energy transfers in eco systems

Question 1

what produces biomass

Answer 1

plants when they photosynthesise

Question 2

what does an ecosystem include

Answer 2

An ecosystem includes all the organisms living in a p articular area
and all the non-living (abiotic) conditions

Question 3

what are producers

Answer 3

organisms that make their own food,

e.g. plants and algae produce their own food through photosynthesis

Question 4

during photosynthesis what do plans use

Answer 4

energy (from sunlight) and carb on dioxide (from the atmosphere in land-based
ecosystems, or dissolved in water in aquatic ecosystems) to make glucose and other sugars

Question 5

what are some of the sugars in photosynthesis used in

Answer 5

respiration, to release energy for growth.

Question 6

what is the rest of the glucose used to make

Answer 6

other biological molecules, such as cellulose (a component of plant cell
walls). These biological molecules make up the plant’s biomass — the mass of living material.

Question 7

what can biomass also be thought of as

Answer 7

the chemical energy stored in the plant.

Question 8

what is energy transferred through

Answer 8

the living organisms of an ecosystem when organisms eat other organisms,
e.g. producers are eaten by organisms called primary consumers. Primary consumers are then eaten by
secondary consumers and secondary consumers are eaten by tertiary consumers. This is a food chain

Question 9

how can biomass be measured as or using

Answer 9

it can be measured as dry mass or using a calorimeter

Question 10

what can biomass be measured in terms of

Answer 10

in terms of the mass of carbon that an organism

contains or the dry mass of its tissue per unit area.

Question 11

what is dry mass

Answer 11

Dry mass is the mass of the organism with the water remove d

Question 12

how do you measure the dry mass

Answer 12

To measure the dry mass, a sample of the organism is dried, often in an oven set to a low temperature.
The sample is then weighed at regular intervals (e.g. every day). Once the mass becomes constant
you know that all the water has been removed.

Question 13

what is the typical unit for dry mass

Answer 13

kg m^-2

Question 14

what can the result from the dry mass sample be scaled up to give

Answer 14

If needed, the result from the sample can be scaled up to give the dry mass (biomass) of the total
population or the area being investigated.

Question 15

what is 50% of the dry mass made up of

Answer 15

carbon

Question 16

how can you estimate the amount of chemical energy stored in biomass

Answer 16

by burning the biomass in a calorimeter.
The amount of heat given off tells you how much energy is in it. Energy is measured in joules (J) or kilojoules (kj)

1) A sample of dry biomass is burnt and the energy released is used to heat a known volume of water.
2) The change in temperature of the water is used to calculate the chemical energy of the dry biomass.

Question 17

what are examples of chemical stores

Answer 17

GPP and NPP

Question 18

what is GPP

Answer 18

Gross primary production (GPP) is the total amount of chemical energy
converted from light energy by plants, in a given area

Question 19

what happens to 50% of the GPP

Answer 19

Approximately 50% of the gross primary pro duction is lost to the environment
as heat when the plants respire. This is called respiratory loss (R).

Question 20

what is the remaining chemical energy called

Answer 20

The remaining chemical energy is called the net primary production (NPP). So NPP = GPP - R

Question 21

what is NPP

Answer 21

The NPP is the energy available to the plant for growth and reproduction — the energy is stored in the plant’s
biomass. It is also the energy available to organisms at the next stage in the food chain (the next trophic level)

These include herbivores (animals that eat the plants) and decomposers

Question 22

what is primary production expressed as

Answer 22

Often primary pro duction is expressed as a rate — i.e. the total amount of chemical energy (or biomass) in a
given area, in a given time. Typical units might be kj ha 1 y e a r1(kilojoules per hectare per year) or kj n r2y r 1.
W hen primary pro duction is expressed as a rate, it is called primary productivity.