Topic 4.2: Energy Flow

Question 1

Importance of sunlight

Answer 1

Initial source for almost all communities

Question 2

Autotrophs that do not use light as energy source

Answer 2

Producers derive energy from chemical processes

Question 3

How is light converted into chemical energy (e.g., organic compounds)?

Answer 3

Photosynthesis

Question 4

How is light converted into useful chemical energy by autotrophs?

Answer 4

It is used to make organic compounds from inorganic sources

Question 5

How is chemical energy obtained by heterotrophs?

Answer 5

Ingestion (feeding) of organic compounds produced by photoautotrophs to derive their chemical energy

Question 6

How is energy stored in organic molecule released?

Answer 6

a) Released by cell respiration (in autotrophs / heterotrophs)
b) ATP is produced via cell respiration to fuel metabolic reactions.

Question 7

Are energy process in living organisms 100% efficient? If not, how much?

Answer 7

No. They are ~10% efficient, with about 90% available energy lost between trophic levels.

Question 8

Reasons for energy loss

Answer 8

a) Heat is a by-product of metabolic reactions
b) Not all the parts of an organism can be swallowed, digested and used
c) Some organisms die before being eaten by an organism in the next trophic level

Question 9

What is a consequence of the energy loss between trophic levels?

Answer 9

It restricts the length of food chains and the biomass of higher trophic levels.

Question 10

What forms of energy can chemical energy produced by an organism converted into?

Answer 10

a) Kinetic energy (e.g., muscular contractions)
b) Electrical energy (e.g., during the transmission of nerve impulses)
c) Light energy (e.g., producing bioluminescence)

Question 11

Can an organism convert heat energy into any other form of energy?

Answer 11

No

Question 12

What is a consequence of not being able to convert heat into other forms of usable forms of usable energy?

Answer 12

a) Heat is lost from living organisms and ecosystems, so it is radiated into the atmosphere.
b) Ecosystems require a continuous influx of energy from an external source (e.g., sunlight)

Question 13

Definition of Energy Flow

Answer 13

Process of passing energy from one organism to another through feeding

Question 14

Definition of Food Chain

Answer 14

Representation of the flow of energy through the trophic levels of a feeding relationship.

Question 15

What do the arrows in a food chain represent?

Answer 15

Transfer of energy and matter as one organism is eaten by another

Question 16

Definition of Trophic Levels

Answer 16

Feeding position of an organism in a food chain

Question 17

Name of the Trophic Levels

a) Level 1
b) Level 2
c) Level 3
d) Level 4

Answer 17

a) Producer
b) Primary consumer
c) Secondary consumer
d) Tertiary consumer

Question 18

Definition of Biomass

Answer 18

The total mass of a group of organisms – consisting of the carbon compounds contained in the cells and tissues

Question 19

Relationship between trophic level and its biomass

Answer 19

a) Biomass disminished along food chains with the loss of CO2, H2O and waste products to the environment (e.g., urea)
b) Higher trophic levels store less energy as carbon compounds and have less biomass

Question 20

Relationship between biomass and energy

Answer 20

Since organic compounds store energy, the amount of energy in a trophic level can be measured as biomass

Question 21

Definition of pyramids of energy

Answer 21

Diagram that shows the amount of energy available at each trophic level

Question 22

Units of the energy at a given trophic level

Answer 22

kJ m-2 year-1

Question 23

Will pyramids of energy appear inverted? Why?

Answer 23

No. As so much energy is lost as heat and after many trophic levels, no much energy is left.

Question 24

How much energy is transferred from one trophic level to the next?

Answer 24

~ 10%