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I. Ecosystems and Ecology

• Definition: An Ecosystem is a particular location on Earth distinguished by its mix of biotic and abiotic factors.

• Scale:

    ◦ It is harder to define fixed boundaries on terrestrial ecosystems, such as the Greater Yellowstone Ecosystem (a macro ecosystem).

    ◦ An example of a micro ecosystem is a divet in a tree holding water.

• Examples/Characteristics:

    ◦ Caves are great examples of defined ecosystems, except for water flowing in and out and bats flying in and out.

    ◦ It is much easier to study cave ecosystems than open land ecosystems.

    ◦ Bats bring outside nutrients into the cave.

• Matter and Energy:

    ◦ Energy flows through the atmosphere and is constantly replenished by the Sun, making it an open system.

    ◦ Matter has to be recycled; it is within a closed system.

    ◦ Biogeochemical Cycles involve the recycling of elements through abiotic and biotic factors.

Deforestation of Haiti

• Haitians rely on charcoal for cooking, heating homes, and seeking shelter.

• Forests are harvested faster than they can be replenished.

• Deforestation disrupts the ecosystem by eroding the earth and causing disruptions of the natural water and soil surfaces.

• Ecosystems are influenced by human decisions.

• Historical Coverage: In 1923, 60% of the country was covered by forested land. By 2017, only 2% was covered/forested land.

• Consequences: Heavy rains following deforestation result in mudslides and severe flooding.

• Ecosystem Services: Healthy forests provide stable root systems that prevent flooding and support nutrient-rich soil.

• Solutions: Programs implemented by the Haitian government and USAID help Haitians plant and census trees. If mango trees mature, they can become a source of income (estimated at 60–130/month), giving Haitians an incentive to let trees mature.

II. Energy Flow, Trophic Levels, and Productivity

Trophic Levels

• Trophic Levels are successive levels of organisms consuming each other.

• Producers (Autotrophs):

    ◦ Are always the 1st trophic level.

    ◦ Include plants and algae.

    ◦ They convert solar energy into a usable form.

    ◦ An Autotroph is a "self feeder" and makes its own food ("plants").

• Consumers (Heterotrophs):

    ◦ Primary Consumers are herbivores that consume producers.

    ◦ Secondary Consumers are carnivores that eat primary consumers.

    ◦ Tertiary Consumers are carnivores that eat secondary consumers.

Feeding Types

• All energy comes from the SUN!.

• Herbivores: eat plants.

• Carnivores: eat animals.

• Omnivores: eat both.

Food Chains and Food Webs

• A Food Chain shows 1 interaction of the flow of energy and matter moving through trophic levels.

• A Food Web shows all possible interactions within an ecosystem and illustrates the interconnectedness between all organisms.

• Food webs are generally more complex than food chains.

Energy Transfer and Ecological Efficiency

• Biomass and Energy: Most energy and biomass are found at the producer level. As you move up the trophic levels, biomass and energy decrease.

• Ecological Efficiency (Rule of 10%): This is the Rule of 10%, representing the average energy transfer between trophic levels.

• Only about 10% of biomass energy is converted into energy at the next higher trophic level.

• Energy used by an organism is given off as heat.

• Energy converted into consumer biomass by growth and reproduction is available to the next trophic level.

• The energy that an organism holds onto is dedicated to growing and repairing the biomass (muscle, bone, skin, cuts).

Ecosystem Productivity

• The amount of energy available in an ecosystem determines how much life the ecosystem can support.

• Gross Primary Productivity (GPP): The total amount of solar energy that the producers in an ecosystem capture (rate).

• Net Primary Productivity (NPP): Energy captured minus the energy respired by producers.

    ◦ Formula: NPP = GPP - Respiration by Producers.

• GPP is always bigger than NPP.

• These measures allow comparison of the productivity of different ecosystems.

• Efficiency: Producers have a low efficiency rate. Only 1% of incoming solar radiation is converted into usable energy/biomass.

Biomass and Standing Crop

• Biomass is the total mass of all living matter in a specific area.

• Standing Crop is the amount of biomass present in an ecosystem at a particular time, but it is NOT the rate of energy production.

• Standing crop changes in regions with seasonal variations in climate (e.g., more plants are alive and thriving in June than January in New Jersey).

III. Core Biological Processes

Photosynthesis

• Performed by plants, algae, and some bacteria.

• Equation: Solar energy + 6H₂O + 6CO₂ → C₆H₁₂O₆ (glucose) + 6O₂.

• C₆H₁₂O₆ (glucose) is the foundation molecule of all biomass on the planet.

Cellular Respiration

• Consumers/Heterotrophs eat plants and other animals and gain energy from the chemical energy.

• Equation (Cellular Respiration): 6O₂ + C₆H₁₂O₆ → 6H₂O + 6CO₂ + ATP.

• Equation (Respiration, performed by all organisms): Energy + 6H₂O + 6CO₂ ← C₆H₁₂O₆ + 6O₂.

Decomposition and Waste Management

• Detritivores: break down dead tissues and waste products.

• Scavengers: carnivores that consume dead animals.

• Decomposers: fungi and bacteria that complete the breakdown process by recycling nutrients.

• Decomposers are very important to an ecosystem because they recycle organic matter and energy and get rid of dead animals and waste products.

IV. Biogeochemical Cycles

The four main cycles discussed are Water, Carbon, Nitrogen, and Phosphorus.

A. Hydrologic (Water) Cycle

• Involves the movement of water through the biosphere.

• Processes:

    ◦ Evaporation: solar energy heats the Earth and vaporizes rivers, lakes, streams, and oceans.

    ◦ Transpiration: plants release water from their leaves.

    ◦ Evapotranspiration: involves both evaporation and transpiration.

    ◦ Runoff: water moves across the land into bigger bodies.

    ◦ Precipitation: rain, snow, hail.

• Human Impacts: Deforestation, paving roads, and diverting water.

• Urbanization Effect: Surface runoff increases in urban areas with lots of concrete material and roads (impermeable surfaces) compared to grass, forests, and barren land (permeable surfaces).

B. Carbon Cycle

• Incorporation: Carbon is incorporated into the tissues of plants (producers) in the form of glucose.

• Processes:

    1. Photosynthesis takes CO₂ and incorporates it into tissues.

    2. Some carbon returns when organisms respire and die.

    3. Sugars are converted back into CO₂.

    4. CO₂ combines with calcium ions and becomes calcium carbonate (buried limestone and sedimentary rock).

    5. Buried dead organic matter is turned into fossil fuels.

    6. Extracting fossil fuels and combustion release carbon into the atmosphere or soil as ash.

    7. CO₂ can dissolve directly into the ocean.

• Human Impacts Example: Burning forests to clear land, industrial energy consumption, and industrial agriculture.

C. Nitrogen Cycle

• Macronutrient Status: Organisms need nitrogen in relatively large amounts. It is often a limiting nutrient.

• Purpose: The whole purpose of the N cycle is to convert N₂ gas into a usable form for plants, which is either NH₄⁺ (ammonium) or NO₃⁻ (nitrate).

• Processes:

    1. Nitrogen fixation: N₂ is converted directly into ammonia (NH₃) by cyanobacteria and bacteria in the roots of legumes. NH₃ is readily formed to NH₄⁺ (ammonium) in the soil. This can also happen abiotically (e.g., lightning or fertilizer).

    2. Assimilation: Producers take up ammonium or nitrate. Consumers assimilate nitrogen by eating producers. Plants use NO₃⁻ to make amino acids, protein, and nucleic acids (DNA/RNA).

    3. Ammonification: Decomposers break down N compounds into ammonium (NH₄⁺) during excretion and decomposition of dead organisms.

    4. Nitrification: Nitrifying bacteria convert ammonium to nitrite (NO₂⁻) and then into nitrate (NO₃⁻).

    5. Denitrification: Denitrifying bacteria convert nitrate (NO₃⁻) into nitrous oxide and eventually nitrogen gas, which process returns N₂ back into the atmosphere.

• Human Use: Farmers use fertilizer to apply large amounts of N to the soil so that plants/crops can grow and thrive.

• Pollution: Excess nitrogen can alter the environment.

D. Phosphorus Cycle

• Rate: The Phosphorus Cycle is Very Slow.

• Location: Phosphorus is found in rock and needs to be eroded or weathered to be released.

• Processes:

    ◦ Weathering of rocks.

    ◦ Phosphate rocks uplift from the ocean floor. This only happens when tectonic plates slam together and create mountain chains, like every 500 million years.

    ◦ Phosphorus fertilizer is added to farms and can run off into rivers, lakes, and streams.

    ◦ Excretion of animals.

    ◦ Dissolved phosphates precipitate out of solution and contribute to the ocean sediments.

• Eutrophication/Hypoxia: When phosphorus is added to stream and river systems, there is a huge growth of producers (algal bloom). When algae die, their decomposition consumes large amounts of oxygen, resulting in hypoxic (low oxygen) conditions.

E. Atmospheric Composition (by volume)

• N₂: 78%

• O₂: 21%

• Argon: 0.93%

• CO₂: 0.04% (also noted as 0.07%)

• Also present: Water Vapor, Methane, Noble gases (Ne, He, Kr, Xe)