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BIOL 1070
David Dyck

Biodiversity 1/9/2013 8:27:00 AM Introduction  Biodiversity is the variety of genes, species and ecosystems  Shaped by billions of years of evolutionary history of interaction between environments and life forms (natural phenomenon, other species, etc.)  Human activity can have lasting impacts at large scales that are difficult to predict  Descent with modification from common ancestors Mussels  What factors contribute to the threats to native freshwater mussel biodiversity in the Great Lakes Region? o MASS PROPAGATION OF MUSSELS o POLLUTION o HUMAN IMPACTS o INVASIVE SPECIES o POLLUTION o OVERFISHING o TEMPERATURE FLUCTUATION Bivalves develop in 3 ways (Ontogenic Variation; not all freshwater mussels develop in the same way)  By passing early development as a parasitic stage on a host (Unionids)  By producing veliger larvae ( in Dreissena polymorpha)  By releasing fully developed young mussels (rare)  Dioeceous (Male and female; both genders)  Production: releases sperm from the exhalant siphon, female takes in sperm from the inhalant siphon; female now has sperm and egg in the same area internally; once the egg is fertilized it is an embryo, the embryo is then held within a little chamber within the gills called a marsupium; those embryos develop and then release Glochidia which attach to a fish gills by clamping down onto the finger-like gill extensions, suck nutrients out of the blood of the fish; Eventually leave the fish and grow till the become a full sized adult) Glochidia  Cannot swim or crawl  Attach to host fish gills  Sometimes release a few million of these glochidia  As few as 10 out of a million can attach to a fish gill Strategies for Infection  Using Lures to attract the fish (modified mantle tissue that mimics fish or invertebrate prey to attract fish host)  Conglutinate : a membranous sac that is released by the mussel, attached by a thread that is filled with glochidia  Host capture: Mussel may physically grip host and pump glochidia over the gills (snuffbox mussel) Veliger Larvae  Trocophore (stage at which larvae are released into the water column)  Veliger larvae that can move in the water and are carried a long distance away and do not require a host to complete their life cycle  Go under metamorphosis after the Pediveliger stage to form a juvenile  Starts are Embryo, embryo becomes veliger larvae, undergoes some transformations and undergoes complete tissue and structure metamorphosis into a juvenile settled larvae until it grows into an adult (think of a tadpole -> Frog; lungs develop, loses fins and gills, gains limbs) Biological Variation A secondary source of genetic variation is Recombination Gene Flow: Movement of genes among populations that brings variation into a population Genetic Drift: Evolution By chance due to a random event . Random changes in allele frequencies due to chance.  Can cause the population bottle neck, when a population is severely reduced in size. Loss of individuals not related to particular traits (happens at random) usually because of a catastrophe of some sort.  Founder effect is the loss of genetic variation that occurs when a new smaller population is established. Natural Selection  Variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved  From the principle of inheritance they tend to produce offspring similarly characterized this principle of preservation is called Natural Selection  If useful allele appears it is passed on and with time allele frequency for this allele increases.  Heritability and Overproduction are key components of natural selection as well as variation in alleles Mutations  Mutations are random  Good, bad and neutral mutations happen with equal probability  Beneficial mutations increase in frequency and deleterious once decrease in frequency under natural selection (Change in proportion of mutations is non-random under natural selection) Mussel Anatomy  Surface area of gills is high, these Mussels have to extract oxygen from the water  Water is drawn in through the inhalant siphon and passes over the gills and then water is expelled from exhalent siphon  All molluscs have mantle but within the phylum there is great disparity  Mantle: Folding of the body wall that lines shell and secrets shell substance (CaCO3) and houses gills Note: Adaptation is the evolutionary change over thousands of generations, enhances survival and reproduction through natural selection  Co-option of a functional tissue into a new and additional function. (I.E: Mantle -> Complex lure)  Extirpated: Disappeared from a region, but not extinct yet Extinction  Failure to adapt to a changing physical environment or find a new suitable habitat (Not enough variation? No gene flow?)  Failure to keep up with the evolution of a competitor, predator, host pathogen, etc.  Being driven to extinction by a newly encountered competitor, pathogen, or predator  Losing an essential host , prey, or partner species HOW DO THESE RELATE TO MUSSELS? What matters most for speciation is that there is a barrier to gene flow, which allows one species to split into two. What kind of Barriers?  New Rivers, mountain building, continental drift, reproductive biological barrier, behavior  Allopatric speciation (different place) : Species is split due to a geographic barrier or because some individuals move to a separate place. Through natural selection have evolved and changed, the animals that are moved away can no longer breed together and are not compatible. When viable offspring cannot be created, they are now different species.  Sympatric speciation (same place): Species is split by reproductive separation without any geographic barriers. For example Maggots were only laid on hawthorns, 200 years ago immigration brought in apple trees, now the maggots are laying eggs on apple and hawthorn trees 2 populations begin to differentiate a lot because of the different locations that the maggots are born on. Maggots born on apple trees only like apples, maggots born on hawthorns prefer laying eggs on hawthorns. Hypothesis Definition  Hypothesis: A proposed explanation for a fairly narrow set of phenomena, usually based on prior experience, scientific background knowledge, prelimina
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