APES Chapter 3

Where do photosynthesis and cellular respiration happen?

photosynthesis - chloroplast

cellular respiration - mitochondria

Inputs → Outputs of photosynthesis and cellular respiration

photosynthesis - sunlight, CO₂, water → glucose and oxygen

cellular respiration - oxygen, glucose → carbon dioxide, H₂O

Who performs photosynthesis? Who performs cellular respiration?

photosynthesis - plants, algae, and some bacteria

cellular respiration - all organism

What is the point of photosynthesis and cellular respiration?

photosynthesis - to make glucose

cellular respiration - to make energy (ATP)

Chemical Equation of Photosynthesis

(sun)+6H₂O+6CO₂→C₆H₁₂O₆+6O₂

Chemical Equation of Cellular Respiration

C₆H₁₂O₆+6O₂→6CO₂+6H₂O

Gross Primary Productivity/GPP

the total amount of solar energy that the producer gets in an ecosystem (through photosynthesis!)

Net Primary Productivity/NPP

energy captured by producers minus the energy producers respire (cellular respiration!)

the 10% rule

the ecological efficiency is usually about 10 percent of the NPP

Hydrologic cycle

the movement of water through the biosphere

1. heat from the sun causes water to evaporate from oceans, lakes, and soils. solar energy also gives plants energy for photosynthesis, causing the plants to release water from their leaves into the atmosphere (transpiration). this combined amount of evaporation and transpiration is called evapotranspiration

2. the water vapor that enters the atmosphere cools and forms clouds, which produce rain, snow, and hail (all precipitation). some precipitation falls back into the ocean and some on land (this causes plant uptake and surface runoff)

humans alter the cycle by harvesting trees, which reduces evapotranspiration by reducing plant biomass.

Carbon Cycle

the movement of carbon around the biosphere

• producers photosynthesize, taking in atmospheric CO₂; they release CO₂ back into the atmosphere after cellular respiration and when organisms die.

• carbon is exchanges between the atmosphere and the ocean; the amount released from the ocean is approximately the amount that diffuses into ocean water

  • some of the CO₂ dissolved in the ocean enters the food web through photosynthesis by algae

  • some of the CO₂ dissolved in the ocean combines with calcium to form calcium carbonate (CaCO₃), which can precipitate out of water and form limestone and dolomite rock via sedementation and burial

• when humans extract fossil fuels, carbon is brought to earth’s surface, where it can be combusted.

humans combusting fossil fuels releases fossilized carbon into the atmosphere, increasing atmospheric carbon concentrations. this upsets the balance between Earth’s carbon pools and the atmosphere. this increases heat energy retention in the biosphere, resulting in global warming

Nitrogen Cycle

the movement of nitrogen around the biosphere

• nitrogen fixation, nitrification, assimilation, mineralization, and denitrification

Nitrogen Fixation

converts N₂ from the atmosphere; biotic fixation produces ammonia (NH₄⁺), abiotic produces nitrates (NO₃^-)

Nitrification

nitrifying bacteria convert ammonium (NH₄⁺) into nitrite (NO₂^-) then into nitrate (NO₃^-)

Assimilation

Producers take up either ammonium (NH₄⁺) or nitrate (NO₃^-). Consumers assimilate nitrogen by eating producers.

Mineralization

Decomposers in soil and water break down biological nitrogen compounds into ammonium (NH₄⁺)

Denitrification

dentrifying bacteria in oxygen-poor soil and stagnant water convert nitrate (NO₃^-) into nitrous oxide (N₂O) and eventually nitrogen gas (N₂)

Phosphorus Cycle

the movement of phosphorus around the biosphere

• biotic - producers on land and in water take up inorganic phosphate and assimilate in into their tissues as organic phosphorus. the waste products and eventual dead bodies of these organisms are decomposed by fungi and bacteria, which causes the mineralization of organic phosphorus back to inorganic phosphate

• abiotic - in water, phosphorus isnt very soluble. it precipitates out of solution in the form of phosphate-laden sediments in the ocean. over time, geologic forces lift these ocean layers up and they become mountains. the phosphate rocks in the mountains are slowly weathered. since it isn’t easily weathered, it’s a limiting nutrient in many aquatic systems

humans mine phosphate from mountains for fertilizer. when that fertilizer is used, excess phosphorus leaches into water bodies. since there isnt much phosphorus in aquatic systems, this causes rapid growth of algae. as the algae die, decomposition takes a lot of oxygen (which makes the water hypoxic), creating a dead zone. this also happened in the 1940s-1990s, when laundry detergents (which unintentionally fertilized aquatic systems) contained phosphates. they took it out of the detergents due to the damage

Dead Zone

when oxygen concentrations become so low that it kills fish and other aquatic animals

Sulfur Cycle

Most sulfur exists as rocks. As these rocks are weathered over time, they release sulfate ions (SO₄^2-) that producers can take up and assimilate. This assimilated sulfur then passes through the food web. Volcanoes, the burning of fossil fuels, and the mining of copper put sulfur dioxide (SO₂) into the atmosphere. In the atmosphere, sulfur dioxide combines with water to form sulfuric acid (H₂SO₄). This sulfuric acid is carried back to Earth when it rains or snows.

Resistance

A measure of how much a disturbance can affect flows of energy and matter in an ecosystem.

Resilience

The rate at which an ecosystem returns to its original state after a disturbance.

Watershed

the area of land that drains into a particular body of water

Intermediate Disturbance Hypothesis

the hypothesis that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels