures Wings of insects and birds = evolved independently despite both are flight equipment and built from entirely different structures Early 1800’s Jean Baptiste Lamarck attempted to explain Buffon’s observations Proposed that life evolves/changes Species are not permanent Evolution is a process of adaptation Today – unfairly remembered for mistaken explanation of how adaptations evolve (make sure you know what these are – pg. 293) Voyage of the Beagle December 1831 Mission – chart poorly known stretches of the S. American coastline for the British navy Charles Darwin, 22, was on the ship Interested in studying geology, plants, animals encountered on voyage Pivotal trip in that it changed the thinking of many Darwin’s Observations Darwin spent a lot of time on shore while ship’s crew surveyed Collected many species of plants and animals Documented everything in extensive journals (observations, studies, personal thoughts) Journals documented Darwin’s thoughts from before the journey until he returned to port in England Darwin’s Observations (cont.) Noticed that plants and animals all had definite S. Am. Character Distinct from species in Europe Deduced that species in S. Am. descended from ancestral species on that continent Intrigued by life on Galápagos Island Species were similar to plants and animals on nearest mainland (not exactly same) Allowed Darwin to suggest that species that left the mainland adapted to new lives on islands Ideas from Geology Darwin read a lot despite puking Read from Lyell’s writings Proposed that gradual and observable geologic processes (erosion) could explain the physical features of today’s Earth River erosion = deep, river-carved canyon Mountain range rises = earthquakes Ideas from Geology (cont.) Darwin personally experienced an earthquake in Andes Mountains He collected fossils of ocean organisms high in the Andes Concluded that (based on Lyell’s work) that the earthquakes gradually lifted the rock. 2 conclusions: 1. Slow processes of mountain building and erosion suggested an Earth that must be very cold 2. These slow and gradual processes occurring over vast spans of time could cause enormous change on Earth Darwin was at sea for 5 years Over this time he sent letters and specimens back to England This established his reputation with other scientists Left as young graduate Returned as a famous naturalist After analysis of his data, he became convinced that Earth was ancient and that species change through time. Thomas Malthus (wrote essay few decades before Darwin) Contended that much of human suffering was due to the human population’s potential to grow Populations grow IF food supplies and other resources can be produced If this does not happen = it is a struggle for existence This helped Darwin to propose a mechanism of evolutionary change. Darwin’s essay (1844) 200 pages Didn’t release it to the public Colleagues urged Darwin to publish before someone else did Alfred Wallace (1858) came to same conclusion and wrote to Darwin explaining his findings Within a month, both had findings presented to public together Darwin published The Origin of Species about a year later Darwin made 2 main points in his book 1. He argued from evidence that the species of organisms living on Earth today descended from ancestral species 1. Life has a history of change 2. Descendants of the earliest organisms spread into various habitats over millions of years 1. Accumulated different modifications = “Descent with Modification” 2. Accounts for diversity of life Darwin’s 2nd point His argument for natural selection was the mechanism for evolution Natural selection can cause a population to change over time Result = adaptation Homologous vs. Analogous Structures (evidence of evolution) Homologous = similar features that originated in a shared ancestor (see page 289 in your text)-orcomplete online activity 14.2 in Exploring Life Look different but have similar skeletal structure Derive from same structures in embryo Analogous = serve identical functions and look somewhat alike Very different embryological development Just keeping you on your toes!!!!! Vestigial Structures – features seem to serve no useful function now (human’s tailbone) but may have done so historically Similarities in Embryology – See page 291, Figure 15-9 Ernst Haeckel – embryological development repeats evolutionary history! (slightly exaggerated; similarities fade as development proceeds) Similarities in Macromolecules - homologous proteins; RNA and DNA; amino acid sequence is similar between different species Coevolution – change of 2 or more species in close association with each other Predators and their prey; parasites and hosts; plant- eating animals and their chosen plant Convergent Evolution – Organisms appear to be similar but are not closely related at all – analogous structures are similar adaptations that result from this Divergent Evolution – 2 or more related populations become more and more dissimilar Adaptive radiation Artificial selection Page 321…differences between human and ape Anthropoid Primate Prosimian Primate Marmosets Lemurs Monkeys Lorises Apes Tarsiers Humans Movable fingers and toes Most have flattened nails rather than claws Some have prehensile hands (grasping) Color vision (due to activity during day) Anthropoids Ex. Gibbon Well-developed collarbone Rotating shoulder joints Partially rotating elbow Opposable thumb Similar dental formula Large brains Humans Specific anthropoid Bipedal Cup-shaped pelvis S-shaped spine Larger brain Bipedalism defines first hominid line 1974 Donald Johanson found “Lucy” in the Afar Valley region of Africa…very well preserved Cranial capacity size of chimpanzee Originally thought that bipedalism and large brain evolved at same time, but the “Lucy” find proved that upright walking… • “Lucy” was given this name • Means “southern ape of Afar Valley” • About 3.2 million years old • • • • Dates from about 2.3 – 3 million years ago Probably descended from A. afarensis Taller and heavier than “Lucy” Had a slightly larger cranial capacity Australopithecus robustus Australopithecus boisei May have descended May have descended from “Lucy” but were probably not ancestral to modern humans from “Lucy” but were probably not ancestral to modern humans • In 1995, Tim White discovered fossils that may Predate earliest known australopithecines by 200,000 years • Unsure whether it is ancestral to australopithecines Found with stone tools “Handy Human” Between 1.6-2.5 million years old Region of the brain essential to speech may have existed • Tool marks on animal bones found near fossils suggest H. habilis ate meat • • • • “Upright human” 1.8 million – 50,000 years ago Thick skull Large brow ridges Low forehead Large, protruding teeth Average brain size 2/3 that of modern humans Adults could easily have been as tall as modern humans • Charred bones found near fossils indicate H. erectus were hunters who used fire (cooking and heat) • In colder climates, may have lived in caves • • • • • • • • Neanderthals 230,000 – 30,000 years ago Heavy bones, thick brow ridges, protruding teeth Cranial capacity slightly larger than modern humans Stone tools led scientists to believe that they wore animal skins Not ancestral to modern humans Disappeared approximately same time as modern H. sapiens arrived (killed off Neanderthals or killed by disease) Modern Homo sapiens Fossils about 35,000 years old Found in southwestern France Cro-Magnons Cranial capacity equal to that of modern humans High forehead Lack of protruding brow ridge and teeth Taller than Neanderthals Oldest are 100,000 years old Parallel populations of H. sapiens evolved from different H. erectus populations around the world Modern H. sapiens evolved in Africa and spread throughout the world, replacing populations of H. erectus and early H. sapiens RNA molecules can take on a great variety of shapes (t- shaped tRNA)…dictated by H bonds between particular nucleotides Much like the shape of the protein depends on the H bonds between particular a.a. Speculation that some RNA molecules might actually behave like proteins and catalyze chem. rxns. Thomas Cech Ribozyme…act as an enzyme Early Earth had little or no O, so first cells must have been anaerobic; fossils indicated that they were prokaryotes and probably heterotrophs Chemosynthesis…CO2 serves as C source for assembly of organic molecules…many archaebacteria (live in extreme and harsh conditions) obtain E this way Photosynthesis and Aerobic Respiration O was damaging to some unicellular organism Early function of aerobic may have been to prevent the destruction of essential organic compounds by O Believed that between 2.0 and 1.5 billion years ago a type of small aerobic prokaryote entered (endosymbiosis) and began to live and reproduce inside larger, anaerobic prokaryotes Lynn Margulis proposed that “invasion” turned mutually beneficial = giving way to mitochondria Second invasion may have been related to cyanobacteria…eventually gave rise to chloroplasts
