Ecosystem Components and Biomes: Food Webs, Cycles, and Climate Zones

Ecosystem

A system of living organisms (plants, animals, microbes) interacting with each other and with nonliving components (climate, water, soil, sunlight). Shows how energy flows and matter cycles between biotic and abiotic factors.

Biotic factors

The living parts of an ecosystem, including plants, animals, fungi, and microorganisms. They interact through feeding, competition, and symbiosis.

Abiotic factors

Nonliving components of the environment, such as temperature, precipitation, soil type, pH, and sunlight, which shape which organisms can live in a given ecosystem.

Food chain

A single linear pathway showing how energy flows from producers to herbivores to carnivores to decomposers.

Food web

A complex network of interconnected food chains that illustrates multiple feeding relationships in an ecosystem.

Trophic levels

The feeding positions in an ecosystem: producers (plants), primary consumers (herbivores), secondary consumers (small carnivores), tertiary consumers (top predators), and decomposers.

Autotroph (Producer)

An organism (plants, algae, some bacteria) that produces its own food using sunlight (photosynthesis) or chemicals (chemosynthesis).

Heterotroph (Consumer)

Organisms that cannot produce their own food and must eat other organisms. Includes herbivores, carnivores, and omnivores.

Decomposer

Organisms (fungi, bacteria) that break down dead organisms and recycle nutrients back into the soil and atmosphere.

Gross Primary Productivity (GPP)

The total amount of solar energy captured by producers through photosynthesis in a given time period.

Net Primary Productivity (NPP)

The energy available to consumers after producers use some for respiration (NPP = GPP - Respiration). Drives most food webs.

Biogeochemical cycles

Natural movement and recycling of matter (carbon, nitrogen, phosphorus, water) through Earth's spheres. Ensure resources are reused.

Hydrologic cycle (Water cycle)

Continuous movement of water on Earth through evaporation, condensation, precipitation, infiltration, and runoff.

Carbon cycle

Movement of carbon among atmosphere, biosphere, oceans, and geosphere via processes like photosynthesis, respiration, decomposition, and combustion.

Nitrogen cycle

Movement of nitrogen through fixation (N₂ → ammonia), nitrification, assimilation, ammonification, and denitrification. Essential for proteins and DNA.

Phosphorus cycle

Circulation of phosphorus through rocks, soil, plants, and water. Lacks an atmospheric phase; vital for DNA, ATP, and cell membranes.

Keystone species

A species with a disproportionately large effect on ecosystem balance (e.g., sea otters control sea urchin populations).

Trophic cascade

Powerful indirect effects in a food web that occur when predators are removed or added, changing species abundance and ecosystem structure.

Ecological efficiency

The percentage of usable energy transferred from one trophic level to the next, typically ~10%; explains why food chains are short.

Tundra

Cold, treeless biome with permafrost soil, short growing seasons, low biodiversity. Found in Arctic regions and high mountaintops.

Boreal Forest (Taiga)

Cold, dense forests dominated by coniferous trees. Long winters, moderate precipitation, nutrient-poor soil. Found in Canada, Russia, and northern Europe.

Temperate Rainforest

Coastal biome with moderate temperatures and very high precipitation. Dominated by conifers and mosses; found in Pacific Northwest.

Temperate Seasonal Forest (Deciduous Forest)

Moderate climate with warm summers, cold winters, and significant seasonal changes. Rich soils, broadleaf trees like oak and maple.

Woodland/Shrubland (Chaparral)

Hot, dry summers and mild, rainy winters. Adapted plants include drought-resistant shrubs; prone to wildfires. Found in California, Mediterranean.

Temperate Grassland (Prairie/Steppe)

Cold winters, hot summers, and moderate rainfall. Dominated by grasses, fertile soil, frequent fires. Found in Midwest U.S., central Asia.

Tropical Rainforest

Warm year-round with high rainfall. Extremely high biodiversity, dense canopy layers, nutrient-poor soil due to rapid decomposition. Found near the equator.

Savanna (Tropical Seasonal Forest/Grassland)

Warm temperatures, seasonal rainfall with long dry seasons. Grasses with scattered trees; supports grazing animals. Found in Africa, South America, India.

Desert

Very low precipitation, extreme temperature fluctuations between day and night. Sparse vegetation adapted to conserve water (cacti, succulents). Found in Africa, Australia, Southwest U.S.

Freshwater biomes

Lakes, rivers, streams, wetlands. Provide drinking water, habitats, and nutrient cycling.

Marine biomes

Oceans, coral reefs, estuaries, salt marshes. Cover most of Earth's surface and regulate climate through carbon storage.