Energy Flow in Ecosystems (LT 1.6)

This lecture will help you understand Feeding relationships Food Webs Trophic levels Energy flow Productivity ….. Ecology & the ecosystem

All the parts of an ecosystem are interrelated. Biotic (living): trees, animals, insects, bacteria & abiotic (nonliving): sunlight, temperature, soil, water, pH, nutrients Highly dependent on climate. Boundaries are important because they help distinguish ecosystems. Knowing boundaries help us identify components and trace energy/matter cycles.

Ecosystems interact with each other by exchanging energy and matter. Energy flows through ecosystems. Solar energy enters through plants Spreads to producers (autotrophs) & consumers (heterotrophs). 2nd law of thermodynamics says energy conversion is not 100% efficient –not all energy is transferred to consumer, some is lost as heat.

Food Chain vs. Food Web – What do the arrows show us?

Trophic levels: organism’s role/place/order in the food chain Food chain vs food web: Food chain: what eats what – producers to tertiary consumers Food web: a bunch of food chains interacting

Heterotrophs = consumers Primary consumers – eat producers Secondary consumers – eat primary consumers tertiary consumers – eat secondary consumers Scavengers: carnivores that eat dead animals Detritivores: break down detritus (dead tissue/waste) into smaller particles – responsible for cycling matter Decomposers: Break down the particles from detritivores

Laws of Thermodynamics 1st Law: Energy cannot be created nor destroyed, only transformed. 2nd Law: When energy is transformed, it loses quality.

Nearly all energy that powers ecosystems is solar energy, a form of kinetic energy. Producers (autotrophs) use sun’s energy to produce usable forms of energy through photosynthesis.

Cellular respiration = unlocks chemical energy stored in food sources (like glucose). All organisms perform cellular respiration.

The amount of energy available determines how much life can be supported. Gross Primary Productivity (GPP): total amount of solar energy captured by producers Net Primary Productivity (NPP): energy captured minus energy respired NPP = GPP – respiration by producers Determine the rate of photosynthesis by: measuring the compounds that participate in the reaction (example: CO2) NPP efficiency ranges from 25% to 50% of GPP. *measure NPP is a. useful way to compare ecosystem productivity

Biomass: total mass of all living matter in an area Rate of production determined by NPP Standing crop: amount of biomass present at a particular time Ecological efficiency: Proportion of consumed energy that can be passed up the trophic levels (5-20%) What is the 10% Rule? Only 10% of biomass can be passed up to the next level. For example, producers get 100J of energy, primary consumers would only get 10J.

Trophic pyramid: diagram to represent the distribution of biomass (using the 10% rule)