Energy and Ecosystems

Question 1

Define Population

Answer 1

all the organisms of one species in a habitat

Question 2

Define community

Answer 2

all the different organisms of all species living in a habitat at a particular time

Question 3

Define habitat

Answer 3

the place where an organism lives

Question 4

Define niche

Answer 4

the role of a species in an ecosystem

Question 5

Define trophic level

Answer 5

a stage of the food chain

Question 6

What is productivity

Answer 6

the amount of energy transferred between trophic levels

Question 7

What is gross primary production

Answer 7

The total amount of energy made by a producer KJm-2yr-2

Question 8

What is respiratory loss

Answer 8

energy used in respiration

Question 9

What is nett primary production

Answer 9

The amount of chemical energy the producer stores as biomass

Question 10

How do we calculate net production?

Answer 10

N = I (R+F) where I is total energy ingested

R is respiratory loss, and F is energy lost via faeces/urine

Question 11

Why is the efficiency of energy transfer between the sun and a plant very low? (approx. 2%)

Answer 11

• wrong WL of light
• light hits non photosynthetic region eg) bark
• light reflected
• lost as heat

Question 12

Why is the efficiency of energy transfer between the plant and a consumer low? (approx. 10%)

Answer 12

• respiratory loss
• lost as heat
• not all plant is eaten
• some not digested

Question 13

Why is the efficiency of energy transfer between the consumer and a secondary consumer low? (approx. 10 -15%)

Answer 13

• respiratory loss
• primary consumer uses energy for metabolism
• not all is eaten
• faeces
• lost as heat

Question 14

Why might energy transfer be low?

Answer 14

• old animal - less energy into biomass
• herbivores - more faeces
• homiotherms/ endotherms (warm blooded)

Question 15

How can farmers increase energy transfer efficiency within plant crops?

Answer 15

• reduce competition (herbicide/ insecticide)

- fertilisers - eg) nitrates

Question 16

How can a farmer increase yield with animals?

Answer 16

• restrict movement - reduce respiratory loss
• keep warm
• slaughter the animal whilst it is still young
• control diet so a higher % of food is digested

Question 17

what technique to increase yield can be applied to both animals and plants?

Answer 17

selective breeding

Question 18

How can we measure an organisms dry biomass?

Answer 18

warm sample on a scale until mass remains constant (water has been removed)

Question 19

when measuring biomass why is the temperature kept below 80 degrees Celsius?

Answer 19

to avoid combustion CO2 = biomass

Question 20

Why do we use dry biomass to compare samples?

Answer 20

amount of water varies eg) cucumber and potato

dry biomass is more representative

Question 21

What are the units for biomass?

Answer 21

Kgm-2

Question 22

How else can we compare organisms?

Answer 22

mass of carbon

Question 23

What are the units for mass of carbon?

Answer 23

kgm-2yr-1

Question 24

Why don’t we use mass of carbon as much as dry biomass?

Answer 24

hard to measure

Question 25

How can we use calorimetry to estimate the energy stored in dried biomass?

Answer 25

burn substance completely
to heat a known volume of water
measure the temperature change and calculate the energy released

Question 26

describe the 6 stages of the nitrogen cycle

Answer 26

1) Ammonium ions —> nitr1tes by nitrification
2) nitrites —–> nitrate (late) by nitrification
3) denitrification in anaerobic conditions to nitrogen gas in atmosphere (unreactive)
4) nitrates to plants or nitrogen fixation of nitrogen in the atmosphere by leguminous plants
5) saprobiotic nutrition of animals and plants by decomposers
6) Ammonification of decomposer = back at 1

Question 27

what are the 2 ways phosphate ions are returned to the soil in the phosphorous cycle?

Answer 27

weathering and erosion of rocks

saprobiotic nutrition

Question 28

What is the role of microorganisms in the recycling of nutrients?

Answer 28

break down large organic compounds into small inorganic compounds (often soluble so they can be absorbed by plants)

Question 29

What is a saprobiont?

Answer 29

digests food using extracellular enzymes by saprobiotic nutrition

Question 30

Define Saprobiotic nutrition

Answer 30

digestion of organic matter by extracellular enzymes

Question 31

What are Mycorrizhae?

Answer 31

fungi that grow in a mutualistic relationship with plant roots

Question 32

how do plants benefit from the mycorrhizae?

Answer 32

increased SA of roots increases absorbtion of water and minerals

Question 33

how do mycorrhizae benefit from the relationship with plants?

Answer 33

exchange of organic substances eg) sucrose

Question 34

What is a natural fertiliser?

Answer 34

contain nitrogen and phosphorous in organic compounds eg)compost

Question 35

What are the disadvantages of natural fertilisers?

Answer 35

still need to be broken down by saprobionts so slower release of phosphate ions and nitrates

Question 36

what are the advantages of natural fertilisers?

Answer 36

aerates soil - decreases anaerobic denitrification
wider range of elements
less leaching
uses less energy

Question 37

what is the impact of farming/use of fertiliser?

Answer 37

removes N and P from cycle so soil becomes depleted
fertiliser is added
too much fertiliser can alter the water potential (more negative) making it harder for the plants to absorb water by osmosis

Question 38

what is artificial fertiliser?

Answer 38

inorganic chemical compounds that contain nitrogen and phosphorous

Question 39

what is leaching?

Answer 39

when soluble compounds are washed off the land by rain - more common in artificial fertilisers as they are soluble

Question 40

Describe the 7 steps of eutrophication

Answer 40

1) nitrates/ phosphate ions are leached into fresh water
2) Algal bloom
3) blocks out light
4) plants below surface cannot photosynthesise so die
5) saprobionts break down dead plants
6) saprobionts respire anaerobically and use up O2
7) fish and other organisms die