Ecosystems and Environmental Factors

Ecosystems

  • Ecosystem: A community of living organisms and their abiotic environment.
    • Builds upon previous concepts: population (individuals of one species), community (populations of different species), and now including the environment.
    • Can be small (e.g., tide pool) or large (e.g., rainforests).
    • Focus on abiotic factors: sunlight, water, temperature.

Types of Ecosystems

  • Three broad categories:
    • Freshwater: Rivers, lakes, streams.
    • Marine: Oceans (saltwater).
    • Terrestrial: Land-based ecosystems.
    • Each category has different types of ecosystems.

Terrestrial Ecosystems

  • Distinguished by temperature (average annual) and rainfall (mean annual).
  • Map patterns:
    • Bands of color across the map indicate similar ecosystems at similar latitudes.
    • Examples: boreal forests in Northern US/Canada and Northern Europe/Russia.
    • Tropical forests near the Equator in Central/South America, Africa, India, and Australia.
    • Deserts around 30° north and south of the equator.
      • Air movement, water currents, and cloud formation influence these patterns.
  • Ecosystems affect one another (e.g. mountain ranges affecting local rainfall patterns).

Temperature and Rainfall

  • Both are needed to categorize terrestrial ecosystems.
  • Example: Desert
    • High mean annual temperature (e.g., 30°C or 86°F).
      • T<em>°F=T</em>°C∗(9/5)+32T<em>{°F} = T</em>{°C} * (9/5) + 32
    • Low rainfall (e.g., 5 cm per year in some deserts).
  • Example: Tundra
    • Low rainfall (similar to desert).
    • Very cold average temperature (e.g., -8°C, below freezing).

Plant Life

  • Vegetation indicates ecosystem type since plants adapt to their environments.
  • Desert: Succulents, cacti (adapted for water conservation).
  • Tropical Rainforest: Tall trees, undergrowth, high species diversity (due to ample water).
  • Tundra: Small plants close to the ground, mosses, perennial plants (short growing season, 60 days or less).

Animals

  • Affected by the plant life, which is a food source for them.

Aquatic Ecosystems

  • Distinguished by water depth and distance from the shore (especially ocean ecosystems).

Light Penetration

  • Photic Zone: Where light penetrates, allowing photosynthesis (oceanic, neuritic, and intertidal zones).
  • Aphotic Zone: Below 200 meters (650 feet), no sunlight penetration. Any light is produced by other organisms.

Ocean Depth

  • Challenger Deep: Deepest part of the ocean (Mariana Trench), 11,000 meters (6.8 miles) deep, most of the ocean is not this deep.
  • Deep ocean studies are largely robotic due to safety and cost.

Deep Sea Ecosystem Example: Titanic Shipwreck

  • Located at 3,800 meters (completely dark).
  • Abyssal Plane: Completely dark environment.
    • Eels, fish, crabs, corals, and bacteria live there.
    • Bacteria are the "star" as a species of bacteria consumes the ship itself.
    • Ship may largely disintegrate by as early as 2050.
    • Unknown how the ecosystem will be affected once the ship is gone and the bacteria runs out of food.

Coral Reefs

  • Formed by calcium carbonate skeletons of coral (cnidarians).
  • High biodiversity, especially for fish. (4,000 known species inhabit coral reefs).
  • Threatened by human activity.
Bleaching
  • Algae leaves due to heat stress (e.g., global warming).
  • Food source is lost, collapsing the food chain.
  • Example: Coral reef dieback in Thailand (2007-2010).
  • Coral reefs can recover, but prolonged warmer weather is fatal.

Freshwater Ecosystems

Lakes

  • Small to large (e.g., Sunbeam Lake vs. Great Lakes).
  • Diverse species: algae, fish, crustaceans.
Algal Bloom
  • Excess nutrients (sewage, fertilizer runoff) cause rapid algae growth.
  • Less light penetration.
  • Algae dieback consumes oxygen, suffocating fish and other organisms.

Rivers

  • Water moves in a specific direction.
  • Source water: Typically from snowmelt in mountains, cold and low in nutrients.
  • Nutrients increase as water flows downstream.
  • Rivers flow into oceans or lakes.
  • Home to fish, frogs, river otters, beavers, algae, etc.

Wetlands

  • Soil saturated with water (permanent or periodical).
  • Marshes, swamps, bogs, mudflats.
  • Marshes and swamps have slow, steady water flow.
  • Bogs have little to no water flow.
    • Low oxygen, few organisms.
  • Marshes and swamps have steady nutrient cycling and more organisms.