Productivity in Ecosystems

Productivity is a crucial concept in understanding energy flow in ecosystems. It refers to the amount of glucose or energy available to organisms at different trophic levels.

There are several types of productivity:

1. Primary Productivity: The amount of glucose/energy available in plants.

   • Gross Primary Productivity: Total amount of glucose made by plants through photosynthesis.
   • Net Primary Productivity: Amount of glucose stored as starch after respiration losses.

2. Secondary Productivity: The amount of glucose/energy available in animals.

   • Gross Secondary Productivity: Amount of glucose consumed by an animal.
   • Net Secondary Productivity: Amount of glucose stored as glycogen after respiration losses.

Definition: Net Productivity = Gross Productivity - Respiratory [and Faeces] Losses

Net productivity represents the glucose/energy available to organisms at the next stage of the food chain. It's important to note that respiratory losses are generally higher in consumers than in producers due to movement. Additionally, secondary/tertiary/quaternary consumers have higher respiratory losses as they move more to hunt for food.

Highlight: Endotherms (warm-blooded animals) have higher respiratory losses as they maintain a constant body temperature.

Understanding productivity helps in assessing the energy transfer efficiency in ecosystems and the potential biomass at each trophic level.

Energy Sources and Roles in Ecosystems

This page introduces the key players in ecosystem energy flow and their roles. Producers, consumers, and decomposers in ecosystem each have distinct functions:

Definition: Producers are organisms, typically plants, that can create their own food through photosynthesis, using sunlight as their primary energy source.

Producers use light energy to synthesize biological molecules through photosynthesis. These molecules, such as glucose, amino acids, and fatty acids, are essential for various cellular processes.

Example: Plants use glucose for respiration, store it as starch, and use it to make cellulose for cell walls.

Consumers cannot produce their own food and must obtain biological molecules by eating other organisms. They are classified as primary (herbivores), secondary, or tertiary consumers (carnivores) based on their position in the food chain.

Vocabulary: Primary consumers eat plants directly, while secondary and tertiary consumers eat other animals.

Decomposers, such as bacteria and fungi, break down dead organic matter through saprobiotic decomposition. They release enzymes to break down dead plants, animals, and waste, obtaining necessary biological molecules in the process.

The page also explains why each group needs specific biological molecules, highlighting the interconnectedness of ecosystem components.

Highlight: Energy in ecosystems is primarily carried as glucose, stored as starch in plants and glycogen in animals. Lipids and proteins serve as alternative energy sources.