productivity exam questions

Question 1

Arbuscular mycorrhiza fungi (AMF) are fungi that grow on, and into the roots of plants

AMF can increase the uptake of inorganic ions such as phosphate ions

Suggest one way in which AMF may benefit from their association which plants

Answer 1

can use the amino acids/ carbon-containing molecules in the plant

Question 2

how do we work out the mass from density and mass

Answer 2

density x volume

Question 3

the ecologist dried the samples in an oven at 103C for 24 hours

Describe how the ecologist could have determined whether or not this drying removed all the water from a sample of wood

Answer 3

record mass and rehat

until constant mass recorded

Question 4

what does the graph show about the relationship between the diameter of the trunk

Answer 4

as the diameter increases the biomass increases (1 mark)

for the extra point, further, stat the relationship e.g. is it linear, does it level out
however, this relationship is not linear (1 mark)

Question 5

Plantations of trees are often created to remove carbon dioxide from the atmosphere, to help to balance the carbon dioxide released by burning fossil fuels.

For different species of tree, information is available for:
•the relationship between diameter of trunk and freshly cut biomass•the percentage of water in fresh-cut wood
•the mean dried density of wood.

Using only the information provided in part (c), suggest how the mass of carbon in the wood of a plantation of trees of a particular species could be estimated.

Start with measuring the diameter of a large number of trees.
Assume that the dry biomass of a tree consists of biological molecules that contain carbon.

Answer 5

1. Calculate a mean diameter;
2. (Use this to) estimate / determine the mean fresh biomass of trees;
3. Use the percentage water content to find the dried biomass
   ;4. Use the dried density to calculate the mass of the tree;
4. Count / estimate the number of trees in plantation and multiply by (mean) carbon content (to find total carbon);

Question 6

what is a chi-squared test used for

Answer 6

assess the significant difference between observed and expected data

Question 7

give two ways in which energy is lost between PRODUCERS and HERBIVORES

Answer 7

Repository loss

heat/ undigested

Question 8

what is the importance of decomposes to the producers

Answer 8

supply of inorganic molecules e.g. CO2/ nitrates

releases CO2

Question 9

there are more secondary consumers than primary consumers in this pyramid

Suggest one reason why

Answer 9

the secondary consumer is small/ has a rapid reproductive cycle

Question 10

what is important to note about trophic levels

Answer 10

the bottom level is not a consumer but is actually the producer

Question 11

explain why a food chain rarely contains more than 4 trophic level

Answer 11

energy is used at each trophic level
energy is lost via excretion and respiratory loss

therefore little is left to sustain higher trophic levels

Question 12

red blood cells do not contain mitochondria but they use ATP

By what processes do red blood cells produce ATP

Suggest a reason for your answer

Answer 12

Glycolysis

does not occur in mitochondria/ takes place in the cytoplam

Question 13

not all light energy entering the leaves of the oak tree is used in photosynthesis

Answer 13

light is the wrong frequency

Question 14

why are micro-organisms important in ecosystems

Answer 14

nutrients are recycled within nutrient ecosystems

microorganisms play a vital role in recycling chemical elements such as phosphorus and nitrogen

Question 15

what are saprobiants

Answer 15

saprobiants are organisms that digest their “food” externally and then absorbs the products

Question 16

what are mycorrhizae

Answer 16

these are fungi “associates between plant roots and fungi

they provide a large surface area for uptake of water and inorganic ions

-they act like a “sponge” so can absorb and hold water and minerals easily

Question 17

what is the relationship between mycorrhizae and the plants

Answer 17

the relationship between plants and fungi is symbiotic as the plant provides the fungi with carbohydrates

they both benefit each other

Question 18

what are the stages of the nitrogen cycle

Answer 18

1. nitrogen fixation
2. ammonification
3. nitrification
4. Denitrification

Question 19

what is nitrogen fixation

Answer 19

nitrogen-fixing bacteria convert atmosphere N2 to ammonium ions

either free-living in the soil or have a mutualistic relationship with leguminous plants e.g. clovers and beans as they can live in their root nodes

Question 20

what is ammonification

Answer 20

ORGANIC NITROGEN from decomposition of proteins, DNA, urea e.t.c are converted to ammonium ions which are released into the soil

This is carried out by sapriobionts

Question 21

what is nitrification

Answer 21

Ammonium ions in the soil are oxidised to nitrates then nitrites by nitryfying bacteria

this is two stage oxidation reaction

Question 22

what is denitrification

Answer 22

it converts nitrogen in compounds back to nitrogen gas

This is a cycle as the nitrogen gas cannot be absorbed by plants
This occurs in anaerobic conditions hence why farmers aerate their soils

Question 23

what is the phosphorus cycle

Answer 23

1. environmental conditions e.g. erosion and weathering causes the release of phosphate ions by rocks into soil and bodies of water
2. plants take in these phosphate ions
3. animal eat the plants ad use these ions to synthesis organic materials
4. animals die and decompose, returning phosphate ions to the soil
5. Bacteria in the soil break down phosphate into inorganic forms
6. inorganic forms of phosphorus can end up in waterways again and be assimilated by plants

Question 24

what are the different types of fertilisers used

Answer 24

natural and artificial

Question 25

why do we use fertilisers

Answer 25

they replace nitrogen and phosphates by harvesting plants and removing livestock

Question 26

what are natural fertilisers

Answer 26

manure, seaweed,peat guano e.tc.

cheap
free if from own livestock

negatives
exact amount and proportions of minerals can’t be controlled

Question 27

what are artificial fertilisers

Answer 27

contains the exact amount of minerals

strengths
more water-soluble so higher absorption of inorganic ions

negatives
leads to eutrophication and leaching if there is rainfall/ flooding

Question 28

what is leaching

Answer 28

water soluble components are washed away into bodies of water e.g. rivers and ponds

this is caused by flooding and heavy rainfall

Question 29

what iseutrophication

Answer 29

1. leached nitrates in bodies of water causes algae growth
2. excessive algae growth blocks light, so plants below the surface can’t photosythesise and therefore die
3. aerobic bacteria feed on dead plant matter and respire using up the oxygen in the eater
4. fish and other aquatic organisms die due to the lack of oxygen