4.2 Energy Flow

Question 1

What are the trophic levels?

Answer 1

1. Producer
2. Primary consumer
3. Secondary consumer
4. Tertiary consumer

Question 2

What do food chains show?

Answer 2

A food chain shows linear feeding relationship between species in a community

Question 3

What does the arrow on food chains show?

Answer 3

Transfer of energy

Question 4

Why is not all energy that is stored transferred via heterotrophic feeding - how is some of the chemical energy is lost? (2)

Answer 4

• being excreted as past of the organism’s faeces
• remaining unconsumed as the uneaten portions of the food

Question 5

What three ways can chemical energy that is produced by an organisms be converted? (All are exothermique and release thermal energy as a byproduct)

Answer 5

• Kinetic energy (during muscular contactions)
• electrical energy (transmission of nerve impulses)
• light energy (producing bioluminescence)

Question 6

Why do ecosystems require a continuous influx of energy from an external source? (Eg the sun) (3)

Answer 6

• (kinetic, electric, light) energy are exothermic and release thermal energy as a byproduct
• living organisms cannot turn this heat into other forms of usable energy
• thermal energy is released from the organisms and is lost from the ecosystem

Question 7

How is energy lost to the organism? (~10% efficient) (4)

Answer 7

Respiration, released as heat, created in faeces or unconsumed

Question 8

As energy is lost between trophic levels what happens to the biomass?

Answer 8

The higher trophic levels store less energy as carbon compounds and has less biomass

Question 9

What is biomass?

Answer 9

The total mass of a group of organisms (carbon compounds contained in the cells and tissues)

Question 10

How do scientists measure the amount of energy?

Answer 10

Through carbon compounds as cc store energy, scientists can measure the amount of energy added to organisms as biomass

Question 11

How does biomass diminish along the food chain? (3)

Answer 11

Loss of carbon dioxide, water and waste products

Question 12

Why is the number of potential trophic levels limited? (3 step reason)

Answer 12

• Higher trophic levels receive less energy / biomass from feeding so need to eat larger quantities to obtain sufficient amounts
• Higher trophic levels need to eat more, they expand more energy hunting for food
• If the energy required to hunt food exceeds the energy available from the food eaten, trophic levels become unviable

Question 13

What units are pyramids of energy measured in?

Answer 13

In units of energy per area per time (eg. kJ^-2 year^-1)

Question 14

What r are pyramids of energy?

Answer 14

Graphical representation of amounts of energy at each trophic level of food chain

Question 15

Why will pyramids of energy never appear as inverted?

Answer 15

Some of the energy stored in one source is lost upon transfer (around one tenth)