Energy Flow

Question 1

What is the 1st law of thermodynamics?

Answer 1

energy can neither be created nor destroyed, only transformed.

Question 2

What is the 2nd law of thermodynamics?

Answer 2

all systems in the universe tend to move towards a state of greater disorder (entropy). During energy conversions, some energy is always lost

Question 3

What is a photoautotroph?

Answer 3

An organism that uses pigment to trap light energy and convert it to chemical energy (i.e: photosynthesis)

Question 4

What does an autotroph do?

Answer 4

Produces its own food/ energy from inorganic substances

Question 5

What is the name for an organism that consumes other organisms for energy?

Answer 5

Heterotrophs

Question 6

What does a heterotroph do?

Answer 6

Consumes other organisms to obtain organic molecules for energy

Question 7

What is the Euglena genus an example of?

Answer 7

a mixotroph

Question 8

What are the 4 main types of heterotroph?

Answer 8

Carnivores
Omnivores
Herbivores
Scavengers

Question 9

What is the difference between carnivores and scavengers?

Answer 9

Scavengers are a specialised type of carnivore that mostly feeds on dead and decaying animal matter rather than killing and eating it fresh

Question 10

What are the 2 main types of decomposers and what do they do?

Answer 10

Detritivores - obtain nutrients by consuming non-living organic sources (like detritus and humus)
Saprotrophs - live in/ on non-living organic matter, secrete digestive enzymes and absorb the products of digestion externally

Question 11

Give an example of a detritivore and a saprotroph

Answer 11

Detritivore - earthworm, dung beetle

Saprotroph -bacteria, fungi

Question 12

Are saprotrophs consumers?

Answer 12

No - because they don’t ingest food, they ingest the products of external digestion

Question 13

What does a consumer do?

Answer 13

Ingests organic matter which is living or recently killed

Question 14

What are 2 issues with trophic level models?

Answer 14

Simplistic - some omnivores are opportunistic and will feed and multiple trophic levels
Mixotrophs - fit into both producer and primary consumer levels

Question 15

What is the primary production?

Answer 15

the amount of energy converted by autotrophs to organic molecules over a time period - it represents the starting point of energy flow in an ecosystem

Question 16

what is secondary production?

Answer 16

amount of chemical energy converted into new biomass (growth and reproduction) by consumers

Question 17

What are 3 reasons energy transfer is inefficient?

Answer 17

Toxic waste is excreted
Some ingested material is not absorbed
Some organic material remains uneaten (i.e: bones, fur)
Most energy is lost as heat/ thermal energy

Question 18

How do you calculate production efficiency?

Answer 18

(Net secondary production X 100) / absorption of primary production

Question 19

What % of energy is transferred to each trophic level?

Answer 19

10%

Question 20

Why is there often only 4 trophic levels?

Answer 20

Because the rule of tenths means only 10% of energy is transferred from each trophic level to the next - there wouldn’t be enough food for the 5th trophic level to consume to sustain life

Question 21

Where is the other 90% of energy lost to per trophic level?

Answer 21

• not eaten
• not digested
• excreted
• lost as heat

Question 22

What unit are pyramids of energy measured in?

Answer 22

KJ m-2 y-1

energy KJ per area per time

Question 23

In a pyramid of energy, which level is the biggest?

Answer 23

The bottom (producers)

Question 24

Why are food webs better models than pyramids of biomass

Answer 24

Pyramids only show a simplified food chain, whereas food webs show more complex ecological interactions between multiple food chains

Question 25

Name 3 limitations of food web models?

Answer 25

Still too simplistic
Trophic interactions can change over time
Doesn’t account for migratory animals
Micro-organisms are not accounted for
The strength of relationships cannot be measured
Doesn’t recognise mutualistic relationships
Often difficult to interpret