Biol 1070 Exam Review 2012.docx

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8 Apr 2012
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Biol 1070 Exam Review 2012
Factors affecting mussels:
- Invasive zebra mussels
- Changes to rivers: drainage and irrigation practices causing erosion of riverbanks and build-up of
sediments in rivers, damns and channels affecting water flow effecting also local freshwater
biodiversity
- Pollution: run off of pesticides, fertilizers, industrial pollutants, pharmaceuticals?
- Over-exploitation of mussels for pearls or shells- buttons and fish hosts
- Changes in water temperature: climate change unknown impact
- Changes in predation on mussels or host fish
Unionidae
Dreissenidae
Two siphons, bivalve shell
Two siphons, bivalve shell
Obligate parasitic larval stage
Free-living, planktonic larvae
Dioecious (separate male and female)
Dioecious
Internal fertilization
External fertilization
Burron in sand
Attach to any solid substrate
Unionid life cycle:
Larvae: glochidia- can’t swim or crawl- attach to host fish
gills; ovisacs- glochidia enclosed in membranous capsules
that mimic host prey for infecting fish hosts;
conglutinates- packets of glochidia- eaten by host or stick
to host; mussel physically grips host and pumps glochidia
into gills
Simple lures- modified mantle tissue mimics fish or
invertebrate prey to catch fish attention to attract host
Zebra mussel lifecycle:
Veliger larvae: released into water- doesn’t
need fish host, settles on to any solid surface.
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Genetic variation- differences at the DNA level among individuals within a population or species, can
change within populations in by: mutation, natural selection, genetic drift, gene flow
Alleles- different version of the same gene
Mutation- primary source of genetic variation, errors in DNA replication- occur randomly, DON’T
occur in order to benefit organism, good, bad, neutral mutations equally likely, beneficial mutations
occur with increasing frequency and deleterious mutations decrease frequency under natural selection
(change proportion of mutations is non-random under natural selection), whether mutation is beneficial
or harmful depends on environment
Kinds of mutation:
Natural selection- NON-RANDOM differences in survival and/or reproduction among individual
entities on the basis of differences in heritable characteristics
Genetic drift- evolution by chance due to sampling error, random changes in allele frequencies in a
population due to chance
Causes: population bottlenecks- sudden severe
reduction in population size- loss not related to
individuals particular traits (random).
Founder effect- movement to an isolated area
Gene flow- movement of genes among populations,
sharing of alleles among populations
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Evolutionary trees:
Can’t read across tips (terminal nodes)!
topology (pattern of branching) is what matters
Just because only one representative of lineage
is pictured doesn’t mean there has been no
other branching in the lineage
Lineages of all living (extant) species have
been evolving for exactly the same time bc all
go back to shared ancestor
Homology- inherited from a common ancestor
Homoplasy- convergence, evolved independently
Extinction- failure to adapt to changing physical environment or to find new suitable habitat (not
enough variation, no gene flow), failure to keep up with evolution of competitor, predator, host,
pathogen,; being driven to extinction by newly encountered competitor, pathogen, predator; losing an
essential host, prey, or partner species
Cause and Effect: opening niches following Triassic-Jurassic extinction event allowed dinos to
overcome dominant terrestrial vertebrates; K-T extinction allowed niches for mammals by eliminating
dinos
Speciation- formation of new species, involves splitting or branching into 2 descendants species aka
cladogenesis; there is a barrier to gene flow allowing species to split in 2:
Allopatric speciation- species split due to geographic barrier or because some individuals move to
separate place
Sympatric speciation- species split by reproductive separation without geographic barrier
Populations evolve when allele frequencies change from one generation to another, evolution involves
change in proportion of variants in a population therefore can only occur if variation in population
Indented key uses indents and numbers
Ecosystem- system formed by interaction of community of organisms
with their physical environment, can be large or small
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