Energy And Ecosystems

Question 1

Can you explain how energy enters an ecosystem?

Answer 1

All energy in ecosystem comes from sunlight, which is conserved as chemical energy in plants

Question 2

Can you explain how energy is transferred between the organisms in the ecosystem?

Answer 2

When biomass is consumed

Question 3

Trophic level definition

Answer 3

Each stage in a food CHAIN

Question 4

Food chain definition

Answer 4

Feeding relationship in which producers are eaten by primary consumers, which are eaten by secondary consumers and so on

Question 5

Food web definition

Answer 5

Linking of food chains in a single habitat or ecosystem

Question 6

Producer definition

Answer 6

An organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water. Generally photosynthetic.

Question 7

Consumers definition

Answer 7

Organisms that obtain their energy by feeding on other organisms - directly on producers = primary

Question 8

Decomposer/ Saprobionts definition

Answer 8

An organism that obtains its food from the dead or decaying remains of other organisms

Question 9

Biomass definition (x2)

Answer 9

Total mass of living material in a specific area over specific time

Total chemical energy stored in an organism

Question 10

Explain how biomass is measured using calirometer

Answer 10

Calirometry

Burn dry biomass in calirometer
Burning smoke heats a known value of water
Change in temperature can be used as an estimate of the chemical energy of the aamole

Question 11

Biomass must always be

Answer 11

The dry mass/ mass of carbon (50% of dry mass sample)

Question 12

When calculating biomass remember

Answer 12

Units may need time ie yr -1

Question 13

Calculations dry mass process

Answer 13

Weight empty crucible
Place sample in crucible and then in oven at low temperature (to avoid burning sample)
Remove and weight at regular intervals
When mass stops decreasing, sample if fully dehydrated
Subtract this crucible mass from this mass = dry mass

Question 14

Biomass calirometer limitation and solution

Answer 14

Heat energy lost to surroundings

Use a bomb calirometer

Question 15

Limitations of calculating dry mass process

Answer 15

Long time to fully dehydrate

Need precise weighing scale

Question 16

Why is most of suns energy not converted to organic matter by photosynthesis?

Answer 16

Over 90% reflected back into space or is absorbed by atmosphere
Not all wavelengths of light can be absorbed and used for photosynthesis
Light may not fall on a chlorophyll molecule
Low CO2 levels may limit rate of photosynthesis - any factor that limits photosynthesis

Question 17

What is GPP/ gross primary production?

Answer 17

Total quantity of light energy converted into chemical energy in a given area

Question 18

Why does GPP≠ NPP
GPP - gross primary production
NPP - net primary production

Answer 18

20-50% of chemical energy is used for respiration

Question 19

NPP/ net primary production formula

Answer 19

NPP = GPP - R

Net primary production = gross primary production - respiratory losses

Question 20

Is energy transferred to primary producers from plants more efficient then energy transferred to secondary/tertiary consumers and explain

Answer 20

Energy transferred to secondary and tertiary consumers is slightly more efficient because not all parts of plant can be eaten like the bark, not 100% digested.

Question 21

Why is energy lost during transfer between consumers (4)

Answer 21

Some of organisms is not consumed
Some parts were consumed but can not be digested
Some energy lost in excretory material
Some energy losses occur due to heat from respiration; high in mammals and birds because of a high body temperature so a lot of energy is needed to maintain as heat is constantly being lost to the environment

Question 22

Net primary production of consumers equation

Answer 22

N = I - (F+R)

Net primary production = chemical energy ingested - (faecal + respiratory losses)

Question 23

Efficiency equation for sun to producer

Answer 23

(GPP/light energy falling on producer) x 100

Question 24

Efficiency equation from producer to primary consumer

Answer 24

(Net consumer productivity / net primary productivity) x 100

Chemical energy of producer = net primary productivity

Chemical energy in consumer = net consumer productivity

Question 25

Efficiency equation from secondary to tertiary consumers etc

Answer 25

(NPP of tertiary/ NPP of seocndary) x 100

Question 26

How to increase yield of energy? (Abiotic and biotic factors)

Answer 26

Reduce energy loss from crops to other organism (abiotic like temp) or by removing pests (biotic)
Reduce loss through respiration by restricting movement

Question 27

Summarise the common features of all nutrients cycles.

Answer 27

Nutrients are taken up by producers as simple inorganic
The producer incorporates the nutrient into complex organic molecules
When producer is eaten, the nutrients pass into consumers
It then passes along the food chain into other consumers (when eaten)
When producers and consumers die, their complex molecules are broken down by saprobionts, which release nutrients back into their original, simple form l

Question 28

Why are saprobionts so necessary?

Answer 28

Driving force that ensures nutrients are released for reuse

Question 29

Importance of nitrogen cycle?

Answer 29

Nitrogen is needed to make proteins and nuclei acids.

78% of atmosphere is N2 but is inaccessible to plants and animals

Question 30

5 steps of nitrogen cycle (state)

Answer 30

Nitrogen Fixation 
Ammonification 
Nitrification 
Denitrification 
Lightening oxidation

Question 31

Nitrogen fixation (4 points)

Answer 31

N2 is converted to NH3 or nitrogen containing compounds
Nitrogen - fixing bacteria convert N2 to NH3
NH4+ (aq) is then absorbed by plants

Free - living bacteria - use the ammonia to make amino acids and release nitrogen compounds when they die

Mutualistic nitrogen fixing bacteria - live in root nodules of leguminous plants and have a symbiotic relationship where plant gives carbohydrates and bacteria gives ammonia (NH3)

Question 32

Ammonification (2)

Answer 32

Nitrogen compounds in urine and faeces and dead organisms are converted into ammonia by saprobionts

Forms NH4+ in soil

Question 33

Nitrification

Answer 33

Nitrifying bacteria convert NH4+ from nitrogen fixation and ammonification into NITRITES (NO2) and then a different nitrifying bacteria converts NITRITE (NO2) into NITRATE (NO3)

NH3 to NO2
NO2 to NO3

Question 34

Denitrification (2)

Answer 34

Denitrifying bacteria use NITRATE (NO3) in soil during ANAEROBIC respiration, which produces N2 (g), which returns to the atmosphere.

Occurs in waterlogged areas and bogs

Question 35

Lightening oxidation (1)

Answer 35

Lightening oxidation of atmospheric nitrogen (N2(g)) to nitrogen oxides, which is then carried to the soil as nitric acid

Question 36

Why is the phosphorous cycle important?

Answer 36

Used in phospholipid membranes
Used in nuclei acids (dna and rna)
ATP

Question 37

Phosphorus cycle (5)

Answer 37

Phosphorous slowly released into the soil in form of phosphate ions (PO4, -3) by WEATHERING/EROSION
Phosphate ions taken up from soil by plants or absorbed from H2O by algae
Phosphate ions transferred to consumers in feeding
Phosphate ions in waster products/dead organisms are released into soil/water during decomposition by saprobionts
Phosphate ions can be taken up and used again by products or trapped in sediments and undergo sedimentation and become rock containing phosphorus

Question 38

Role of mycorrhizae in nutrient cycles

Answer 38

Fungi act like extensions of the plants root system and vastly increase total surface area for absorption of water and nutrients.
Fungi holds nutrients and water near roots of plants allowing for a plant better resistant to drought and take up ions easily.

MUTUALSITIC RELATIONSHIP = fungi receives organic compounds like sugars and amino acids, plant receives water and ions

Question 39

Explain why fertilisers are needed in agricultural ecosystems?

Answer 39

Crops absorb minerals and are harvested, hence minerals are not released back into soil by decomposition resulting in soil with a lack of mineral ions which prevent re-growth of crop. Extra nutrients need so that plant growth is not LIMITED by lack of nutrients.

Question 40

Distinguish between natural and artificial fertilisers.

Answer 40

Natural = organic = dead and decaying remains of plants and animals along with animal waste

Artificial = inorganic = mined from rocks and deposits and then are converted into different forms. Almost always contains potassium, phosphorus and nitrogen

Question 41

How fertilisers increase productivity?

Answer 41

Minerals are needed for growth. Nitrogen needed in amino acids, nuclei cells acids and ATO. Where these mineral ions are readily available, plants are likely to develop earlier, grow taller and have a greater leaf area. This increases the rate of photosynthesis and improves crop productivity.

Question 42

State three environmental effects of nitrogen containing fertilisers

Answer 42

Reduced species diversity
Leaching
Eutrophication

Question 43

Reduced species diversity as an environmental effects of nitrogen containing fertilisers - explain.

Answer 43

Nitrogen rich soil favours growth of grasses and nettles, which grow rapidly and then outcompete other species, which die as a result.

Question 44

Leaching - three environmental effects of nitrogen containing fertilisers - explain

Answer 44

Process by which nutrients are removed from the soil.
Rainwater dissolves soluble nutrients, which eventually run off into watercourses which can be extremely harmful if used as drinking water. Prevents efficient oxygen transport in babies and links to stomach cancer.
Eutrophication

Question 45

Eutrophication- three environmental effects of nitrogen containing fertilisers - explain

Answer 45

Process by which nutrient concentrations increase in bodies of water
Nitrate ion concentration increases, hence no longer a limiting factor in algal growth
Mainly grows at surface
Forms a dense layer which absorbs light
Light becomes a limiting factor for plants in depths, which then die
Lack of dead plants is no longer limiting factor hence saprobionts population grows
Hence increased demand for oxygen for respiration
Oxygen becomes limiting factor for fish which die
More nitrogen released from dead matter
Anaerobic organisms release more nitrates, and hydrogen sulphides which make water putrid

Question 46

Advantage of using dry mass and not fresh mass ti compare yield of plants? 2 marks

Answer 46

Amount of water present will cary depedning on plant and environemnt - will affect fresh mass not dry mass

Question 47

Explain how farming practices increases the productivity of agricultural crops. (5 marks)

Answer 47

Fertilisers increase concentration of mineral ions like phosphorus or nitrogen in soil. Phosphorous need to form ATP/ nucleic acids and nitrogen needed for amino acids/nucleic acids.
Genetic modification of crops to increase speed of growth
Ploughing and aeration allows for more nitrification and decreases denitrification hence more nitrogen compounds in soil
Crop rotation -> adding leguminous (nitrogen fixing bacteria in root nodules) plants allows for an increase in NH4+ in soil hence more fertile soil