September 14 2011
What is biodiversity?
- Biodiversity is the variety of genes, species and ecosystems.
- Shaped by billions of years of evolutionary history of life forms interactions with each other and their
- Altered by human activity with lasting impacts at large scales that are difficult to predict.
What is evolution?
- Descent with modification from common ancestors. Can only occur if there is variation.
- Evolution evolves in change of proportions of variants in population.
What factors contribute to threats to native freshwater mussel biodiversity?
- Habitat destruction
- Human impacts / Overfishing
- Agriculture runoff
- Chemicals in water
- Invasive species
- Water temperature fluctuations
List of characteristics of Unionids & Dreissenids
What is the larval form? Glochidia Veligers
Does it need a host? Host-dependant Not host-dependant.
Can attach to any solid surface.
What type of larval dispersal? Larvae dispersed by host Dispersed in water
Freshwater bivalves develop in 3 ways
1. By producing veligers larvae (Dreissena Polymorphall)
2. By releasing ully developed young mussels (rare)
3. By passing early development as a parasitic stage on a host (Unionids)
Glochidia – Can’t swim or crawl – Attach to host fish grills
Strategies for infecting fish hosts
1. Conglutinates – Glochidia enclosed in membranous capsules that mimic host prey.
2. Lures – Modified mantle tissue, mimics fish or invertebrate prey item to attract fish host.
- Mussel may physically grip host and pump glochidia over the gills. September 19 2011
- Variation occurs in all species
- A well sampled population = A normal distribution
What causes the variation?
- Genotypic variation
- Phenotypic variation
Agent Definition Effect on Genetic Variation
Mutation A heritable change in DNA Introduces new genetic flow
Gene Flow Change in allele frequencies May introduce genetic variation from another
as individuals join a population
population and reproduce
Genetic Drift Random changes in allele Reduces genetic variation, especially in small
frequencies caused by chance populations; can eliminate alleles
Natural Selection Differential survivorship or One allele can replace another or allelic variation
reproduction of individuals can be preserved
with different genotypes
What is a gene?
- A molecular unit of heredity in a living organism.
- It is made up of stretches of DNA and RNA that may code for a type of protei