U1T4 - Ecosystems (3)

Question 1

What is the difference between how energy goes through an ecosystem vs. nutrients?

Answer 1

Energy flows through it whilst nutrients must cycle as there is a finite amount of matter available on earth for organisms to use to build their bodies. (Nutrient recycling)

Question 2

What are the similarities and differences of energy vs nutrient transfer?

Answer 2

Transfer from producer to consumer, between consumers + through decomposer food chain but nutrient enters producer from within ecosystem plants absorb CO2 in photosynthesis.

Question 3

What is significant about carbon?

Answer 3

Forms component of all major biological molecules (carbs, proteins, lipids + nucleic acids) Exchanged with air + passed along food chains + recycled using particular biochemical processes.

Question 4

In what biochemical processes is carbon recycled (in order)?

Answer 4

Photosynthesis, ingestion digestion + assimilation, respiration, decay + decomposition + fossilisation.

Question 5

How is carbon recycled in photosynthesis?

Answer 5

Inorganic CO2 is taken in by plants from atmosphere/solution in water + fixed during photosynthesis into organic sugars.

Question 6

How is carbon recycled in ingestion, digestion + assimilation?

Answer 6

Carbon passed along food chain as consumers feed on organisms, by digestion + assimilation of complex organic compounds when carbon incorporated into cells + tissues of organisms.

Question 7

How is carbon recycled in respiration?

Answer 7

Carbon returned to air when organic compounds are respired to produce ATP + CO2 as by-products.

Question 8

How is carbon recycled in decay + decomposition?

Answer 8

When saprobiotic microorganisms break down the organic molecules in dead organisms + release CO2 (via resp)

Question 9

How is carbon recycled in fossilisation?

Answer 9

When dead organisms preserved in environments hostile to decay (coal, gas + peat) Carbon release many millions of years later by combustion.

Question 10

Where is there a reserve of carbon?

Answer 10

In the oceans. In form of hydrogen carbonate ions (HCO3-) due to CO2 being dissolved in water. Acts as buffer being able to take up or return CO2 to atmospheric pool.

Question 11

Levels of what have increased over the last few hundred years?

Answer 11

Increase in atmospheric CO2 levels, mainly due to combustion of fossil fuels + deforestation.

Question 12

List the 3 processes which add CO2 to the atmosphere.

Answer 12

Respiration, combustion + decomposition.

Question 13

List the 2 processes which remove CO2 from the atmosphere.

Answer 13

Photosynthesis + fossilisation.

Question 14

Why is a source of nitrogen necessary?

Answer 14

To make essential nitrogen containing compounds such as proteins, nucleic acids (DNA + RNA) + ATP. Proteins responsible for plant growth so nitrogen availability to plants determine how much new plant biomass produced.

Question 15

How much nitrogen is in the atmosphere?

Answer 15

79%. Stable gas so relatively unreactive + can’t be directly used by plants so needs to be changed.

Question 16

How do autotrophs get nitrogen?

Answer 16

Use nitrate ions (NO3-) taken up by active transport or ammonium ions (NH4+) from soil/water.

Question 17

How do heterotrophs get nitrogen?

Answer 17

From digestion + assimilation of organic materials (plants/other animals). Excess nitrogen excreted or egested or ends up as non-living organic matter after death.

Question 18

How do saprobiotic organisms get nitrogen?

Answer 18

Recycle nitrogen containing compounds via decay + decomposition to useable inorganic form via mineralisation (involves ammonification + nitrification)

Question 19

How do detritivores help other orrganisms?

Answer 19

(Earthworms) Involved in decay process. Provide additional benefits. Burrows aerate + drain soil, encouraging activity of aerobic bacteria + reducing that of anaerobic bacteria.

Question 20

How does lightning convert nitrogen gas into nitrogen containing compounds?

Answer 20

5% of nitrogen fixed this way, Lightning provides energy to break bonds in diatomic nitrogen allowing formation of oxides of nitrogen which dissolve in rainwater, washed into soil where absorbed by plants as nitrates.

Question 21

Give an example of a nitrogen fixing bacteria relationship.

Answer 21

Rhizobium + leguminous plants (peas) in root nodules. Mutualistic relationship. Bacterium gains carbs for energy whilst plants gain ammonia produced by bacteria to make amino acids necessary for growth.

Question 22

What is the equation for nitrogen fixation?

Answer 22

(N2) + (hH+) + (6e-) -> (2NH3)

Question 23

What are the 2 stages of nitrification?

Answer 23

Oxidation of ammonium ions/ammonia to nitrates (NO2-) by Nitrifying Bacteria of genus ‘Nitrosomonas’.
Oxidation of nitrates (NO2-) to nitrates (NO3-) by nitrifying bacteria of genus ‘Nitrobacter’.

Question 24

What happens after nitrification?

Answer 24

Nitrates produced absorbed by active transport to make proteins. Low temps slow formation of nitrates so most formed in soils in spring + summer when most plant growth occurs. Nitrate v.soluble so can be washed out of soils due to heavy rain (leaching)

Question 25

What happens during respiration?

Answer 25

Organic products such as carbs, fats + proteins are broken down to produce ATP with CO2 released as a waste product.

Question 26

Why might it be good for crops to be covered with photobiodegradable plastic?

Answer 26

Less wasteful as won’t go to landfill + doesn’t interfere with crop harvest as should be broken down by then.