Case Studies:

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Key Vocab:

• Biome: Large area classified by characteristic plant & animal life.
• Ecosystem: Community of living organisms interacting with their environment.
• Abiotic: Non-living factors (e.g., soil, temperature, rainfall).
• Biotic: Living factors (plants, animals, fungi).
• Latitude: Distance from equator → affects sunlight & temperature.
• Altitude: Height above sea level → higher = colder.
• ITCZ (Intertropical Convergence Zone): Area near equator with rising air → heavy rain.
• Hadley Cell: Circulation of air creating tropical rainforests & deserts.
• Continentality: Distance from ocean → more extreme temperatures inland.
• Ocean Current: Warm/cold currents affect rainfall & temperature.
• Seasonality: Variation in climate between seasons.
• Adaptation: Adjustments by organisms or humans to survive environmental conditions. </aside>

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• Trophic Level: Position in a food chain/web.
• Producer: Organisms that make their own food (plants, algae).
• Consumer: Organisms that eat others (herbivores, carnivores, omnivores).
• Decomposer: Break down dead matter → nutrients return to soil.
• Leaching: Rain washes nutrients from soil → can reduce fertility.
• Biomass: Total mass of living material in an ecosystem.
• Litter: Dead plant material on soil surface.
• Humus: Decomposed organic matter enriching soil.
• Feedback Loop: Cycle where outputs influence inputs (positive/negative).
• Sustainability: Using resources without depleting them.
• Equity: Fair distribution of resources.
• Management: Maintaining ecosystems through policies or practices.
• Intervention: Human action to alter natural processes. </aside>

biome location factors

Climate is the most important factor in determining where a biome is found.

• Latitude (distance from equator):

  • Areas near the equator receive direct sunlight all year, resulting in high temperatures and heavy rainfall. This is ideal for tropical rainforests.
  • The polar regions receive sunlight at a very slanted angle, resulting in cold temperatures, which supports tundra and polar biomes.
  • Mid-latitude regions experience moderate temperatures and seasons, which are suitable for deciduous forests and grasslands.

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  Key idea: The farther from the equator, the colder and often drier the climate becomes.

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• Continentality (distance from the sea):

  • Coastal areas are cooler in summer and warmer in winter due to the ocean’s ability to store heat
  • Inland areas experience more extreme temperatures, with hotter summers and colder winters, as well as lower rainfall, which often results in grasslands or deserts.

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  Key idea: The farther from the sea, the more extreme and dry the climate.

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• Altitude (height above sea level):

  • The higher the altitude, the colder the temperature and the thinner the air becomes. This results in fewer plant species and less oxygen.
  • High mountains near the equator, such as the Andes or the Himalayas, can support alpine tundra conditions despite their proximity to the equator.

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  Key idea: Higher up = less oxygen, lower temperatures, and fewer plant species.

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• Ocean Currents:

  • Warm ocean currents bring warm, moist air to coastal regions, increasing rainfall and supporting forests.
  • Cold ocean currents cool the surrounding land and reduce rainfall, which can create desert conditions, such as in the Atacama Desert.

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  Key idea: Ocean currents change the temperature and rainfall of coastal regions, which changes what life can survive there.

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• Pressure Belts and Wind:

  • Low-pressure zones near the equator result in rising warm air and heavy rainfall, creating tropical rainforest environments.
  • High-pressure zones near 30° north and south latitude result in descending, dry air, which contributes to the formation of deserts

  

• Seasonality:

  • Seasonal variations in rainfall and temperature affect the growing cycles of plants and the migration patterns of animals.
  • Areas with strong seasonality often support deciduous forests and temperate grasslands, while areas with little seasonal change support tropical rainforests.

biome characteristics

• Tropical Rainforest:
• Deciduous Forest:
• Desert
• Grassland/Savannah:
• Taiga:
• Tundra:

soil horizons

All soils have distinct layers (horizons), though their thickness and composition vary by biome:

• O Horizon: Surface layer of organic matter, including dead leaves, branches, and decomposing material.
  • Thick in deciduous forests; very thin or absent in deserts.
• A Horizon (Topsoil): Rich in humus and nutrients; high biological activity from plants, roots, and soil organisms.
  • Thick in grasslands; thin in rainforests (because nutrients are mostly in biomass).
• B Horizon (Subsoil): Layer where leached minerals accumulate, such as iron, clay, or salts.
• C Horizon: Weathered parent rock, which gradually breaks down to form soil over time.
• Permafrost Layer (Tundra): Permanently frozen soil beneath the active layer that prevents deep root growth and water drainage.

nutrient cycles

• Biomass: This refers to all living organisms in an ecosystem, including plants, animals, and microorganisms. Biomass acts as a store of nutrients, such as nitrogen, phosphorus, and carbon, which are constantly recycled through the ecosystem.
• Litter: Litter consists of dead plant material, such as fallen leaves, branches, and dead roots. It forms the first step in nutrient recycling, providing food for decomposers and eventually breaking down into humus.
• Humus: Humus is the dark, organic layer in the soil formed from decomposed litter. It is rich in nutrients and improves soil structure, water retention, and fertility.
• Decomposers: Fungi, bacteria, and detritivores break down litter and dead organisms, releasing nutrients back into the soil. This step is critical for maintaining ecosystem productivity.
• Leaching: Leaching occurs when water percolates through the soil, washing away soluble nutrients such as nitrates or potassium from the topsoil. Excessive leaching can reduce soil fertility.