Biology of Organisms • Why is an introduction to life’s diversity important? Comparative Biology • Uses phylogenetic relationships to study the features that unite and distinguish different groups. • Allows us to understand everything in biology from genes to behavior to anatomy to ecology to distributions in a holistic manner. Escherichia coli Saccharomyces cerevisiae Arabidopsis Zea mays thaliana Caenorhabditis elegans Drosophila melanogaster Danio rerio Xenopus laevis Mus musculus Macaca mulatta Comparative Biology • This is why we can study human diseases using mouse models. • This is why principles of genetics derived from fruit flies are generalizable. • This all goes back to the unity of life. Comparative Biology • Some of the most exciting recent discoveries in biology include the elucidation of common genetic elements of animal development. • HOX genes. Biology of Organisms • Interactions between life’s diversity underlie essentially all of biology. • How might this be relevant to your future interests? • Medicine? Biology of Organisms • Interactions between life’s diversity underlie essentially all of biology. • How many interactions are going on here? Ceno- zoic Humans Colonization of land Animals Origin of solar Today, system and Earth Module 1: Origins, 1 4 History, & Proterozoic Archaean Prokaryotes Unity of Life 2 3 Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen What is life? • What would we look for in a life form? • What defines life? • It’s been around for 3.8-3.5 billion years – Oldest rocks are 4.0-3.8 billion years • Any thoughts? What is life? • Reproduction Asexual Sexual What is life? • Reproduction • Metabolism: – the set of chemical reactions that occur in living organisms that manage the material and energy resources of the cell. What is life? • Reproduction • Metabolism • Organization – Non-random – Hierarchies – Emergent properties What is life? • Reproduction • Metabolism • Organization • Growth & Development – Heritability – Cells What is life? • Reproduction • Metabolism • Organization • Growth & Development • Homeostasis – Regulating internal environment What is life? • Reproduction • Metabolism • Organization • Growth & Development • Homeostasis • Responds to the environment – Temperature, moisture, sunlight, substrate What is life? • Reproduction • Metabolism • Organization • Growth & Development • Homeostasis • Responds to the environment • Evolution, Adaptation, & Extinction III. A hierarchy organelle of organization atom molecule • From atoms to grasslands • There are increasing levels of complexity tissue cell – An upside-down pyramid of organ increasing structural and functional complexity. • At each increasing level, the whole is more than the sum Population/ organism of its parts Species organ system biome ecosystem Community IV. Emergent Properties • With increasing complexity the hierarchical level becomes more than the sum of its parts. • These are known as emergent properties. • These are novel properties that emerge from interactions at lower levels. • How is this cathedral termite mound an example of an emergent property? IV. Emergent Properties • As biologists, to understand the whole we need to break it down and examine its parts. • Reductionist perspective. • But we always must keep in mind that when we do this that the whole loses its emergent properties. V: Correlation: structure, function, diversity • Divergence through evolution. – a.k.a. descent with modification. • Organisms have both a shared ancestry and new attributes. Mammalian Forelimb V: Correlation: structure, function, diversity • The pentamerous (five-digit) arrangement of the mammalian forelimb indicates homology. – Features that are similar as a result of descent. Mammalian Forelimb V: Correlation: structure, function, diversity • This pentamerous arrangement has been subsequently been modified through adaptation. VI. Unity in diversity • Sometimes it is difficult to see unity in diversity. • What, for example, could a hummingbird and a mushroom have in common? VI. Unity in diversity • Fungi and Animals diverged some 965 million years ago! • Evolution will, of course, obscure these relationships. • But they are all part of the hierarchy of life. VI. Unity in diversity • Over 1.5 million species are named. • But more than 98% of all species that have ever existed have become extinct. • This also obscures relationships. VI. Unity in diversity: Phylogenetics and Taxonomy • The study of diversity is known as SYSTEMATICS. • Phylogenetics is the practice of elucidating relationships. • Taxonomy is the practice of naming organisms. • Classification arranges organisms. VII: Pattern & Process • Pattern: Description of the WHAT? • Process: Description of the HOW? • This course will mainly be about the description. • Because we must know what exists before we attempt to explain I. Fossils & Sedimentation • Fossils are the most readily observable record of the history of life. • Key to the field of macroevolution. • Paleontology is the study of fossils. I. Fossils & Sedimentation • Unfortunately, the fossil record is both biased and incomplete. • Why would it be biased? • Why would it be incomplete? I. Fossils & Sedimentation • Taphonomic conditions must be appropriate. – These are the conditions that permit decaying organisms to become fossilized. Will this wombat skeleton fossilize? I. Fossils & Sedimentation • Taphonomic conditions depend upon: • Geological processes • Type of fossil • Age of fossils Shales are particularly good for preserving fossils I. Fossils & Sedimentation • Geological Processes • Most fossils are found in sedimentary rock. • How are sediments formed? What are the implications of this for the abundance of fossils? • Also mineralized amber and ice. I. Fossils & Sedimentation • Types of Fossils • The vast majority are of hard parts. Why? I. Fossils & Sedimentation • Types of Fossils • Trace fossils provide information on interactions, ecology, behavior, functional morphology. • How? • These are rare! Dinosaur tracks Leaf-mining insects I. Fossils & Sedimentation • Ages of Fossils • Older fossils are much more rare. • Why? Stromatolites Fossilized stromatolite I. Fossils & Sedimentation • The rarity of appropriate taphonomic conditions results in this bias and incompleteness. • Despite this, the fossil “eBay insect fossil is new species” record provides remarkable insights into the history of life on earth. II. Dating of major events • How do paleontologists estimate fossil/strata ages? – Relative – Absolute One second before the end of the dinosaurs… II. Dating of major events • Relative dating: • Usually older fossils at bottom of strata, younger towards top. II. Dating of major events • Absolute dating. • Radioactive elements: isotopes that decay at a constant rate. • The ratio of these versus the stable isotopes that they decay into gives us a metric of the age that the sediment was formed – or the fossil itself if any organic Carbon is lucky enough to be preserved. II. Dating of major events Common isotope ratios used in radiometric dating II. Dating of major events • Generalizations: • Index fossils help correlate ages of strata over wide areas. • Based on well- documented fossils of short-lived (but abundant) species. Viviparus glacialis is an index fossil for 2.3-1.8 mya III. The Geological Time Scale IV. Major Episodes • A combination of: – Relative dating – Absolute dating – Major events in the history of life • Give us the Geological Time Scale – You should become familiar with the names, dates, and major events in this time scale. I highly recommend that you study Table 25.1 from your book! The geologic record is divided into the Archaean, the Proterozoic, and the Phanerozoic eons. The Archaean & Proterozoic together are commonly known as the Precambrian Era The Archaean: 4.6-2.5 bya • Probably absent of life until 3.5 bya (first rocks 3.8 bya) • Prokaryotes appear (3.5 bya) • Massive increase in Oxygen (of biological Stromatolites origin) and first significant extinction at Fossilized end of Archaean 2.5 stromatolite bya The Proterozoic: 2500-542 mya • First Eukaryotes and multicellular organisms appear. • Familiarize yourself with pages 516-517 and figure 25.9 in the textbook for this. The Proterozoic: 2500-542 mya • First Eukaryotes and multicellular organisms appear. • Low diversity early (Snowball Earth) • Later characterized by the “Ediacaran” or “Vendian” biota. • Mass extinction of these forms at the end of this boundary. • Why? Phanerozoic: 542 mya-present • The Phanerozoic encompasses multicellular eukaryotic life • The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic • Major boundaries between geological divisions correspond to extinction events in the fossil record The Paleozoic Era: 542-251 mya • Began with the Cambrian Explosion. • Sudden appearance of modern animal phyla in the fossil record. • Localized fossils and DNA evidence suggest earlier origins (Conway Morris’ long fuse). • BUT the explosion refers to their widespread emergence and dominance. The Paleozoic Era: 542-251 mya • Major features: – Colonization of land – Appearance of vascular plants – Origins of seed plants – Diversification of insect orders – Radiation of vertebrates The Paleozoic Era: 542-251 mya • Ended with the PERMIAN extinction. • Correlated with formation of PANGEA. Continental Drift • The movement of earth’s continents relative to each other. • Based on the theory of plate tectonics. • Tectonic plates move in relation to each other causing