🩷 3.5 - 3.5.3 Energy and ecosystems (A-level only)

Question 1

What do plants produce, beginning with B, when they photosynthesise?

Answer 1

Biomass.

Question 2

Biomass definition.

Answer 2

The mass of living material.

Question 3

What does an ecosystem include?

Answer 3

All the organisms living in a particular area and all the non-living (abiotic) conditions.

Question 4

What are producers in an ecosystem?
(+ an example)

Answer 4

Producers are organisms which make their own food.
Example: Plants and algae produce their own food through photosynthesise.

Question 5

What do plants use during photosynthesis and what do they make?

Answer 5

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

Question 6

What process are some of the sugars produced during photosynthesis used in?

Answer 6

Respiration, to release energy for growth.

Question 7

After the sugars which are made during photosynthesis are used in respiration what are they used to make?

Answer 7

They are used to make other biological molecules, such as cellulose.

Question 8

What do the biological molecules which are in plants make up?

Answer 8

The plants biomass which is the mass of living material.

Question 9

Biomass can also be thought of as the c _ _ _ _ _ _ _ e _ _ _ _ _ s _ _ _ _ _ in the plant.

Answer 9

chemical energy stored.

Question 10

When is energy transferred through the living organisms of an ecosystem?

Answer 10

When organisms eat other organisms.

Question 11

What are producers eaten by?

Answer 11

Primary consumers.

Question 12

What are primary consumers eaten by?

Answer 12

Secondary consumers.

Question 13

What are secondary consumers eaten by?

Answer 13

Tertiary consumers.

Question 14

Biomass can be measured as r m_ _ _ or using a cal_ _ _ _ _ _ _ _.

Answer 14

dry mass or using a calorimeter.

Question 15

What can biomass be measured in terms of the?

Answer 15

Mass of carbon that an organism contains or the dry mass of its tissue per unit area.

Question 16

Dry mass definition.

Answer 16

The mass of the organism with the water removed.

Question 17

How do you measure the dry mass?

Answer 17

A sample of the organism is dried, often in an oven set to a low temperature, it is then weighed at regular intervals and once the mass becomes constant you know that all the water has been removed.

Question 18

What might a typical unit for dry mass be?

Answer 18

kg m^-2.

Question 19

The mass of carbon present is generally taken to be _ _% of the dry mass.

Answer 19

50%.

Question 20

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

Answer 20

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).

Question 21

How is the chemical energy of the dry biomass found and calculated?

Answer 21

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 22

GPP and NPP are both what?

Answer 22

Chemical energy stores.

Question 23

What does GPP stand for?

Answer 23

Gross Primary Production.

Question 24

What does NPP stand for?

Answer 24

Net Primary Production.

Question 25

Gross Primary Production definition.

Answer 25

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

Question 26

Approximately what % of the GPP is lost to the environment as heat when the plants respire?

Answer 26

50%

Question 27

What is it called when approximately 50% of the GPP is lost to the environment as heat when the plants respire?

Answer 27

Respiratory loss (R).

Question 28

What is the remaining chemical energy called after approximately 50% of the GPP is lost to the environment as heat when the plants respire?

Answer 28

The net primary production (NPP).

Question 29

What is the equation which links NPP, R and GPP?

Answer 29

NPP = GPP - R.

Question 30

Net Primary Production definition.

Answer 30

The energy available to the plant for growth and reproduction. The energy is stored in the plants 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 31

How do consumers get energy?

Answer 31

They get energy by ingesting plant material, or animals that have eaten plant material.

Question 32

Why is around 90% of the total available energy lost when not all the chemical energy stored in the consumers food is transferred to the next trophic level?

Answer 32

1) Not all of the food is eaten (plant roots/bones) so the energy it contains is not taken in. Some are indigestible, so are egested as faeces. Some is also lost to the environment through respiration or excretion of urine.

Question 33

What is the energy thats left after all this is stored in the consumers biomass and is available to the next trophic level called?

Answer 33

This energy is the consumers net production.

Question 34

What is the formula which is used to calculate the net production of consumers?

Answer 34

N = I - ( F + R )

Question 35

N = I - ( F + R )
What does the F in this equation to calculate the net production of consumers stand for?

Answer 35

F = Chemical energy lost in faeces and urine.

Question 36

N = I - ( F + R )
What does the R in this equation to calculate the net production of consumers stand for?

Answer 36

R = Energy lost through respiration.

Question 37

Remember, when production is expressed as a rate it is called pro_u_ _ _ _ _ _ _.

Answer 37

productivity.

Question 38

What can the net production of consumers also be called?

Answer 38

Secondary production (or secondary productivity when its expressed as a rate).

Question 39

What do food chains are food webs show?

Answer 39

They show how energy is transferred through an ecosystem.

Question 40

What do food chains show?

Answer 40

Food chains show simple lines of energy transfer. Each of the stages in a food chain is called a trophic level.

Question 41

What do food webs show?

Answer 41

Food webs show lots of food chains in an ecosystem and how they overlap.

Question 42

What is the role of decomposers?

Answer 42

They break down dead or undigested material, allowing nutrients to be recycled.

Question 43

What do most farming practices aim to increase?

Answer 43

The amount of energy that is available for human consumption.

Question 44

What are 2 farming practices which can be done to increase the amount of energy that is available for human consumption?

Answer 44

1) The energy lost to other organisms, e.g. pests, can be reduced.
2) The energy lost through respiration can be reduced.

Question 45

What does simplifying the food web mean?

Answer 45

It means getting rid of pests (farmers need).

Question 46

What type of pesticides can be used to reduce pest numbers?

Answer 46

Chemical pesticides.

Question 47

What does killing insect pests mean?

Answer 47

If insecticides are used to kill insect pests that eat and damage crops, it means that less biomass is lots from crops, so they grow to be larger, which means NPP is greater.

Question 48

What does killing weeds mean?

Answer 48

If herbicides are used to kill weeds, direct competition with the crop for energy from the sun is removed. It can also remove the preferred habitat or food source of the insect pests, reducing their numbers and simplifying the food web.

Question 49

What does it mean if the numbers of pests is reduced due to biological agents?

Answer 49

Crops lose energy less energy and biomass, increasing the efficiency of energy transfer to humans.

Question 50

True or false?
Parasites live in or lay their eggs on a pest insect.

Answer 50

True.

Question 51

What are two things parasites do?

Answer 51

They either kill the insect or reduce its ability to function.

Question 52

What are used to kill pests?

Answer 52

Pathogenic (disease-causing) bacteria and viruses are used.

Question 53

What systems do farmers use to combine both chemical and biological methods?

Answer 53

Integrated systems.

Question 54

What is the positive of farmers using integrated systems?

Answer 54

It can reduce pest numbers even more than either method alone, meaning NPP is increased even more.

Question 55

What does it mean if respiratory losses are reduced?

Answer 55

It means that energy is transferred more efficiently.

Question 56

What is one way in which farmers can increase the net production of their livestock?

Answer 56

By controlling the conditions that they live in, so that more of their energy is used for growth and less is lost through respiration (and activities that increase the rate of respiration).

Question 57

Give two ways of how farmers might reduce the respiration rate of their livestock.

Answer 57

1) Decrease their movement by keeping their animals in pens so their movement is restricted = respiration rate decreased.
2) Keeping the pens indoors and keeping them warm to reduce the amount of energy used for generating body heat = respiration rate decreased.

Question 58

What does it equal when farmers reduce the respiratory of their livestock by keeping them in pens?

Answer 58

It means that more biomass is produced and more chemical energy can be stored, increasing net production and the efficiency of energy transfer to humans.

Question 59

What is the benefit of keeping animals in pens, reducing their respiratory rate?

Answer 59

More food can be produced in a shorter space of time, often at a lower cost.

Question 60

What is the disadvantage of keeping animals in pens, reducing their respiratory rate?

Answer 60

Raises ethical issues.
(some people believe that the conditions intensively reared animals are kept in cause the animals pain, distress or restricts their natural behaviour, so it should not be done).