LS 1 Alfaro Michael 2012 Fall Weeks 1 3 Midterm 1 Study Guide Lectures 1 8 Lecture 1 October 1st Describe the biodiversity across the tree of life What is the cause for high and low diversity and high and low species richness The tree of life shows the evolved diversity among all living organisms All organisms originate from bacteria eukarya or archaea Evolution is the driving force behind the amount of diversity the number of individuals in a species is called species richness The cause of high or low levels of diversity among a group of organisms is a reflection of how the organisms have been changed by their environment or natural selection There are many factors that contribute to the rise of a new species Why did the dinosaurs go extinct Dinosaurs dominated the terrestrial environments from 235 mya 65 mya There are four main theories as to why they went extinct The lineages of the dinosaurs became too old racial senescence the competition from other species increased too much an asteroid hit earth and caused mass destruction or volcanic activity caused a major deficit in resources and the dinosaurs could not survive The first two hypothesis aren t supported much because the decreased species richness of dinosaurs and increased species richness of competitors is not reflected in the fossil record The asteroid theory is supported because high levels of iridium a byproduct of asteroid collision are found in the fossil record around the time period when dinosaurs went extinct Lecture 2 October 3rd What do phylogenies represent and how can they be constructed Phylogenies are a way to organize individuals and show the relationship between different species of organisms There are different levels of organization within a phylogeny including clades sister taxa lineages etc However the purpose of a phylogeny is to show the evolutionary history of different species They can be constructed in several ways the three most accessible being through the fossil record DNA and genetic information and morphology Morphology is the study of how similar structural features between organisms evolved How did whales evolve and what data supports the hypothesis The closest known relative to the whale is the hippopotamus Given the phylogeny of whales constructed from DNA samples morphology and the fossil record whales most likely evolved from a These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute marine reptile This reptile had structures similar to whale fins and tails and the beginning of whale evolution may have started about 25 mya Today there are about 84 species of whales Describe homoplasies and synapamorphies Both homoplasies and synapomorphies are phenomenons that occur on a phylogeny A homoplasy refers to a characteristic or trait that is shared with another species but is not derived from a common ancestor A synapomorphy is a common characteristic or trait between two species that have derived from the same common ancestor Lecture 3 October 5th How can time be introduced to a phylogeny How is it indicative of relationships between species When time is introduced to a phylogeny it is called a chronogram Time gives a rough estimate as to when an event of speciation occurred On a chronogram not only can the qualitative relationship between species be seen but the chronological differences between species can also be analyzed How did feathers evolve on birds The early fossil record shows that some dinosaurs had feathers Feather attachment sites were found on limb bones of dinosaurs however the perceived function of these feathers was to provide wing assisted running and insulation These were the common ancestors to these birds and thus as feathers evolved they took on a new function of flight assistance this is called an exaptation Lecture 4 October 8th Describe the major geological eras periods and the significance of each period Chart of Eras Periods and Bio historical Significance Era Period Time Significance Precambrian Precambrian 4 6bya 542mya Origin of life eukaryotes evolve early fossils of animals Paleozoic Cambrian 542mya 488mya Diversification of multi cellular animals and protists Ordovician 488mya 444mya Mass extinction wipes out 75 of living organisms Mesozoic Cenozoic Silurian 444mya 416mya Ray finned fishes and terrestrial plants animals evolve Devonian 416mya 359mya Fishes insects and amphibians diversify mass extinction wipes out 75 of species Carboniferous 359mya 297mya Fern forests appear reptiles appear and insects diversify Permian 297mya 251mya Reptiles diversify and large amphibians appear mass extinction that wipes out 96 of species Triassic 251mya 200mya First mammals appear dinosaurs evolve mass extinction that wipes out 65 of species Jurassic 200mya 145mya Dinosaurs diversify first fossils of flowering plants found Cretaceous 145mya 65mya A mass extinction wipes out 76 of species Tertiary 65mya 2 6mya Diversification of birds mammals flowers and insects Quaternary 2 6mya Present Many older mammals go extinct and humans evolve Lecture 5 October 10th How do organisms diversify through dispersal and vicariance Dispersal is the pattern that suggests that independent speciation and diversification occur because populations and individuals of one species migrate from one environment to another Living in a different habitat causes a different type of evolution Vicariance suggests that independent speciation occurs because of geographical or reproductive barriers between different species How did marsupials diversify and what evidence supports the theory Today marsupials are found primarily in Australia however the fossil record suggests that the first marsupials were found in North America and China To reconstruct the biogeographical history of marsupials scientists looked first at the geographical map from when Pangaea existed Following the oldest marsupial fossils in North America and China scientists found that marsupials had migrated to South America and Antarctica before reaching Australia and undergoing adaptive radiation in Australia This is why most species of marsupials today are found in Australia Lecture 6 October 12th What is the latitudinal species gradient and the three hypotheses that explain how species are distributed Which theory ies are supported The latitudinal species gradient is a measure of species density from the equator outwards latitudinally Most