Unit 11 Test
The arctic of the past
There once were lush forests and a variety of terrestrial and aquatic habitats that today
are found only at much lower latitudes.
Churchill, Manitoba and Resolute, Nunavut are home to enormous numbers of fossil
Puijila darwini, an extinct mammal that is thought to be a transitional form in the
evolution of modern seals.
Arctic in the present
Osmosis is the passive movement of water across a membrane from a solution of low
solute concentration to a solution of high solute concentration.
The terms “hypertonic”, “isotonic”, and “hypotonic”describe the effect that solutions have
When tissues are exposed to temperatures below freezing, ice crystals form in the
extracellular fluid and they reduce the amount of free water outside the cell, which
creates an increase in osmotic pressure.
Osmosis occurs from a solution with lower osmotic pressure to one with higher osmotic
Freeze tolerant insects start producing ice nucleating agents in the autumn to initiate
freezing outside of the cells in the extracellular fluids. If the fluid inside the cells or
intracellular fluid (cytosol) freezes, then sharp ice crystals may puncture the delicate
Freeze tolerant insects produce glycerol and/or sugars to decrease the freezing point of
the cytosol to protect their cells.
Freeze tolerant animals may also synthesize antifreeze proteins which slow down or
inhibit ice crystal formation in specific tissues or cells.
In frozen wood frogs, ice forms throughout the body, in between cells and in body
cavities so that 65% of total body wate