Biology · Unity and diversity
A1.1 — Water
Biology · SL / HL · syllabus-mapped notes
A1.1.1
Water as the medium for life
State that life began in water and that most processes of life still occur in water.
A1.1.2
Hydrogen bonds as a consequence of the polar covalent bonds within water molecules
Explain how unequal sharing of electrons makes water polar, and how that polarity produces hydrogen bonds between water molecules. Represent them with the correct notation.
A1.1.3
Cohesion of water molecules due to hydrogen bonding and consequences for organisms
Explain how cohesion lets water be pulled up xylem under tension, and how surface tension makes the water surface a habitat.
A1.1.4
Adhesion of water to materials that are polar or charged and impacts for organisms
Explain how adhesion causes capillary action, in soil and in plant cell walls.
A1.1.5
Solvent properties of water linked to its role as a medium for metabolism and for transport in plants and animals
Explain how water's solvent properties make it the medium for metabolism and for transport in plants and animals, including why some molecules must be insoluble.
A1.1.6
Physical properties of water and the consequences for animals in aquatic habitats
Contrast, using examples, how the physical properties of water and air have consequences for animals living in each.
A1.1.7
Extraplanetary origin of water on Earth and reasons for its retention
Explain how water reached Earth from asteroids, and why it has been retained since.
A1.1.8
Relationship between the search for extraterrestrial life and the presence of water
Explain why the search for extraterrestrial life is a search for liquid water, including the Goldilocks zone.