biomass transfer through ecosystems

Question 1

define 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 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 insufficient 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

mass of living material present in a particular place or organism

Question 7

how would you calculate biomass at each trophic level?

Answer 7

biomass present x total number of organisms in trophic level

Question 8

define ecological efficiency

Answer 8

efficiency by which biomass/energy is transferred

Question 9

what makes up biomass?

Answer 9

cells and tissues composed of carbon compounds

Question 10

what are the 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 mass

Question 12

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

Answer 12

organisms have varied amounts of water
- makes data unreliable unless large sample is taken

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.
- so biomass can be equated to energy content

Question 15

what is meant by gross primary production?

Answer 15

rate at which chemical energy is stored by producers

Question 16

define net primary production

Answer 16

energy left over after respiration in plants

Question 17

how is energy transferred from one trophic level to the next?

Answer 17

consumption

Question 18

how is ecological efficiency calculated?

Answer 18

energy or biomass available after transfer / energy or biomass available before the transfer x 100

Question 19

explain 3 reasons why 1-3% of sunlight producers receive is converted into chemical energy

Answer 19

• not all solar energy is used for photosynthesis - 90% is reflected, some transmitted through leaf and some is of unusable wavelength
• other factors may limit photosynthesis
• proportion of energy is lost and used for photosynthetic reactions

Question 20

define primary production

Answer 20

generation of biomass in a producer

Question 21

define secondary production

Answer 21

generation of biomass in a consumer

Question 22

explain 4 reasons why consumers at each trophic level convert only a small amount of biomass in the trophic level to their own organic tissue.

Answer 22

• not all biomass of an organism is eaten - plant roots/animal bones
• some energy transferred to environment as metabolic heat as result of movement/respiration
• some parts that are eaten are indigestible
• some energy lost in excretory materials (urine)

Question 23

explain why biomass decreases at each trophic level in a food chain.

Answer 23

• organic compounds of organisms store energy
• so biomass is equated to energy content
• small proportion of food ingested by animals is converted into new tissue - only part of biomass/energy available for next trophic level

Question 24

describe how humans have manipulated energy transfer through trophic levels in the farming of plants and animals to our advantage.

Answer 24

• agriculture results in simple food chain of 3 or 2 trophic levels
• animal feed (producer) -> livestock (primary consumer) -> humans (secondary consumer)
• minimal energy is lost bc fewer trophic levels - as much energy as possible transferred into biomass eaten by humans