AP Environmental Science: Unit 1 Review

Introduction to Ecosystems

• An ecosystem is the interaction of living and non-living things in a specific region.
• The term environment refers to the entire natural world, while a habitat is the specific environmental conditions that a species needs to survive.
  • Example: The Arctic is a great habitat for caribou but not for capybaras.

Species Interactions

• Symbiosis refers to any close proximity of organisms, which can be beneficial or harmful.
• Mutualism is a type of symbiosis where both species benefit from the interaction (e.g., bees and flowering plants).
• Misconception: Confusing symbiosis with mutualism.
  • Example: If a person gets a tapeworm, it is symbiosis, but not mutualism.

Biomes

• A biome is a region defined by consistent yearly average temperature and precipitation patterns.
  • Examples: Tropical rainforest (high precipitation and temperature) and tundra (low precipitation and temperature).
• Changes in temperature and precipitation can cause shifts in biome locations, as observed with the expansion of tropics due to global warming.

Aquatic Biomes

• Influenced by temperature, precipitation, salinity, flow, and depth.
• Estuaries are a key aquatic biome where fresh and saltwater mix, resulting in productive ecosystems due to nutrient-rich sediments.

Matter Cycling in Ecosystems

• Law of conservation of matter: Matter is never created or destroyed; it just changes forms.
• Important terms:
  • Reservoirs: temporary storage areas of matter.
  • Sources: processes that move matter.
  • Sinks: reservoirs that take in more matter than they release.

Carbon Cycle

• Carbon sources return carbon to the atmosphere, while sinks take carbon out.
• Carbon is stored in various reservoirs, including the atmosphere, which is crucial for global climate.
• Photosynthesis plays a vital role by converting atmospheric carbon into organic matter.
• Respiration returns carbon to the atmosphere, while combustion (e.g., fossil fuels) releases ancient sequestered carbon.
• The importance of understanding the rate of carbon cycling for climate regulation.

Nitrogen Cycle

• Nitrogen cycles more quickly than carbon and is primarily in the unusable gas form ( ext{N}_2).
• Nitrogen fixation is crucial, converting unusable nitrogen into ammonia or nitrate, primarily through bacteria (rhizobacteria) or lightning.
• Understanding nitrogen fixation is essential because plants require nitrogen in a fixed form for growth.

Phosphorus Cycle

• Unlike carbon and nitrogen cycles, phosphorus does not have a gas phase and cycles more slowly.
• Major phosphorus reservoirs are rocks, and it is released through weathering.
• Phosphorus is often a limiting nutrient due to slow cycling rates, impacting plant growth.

Hydrologic Cycle (Water Cycle)

• Driven by solar energy, involving processes like evaporation, condensation, infiltration, and transpiration.
• Major water reservoir is the ocean, but accessible freshwater is found in lakes and groundwater.
• Importance of freshwater reservoirs for human use and ecological balance.

Energy Flow in Ecosystems

• Primary productivity is the rate of photosynthesis in an area, measured as energy per area over time.
• Gross primary productivity (GPP) is total energy produced, while net primary productivity (NPP) is what is available after respiration loss:
  NPP = GPP - RL
• Example calculation:
  • GPP = 1000 kcal/m²/year, RL = 250 kcal/m²/year → NPP = 750 kcal/m²/year.

Trophic Pyramids

• Represents energy flow in ecosystems; producers at the base, followed by primary consumers (herbivores), secondary consumers, and tertiary consumers (top predators).
• 10% rule: Only about 10% of energy is transferred to the next trophic level, with the rest lost as heat or waste.
• Importance of understanding energy loss at each level for ecosystem health and predator-prey dynamics.

Food Webs and Chains

• Arrows in food webs/chains indicate the direction of energy transfer.
• Removal of one species can drastically affect ecosystem dynamics (trophic cascades).
• Example of how apex predators control herbivore populations, influencing plant abundance.

Conclusion

• Emphasis on importance of understanding ecosystems for the AP Environmental Science exam and beyond.
• Reminder to utilize the Ultimate Review Packet for practice and deeper learning on these topics.