Energy transfer in ecosystems

Question 1

What is an ecosystem?

Answer 1

All of the living organisms in a particular area and all of the abiotic conditions

Question 2

What is biomass?

Answer 2

The mass of living material in an organism

Question 3

How is energy transferred through an ecosystem?

Answer 3

When one organism eats another organisms

Question 4

Why is dry mass measured rather than wet mass?

Answer 4

The water content of living tissue varies

Question 5

How is mass dried?

Answer 5

Dried in an oven set a low temperature

Weighed at regular intervals until the mass remains constant - all water removed

Question 6

What are typical units for dry mass?

Answer 6

kg m-2

Question 7

What are typical units for biomass?

Answer 7

kg m-2 yr-1

Question 8

What is used to measure the amount of chemical energy stored in biomass?

Answer 8

Calorimetry

Question 9

How does calorimetry work?

Answer 9

A sample of dry biomass is burnt and the energy released is used to heat a known volume of water, the change in temperature is used to calculate energy

Question 10

In calorimetry, what is the amount of energy released measured in?

Answer 10

Joules or kilojoules

Question 11

How do you get from kilojoules to joules?

Answer 11

x 1000

Question 12

What is Gross primary production (GPP)?

Answer 12

The total amount of chemical energy converted from light energy by plants, in a given area, at a given time

Question 13

What is the NPP?

Answer 13

The energy available to the plant for growth and reproduction, stored in the plant’s biomass, and the energy available at the next stage in the food chain

Question 14

What is the equation for NPP?

Answer 14

NPP = GPP - R

Question 15

Why is photosynthesis not 100% effective?

Answer 15

Not all light energy absorbed by a plant will be converted to chemical energy

Question 16

How much of the energy is lost and not transferred to the next trophic level?

Answer 16

90%

Question 17

How is energy lost in food chains?

Answer 17

Not all food is eaten
Some parts are indigestible
Some lost to environment through respiration and excretion

Question 18

What is a consumers net production?

Answer 18

The energy thats left after all loses stored in the consumers’ biomass and is available to the next trophic level

Question 19

Whta is the equation for the consumers net production ?

Answer 19

N = I - ( F+R )

Question 20

What does each part of the equation for the consumers net production stand for?

Answer 20

N = net production 
I = Chemical energy in ingested food
F = Chemical energy lost in faeces and urine 
R = energy lost through respiration

Question 21

How do you calculate the efficiency of energy transfer?

Answer 21

% efficiency of energy transfer =
net production of trophic level
——————————————– x100
net production of previous trophic level