23.2 biomass transfer through an ecosystem Flashcards Preview

BIOLOGY chapter 23 > 23.2 biomass transfer through an ecosystem > Flashcards

Flashcards in 23.2 biomass transfer through an ecosystem Deck (19):
1

what is a trophic level

each stage in a food chain

2

what is the first trophic level

producers - organism which converts light energy into chemical energy by photosynthesis

3

what are the subsequent trophic levels

consumers - organism that obtains energy by feeding on other organisms

4

define biomass

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

5

how do you calculate biomass at each trophic level

biomass present in each organism X total number of organisms present

6

what is biomass measured in

grams per square meter (g/m²)
grams per cubic meter (g/m³)

7

how do you measure biomass

- measure the mass of fresh material present
- water content has to be discounted
- dry mass has to be calculated

8

how do you calculate dry mass

1. organisms are killed and dried
2. placed in an oven at 80C until all water is evaporated
3. to minimise destruction, only a small sample is taken BUT it may not be representative

9

define ecological effieciency

the efficiency with which biomass or energy is transferred from one trophic level to the next

10

define gross production

- total solar energy that plant converts into organic matter
- around 20-50% of energy is used in respiration

11

how do you calculate net production

gross production - respiratory losses

12

efficiency at producer level

producers only convert 1-3% of light into biomass because:
- not all solar energy is available for photosynthesis (90%=reflected and some is transmitted)
- other factors list photosynthesis
- proportion of 'energy' is lost as it is used in photosynthesis rezctions

13

efficiency at consumer levels

consumers covert 10% of biomass into their own organic tissue because:
- not all biomass of an organism is eaten
- energy is transferred to the environment as metabolic heat due to movement/respiration
- some parts of organisms are indigestible and are egested
- energy is lost in excretory materials such as urine

14

how much of energy from sunlight is embodied as biomass in a tertiary consumer

0.001%

15

how do you calculate ecological efficiency

biomass available after transfer/biomass available before transfer
X100

16

what do humans depend on which manipulates the environment

- agriculture manipulates environment to favour crops and rear animals for food/produce
- provided with necessary abiotic conditions
- competition from other species and predators are removed

17

how does agriculture affect food chains

simplifies food chains as fewer trophic levels are present so as much energy as possible is transferred into biomass

18

farming animals for food - TROPHIC LEVELS

producers - animal feed
primary consumers - livestock
secondary consumers - humans

19

cultivating plants for human consumption - TROPHIC LEVELS

producers - crops
primary consumers - humans