Biomass transfer 23.2

Question 1

What is the main source of energy in all ecosystems and why?

Answer 1

The sun is the main source of energy as it is converted into chemical energy in plants during photosynthesis. The plants are then eaten by animals and that chemical energy is transferred as food.

Question 2

What is biomass?

Answer 2

The mass of living material present in a particular organism or place.

Question 3

What do food chains and webs show?

Answer 3

The transfer of biomass and energy through organisms

Question 4

What is a trophic level?

Answer 4

A trophic level is a stage in a food chain

Question 5

What is the first trophic level in a food chain?

Answer 5

Producers are the first trophic level which are organisms that convert light energy from the sun into chemical energy (usually plants)

Question 6

What is the second trophic level in a food chain?

Answer 6

Primary consumers are the second trophic level and these are organisms that consume producers and obtain energy from them.

Question 7

Why do food chains not have many trophic levels?

Answer 7

Biomass will decrease further and further up the trophic levels so eventually there isn’t enough energy left to support any other organisms.

Question 8

What are decomposers?

Answer 8

Decomposers are organisms that break down dead organisms to release nutrients back into the soil.

Question 9

How do you draw a pyramid of biomass?

Answer 9

You multiply the biomass present with the number of organisms in the trophic level. You then draw a rectangle to represent it. The producers always go at the bottom and will have the biggest biomass

Question 10

How do you measure biomass?

Answer 10

You have to measure the dry mass of an organism which means it has to have no water in it. The organism has to be killed and placed in an oven at 80 degrees until all of the water has evaporated. There then need to be two identical measurements taken to prove all the water is gone.

Question 11

Why do you need dry mass for the biomass measurement?

Answer 11

There are varying amounts of water in different organisms and when measuring the biomass, you want the living material only that is going to be used as energy. To measure this, you must eliminate the water from the organisms or it will be unreliable.

Question 12

What do scientists do to minimise destruction when measuring biomass, how can this affect results?

Answer 12

They take small samples of organisms to dry out and this may not be representative of the entire population.

Question 13

Why does biomass decrease through each successive trophic level?

Answer 13

Biomass consists of all cells and tissues in a living organism. Carbon compounds are the store of energy in an animal (organism) and they convert only a small fraction of what they have eaten into new tissues. When a consumer eats that animal, the new tissues convert are all that the consumer has to eat, this is why biomass decreases.

Question 14

What is productivity?

Answer 14

The rate at which an organism converts energy

Question 15

What is primary productivity?

Answer 15

The rate at which a producer converts light energy into chemical energy

Question 16

How do you measure primary productivity?

Answer 16

• Harvest method where you measure the biomass and divide it by the area and unit of time - CO2 assimilation where you measure the CO2 taken up by photosynthesis and released by respiration - O2 production where you measure the amount of CO2 taken up and released

Question 17

What is ecological efficiency?

Answer 17

This is the efficiency with which biomass is transferred between trophic levels.

Question 18

How efficient are producers at converting sunlight to chemical energy?

Answer 18

Producers only convert 1-3% of sunlight energy. This is because: - a lot of light is reflected off the plant - factors like temperature and water availability can affect photosynthesis - some energy is used for photosynthesis to occur

Question 19

What is the gross primary productivity (GPP)?

Answer 19

The total energy that an organism has received e.g. total energy a plant converted from sunlight to chemical

Question 20

How efficient are primary consumers?

Answer 20

Primary consumers only convert 20-50% of the gross production energy from plants into biomass. The rest is used for the primary consumer to respire.

Question 21

What is the net primary productivity and how do you calculate it?

Answer 21

NPP = GPP - respiratory losses Net primary productivity is the amount of energy the consumer will convert into biomass

Question 22

How do you increase the NPP?

Answer 22

• Irrigation for good water availabilty - Fertilisers to increase growth - Herbicides to kill weeds that compete - Plant crops close together to maximise light hitting plants

Question 23

What is the biomass production of consumers like and why?

Answer 23

Consumers only convert 10% of the energy they eat to biomass because: - they may not eat all the biomass like the bones of an animal - the energy is transferred to metabolic reactions like respiration - some parts aren’t digested and excreted - some energy is also lost in excretion

Question 24

What is the formula for ecological efficiency?

Answer 24

ecological efficiency = energy available after transfer / x100 energy available before transfer

Question 25

What is agriculture?

Answer 25

Agriculture is manipulating the environment to favour plant species that we can eat (crops).

Question 26

How can human activities manipulate the transfer of biomass?

Answer 26

We are in the 3rd of 4th trophic level in a natural ecosystem, and we know that this means a lot of energy is lost. In agriculture, they make sure there are only 2 trophic levels so the crops are the producers and we are the consumers. We provide optimum temperature, light intensity as water availability as well as eliminating competition and predators.