In what medium are the first cells believed to have evolved?
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In what medium are the first cells believed to have evolved?
The first cells are believed to have evolved in a watery environment, specifically in the deep oceans close to hydrothermal vents in the earth's crust.
Why is liquid water important for life processes?
Liquid water allows dissolved molecules to move around, enabling them to easily collide and react with each other; this is crucial for most life processes.
What is hydrogen bonding?
Hydrogen bonds are weak electrostatic attractive forces between a slightly positive hydrogen atom of one molecule and a slightly negative atom (usually oxygen or nitrogen) of another molecule.
True or False?
Water is a non-polar molecule.
False.
Water is a polar molecule due to the uneven sharing of electrons between oxygen and hydrogen atoms.
Which area of a water molecule is δ- and which area is δ+?
In a water molecule the oxygen atom is δ- and the hydrogen atoms are δ+.
How does the polarity of water molecules lead to hydrogen bonding?
The polarity of water molecules leads to hydrogen bonding because the slightly positive hydrogen atoms of one water molecule are attracted to the slightly negative oxygen atoms of adjacent water molecules.
True or False?
Hydrogen bonds between water molecules are strong bonds.
False.
Hydrogen bonds are weak, so they are constantly breaking and reforming.
Define the term cohesion in relation to water molecules.
Cohesion is the strong attraction between water molecules that is present due to hydrogen bonding.
Why is cohesion important for living organisms?
Cohesion is important for living organisms because it allows, e.g.:
transport of water under tension in xylem vessels
the use of water surfaces as habitats due to surface tension
What is adhesion in the context of water?
Adhesion is when water molecules forms hydrogen bonds with other polar or charged molecules.
What is an example of adhesion in living organisms?
An example of adhesion in living organisms is the capillary action that allows water movement in:
xylem
soil
plant cell walls.
True or False?
Non-polar molecules can form hydrogen bonds with water molecules.
False.
Non-polar molecules, with no positive or negative charge, cannot form hydrogen bonds with water.
Why is water considered a universal solvent?
Water is considered a universal solvent because most biological molecules are hydrophilic and can be dissolved in it; this is due to water's polarity.
Define the term specific heat capacity.
Specific heat capacity is a measure of the energy required to raise the temperature of 1 kg of a substance by 1 °C.
The specific heat capacity of water is 4200 J/kg/°C.
How does water's high specific heat capacity benefit living organisms?
Water's high specific heat capacity means that it can absorb a lot of heat energy without wide temperature fluctuations. This means that it can provide temperature-stable aquatic habitats where it is easy for organisms to maintain the optimum temperature for enzyme activity.
Define the term thermal conductivity.
Thermal conductivity refers to the ability of a substance to conduct heat.
How does the thermal conductivity of water compare to that of the air?
The thermal conductivity of water is higher than that of air, which makes air a very good insulator for organisms living in colder climates.
What is viscosity, and how does it affect aquatic organisms?
Viscosity is the resistance of a fluid to flow.
Aquatic organisms like seals and loons need body shapes adapted to move efficiently through viscous water.
What are examples of adaptations of animals that live in water and in air?
Examples of adaptations of animals that live in water and in air are:
the ability to regulate buoyancy
streamlined body and webbed feet / flippers
insulation that functions in water and in air