Biology by Bradford
A1.1.2A polar molecule
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Oxygen pulls the shared electrons harder than hydrogen, so the oxygen end carries a partial charge and the hydrogen ends a partial charge. The attraction between them, from one molecule to the next, is a .
A1.1 Water: revision map
The subtopic in the middle and eight tasks round it: label a diagram, complete a table and fill 34 gaps. Every standard level statement has a box; the one box for higher level only is dashed and badged HL, and drops off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Water
Molecules · Unity and diversityHover over a box to see it. Untick it to leave it off this sheet and its printout.
NameA1.1.4Adhesion
Water is attracted to materials that are polar or , such as cellulose: this is . It draws water along narrow spaces by , keeping the cell walls of a leaf wet and moving water through soil.
A1.1.7, A1.1.8Water from spaceHL
Much of Earth's water probably arrived from colliding with the young planet. Earth kept it because its holds an atmosphere and its distance from the Sun keeps water . The search for life on other planets looks first at planets in a star's .
A1.1.1Where life began
The first cells probably arose in . Water is still the medium in which most processes of life happen: a living cell is mostly water, and most of its chemical reactions take place between particles in it.
A1.1.3Cohesion
Hydrogen bonds hold water molecules to one another: this is . It lets water be pulled up vessels as an unbroken column under tension, and gives water a that a pond skater can stand on.
A1.1Water
A1.1.6Water against air
| Property | Water, compared with air | What it means for an aquatic animal |
|---|---|---|
| Buoyancy | Water holds a body up, so less is needed to support it | |
| Viscosity | More drag: a streamlined shape saves energy | |
| Thermal conductivity | Heat leaves the body : insulation such as blubber | |
| Specific heat capacity | Water temperature changes , so habitats stay stable |
A1.1.5The solvent of life
Round a Na⁺ ion, water molecules turn their ends inwards; round a Cl⁻ ion, their ends. Substances that dissolve in water are ; non-polar ones, such as lipids, are . So the cytoplasm is the medium for , and blood plasma and carry dissolved substances round the organism.
A1.1.6Densest at 4 °C
Liquid water is densest at °C. Ice is dense than liquid water, so it floats and the water beneath, which stays liquid for the animals living in it.
Word bank 4adhesionasteroidscapillary actionchargedcohesioncovalent bonddissolvedfastergravityhabitable zonehigherhydrogenhydrogen bondhydrophilichydrophobicinsulateslessliquidmetabolismnegativeoxygenpositiveslowlysurface tensionwaterxylem
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
GapsWhere life began
The first cells probably arose in water. Water is still the medium in which most processes of life happen: a living cell is mostly water, and most of its chemical reactions take place between particles dissolved in it.
LabelA polar molecule
- oxygen
- hydrogen
- covalent bond
- hydrogen bond
Oxygen pulls the shared electrons harder than hydrogen, so the oxygen end carries a partial negative charge and the hydrogen ends a partial positive charge. The attraction between them, from one molecule to the next, is a hydrogen bond.
GapsCohesion
Hydrogen bonds hold water molecules to one another: this is cohesion. It lets water be pulled up xylem vessels as an unbroken column under tension, and gives water a surface tension that a pond skater can stand on.
GapsAdhesion
Water is attracted to materials that are polar or charged, such as cellulose: this is adhesion. It draws water along narrow spaces by capillary action, keeping the cell walls of a leaf wet and moving water through soil.
GapsThe solvent of life
Round a Na⁺ ion, water molecules turn their oxygen ends inwards; round a Cl⁻ ion, their hydrogen ends. Substances that dissolve in water are hydrophilic; non-polar ones, such as lipids, are hydrophobic. So the cytoplasm is the medium for metabolism, and blood plasma and xylem carry dissolved substances round the organism.
TableWater against air
Property Water, compared with air What it means for an aquatic animal Buoyancy higher Water holds a body up, so less is needed to support it Viscosity higher More drag: a streamlined shape saves energy Thermal conductivity higher Heat leaves the body faster: insulation such as blubber Specific heat capacity higher Water temperature changes slowly, so habitats stay stable GapsDensest at 4 °C
Liquid water is densest at 4 °C. Ice is less dense than liquid water, so it floats and insulates the water beneath, which stays liquid for the animals living in it.
GapsWater from space HL
Much of Earth's water probably arrived from asteroids colliding with the young planet. Earth kept it because its gravity holds an atmosphere and its distance from the Sun keeps water liquid. The search for life on other planets looks first at planets in a star's habitable zone.