3.5.3 energy transfers in ecosystems

Question 1

what is the equation for energy transfer?

Answer 1

energy transfer = energy available after the transfer / energy available before the transfer x 100

Question 2

what is a saprobiont?

Answer 2

a organism that breaks down dead, organic matter using the secretion of extracellular enzymes.

Question 3

why is energy transfer so inefficient from the sun?

Answer 3

• not all light is absorbed by chloroplasts.
• some light is reflected as wrong wavelengths so not absorbed.

Question 4

why is energy transfer inefficient between trophic levels?

Answer 4

• energy used in movement.
• not all eaten.
• not all digested.
• excretion = urine.
• respiration.
• heat loss/homeostasis.

Question 5

what is GPP?

Answer 5

gross primary productivity

chemical energy store in plant biomass in a given area or volume.

Question 6

what is NPP?

Answer 6

net primary productivity

chemical energy store in plant biomass after respiratory losses to the environment has been taken into account.

Question 7

how is biomass formed?

Answer 7

• sugar synthesised by plants and used as a respiratory substrate.
• rest are used to make other groups of biological molecules = forming biomass.

Question 8

what is biomass?

Answer 8

the total mass of carbon or dry mass of tissue in a given area/volume

Question 9

how is the chemical energy store of dry biomass estimated?

Answer 9

calorimetry

Question 10

what is the equation for the net production of consumers?

Answer 10

N = I - (F+R)

N = net production of consumers.
I = chemical energy store of ingested food.
F = energy lost in faeces and urine.
R = energy lost in respiration.

Question 11

what is productivity?

Answer 11

• the rate of primary or secondary production.
• measured in biomass in a given area in a given time.
• units: kJ ha-1 year-1

Question 12

what do farmers do in GM/ selective breeding?

Answer 12

identify individuals with desired traits:
- fast growth rate.
- high meat/milk production.
- large crop yield.
then breed over multiple populations to increase productivity and efficiency.

Question 13

how does GM/selective breeding increase efficiency?

Answer 13

• shorter growing periods = meet market readiness with faster turnovers in production cycles.
• increase profitability = more products in less time.
• supports growing global demands = far more food with less land and resources.

Question 14

what are the issues with GM/selective breeding?

Answer 14

• cost of acquiring high performance breeds = expensive for less developed farming operations.
• reduced genetic diversity.
• less adaptable to changing environment.
  > overall threats to food security.

Question 15

what do farmers do in intensive farming practise (factory farming)?

Answer 15

• feed animals with specialist high protein foods.
• place animals in confined spaces to maximise space.
• dark to reduce movement.
• control temperatures.
• give animals antibiotics to reduce disease.

Question 16

how does intensive farming practise (factory farming) increase efficiency?

Answer 16

• low energy needed = animals require less food.
• less death by disease.
• decreased respiration.

Question 17

what are the issues with intensive farming practise (factory farming)?

Answer 17

• significant ethical concerns.
• nutritional concerns = affects taste and nutritional value of food.
• hidden ethical and health costs.
• not sustainable, bad for welfare and decreases food quality.

Question 18

what do farmers do to simplify food webs?

Answer 18

monocultures.
monocultures = single plant species cultivated in large area. Other species removed (pesticides).

Question 19

how does simplifying food webs increase efficiency?

Answer 19

• GPP increases as more energy from sunlight converted into biomass by target species.
• NPP increases as fewer organisms consuming crop and lower loss of edible biomass.

Question 20

what are the issues with simplifying food webs?

Answer 20

• pesticides can cause:
  > lack of biodiversity.
  > problems with ecosystem balance.
  > bioaccumulation.
• monocultures decrease number of pollinators in areas as there is a lack of biodiversity.

Question 21

what is an autotroph?

Answer 21

an organism that can produce its own food using energy from sunlight (photosynthesis) or chemical reactions (chemosynthesis).

Question 22

what is a heterotroph?

Answer 22

an organism that cannot produce its own food and obtains energy and nutrients by consuming other organisms or their organic matter.

Question 23

what is a consumer?

Answer 23

an organism that obtains its energy and nutrients by feeding on other organisms, either directly or indirectly.

Question 24

what is a producer?

Answer 24

an organism that synthesises its own food from inorganic compounds, typically using sunlight through photosynthesis.

Question 25

what are respiratory losses?

Answer 25

the energy that is lost during respiration, which is then converted into heat and is not available for biomass production or transfer to the next trophic level.