biomass transfer through ecosystems

Question 1

what is a trophic level?

Answer 1

each stage in a food chain

Question 2

what are food chains/webs used to demonstrate?

Answer 2

transfer of biomass (energy) through organisms in an ecosystem

Question 3

describe the first trophic level

Answer 3

producer - an organism that converts light energy into chemical energy via photosynthesis

Question 4

why is there a limited number of trophic levels?

Answer 4

there is not sufficient biomass and stored energy left to support further organisms

Question 5

what is the role of decomposers?

Answer 5

break down dead organisms and release nutrients back into the ecosystem

Question 6

what is ‘biomass’?

Answer 6

the mass of living material present in a particular place or organisms

Question 7

how would you calculate the biomass at each trophic level?

Answer 7

biomass present x total number of organisms in trophic level

Question 8

what is meant by ‘ecological efficiency’?

Answer 8

the efficiency by which biomass/energy is transferred

Question 9

what makes up the biomass?

Answer 9

cells and tissues composed of carbon compounds

Question 10

what are units for biomass on land and water?

Answer 10

land = gm-2
water = gm-3

Question 11

how is biomass measured?

Answer 11

discount water and measure the mass

Question 12

why is it important to not consider the water and use dry mass?

Answer 12

organisms have varied amounts of water

Question 13

what are the limitations of pyramids of biomass?

Answer 13

fails to consider how climate plays a role in trophic level activities

Question 14

how are biomass and energy linked?

Answer 14

light energy is captured by plants and transferred to organic compounds, forming biomass.
- therefore biomass can be equated to energy content

Question 15

what is meant by gross primary production?

Answer 15

the rate at which chemical energy is stored by producers

Question 16

what is meant by net primary production?

Answer 16

the energy left over after respiration in plants

Question 17

why is a rabbit more energy efficient than a lizard?

Answer 17

lizard
- mammals have consumed less energy available for next consumer
- mammals have a high body temp so requires a high rate of respiration and loses a higher proportion of energy
- higher proportion of food the lizard eats can be converted into new cells/tissues so a higher proportion of energy available to predator

Question 18

how is net primary production calculated?

Answer 18

gross primary production - energy used in respiration

Question 19

how can energy be lost from plants? (5 points)

Answer 19

• reflection from leaf surface
• transmission through leaf
• light not correct wavelength
• limited photosynthesis due to water availability
• energy lost via photosynthesis

Question 20

how can energy be lost from consumers? (4 points)

Answer 20

• not all biomass of organism is eaten, e.g. roots or bones
• heat loss via movement/respiration
• some parts of organism eaten are not digested
• excretory material, e.g urine

Question 21

what is the calculation for ecological efficiency?

Answer 21

(biomass or energy available AFTER transfer / biomass or energy available BEFORE transfer) x 100

Question 22

what is the calculation for energy consumed?

Answer 22

biomass + respiration + waste

Question 23

describe and explain how energy efficiency differs through an ecosystem

Answer 23

• first stage = producer
• 1-3% light energy is converted into chemical energy in photosynthesis due to factors such as reflection, transmission, incorrect wavelength
• second stage = consumer
• 10% energy is used
• energy lost due to heat/respiration but the organisms consumed contain more energy which is transferred to form biomass

Question 24

how does intensive rearing of animals create more energy efficient transfer?

Answer 24

• converting smallest amount of food energy into greatest quantity of animal mass
• ensure that energy goes into growth rather than other activities

Question 25

what methods do intensive farms use to maximise output? (5 points)

Answer 25

• specially bred animals for high growth rate
• highly digestible diet including growth hormones and antibiotics
• restricted movement to reduce energy output
• exclusion of predators
• slaughtered young as more energy is transferred to biomass