Molecules

• Hydrogen bonds


  Weak bonds formed between a hydrogen atom covalently bonded to an electronegative atom (oxygen/nitrogen) and another electronegative atom
• Polar covalent bonds


  Chemical bond where two atoms share a pair of electrons unequally
• Cohesion


  Water to water H bonds - molecules stick to each other (attracted)
• Adhesion


  Water to other polar molecules bonds
• Surface tension


  Elastic-like force existing at the surface of a liquid due to the cohesive forces between the molecules at the surface
• Xylem


  Thin narrow tubes which transport water (and dissolved materials) from roots to the leaves of plants
• Solvent


  Substance that dissolves in a solute, resulting in a solution
• Metabolism


  All chemical reactions that occur within an organism to maintain life
• Capillary action


  Ability of a liquid to flow in narrow spaces without the help of external forces (gravity)
• Hydrophobic (non-polar)


  Repels water/do not mix well with water
• Hydrophilic (polar)


  Attracted to water and can dissolve/mix well with water
• Buoyancy


  The ability of an object to float in water
• Viscosity


  Resistance for a fluid to flow
• Thermal conductivity


  Ability of a substance to conduct heat
• Apoplast pathway


  Route through the cell walls and intercellular spaces of plants through which water and dissolved substances can travel - movement of water and solutes from cell to cell without crossing any cell membranes
• specific heat capacity:

  amount of energy that a given mass of substance (1g or 1kg) can absorb that produces a 1C increase in temperature.
• Specific heat capacity


  A measure of the energy required to raise the temperature of 1 kg of a substance by 1C
• Water has a higher specific heat capacity (4200 J/kg/C) compared to air (1000 J/kg/°C)
• Reason for high specific heat capacity of water

  Many hydrogen bonds present in water
• It takes a lot of thermal energy to break these bonds and a lot of energy to build them, thus the temperature of water does not fluctuate greatly
• Advantage of high specific heat capacity for living organisms


  • Provides suitable, stable aquatic habitats since water temperatures will change more slowly than air temperatures
  • Able to maintain a constant temperature as water is able to absorb a lot of heat without wide temperature fluctuations
  • Vital in maintaining temperatures that are optimal for enzyme activity
• Artic and sub-artic species

  • Ringed seal (Pusa hispida)
• The density of ice is lower than the density of liquid water, which means that ice floats on water
• This forms a habitat for the seals both on the floating ice sheets, as well as below the ice
• Thermal conductivity


  The ability of a substance to conduct heat
• The thermal conductivity of water is almost 30 times higher than that of air, which makes air a very good insulator for organisms living in colder climates
• Black-throated loon (Gavia arctica)

  • Their feathers trap an insulating layer of air, which assists them with regulating their body temperature
• Ringed seal


  • Relies on a layer of fat called blubber to insulate it from the outside air
• Ice in its environment will also form an insulating layer above the water, since the thermal conductivity of ice is much lower than liquid water
• This increases the sea temperature below the ice as thermal energy is trapped
• Buoyancy


  The ability of an object to float in water
• To overcome the problem of buoyancy, the black-throated loon has solid bones, unlike the hollow bones that most bird species have to assist them with flight
• This increases the weight of the bird and compresses air out of the lungs and feathers during a dive - air sacs
• For the ringed seal, the layer of blubber under its skin will improve the buoyancy of the animal, along with providing a layer of insulation against the cold temperatures of its habitat
• Viscosity


  The resistance of a fluid to flow
• The viscosity of water is much higher than air, which enables the black-throated loon to fly through the air without much friction
• The body shapes of both the loon and seal makes it easy for them to move through water
• Adaptations for movement through water


  • Seal has flippers to propel itself
  • Loon uses its webbed feet to push against the water and the lateral location of its feet reduces drag as it moves through water