A3 - The Role of Water in Matter Cycles (Updated 2024) PDF

A3 - The Role of Water in Matter Cycles I can… Explain water’s primary role in biogeochemical, considering its chemical and physical properties (i.e. universal and hydrogen bonding) Explain the interrelationship of energy and matter in maintaining homeostasis, and how human activ...

A3 - The Role of Water in Matter Cycles I can… Explain water’s primary role in biogeochemical, considering its chemical and physical properties (i.e. universal and hydrogen bonding) Explain the interrelationship of energy and matter in maintaining homeostasis, and how human activity impacts this balance in different ecosystems Water in the Biosphere Earth is a closed system ○ Limited amount of water in biosphere Water from surface water sources may have come from snow and ice, oceans, or may have been a product of cellular respiration ○ Metabolic water: Water produced during cellular respiration Water in the Biosphere Biogeochemical cycle: Routes that water and other chemical nutrients take through the biotic (living) and abiotic (non-living) components of the biosphere The Hydrologic Cycle 1. Liquid water in lakes/ponds/oceans is turned into a gas through evaporation (or transpiration from the leaves of plants) 2. Water vapour in the atmosphere condenses in clouds 3. Liquid water returns to the ground through precipitation 4. Water re-enters lakes/ponds/oceans through run-off The Hydrologic Cycle The hydrologic cycle is linked to all other cycles of matter ○ Any change in the hydrologic cycle will affect other cycles of matter It is the cycling of water that connects ecosystems across the globe Involves all phases of water (solid, liquid, gas) ○ 97% of water in the biosphere exists as liquid (due to water’s high boiling point) The Hydrologic Cycle Water in our atmosphere acts as a greenhouse gas, trapping heat Transfer of heat throughout our biosphere is also due to water’s ability to absorb large amounts of heat energy ○ Distributes heat energy from equator (wind/ocean currents) Water is the Universal Solvent Water molecules are polar (one end is slightly negative, the other is slightly positive) ○ Can result in an attraction called a hydrogen bond Is a universal solvent - can dissolve many chemicals and transport a wide variety of substances The process of transporting dissolved materials is referred to as biogeochemical cycling Hydrogen Bonding Hydrogen bonds and forces of repulsion between oxygen atoms contributes to open spaces seen in the crystal structure of ice ○ Due to crystal formation of ice, its density is less than that if liquid water ○ Causes solid water (ice) to float Result: Lakes freeze from the top → down Prevents most lakes and ponds from freezing completely solid ○ Contributes to cycling of oxygen gas and nutrients during spring and fall in bodies of water Crystal structure of ice. ○ Provides refuge for aquatic life during winter months Water Stores Heat Hydrogen bonding allows water to remain in a liquid state across a large temperature range ○ This explains why water can continue to dissolve and transport substances over a variety of climates Water has a high heat capacity (lots of energy is needed to make water change state) ○ As a result, water has a high boiling point (100°C) and low melting point (0°C) Water Stores Heat Water stores huge amounts of heat energy Large bodies of H2O will moderate the temperature of surrounding environments due to high specific heat capacity At the level of an individual organism, high specific heat capacity of water prevents body temperature from changing too quickly - moderates body temperature Density When water cools, hydrogen bonds loosen, causing cold or frozen water to have a lower density When water heats up, these bonds tighten, causing warm water to have a higher density Cohesion Because water molecules are polar, they are attracted to each another This causes cohesion, which is responsible for surface tension Adhesion Water molecules are also attracted to molecules of other substances, such as the inner surface of a glass tube or the cell wall of a tree’s xylem Adhesion produces an upward force on water that counteracts the pull of gravity Adhesion vs Cohesion Adhesion: Water sticking to other things Cohesion: Water molecules stick to each other Water and Organisms The human body is composed of 70% water Organisms gain water from the environment through: ○ Eating ○ Drinking ○ Absorption ○ Cellular respiration Organisms lose water through: ○ Breathing ○ Sweating ○ Waste Water and Organisms Metabolic activities require the constant balance of water consumption, retention, and loss Access to clean freshwater is thus essential for the success of many living things Water and the Greenhouse Effect When water is scarce due to drought or extreme heat, plants respond by closing their stomata, which reduces transpiration (this strategy is often utilized by desert plants, such as cacti) Closed stomata mean that plants cannot take in carbon dioxide, slowing the rate of photosynthesis Droughts in areas can be devastating to ecosystems If global temperature rises, droughts will become more common in Alberta, this can affect our economy (farming) Water and the Greenhouse Effect