3.5.3 ecosystem

Question 1

Mutualism in nutrient cycles

Answer 1

Mycorrhizae - associations between fungi and plant roots.

Fungi acts as extensions of the plant root system, increasing its surface area.
Mycorrhizae hold water and minerals around root and enhance mineral ion uptake.

Question 2

Mycorrhizae

Answer 2

associations between fungi and plant roots.

Question 3

How fertilisers increase productivity
(N/P)

Answer 3

Nitrogen is used for:
amino acid and protein synthesis
the bases in nucleotides (ATP, DNA, RNA)

Phosphate is used for:
phospholipids
nucleotides

These substances are required for plants to grow.

Question 4

how is early growth an advantage to plant

Answer 4

Early growth increases the leaf area so that plants can photosynthesise more efficiently leading to greater productivity

Question 5

The difference between natural and artificial fertilisers

Answer 5

Natural Organic Fertilisers: decaying plants and animals, animal wastes

Artificial Inorganic Fertilisers: mined from rocks and chemically synthesised. Blended to contain NPK

Question 6

Can you explain why fertilisers are needed in agricultural ecosystems

Answer 6

Fertilisers increase the growth rate of crops. Minerals can be a limiting factor for growth.
An increase in yield leads to increased profit for farmers and more efficient food production.
When crops are harvested, the minerals in them are removed from the ecosystem, leaving the soil depleted.

Question 7

Eutrophication

Answer 7

Leaching increases nitrate concentrations so that it is no longer a limiting factor for the growth of plants and algae.

Algae grow rapidly at the surface and the upper layer of water becomes densely populated with plants - called an algal bloom.

The dense surface layer absorbs all the light and prevents light penetrating to lower depths.

Light becomes a limiting factor for algae growing at lower depths and many die.

The increase in dead plants and algae in the lower layer stimulates the growth of saprobiontic bacteria as their food supply is no longer a limiting factor.

As the saprobiontic bacteria consume the dead algae they respire and consume oxygen.

The concentration of oxygen in the water is decreased and ammonia is released from the decaying organisms.

Oxygen becomes a limiting factor for aerobic organisms such as fish and many die.

exam ans
1. Algal bloom blocks light so plants (algae) die;
2. Saprobionts a break down dead plant materials;
3. Saprobionts use up oxygen in respiration causing fish to die;

Question 8

advantage and disadvantage of natural and chemical fertiziler

Answer 8

natural
less yield
environmental frindly
(e.g. manure, left fellow, grow clover)

chemial
more yield (powerful way to stimulate plant growth)
need more energy, green hour climate change
eutrophication

Question 9

organism that photosynthesise

Answer 9

producer
Autotroph

Question 10

organism that obtain their energy by feeding on other organism

Answer 10

heterotroph
consumer

Question 11

diagrammatic representation showing feeding relationships between organism in an ecosystem and the direction of energy flow

Answer 11

food web
food chain

Question 12

tropic level

Answer 12

the stage ina food chain where an organism feed

Question 13

decomposer
saprobiont

Answer 13

a group of organism that feed on and breakdown dead organism , releasing mineral and other substances that can be resued by plants

e.g. bacteria and fungi

Question 14

an animal that eats plants

Answer 14

primary consumer
herbivore

Question 15

an animal that eats animal

Answer 15

seccondary consumer
tertiary consumer
carnivore

Question 16

an animal that eats both plants and animal

Answer 16

Omnivore

Question 17

what does arrow in a food chain show

Answer 17

energy transfer/ flow (biomass)

Question 18

Evaluation point (exam)

Answer 18

Real life (place)
Species
Data for all?

Question 19

suggest one way which an increase in uptake of phosphate could increase plant growth

Answer 19

produce ATP , phospholipid, DNA,RNA, RuBP, TP, GP

Question 20

suggest one way in which bacteria/ fungi which grow on plant root may benefit in from their association with plants

Answer 20

Carbonhydrates/ amino acid/ vitamin

Question 21

how is eating animal less efficient than plant in energy transfer

Answer 21

energy lost between trophic level
via respiration heat/ excretion/ faeces

Question 22

what should scientist do to ensure during drying process of the plant to be sure all water is remove to measure biomass

Answer 22

weight the mass at interval
until the mass beccome constant

Question 23

why measure dry mass

Answer 23

it measure increase in biological material (biomass)
water content varies

Question 24

why when grass is grown in the field, fewer nitrate ions are lost than when the field is left with bare soil?

Answer 24

prescence of grass cause less nutrient to be leached

Question 25

leguminous plant

Question 26

Nitrogen cycle

Answer 26

A few organisms can convert nitrogen gas into compounds useful to other organisms in a process known as nitrogen fixation. These organisms can be free-living or live in a relationship with certain plants (legumes) : Most plants obtain their nitrogen by absorbing nitrate ions from the soil through their root hair by active transport. They then convert this to protein/ amino acid/ nucleic , which is passed to animals when they eat the plants.
On death, saprobionts break down these organisms, releasing ammonium ions, which can then be oxidised to form nitrite ions by nitrifying bacteria. Further oxidation by the same type of bacteria forms nitrate ions. These ions may be converted back to atmospheric nitrogen by the activities of denitrifying bacteria.

Question 27

net primary productivity calculation

Answer 27

NPP = GPP - R

Question 28

The net production of consumers caculation

Answer 28

N = I - (F + R)

Question 29

Intensive rearing of livestock

Methods of minimising energy loss to the environment & maximising energy conversion

Answer 29

By keeping animals in confined spaces (small enclosures, barns or cages) - a process called factory farming.

1. Movement is restricted (so more time spent resting & less energy used in respiration and muscle contraction & more energy converted into biomass)
2. The environment is kept warm (reducing energy loss in the form of heat from the body)
3. Animals are kept in the dark for long periods of time - influencing them to sleep
4. Feeding is controlled (unlike grazing on a field) so that the animals receive the optimum amount and type of food for maximum growth
   5.Predators are excluded (so no loss to other organisms in the food web)

Question 30

Methods of minimising energy loss to the environment & maximising energy conversion

Answer 30

Reduce/eliminate other organisms in the food web that compete with the plant/animal that is being farmed eg. weeds that compete with crop plants or insect pests that may damage crops (pest control - maximises survival of the crops/animals)

The problem is the farmer has to satisfy and balance different interests:
- Our demand for cheap food
- Making a living
- The conservation of natural resources to enable us to continue to have food in the future

Question 31

how does ploughing increase and decrease activity of denitrifying and nitrifying bacteria

Answer 31

stimulate nitrification process
introduce air to soil, increase oxygen

denitrifying bacteria
- anaerobic condition
- low O2
- water logged in soil

nitrifying bacteria
- aerobic respiration