4.2 ENERGY FLOW

Question 1

ESSENTIAL IDEA

Answer 1

ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat

Question 2

WHAT DO ECOSYSTEMS RELY ON?

Answer 2

light energy received from the sun

Question 3

ALL PLANTS AND SOME PROKARYOTES ARE

Answer 3

photoautotrophs

they use pigments (chlorophyll) to trap light energy which is converted to chemical energy in carbon compounds

Question 4

CHEMOAUTOTROPHS

Answer 4

volcanic vents on the ocean floor

producers which use energy from chemical processes

Question 5

CONVERSION OF LIGHT ENERGY

Answer 5

the light energy from the sun is used to synthesis carbohydrates

the light energy is transferred into bonds (chemical energy) between the atoms in a carbohydrate M

Question 6

CONSUMERS

Answer 6

ingest organic matter which is living or recently killed

Question 7

FOOD CHAINS

Answer 7

show the flow of energy through the trophic levels of a feeding relationship

Question 8

TROPHIC LEVELS

Answer 8

feeding position of an organism in a food chain

Question 9

WHY DO ECOSYSTEMS REQUIRE A CONTINUOUS SUPPLY OF ENERGY?

Answer 9

no energy transfer is 100% efficient

waste: heat thermal energy is produced too

unlike light/ chemical energy organisms cannot convert heat energy into useful forms

Question 10

PYRAMIDS OF ENERGY

Answer 10

show the flow of energy between trophic levels

Question 11

PYRAMIDS OF ENERGY UNITS

Answer 11

kJ m^-2 y^-1

unit of energy per unit area per time

Question 12

AROUND 90% OF ENERGY IS LOST BETWEEN TROPHIC LEVELS DUE TO (4)

Answer 12

not ingested foods
not digested or assimilated
excreted
lost as heat from respiration

Question 13

AT HIGHER TROPHIC LEVELS PYRAMIDS OF ENERGY ALWAYS…

Answer 13

get smaller due to the loss of energy

Question 14

BOTTOM LEVEL OF PYRAMIDS OF ENERGY =

Answer 14

producers

subsequent levels =
consumers (primary/secondary…)

Question 15

AS THE TROPHIC LEVEL INCREASES

Answer 15

the biomass and energy available decreases

Question 16

HIGHER TROPHIC LEVELS ARE OFTEN LESS EFFICIENT BECAUSE

Answer 16

more energy is spent on foraging more mobile prey

Question 17

WHY IS BIOMASS INDIRECTLY USED AS A MEASURE OF ENERGY TRANSFER

Answer 17

chemical energy is held in molecular bonds

thus, as energy is lost between trophic levels it is natural for biomass to be lost too

Question 18

FORAGE

Answer 18

searching widely for food

Question 19

EVENTUALLY THE ENERGY REQUIRED TO FORAGE

Answer 19

exceeds the energy gained from foraging, making the trophic level unviable

Question 20

BIOMASS IS USUALLY MEASURED AS

Answer 20

the total dry mass of organisms

Question 21

ENERGY FLOWS

Answer 21

energy flows linearly

energy enters from sunlight

autotrophs capture sunlight

energy flows through the trophic levels

energy transfer is 10% from one level to the next

energy loss is due to material not consumed or assimilated/ egested/ excreted

energy passes to decomposers/ detritivores/ saprotrophs in dead organic matter

heat energy is lost through cell respiration = heat

Question 22

NUTRIENT FLOW

Answer 22

nutrients are recycled

nutrients are recycle within ecosystems

nutrients from weathering rocks enter ecosystems

nutrients recycled from decomposition of dead organisms

nutrients move through food chain by digestion of other organisms

nutrients absorbed by producers/ plants/ roots

nutrients lost by leaching/ sedimentation