Ecosystems

Rucete ✏ Biology In a Nutshell

1. Trophic Levels

• Organisms in an ecosystem are categorized into trophic levels based on how they obtain energy

a) Primary Producers

• Plants, algae, and other photosynthetic organisms
• Form the base of the food chain

b) Primary Consumers

• Herbivores that feed on primary producers

c) Secondary Consumers

• Primary carnivores that eat herbivores

d) Tertiary Consumers

• Secondary carnivores that eat other carnivores

e) Detritivores (Decomposers)

• Feed on detritus (dead organic matter)
• Include bacteria, fungi, and scavengers
• Play a key role in nutrient recycling

2. Ecological Pyramids

• Graphical representations of trophic level structure
• Types include:

a) Pyramid of Energy

• Shows energy flow through each level
• Always decreases upward due to heat loss in metabolism

b) Pyramid of Biomass

• Represents the total mass of living organisms at each trophic level
• May be inverted in some aquatic systems

c) Pyramid of Numbers

• Shows the number of organisms at each level
• Can also be inverted, depending on ecosystem

3. Ecological Efficiency

• The percentage of energy transferred from one trophic level to the next
• Usually about 10%
• Energy loss occurs due to metabolic activities (heat, respiration, movement)