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Chapter 19 Macroevolutionary Puzzle Introduction • Geologic time requires time measured in almost incomprehensible lengths • We have dated asteroids impacts and their consequences, such as dinosaur extinctions Fossils: • Are recognizable, physical evidence of organisms that lived long ago– skeletons, shells, leaves, seeds, imprints of leaves an tracks an even fossilized feces • Conditions necessary for fossils: – Hard parts – Buried quickly (absent of oxygen) – Free from decomposers and scavengers Fossils in Sedimentary Rocks • Relative Dating – Stratification, the layering of sedimentary deposits bearing fossils, is quite similar from continent to continent. – Deepest rock strata are assumed to be the oldest, surface layers the youngest. – Abrupt changes in the fossils in the layers wer the basis for dividing earth history into great era, which formed a “geologic time scale” to which actual dates were added later. Interpreting the Fossil Record • The fossil record is far from complete, but some lineage are extensive. • Fossil records vary according to type of organisms, stability of the geographical region, and quality of the specimen Macroevolution • Refers to large-scale evolutionary changes that take place over long time periods. • Speciation is the splitting of one species into two or more species or the transformation of one species into a new species over time; speciation is the final result of changes in gene pool allele and genotypic frequencies. Absolute Dating (Radiometric Dating) • To determine the actual age of the fossil through isotopes in the fossils or rocks • Half-life: the time its for half the radioactive isotopes to break down – Examples: • Carbon-14 will break down to nitrogen-14 (useful with fossils up to 50,000 years old) • Uranium-256 will break down to lead-206 Theory of Uniformity • Mountain building and erosion had repeatedly changed the surface of the Earth in exactly the same ways through time Continental Drift • Alfred Wegener proposed a model of a single continent, named Pangaea, that at one time extended from pole to pole surrounded by a single huge ocean. • The idea of continental drift explains the separation of the continents and the formation of great mountain ranges as the continents collided – Appalachian Mountains formed when Africa and North America collided Continue… • Evidence of continental drift – Magnetic alignment (magnetic North was switched throughout the Earth’s history) – Coal seams (Indicates North America was in the was in a warm swampy environment) – Glacial Deposits – Fossils (Found in different continents) Continue… • Sea-flooring spreading and plate tectonics also show that the Earth’s crust is moving – Divergent Boundaries: Plates separating together (Atlantic Ocean) – Convergent Boundaries: Plates coming together (Pacific Ocean) Comparative Morphology • Provides evidence of evolution by comparing anatomical features to reveal similarities and differences – Also known as homologous structure Morphological Divergence • Features that have departed in appearance and/or function from the ancestral form • These are body features that resemble one another in form or patterning due to descent through common ancestors • Example: Forelimbs bones in birds and bats Morphological Convergence • Also known as adaptive radiation • Is the adoption of similar function over periods of time in animals of evolutionary remote lineages • Analogous body parts perform similar functions in dissimilar and distantly related species • Example: Sharks, penguins, and dolphins (having similar function but not in the structure in their forelimbs Developmental Program of Larkspurs • The common larkspur has a ringlike array of petals to guide honeybees to the nectar, plus the bulging reproductive structure for the bee to hold on to. • More recently evolved larkspur has tight flowers that discourage bees but are attractive to hummingbirds Developmental Program of Vertebrates • Different organisms may show similarities in morphology during their embryonic stages that often indicate evolutionary relationship – The early embryos of vertebrates strongly resemble one another because they have inherited the same ancient plan for development – Some of the variation seen in adult vertebrates is due to mutations in genes that control the rates of growth of different body parts Comparative Biochemistry • Protein Comparisons – Because genes dictate the sequence of amino acids in proteins, analysis of proteins can determine the similarity of genes between species • Nucleic Acid Comparisons – The degree of similarity of nucleotide sequence of DNA reveals information about evolutionary relationships Continue… • Molecular Clock – Neutral mutations have no more measurable effect on survival and reproductions rates than do other alleles for the trait – These mutations accumulate in the DNA can can be used as a “molecular clock” for dating times of divergence of species Identifying, Naming, and Classifying Species • Taxonomy- is the field of biology that attempts to identify, name, and classify organisms. • Binomial nomenclature system – Carl von Linnaeus – scientist to develop the naming system – Rules: • • • • • • Use the Genus and Species Genus: First letter Capital letter Species: Lower case letter Written in italics Language: Latin Example Homo sapiens Classification Schemes • Organized ways of retrieving information about particular species • A hierarchical system (Largest (least related) to smallest (more related) – KingdomPhylumClassOrderFamily GenusSpecies – Traditional Classification has been modified to reflect phylogeny –the evolutionary relationships among species Classification Taxonomy • Classification schemes and evolutionary tree diagrams are constructed to reflect the perceived degree of morphological divergences among major lineages Cladistic Taxonomy • Groups are arranged by branch points in an evolutionary tree diagram – Only species that shared derived traits– novel features that evolved only once and is shared only by descendants of the ancestral species in which it evolved – are grouped past a given branch point, which represents the last shared common ancestor. Continue… – Diagrams called cladograms, do not convey direct information about ancestors and descendants, but rather, portray relative relationships by placing taxa closer togetherr that share a more recent common ancestor. Classification System • Robert Whittaker developed the original fivekingdom systems • Today we use a six-kingdom system Kingdom Monera • Single celled prokaryotes (bacteria) • Display great biochemical diversity but little internal complexity • Producers and decomposers • Today, it has been divided into kingdoms (Archaebacteria (bacteria that lives in harsh environments (volcanoes))and Eubacteria(normal bacteria)) Kingdom Protista • Mostly single-celled eukaryotes • Photoautotrophs (algae) and heterotrophs (protozoas) • More internal complexity than bacteria • Very difficult to classify because this kingdom has organisms that are plantlike or animallike Kingdom Fungi • Multicelled eukaryotes that feed by extracellular digestion and absorption • Hetertrophs include decomposers • Many are pathogens and parasites Kingdom Plantae • Multicelled photosynthetic autotrophs • Producers • Form from embryos Kingdom Animalia • Diverse multicelled hetertrophs • Range from sponges to vertebrates Domains • The domains are a largest hierarchical system than Kingdoms – Divided into three domains – Eubacteria (normal bacteria), Archae (bacteria that lives in harsh environments), and Eukarya (organisms that have nucleus) • Darwin saw evolution of one kind into another as happening gradually, in small increments, over hundreds or thousands of generations • 1861 Fossil evidence of Archaeopteryx was unearthed – These organisms shows a transition from reptiles and birds – Like birds, it was covered with feathers, but like reptiles, it had teeth and long, bony tail