water A1.1

content from water topic A1.1

water as the medium for life

• first cells originated in water

• remains medium in which most processes of life occur

why are there hydrogen bonds?

consequence of the polar covalent bonds within water

why covalent bonds in water

unequal sharing of electrons

why is there unequal sharing of electrons

oxygen has more electronegativity than hydrogen so electrons sit closer to oxygen

charges in water molecule

• hydrogen partial positive

• oxygen partial negative

cohesion

water molecules stick to other water molecules

why/how cohesion occurs

• hydrogen bonds

• usually weak but because of so many they because strong

consequences for organisms due to cohesion

• transport of water in xylem

• water surfaces as habitats due to effect known as surface tension

adhesion

water molecules stick to other surfaces that are polar or charged

impact of adhesion on organisms

capillary action in soil and plant cell walls

structure of water

H2O

solvent

water can dissolve many organic and inorganic substances that have charged or polar regions

hydrophilic

• water loving

• substances that dissolve in water and water adheres to

• polar substances

hydrophobic

• water fearing

• non polar

• lipids

buoyancy

the upward force exerted by a fluid in the opposite direction of the weight of the object. density lower than liquid it will float, if density is higher it will sink

viscosity

• how resistant a fluid is to deformation

• how think a liquid is

thermal conductivity

• how readily a fluid conducts heat

• heat conducts fast in high thermal and slow in low thermal conductivity

specific heat capacity

• how much energy is required to raise one unit of mass by one unit of temperature

• greater capacity greater energy needed to raise temp

ring tailed seal adaptions

Blubber:

• More buoyant

• Doesn't compress under pressure

• Low thermal conductivity reduces heat loss

• Heavy

• Harder to move on land

Streamlined body shape:

• Reduce drag in water (viscosity)

• Feet at rear of body - reduces drag

• Webbing between feet - more surface area to push through water

• Shape and location of feet make it harder to move on land

black throated loon adaptations

BOUYANCY:

Thicker bones (most birds have hollow bones):

• Reduce buoyancy, allows them to dive deep enough to hunt prey

• Larger air sacks to control buoyancy, inflate or deflate to increase or decrease buoyancy 

• Heavier body

• More difficult to achieve and maintain height

• Require large body of water to launch from

VISCOSITY:

Large webbed feet:

• Propel in water

• Much smaller than wings to fly

Streamlined shape:

• Reduce drag in water (more viscos than air)

• Legs and feet at rear, reduces drag

• Secrete a hydrophobic oil on their feathers, further reduces drag

Short wings for body shape:

• Reduce drag in water

• Harder to achieve flight

THERMAL CONDUCTIVITY 

Thick layer of down feathers close to their body

• Trap air to keep body warm in cold water, creates barrier of air

Down feathers are covered by harder, tightly packed contour feathers

• Forms impermeable seal against water

Preening gland on its rump which excludes oil

• Preens contour feathers with this oily (hydrophobic) secretion, increasing their waterproofing