Chapter 2: Cycles of Matter

Why is water essential to humans and ecosystems?

Water plays a central role in nutrient cycles and is a universal solvent.

What property of water allows it to dissolve more substances than other liquids?

Water is a polar solvent.

What are hydrogen bonds and why are they important?

Special bonds between water molecules due to polarity, requiring a lot of energy to break, influencing water's properties.

How does hydrogen bonding affect water's state?

It allows water to remain liquid over a large temperature range due to strong intermolecular forces.

How does the density of water change when it freezes, and why is this significant for aquatic life?

Ice is less dense than liquid water, so it floats, insulating aquatic ecosystems during winter.

At what temperature is water most dense?

4°C

What is cohesion in water?

The attraction of water molecules to each other due to hydrogen bonding, causing surface tension.

What is adhesion in the context of water molecules?

The attraction of water molecules to molecules of other substances, which provides an upward force against gravity.

Define 'heat capacity' in the context of water.

The amount of heat required to change the temperature of a given amount of water by 1°C; water has a high heat capacity.

What are the four key properties of water discussed in the lecture?

Universal solvent, high boiling and melting point, cohesion and adhesion, and high heat capacity.

What are biogeochemical cycles?

The routes that chemicals take through the biosphere, involving biotic and abiotic materials.

What phases of water are involved in the Hydrologic Cycle?

Solid, liquid, and gas.

Define nutrient reservoirs in the context of biogeochemical cycles.

Temporary storage locations for substances cycling through an ecosystem (e.g., organisms, soil, water, air).

What is slow cycling of nutrients?

Long-term storage of nutrients in reservoirs, making them unavailable for extended periods (e.g., fossil fuel deposits).

Define rapid cycling of nutrients.

Quick movement of nutrients through reservoirs, easily moving between abiotic and biotic components.

What is productivity in an ecosystem?

The rate at which an ecosystem captures and stores energy in organic compounds, often measured in energy or biomass per area per year.

Name three factors that affect ecosystem productivity.

Available light, water, and nutrients, as well as the number of producers in the area.

What is homeostasis in the context of the biosphere?

Maintenance of nutrient levels and temperature within certain limits on a global scale.

What is the Gaia Hypothesis?

The theory that the biosphere acts like an organism that regulates itself, maintaining environmental conditions within certain limits.

What evidence is used to understand Earth's changing atmospheric conditions?

Deposits of ancient microorganisms, such as stromatolites, which contain bands of iron oxide.

What do stromatolites containing black iron oxide indicate about Earth's early atmosphere?

Evidence that oceanic oxygen levels were rising due to photosynthetic bacteria.

What is the role of plants in the rapid cycling of the carbon cycle?

Plants consume CO2 from the atmosphere through photosynthesis.

What happens when organic matter burns in the carbon cycle?

Burning organic matter releases large amounts of carbon dioxide back into the atmosphere.

How do limestone rocks contribute to the carbon cycle?

Weathering of limestone rocks returns carbon back into the water.

Where is the largest reservoir of carbon located?

The Earth's core.

What is the relationship between the carbon and oxygen cycles?

They are closely tied, involving many of the same processes, but the gas flows in opposite directions.

How is oxygen generated and consumed?

Oxygen is generated in photosynthesis and consumed by cellular respiration and combustion.

Where is most of the Earth's oxygen located?

Locked in the Earth's crust, bonded to other minerals.

What percentage of the Earth's atmosphere is made up of nitrogen gas?

About 78%.

Why can't organisms directly use diatomic nitrogen?

Plants can only take in nitrogen in the form of nitrites (NO2-) or nitrates (NO3-).

What is nitrogen fixation?

The conversion of N2 gas into ammonia (NH3).

What is nitrification?

The process where ammonia is converted into nitrite (NO2-) and eventually nitrate (NO3-).

How do plants obtain nitrogen?

Through assimilation, taking up nitrates (NO3-) in the soil.

What is ammonification?

Decomposers returning nitrogen back to the soil.

What is denitrification?

Denitrifying bacteria converting nitrate back into N2 gas.

What role does phosphorus play in living organisms?

It is used in our bones, teeth, DNA, and energy-carrying molecules (ATP).

In what form can plants use phosphorus?

Phosphate (PO4 3-).

How does fertilizer runoff impact aquatic ecosystems?

Excess nitrogen and phosphorus cause algae blooms, which deplete oxygen and lead to the death of other organisms.

How does deforestation impact the carbon and oxygen cycles?

Forests are an important carbon sink and oxygen producer; deforestation reduces these functions and increases erosion.

How does burning fossil fuels impact the environment?

Releases carbon dioxide, which Pollutes the air and can create acid rain which disrupts pH of ecosystems.