Lecture 27: Energy Flow

Question 1

Define detritus

Answer 1

An organism that is not consumed by other organisms

• dead organic matter
• feces, urine

Question 2

Detritus vs detritivores

Answer 2

Detritus: grouped with primary producers/autotrophs

Detritivore: grouped with herbivores/primary consumer

Question 3

Why is there energy loss going up the trophic levels?

Answer 3

• limited consumption and assimilation
• respiration
• heat production

Question 4

What is the first law of thermodynamics?

Answer 4

The total amount of energy in the universe is constant - can neither be created or destroyed

Question 5

What is the second law of thermodynamics?

Answer 5

When energy is transferred from one form to another, some of it is lost as heat

Ex: in a trophic level, organisms are warm and their surroundings are colder

Question 6

What is lindeman’s 10% rule?

Answer 6

10% of total energy is lost at each trophic level - explains the reason why there are so few trophic levels

Question 7

What’s one difference between terrestrial and aquatic ecosystems?

Answer 7

Biomass allocation:

In terrestrial ecosystems, biomass is equal. In aquatic ecosystems, energy and biomass are inverted

Question 8

In an energy budget, how is the energy distributed?

Answer 8

15% back into the atmosphere
41% lost as heat
42% absorbed during evapotranspiration
Some captured in the soil, making them a biodiversity hotspot
Very small amounts are consumed by organisms

Question 9

Define bottom-up controls

Answer 9

Physical and chemical factors that influence primary production

Question 10

Define top-down controls

Answer 10

The abundance of one trophic level can influence the ecosystem

Ex: trophic cascade