Bil 160 chapter 25 cont'd and complete ch 26
Bil 160 chapter 25 cont'd and complete ch 26 BIL 160
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This 5 page Class Notes was uploaded by Khrystel Bernard on Friday February 26, 2016. The Class Notes belongs to BIL 160 at University of Miami taught by Paul Groff in Spring 2016. Since its upload, it has received 342 views. For similar materials see EVOLUTION & BIODIVERSITY in Biology at University of Miami.
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Date Created: 02/26/16
Chapter 25 cont’d and complete Chapter 26 note MASS EXTINCTIONS: 1. 443 million years ago (Mya): Most of the species lived in the ocean, however during an ice age the sea levels dropped and the ocean chemistry changed, causing an extreme decline in marine populations. 2. 359 Mya the ocean began to lack enough oxygen to sustain life (reasons are unknown) 3. 248 Mya 96% of all species went extinct (reason aren’t known) 4. 200 Mya, Hypotheses range from massive volcanic activity, to asteroids impacting Earth, and extreme climate change. 5. 65 Mya, volcanic eruptions caused massive clouds or carbon dioxide to cover the sky and prevented the Sun’s light from reaching the ground. Thus caused dramatic drop in temperatures. Furthermore, an asteroid impacted the Yucatan Peninsula; these factors killed many species, including the dinosaurs. th 6. A “6 extinction” may be occurring now due to human activity I. Pollution II. Introducing invasive species to established ecosystems (Example: African rock python hybrid in the Everglades) III. Overkilling [example: hunting elephants for their tusks and overfishing] IV. Genetically altering crops/animals to cause a lack of diversity Example of “lack of genetic diversity”: Humans interbreed corn until all corn crops lack variety in their genetic makeup. If one corn is susceptible to a disease or climatic change, all members of that species will die because ALL have the same genetic makeup, which provides no defense against the disease or climate). Fun Fact: Mass extinction is when about 75% of the living population dies within a 2 millionyear period Before these events, and before multicellular and aerobic organisms existed, the Earth was very inhospitable and was unable to sustain much life. Hypotheses of where organic molecules that makeup life come from 1. Abiotic synthesis of organic molecules spontaneously produced macromolecules (carbohydrates, lipids, nucleic acids, and proteins) 2. Organic molecules rained down from outer space 3. Were synthesized near hydrothermal vents or alkaline vents in the ocean 4. Synthesized when asteroids and comets impacted Earth and brought them here In order to produce life Earth needed some essential elements SPONCH (sulfur, phosphorous, oxygen, nitrogen, carbon, hydrogen)…carbon dioxide (CO2) dominated the atmosphere, which enabled early prokaryotes to perform photosynthesis As Earth began to gain an atmosphere, many anaerobic organisms started to die out (oxygen is toxic poison to them) Photosynthesis from early prokaryotes caused a net gain of oxygen (before O2 built up in the atmosphere it oxidized reduced ions in the ocean (Example: oxidizing iron (Fe) 2+ which caused the “Banded Iron Formations” in seawater) FOSSIL RECORDS Evidence: Fossils accumulate in sedimentary rocks (the oldest fossils in the bottom and the newest are packed closer to the surface) Specific years are predicted using radiometric dating (dating based on decay of its radioactive isotopes of elements that were amassed when the organism was alive, such as carbon) Rate of decay is the halflife (not affected by environmental variables) Age determine by measuring the ratio between carbon14 and carbon₆ Radioactive isotopes with longer halflives are needed to date older fossils (because traces of carbon14 dwindles over time) Limitations: Older organisms are harder to trace because carbon dwindles over time, and elements with longer halflives are not used by animals, such as uranium so it obviously cannot be used to measure the age of these older fossils. Origin of Eukaryotes Timing: Oldest fossils are 1.8 billion years old Unlike prokaryotes, eukaryotes have very developed cytoskeletons which enable them to engulf other cellsIt has been suggested that mitochondria and plasmids (chloroplasts) originated from small prokaryotes which were engulfed by other larger cells (endosymbiont theory) Evidence: The inner membranes of mitochondria and plasmids contain enzymes and transport systems similar to that of the plasma membranes of living prokaryotes Origin of Multicellularity: Oldest form of multicellular eukaryote is the red algae (1.2 billion years ago) Ediacaran biota – larger fossils that appeared 600535 million years ago (Earth was inhabited only by microbial organisms until this) These organisms began to diversify and evolve Adaptive Radiation: An event that causes is lineage to rapidly diversify The new lineages evolve different adaptations Triggers include Less competition/ vacated niches (Mass extinction & Colonization): Once the dinosaurs became extinct, small mammals were allowed to evolve and prosper without competition or predation from dinosaurs Specialization(Evolution causes new characteristics): Many species subdivided to better adapt to the environment and food sources (example: Different species of cichlid fish live in Lake Malawi but have specialized bodies that enable them to eat specific foods) Effects of Developmental Genes Heterochrony: Change in the timing or rate of ontogenetic/developmental events between to taxa (Example: shape of body depends on growth rate during development, such as, puberty) Paedomorphosis: Adult organism retains physical juvenile features (Example: Fairly good retention of skull shape from babyhood to adulthood)…Rate of reproductive development is accelerated Hox geneDetermines position of body parts (Example: Artificially directing Hox gene to grow a foot in a fly’s forehead) Homeotic genes: Any of the master regulatory genes that controls the pattern of body formation during early embryonic development of organisms Tinkering Slight modification (Evolution) http://www.bio.miami.edu/dana/dox/heterochrony.html Continental Drift The continents were all clumped together into the supercontinent Pangea until plate tectonics shifted Caused deepening of ocean basin, shrinking number of shallow water habitats, and colder/drier climates inland CH 26 Synapomorphies: A characteristic or trait that is shared by two or more taxonomic groups and results from evolution from a common ancestral form Cladistics: A system of biological taxonomy that defines taxa distinctively by shared characteristics rather than by shared ancestral groups Clades: Ancestors and ALL descendants Monophyletic: All combinations of ancestors and descendants Paraphyletic: Based on ancestral species and SOME of their descendants Polyphyletic: Includes distantly related species but not those that are more closely related (common ancestor is not part of the group) Sister taxa: Tips of tree represents groups of descendent taxa; nodes represent the common ancestors that these species share. Two descendants that split from the same node are considered “sister taxa” (Taken from http://bio.slu.edu/mayden/systematics/glossary.html; visit their website for more terms) Basal taxa: The earliest taxon whose evolutionary lineage diverged in the history of the group of a phylogeny tree. Shared ancestral (trait was passed down from the ancestor to descendants) vs shared derived (Characteristic unique only to that group) characteristics Outgroup= Diverged before evolutionary lineage (Derived) Maximum Parsimony (simplest scientific explanation) vs maximum likelihood Gene Duplication Increases the number of genes in a genome = more chances of evolution Orthologous (genes in various species that evolved from a common ancestral gene as a result of speciation) vs paralogous genes (genes related by duplication within a genome) Molecular clock: Time when evolutionary change occurs based on based on the observation that genes seem to evolve at the same rate (example dating the origin of HIV) Problems include: Mutations are not selectively mutual Gene Evolution: Number of genes a species has doesn’t increase through duplication at the same rate as phenotypic complexity Genes can code for multiple proteins Horizontal gene transfer: The process of swapping genetic material between neighboring “contemporary” bacteria (Example: Many types of vaccines needed because resistant viruses transfer the genetic information to other viruses to build resistance). http://amrls.cvm.msu.edu/microbiology/molecularbasisforantimicrobial resistance/acquiredresistance/acquisitionofantimicrobialresistancevia horizontalgenetransfer (This website tells you of the three ways that the transfer occurs)
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