1.7 Energy Flow and the 10% Rule

• Energy flow in ecosystems describes how energy moves through different trophic levels, starting with producers capturing sunlight through photosynthesis
• The 10% rule states that only about 10% of the energy at one trophic level is transferred to the next.
• Order the following organisms in a food chain based on their trophic levels, from producers to tertiary consumers:

  1️⃣ Grass

  2️⃣ Grasshoppers

  3️⃣ Frogs

  4️⃣ Snakes
• What do producers use as their energy source?

  Sunlight
• The energy transfer from one trophic level to the next is approximately 10%
• Decomposers return nutrients to the soil by breaking down dead organic matter.
• Match the trophic level with its example organism:

  Producers ↔️ Grass

  Primary Consumers ↔️ Grasshoppers

  Secondary Consumers ↔️ Frogs

  Tertiary Consumers ↔️ Snakes
• Decomposers like bacteria and fungi break down dead organic matter to release nutrients
• What percentage of energy is transferred from one trophic level to the next according to the 10% rule?

  10%
• Energy is lost as heat and through metabolic processes at each trophic level.
• What do trophic levels represent in an ecosystem?

  Feeding positions
• Match the trophic level with its organism type:

  Producers ↔️ Plants

  Primary Consumers ↔️ Herbivores

  Secondary Consumers ↔️ Carnivores or Omnivores

  Tertiary Consumers ↔️ Carnivores
• Energy is lost at each trophic level due to metabolic processes and heat.
• The10% rule states that only about 10% of the energy at one level is transferred to the next
• What is the energy transfer percentage for producers in a food chain?

  100%
• If secondary consumers have 100 J of energy, tertiary consumers would have approximately 1 J
• Order the following trophic levels based on energy transfer percentage, from highest to lowest:

  1️⃣ Producers (100%)

  2️⃣ Primary Consumers (10%)

  3️⃣ Secondary Consumers (1%)

  4️⃣ Tertiary Consumers (0.1%)
• What are the two primary reasons energy is lost at each trophic level?

  Metabolic processes and heat
• Energy flow in ecosystems begins with producers capturing energy from the sun through photosynthesis
• Energy is lost at each trophic level due to the 10% rule.
• What is the primary source of energy in ecosystems?

  Sunlight
• Energy flow in ecosystems begins with producers
• Energy is lost at each trophic level due to metabolic processes and heat.
• What is the 10% rule in energy flow?

  10% of energy is transferred
• An example of a producer in ecosystems is grass
• Arrange the trophic levels in order of energy source.

  1️⃣ Sunlight (Producers)

  2️⃣ Producers (Primary Consumers)

  3️⃣ Primary Consumers (Secondary Consumers)

  4️⃣ Secondary Consumers (Tertiary Consumers)

  5️⃣ Dead organic matter (Decomposers)
• Match the trophic level with its organism type and example:

  Producers ↔️ Plants, Sunlight, Grass

  Primary Consumers ↔️ Herbivores, Producers, Grasshoppers

  Secondary Consumers ↔️ Carnivores, Primary Consumers, Frogs

  Tertiary Consumers ↔️ Carnivores, Secondary Consumers, Snakes

  Decomposers ↔️ Bacteria, Dead organic matter, Earthworms
• Only about 10% of the energy at one trophic level is passed to the next.
• The 10% rule states that 90% of energy is lost at each trophic level.
• What are the main reasons for energy loss at each trophic level?

  Metabolic processes, heat, biomass
• Match the trophic level with its energy usage, loss, and transfer:

  Producers ↔️ 1000 J available, 500 J used, 400 J lost, 100 J transferred

  Primary Consumers ↔️ 100 J available, 50 J used, 40 J lost, 10 J transferred

  Secondary Consumers ↔️ 10 J available, 5 J used, 4 J lost, 1 J transferred
• Energy flow in ecosystems starts with photosynthesis
• At each trophic level, energy is lost through metabolic processes, heat, and non-consumed biomass, causing only about 10% of the energy to be transferred to the next level.
• What is the name given to the rule that states only about 10% of energy is transferred between trophic levels?

  The 10% rule
• Energy flow in ecosystems starts with producers capturing energy from the sun through photosynthesis.
• At each trophic level, energy is lost through metabolic processes and as heat.
• In the given example of a food chain, what percentage of energy is transferred from grass to grasshoppers?

  10%
• Producers, such as plants, are the primary source of energy in ecosystems.
• Match the trophic level with its example organism:

  Producers ↔️ Grass

  Primary Consumers ↔️ Grasshoppers

  Secondary Consumers ↔️ Frogs
• Decomposers, such as bacteria and fungi, break down dead organic matter, returning nutrients to the soil.