A1.1:  Water

Theme:  Unity and Diversity

Unity:
Water's consistent molecular structure and resulting properties (polarity, hydrogen bonding, solvency) unify all life by providing the essential medium for biochemistry.

Diversity:
The varying interactions of organisms with water in different environments has driven an incredible diversity of biological adaptations, structures, and functions.

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• What physical and chemical properties of water make it essential for life?
• What are the challenges and opportunities of water as a habitat?

Linking Questions: 
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• How do the various intermolecular forces of attraction affect biological systems?
• What biological processes only happen at or near surfaces?
• ​What are the implications of solubility differences between chemical substances for living organisms?

Key Terms to Know: * higher level only

Adhesion
Anion
Asteroid
Atom
Buoyancy
Capillary Action
Cation
Cohesion
Condensation
Covalent Bond
Electron
Enzyme

Extraplanetary*
Extraterrestrial*
Goldilocks Zone*
Hydrogen Bond
Hydrophilic
Hydrophobic
Insoluble
Ion
Ionic Bond
Neutron
Non-Polar Covalent Bond
Physical Property

Polar Covalent Bond
Proton
Soluble
Solvation
Specific Heat Capacity
Surface Tension
Thermal Conductivity
Viscosity
Water
Xylem

​

A1.1.1 - Water as medium of life.

• State that the first cells originated in water. 
• ​List reasons why water is a substance on which life depends​

A1.1.2— Hydrogen bonds as a consequence of the polar covalent bonds within water molecules.

• Describe the structure of an atom.
• Outline the formation of ionic and covalent bonds between atoms.
• Explain the sharing of electrons between atoms in a polar covalent bond.
• State the location of the polar covalent bond within a water molecule.
• Explain the partial charges of the oxygen and hydrogen atoms within a water molecule.
• Draw a water molecule, including notation to depict the partial charges of the atoms. 
• Outline the cause of the formation of hydrogen bonds between water molecules.
• Outline the consequences of the collective strength of hydrogen bonds between water molecules.​

A1.1.3— Cohesion of water molecules due to hydrogen bonding and consequences for organisms.

• Define cohesion.
• Describe how water moves through the xylem of a vascular plant.
• Outline the cause of surface tension. 
• State a benefit to living things that results from surface tension.

A1.1.4— Adhesion of water to materials that are polar or charged and impacts for organisms.

• Define adhesion.
• Define polar.
• Define ion.
• Compare cation and anion.
• Explain why water is attracted to molecules that are polar or charged. 
• Outline the cause of capillary action.
• Describe capillary action in plant tissue.
• Outline the cause and effect of capillary action in soil.

 A1.1.5— Solvent properties of water linked to its role as a medium for metabolism and for transport in plants and animals.

• Identify solvent and solutes of a solution.
• Define solvation.
• Explain why water is able to dissolve charged and polar molecules.
• Outline the solvation of hydrophilic and hydrophobic substances.
• State an example of a molecule with a function that depends on it being hydrophobic and insoluble. 
• State an example of a molecule with a function that depends on it being hydrophilic and soluble. 
• Outline the role of water as a medium for metabolism.
• Describe the role of water as a medium for transport in vascular plants.
• Describe the role of water as a medium for transport in animal blood.

A1.1.6— Physical properties of water and the consequences for animals in aquatic habitats.

• Define physical property.
• List physical properties of water that are consequential for animals in aquatic habitats. 
• Outline the cause and effect of buoyancy. 
• Outline the cause and effect of viscosity. 
• Compare viscosity of air to water to blood. 
• Define thermal conductivity.
• ​Outline a consequence to life of the thermal conductivity of air and water.
• Define specific heat capacity.
• Compare less conductive to more conductive materials.
  
• Describe why water has a high specific heat capacity.
• State two benefits to life of the high specific heat capacity of water. 
• Outline a benefit to life of water's high specific heat capacity.
• Compare the physical properties of water to those of air.
• Describe how the  black-throated loon (Gavia arctica) and/or the ringed seal (Pusa hispida) interact with the physical properties of water in their habitat.

AHL  A1.1.7— Extraplanetary origin of water on Earth and reasons for its retention.

• Explain  the hypothesis that asteroids are responsible for the origin of water on Earth.
• State two reasons why water was retained on early Earth.​

AHL  A1.1.8— Relationship between the search for extraterrestrial life and the presence of water.

• Explain why the presence of water is considered fundamental to the search for extraterrestrial life.
• Define “Goldilocks zone” in relation to the search for extraterrestrial life.