8.5 apbio

Ecosystem Definition

• Ecosystem: The sum of all living organisms and abiotic factors in a specific area.
  • Biotic Factors: Living or once-living components (e.g., plants, animals).
  • Abiotic Factors: Nonliving aspects (e.g., sunlight, water, soil).

Laws of Thermodynamics

• 1st Law: Energy cannot be created or destroyed, only transferred (Law of Conservation of Mass).
• 2nd Law: Energy exchanges increase the entropy of the universe.

Energy Gain and Loss in Organisms

• Net Gain: Results in energy storage or growth.
• Net Loss: Leads to reduced mass and potentially death.

Metabolic Rate

• Definition: Total energy an animal uses in a given time (measured in calories, heat loss, or O2 consumption).
• Relation to body mass:
  • Smaller organisms have a higher metabolic rate.
  • Larger organisms exhibit a lower metabolic rate.

Body Temperature Regulation

• Endotherms: Generate heat through metabolism to maintain body temperature.
• Ectotherms: Rely on external sources (e.g., sunlight or other organisms).

Trophic Levels

• Organisms classified by their primary nutrition sources:
  • Primary Producers (Autotrophs): Create organic compounds using light energy (e.g., plants, algae).
  • Heterotrophs: Cannot produce their own food:
  • Primary Consumers: Herbivores.
  • Secondary Consumers: Carnivores eating herbivores.
  • Tertiary Consumers: Carnivores eating other carnivores.
  • Decomposers: Obtain energy from detritus (important for recycling).

Trophic Structure

• Determined by feeding relationships:
  • Food Chain: Linear transfer of food energy.
  • Food Webs: Complex networks of food chains.
  • Arrows indicate energy transfer between organisms.

Energy Availability and Ecosystem Impact

• Changes in energy supply can disrupt ecosystem structure:
  • Changes at the producer level affect all trophic levels.

Primary Production

• Primary Production: Light energy converted to chemical energy.
  • Gross Primary Production (GPP): Total primary production in an ecosystem.
  • Net Primary Production (NPP): GPP minus energy consumed by producers for respiration (R_a).

Secondary Production

• Secondary Production: Energy from food converted to new biomass in consumers.
• Energy transfer efficiency between trophic levels is about 10%.

Matter Cycling

• Matter, unlike energy, cycles through ecosystems and is limited.
• Biogeochemical Cycles: Nutrient cycles involving biotic and abiotic factors:
  • Water Cycle: Essential for life and ecosystem processes.
  • Carbon Cycle: Key for forming organic compounds.
  • Nitrogen Cycle: Crucial for amino acids and proteins.
  • Phosphorus Cycle: Important for nucleic acids and energy (ATP).

Importance of Nutrients

• Each cycle plays a vital role in sustaining life and supporting ecosystem processes.