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BIOL 1070 Study Guide - Midterm Guide: Brachiopod, Local Extinction, Mollusca

Course Code
BIOL 1070
Roger Jacobs
Study Guide

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Biology 1070 midterm 01/23/2015
Peer reviewed, at least two anonymous experts in the field who provided critical comments on the reliability
of the research, the interpretation of data, and the overall quality of the paper
once published, a paper can be seen, commented on, or even refuted by anyone in the scientific
Zebra Mussels
Zebra mussels excessive filter feeding activities began altering the particulate matter in the water
Estimated expenses trying to control zebra mussels is billions of dollars
The zebra mussel (Dreissena polymorpha) is native to eastern Eurasia, specifically the Black Sea and
Caspian Sea.
The most likely mode of transport across the Atlantic was in the ballast water of an ocean liner. (Probably
larvae, though some authors suggest that the stowaways were adults attached to ships).
The zebra mussel was first reported in North America in 1988 in Lake St. Clair, in a peer-reviewed paper by
Hebert et al. (1989). (Incidentally, Prof. Hebert is the Director of the Biodiversity Institute of Ontario here at
the University of Guelph).
From Lake St. Clair, the zebra mussel spread rapidly to lakes throughout the surrounding watershed.
This is not the first time the zebra mussel has invaded new environments — it also invaded western Europe
in the late 1700s and early 1800s.
There has since been a second invasion by a related mussel, the quagga mussel (Dreissena
Native Mussels
North America is the most diverse continent, with more than 300 species present. In Ontario
the native mussels are all members of the family Unionidae
within this there are several distantly related subfamilies.
The Photo Field Guide to the Freshwater Mussels of Ontario lists 41 different species in
our province alone.
freshwater mussels are among the most endangered organisms in North America

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Life Cycle
unionids are particularly interesting because of their complex life cycle, which includes a component of
obligate parasitism (i.e., they must parasitize a host at some stage to complete their reproductive cycle).
Most of the species in Ontario are dioecious (“two houses”), meaning that they have separate males and
Males release their sperm into the water through their exhalant siphon, which are then taken up by females
downstream through their inhalant siphon.
Fertilization is internal (i.e., inside the female’s body), and the embryos develop inside modified pouches of
the female’s gills called a marsupium.
The embryos mature into specialized larvae called glochidia (singular glochidium), and it is these that
represent the parasitic life stage.
Specifically, the glochidia must attach to the gills of a fish in order to continue their development.
Adult unionid mussels exhibit a wide variety of adaptations to attracting a host fish
interesting is the modification of the mantle tissue to form a “lure” that resembles a fish or invertebrate prey
that attracts the host.
Key Points from UNIT 1:
Natural selection and adaptation.
Factors that make zebra mussels excellent invaders and native mussels sensitive to disturbances.
Gene flow and the movement of genes among populations
Genetic drift and non-adaptive evolution
Speciation (origin of new species) and extinction (loss of species)
Phylogenetics (evolutionary relationships) and systematics (evolutionary classification)
The role of historical/geological changes (vicariance)
Key Points in Unit 1

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1. The invasive zebra mussel (Dreissena polymorpha) has had an enormous economic, aesthetic, and
biological impact on the Great Lakes watershed. It originated from eastern Eurasia and is thought to have
been transported by an ocean vessel sometime before 1988.
2. Peer-reviewed primary literature is the standard means by which scientists share their research
findings. It is typically a well regulated system where two or more external referees read and critique the
manuscript providing a recommendation to the journal editor to publish or reject the study.
3. There are 41 native freshwater mussels in Ontario, many of them are endangered. Unionids are obligate
parasites where glochidia (larvae) are released and must attach to the gills of a fish host to complete their
4. Native and invasive mussel species are studied by a variety of different people: undergraduates,
graduates, professors and government scientists. These people explore mussel diversity, adaptations,
distribution, phylogenetics and conservation issues.
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