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Bio 1070 Midterm 1.doc

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BIOL 1070
Wright& Newmaster

Bio Midterm 1Lecture 2WHAT IS BIODIVERSITY A variety of genes speciesecosystems Shaped by billions of years of evolutionary history of life forms interacting with each othertheir environmentAltered by human activity with lasting impacts at large scales that are difficult to predict WHAT IS EVOLUTION Descent with modification from common ancestors WHAT FACTORS CONTRIBUTE TO THREATS OF NATIVE FRESHWATER MUSSEL BIODIVERSITY IN THE GREAT LAKES REGION Invasive species eg zebra mussel Human impacts eg pollution Commercial harvesting eg overfishing Habitat segregationDestruction of habitat Agricultural runoffWater temperature fluctuations TYPES OF MUSSELSUNIONIDS Larval formglochidia Hostdependent Larvae dispersed by hostDREISSENIDS Larval formveligers Not hostdependent can settle onattach to any solid surface Larvae dispersed in waterLIFE CYCLESLARVAL TYPESFreshwater bivalves hinged with 2 shells develop in 3 ways Ontogenic variation1By passing early development as a parasitic stage on a host eg Unionids2By producing veliger larvae eg Dreissena polymorpha3By releasing fully developed young mussels rareUNIONID LIFE CYCLE AdultGlochidiaFish HostJuvenileAdultEmbryo found in the sac in the gills called marsupium Glochidia is a little shell with a tooth used to clamp onto fish gillPrimary reason for attaching to fish gill is for nutrients from fishs blood Female can release up to a million offspringonline about 10 usually live Cysts form around glochidia so that the fish does not leak blood UNIONID STRATEGIES Glochidia attract fish by1 A lure modified mantle tissue mimics fish or invertebrate prey item2 Conglutinates membrane sacs produced by the mussel packed with glochidia mimic host prayHost Capture mussels may physically grip hostpump glochidia over gillsZEBRA MUSSEL LIFE CYCLE EmbryoFree swimming larvaeMetamorphisisSettled juvenile larvaeSettled adultFree swimming larvaeBiological VariationWHAT ARE THE CAUSES oF VARIATION IN FINGER LENGTH Genoypic variation Phenotypic variation Environment can play a big role in phenotypic variation eg for plants water soil sunlight etcGENOTYPIC VARIATIONMUTATION a heritable DNA change introduces new genetic variation into population Errors in DNA replication occur at randomDo NOT occur in order to benefit the organismA secondary source of genetic variation is recombination GENE FLOW change in allele frequencies as individuals join a populationreproduce Sharing of alleles among a population GENETIC DRIFT random changes in allele frequencies caused by change in events eg a portion of a population of beetles gets crushedRandom chance has a role in determining whether an individual survivesreproduces the alleles of the offspring are a random sample of those in the parentsEvolution by chance through many generations
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