Ecosystems & Biomes Summary

Ecosystems

Energy Flow within Ecosystems

  • Food chain: Illustrates the direction of energy flow.
  • Trophic level: Represents the energy level within an ecosystem, indicating an organism's position in a food chain or web.

Trophic Levels

  • Producers: Autotrophic organisms (e.g., plants, phytoplankton) that form the base of the food chain through photosynthesis.
  • Consumers: Heterotrophic organisms (animals) that obtain energy by consuming other organisms.
    • Primary consumers (herbivores): Consume producers.
    • Secondary consumers: Eat herbivores.
    • Tertiary consumers: Eat secondary consumers.
    • Apex consumers: Top-level predators in the food chain.
  • Decomposers: Heterotrophic organisms (e.g., fungi, protists, bacteria) that break down dead organic matter (saprobes).

Energy Content in Trophic Levels

  • Energy decreases at each higher trophic level.
  • Example energy content:
    • Producers: Diatoms, water lettuce, arrowhead, eel grass.
    • Primary consumers: Red-bellied turtle, Florida apple snail, flathead mullet, midge larvae.
    • Secondary consumers: Killifish, bluegill sunfish, whirligig beetle, water strider.
    • Tertiary consumers: Bass, gar, water snake.

Energy Loss

  • Most energy is lost as heat from an organism.
  • 10% Rule: Only about 10% of the energy in a trophic level is available to the next trophic level.
  • Vegetarian diets are more environmentally friendly because they require less energy transfer through trophic levels.

Organism Abundance

  • There are fewer organisms at higher trophic levels.
  • Example Illustration:
    • Tertiary Consumers: 10 J
    • Secondary Consumers: 100 J
    • Primary Consumers: 1,000 J
    • Producers: 10,000 J
    • Sunlight: 1,000,000 J

Food Webs

  • Food webs represent complex relationships not captured by food chains.
  • Organisms can exist at multiple trophic levels.
  • Decomposers are present in every food web, although they are not always explicitly shown.

Biomagnification

  • Biomagnification is the concentration of toxic substances in organisms at higher trophic levels.
  • Persistent toxic substances do not leave animal body tissues.
  • Examples:
    • PCBs: Man-made organic compounds banned in 1979 but still present in the environment.
    • DDT: A pesticide that accumulated in apex predator bald eagles, causing eggshell fragility.

Ecosystem Definition

  • An ecosystem comprises the community and the non-living (abiotic) factors of the environment.

Ecosystem Types

  • Marine ecosystems: Cover 75% of Earth’s surface, including shallow ocean, deep ocean water, and deep ocean bottom.
  • Freshwater ecosystems: (lakes, waters, streams) constitute only 1.8% of Earth’s surface.
  • Terrestrial ecosystems: Are diverse and grouped into biomes.
  • Biome: A large-scale community of organisms defined by climate conditions and dominant plant types.

Terrestrial Biomes

  • Eight major biomes distinguished by temperature and precipitation:
    • Tropical forest
    • Boreal forest
    • Savanna
    • Tundra
    • Desert
    • Mountains
    • Chaparral
    • Polar ice
    • Temperate forest
    • Temperate grassland

Climate Patterns

  • Patterns of temperature and rainfall define the types of communities that become established.
  • Examples:
    • Desert: Low precipitation.
    • Tropical Rainforest: High precipitation and temperature.
    • Taiga: Low temperature.

Biome Characteristics

  • Tropical Rainforest:
    • Near the equator.
    • High stable temperatures and precipitation (33 ft per year).
    • Little seasonal change.
    • Highest diversity among terrestrial biomes.
    • Supports tall evergreen trees and diverse communities.
  • Savanna:
    • Dominated by grass with scattered trees.
    • Limited water availability, making survival difficult for tall plants.
    • High temperatures.
    • Hot, long dry season.
  • Desert:
    • High temperatures and low precipitation.
    • High daily temperature fluctuations.
    • Low species diversity.
    • Organisms adapted to low-water environments.
  • Chaparral:
    • Coastal areas with mild winters and dry summers.
    • Dominated by shrubs – short, woody plants.
    • Plants are small and drought-resistant.
  • Temperate Grassland:
    • Prairies (US), pampas (South America), steppes (Eurasia).
    • Cold winters; warm summers with some rain.
    • Dominated by grasses; low rainfall limits trees.
    • Lack of trees differentiates it from savannah.
    • Fertile soil.
  • Temperate Forest:
    • Four distinct seasons.
    • Moderate temperatures and precipitation.
    • Dominated by deciduous trees (lose leaves in winter).
    • Promotes survival in cold winters.
  • Boreal Forest/Taiga:
    • Low temperatures.
    • Extended cold winters, short mild summers.
    • High latitudes.
    • Dominated by coniferous trees (evergreen) and broad-leaved deciduous hardwoods.
    • Long-lived trees.
  • Tundra:
    • Extremely cold and low precipitation.
    • North of boreal forests.
    • Short growing season.
    • Permafrost: thick layer of soil that is frozen year-round.
    • Small plants, no trees, low biodiversity.

Factors Influencing Biomes

  • Temperature and moisture gradients influence biome distribution.
  • Deserts are found in hot and dry conditions, while rainforests are hot and wet.
  • Tundra is found in cold conditions.

Aquatic Biomes

  • Important abiotic factors: light, temperature, flow, and dissolved solids.
  • Light penetration decreases with water depth.
  • Solar radiation (heat) creates layers within water bodies.

Marine Biomes

  • The ocean is a continuous body of salt water with relatively consistent chemical composition.
    • Pelagic zone/realm: All open water of the ocean.
    • Benthic zone: Ocean floor, from shore to depths.
    • Benthic organisms: Live on, in, or above the seafloor.
Pelagic Realm
*   **Photic zone:** Surface to where light penetrates (~200m); photosynthesis occurs here.
*   **Aphotic zone:** Not enough light for photosynthesis; majority of the ocean.
*   4000m+: No light, very cold, high pressure, very low oxygen, but high nutrients; variety of specialized fish and invertebrates.

Deep Sea Adaptations

  • Bioluminescence: Used as defense, communication, and lure.

Intertidal Zone

  • May be sandy, rocky, muddy, or mangroves.
  • Region submerged by water sometimes and exposed at other times.
  • Extremely variable environment.
  • Experiences waves, wet and dry periods, and temperature extremes.
  • Organisms adapted to prevent drying out.
Zones.
*Spray zone
*High tide zone
*Middle tide zone
*Low tide zone

Coral Reefs

  • Formed by invertebrates in warm, shallow waters.
  • Calcium carbonate skeleton formed by corals and accumulates over time.
  • Corals have a mutualistic relationship with internal photosynthetic algae, providing the majority of nutrients.
  • Extremely diverse biomes.
  • Coral bleaching occurs when corals in warm water expel their algae; can be survived, but bleaching increases the mortality rate.

Estuaries

  • Where freshwater meets the ocean.
  • Brackish water: diluted saltwater; salinity varies with the tides.
  • Form protected areas where many crustaceans, mollusks, and fish begin their lives.
  • Very threatened biomes.

Freshwater Biomes

  • Humans rely on freshwater for drinking water, agriculture, recreation, etc.
  • Include:
    • Wetlands (possess emergent vegetation)
    • Rivers and Streams
    • Lakes and ponds