Energy Flow through Ecosystems

Question 1

How is energy transferred from one part of ecosystem to another?

Answer 1

via consumption, energy is transferred from the bottom to the top of the food web

Question 2

Why are there only 3-4 trophic levels?

Answer 2

energy losses limit number of trophic levels in ecosystems

Question 3

How does energy usually enter the ecosystem as primary producers?

Answer 3

usually via photosynthesis

Question 4

As energy is transferred across trophic levels, energy is lost due to:

Answer 4

• limited consumption and assimilation
• respiration
• heat production

Question 5

Define Entropy

Answer 5

a degree of randomness

Question 6

Define a closed system

Answer 6

a concept in physics to describe an ideal system that does not allow for the transfer of energy in or out

Question 7

First law of thermodynamics

Answer 7

• the total amount of energy in the universe is constant (can neither be created or destroyed)
• in a food web, energy is derived initially from sunlight through primary production
• it is then converted form one biological form to another

Question 8

Second law of thermodynamics

Answer 8

• entropy will increase over time in a closed system
• when energy is transferred from one form to another, energy is lost, usually as heat
• organisms are warm and their surroundings are often colder

Question 9

What is Lindeman’s 10% rule?

Answer 9

only 10% of energy is consumed by a trophic level is assimilated and available to higher trophic levels

Question 10

One major difference between terrestrial and aquatic systems?

Answer 10

biomass allocation

Question 11

Aquatic vs. Terrestrial Ecosystems

Answer 11

-Autotroph biomass removed by zooplankton at a higher rate
than terrestrial autotroph biomass being consumed by
terrestrial herbivores
- Autotrophs (phytoplankton, macroalgae) tend to be short
lived
- Greater proportion of autotrophs consumed by herbivores
than by detritivores compared to terrestrial system

Question 12

What can we learn from energy budgets?

Answer 12

1. the trophic bottom of primary producers is relatively big
2. the organic belowground matter stores a lot of energy
3. consumer components are much smaller than the production components
4. ecosystems are inefficent systems

Question 13

What are bottom-up controls

Answer 13

how physical and chemical factors influence primary production

Question 14

How do Biotic Factors influence energy flow?

Answer 14

changes in the abundance of organisms at one trophic level can influence energy flow at multiple levels

Question 15

What are Top-down Controls?

Answer 15

the influence of consumers on ecosystems

Question 16

Define trophic cascade

Answer 16

when a change in the population size of a species in one trophic level changes/alters populations in the other trophic levels

Question 17

Example of trophic cascade

Answer 17

consequences of a predator extinction from a dominant marine primary producer