U1T4 - Ecosystems (2)

Question 1

What is the rule about energy?

Answer 1

Energy cannot be created or destroyed, only changed from one form into another. It flows through an ecosystem.

Question 2

What does an ecosystem need to exist?

Answer 2

Must have an external source of energy (sunlight) which is harnessed + converted into other forms.

Question 3

How is sunlight energy harnessed?

Answer 3

Plants trap light energy using chlorophyll and convert into chemical energy by producing organic molecules from inorganic. This means they provide energy for all other organisms in ecosystem.

Question 4

What do food chains indicate?

Answer 4

Feeding relationships in ecosystems, energy flow through ecosystems + trophic levels.

Question 5

What happens through the trophic levels?

Answer 5

Energy lost at each level so less available to transfer to next. Chem energy is passed to detritivores + decomposers.

Question 6

What do pyramids represent?

Answer 6

Flow of energy + energy losses at each trophic level in food web/chain.

Question 7

What are the rules when drawing a pyramid?

Answer 7

Producers (TL1) always at pyramid base, pyramids drawn symmetrical about centre, bar width in proportion to numbers/biomass of organisms involved at each trophic leel + bars always same depth.

Question 8

How is the data collected for a pyramid of numbers?

Answer 8

Small area randomly sampled for organisms under study + multiplied up to give estimate of total pop size. e.g. quadrat analysis, nets, humane trapping.

Question 9

What are the issues with pyramids of numbers?

Answer 9

When large numbers involved, nearly impossible to accurately scale bars. Gives quantitative info but doesn’t indicate relative mass of organisms at each trophic level. Leads to inverted pyramids.

Question 10

How do we measure biomass?

Answer 10

Random quadrats have all organisms harvested + weighed. Wet/fresh mass. Average mass calculated for each TL, multiplied by num organisms. Can also use dry mass.

Question 11

What are the issues with pyramids of biomass?

Answer 11

Only shows standing crop, doesn’t account for changes in biomass over time + can lead to inverted pyramids. e.g. marine ecosystems. Hard to get biomass of oak tree + should they just weigh the leaves?

Question 12

Give an example of a marine ecosystem which has difficulty in terms of biomass pyramids.

Answer 12

In Spring, biomass of zooplankton exceeds phytoplankton because primary production of phyto is v.high + rapidly repro so temp support larger biomass of zoop feeding on them. However, phyto overall exceeds zoop.

Question 13

What are the benefits of pyramids of energy?

Answer 13

Energy content of diff tissue varies so give more accurate info than biomass. Never inverted, useful in comparing ecosystems.

Question 14

What are the issues with pyramids of energy?

Answer 14

Data harder to obtain as values need to be obtained over time period to compare before and after.

Question 15

How much energy do primary producers use?

Answer 15

0.5 - 1% of the incipient energy from sunlight, converting it into chemical energy by photosynthesis. Not all solar energy falling on plant is used to make new tissue.

Question 16

In what ways does the plant lose solar energy?

Answer 16

Some wavelengths can’t be absorbed by chlorophyll, some energy transmitted through leaf (misses chloroplasts), some light reflected from leaf surface or by dust/clouds, absorbed by water vapour/dust, some lost from photosynthetic reactions (inefficient) in from of heat + some lost in water evap.

Question 17

What is the equation for photosynthetic energy?

Answer 17

Photosynthetic Energy = Amount of energy incorporated into carbs/amount of energy falling on plant

Question 18

What are GPP + NPP indicators of?

Answer 18

Productivity of ecosystem +, in terrestrial ecosystems, may be limited by temp and moisture.

Question 19

What is the equation for net primary production?

Answer 19

Net Primary Production = Gross Primary Production - Respiration

Question 20

Which is more efficient:
Transfer of energy between producers, primary consumers + consumers or conversion of solar energy into organic compounds?

Answer 20

Both relatively inefficient but transfer of energy between producers + consumers is more efficient.

Question 21

What is trophic efficiency usually greater in?

Answer 21

Aquatic food chains as they’re longer. Have higher GPP + more efficient.

Question 22

What is the equation for efficiency of energy transfer?

Answer 22

Efficiency of energy transfer = (energy in 1 TL/energy in previous TL) x 100

Question 23

Why can’t herbivores use all the potential chemical energy in plants?

Answer 23

Not all parts of plant are edible (cellulose), not all parts are accessible (roots) + there are parts they can’t digest/absorb.

Question 24

How much energy is generally lost/not assimilated between TLs?

Answer 24

90%.

Question 25

Why is so much energy lost between TLs?

Answer 25

Most energy herbivores absorb is lost by egestion due to amount of indigestible material + excretion of metabolic waste (urea), most of organic content eaten by primary consumer used in resp to make AT so lost in heat, endotherms have high resp losses as need to maintain high internal body temp (high metabolic activity so more resp + heat loss) + some parts of plants (deciduous leaves) enter decomposer food chain in autumn so aren’t available to primary consumers.

Question 26

Give examples of endotherms.

Answer 26

Birds + mammals.

Question 27

How does a cow lose energy?

Answer 27

Losses to decomposer food chains (faeces + urine), egestion + excretion (indigestible food) + respiration (heat).

Question 28

What is the average energy transfer efficiency between animals?

Answer 28

10 - 20% as more of an animal can generally be eaten but only small amount of energy in any animal will be converted into organic compounds in next trophic level due to energy losses in excretion, egestion, respiration or death + entry into decomposer food chain.

Question 29

Describe the difference in the human food chain in developed to developing countries.

Answer 29

More energy is available to primary consumers than secondary consumers so more energy to humans eating plants than animal products so veggie diet supports more people than meat diet. This is why little meat eaten in developing countries. Extra energy costs involved in producing animal products. As further along food chain, need more plant material for them to reach size for slaughter/allow efficient milk production.

Question 30

What is the key aim when raising crops or livestock?

Answer 30

Increase efficiency of energy transfer into organisms and reduce energy losses from them.

Question 31

What are some methods used to improve yields in intensive farming?

Answer 31

Fertilisers to increase primary productivity, pesticide use, appropriate crop spacing, livestock confinement to improve resp/production ratio, keeping animals inside, use of high energy foods like silage/high protein foods + young animals convert more food into growth than older so are killed earlier.

Question 32

Describe how use of fertilisers increases primary productivity.

Answer 32

Allows crops to grow at faster rate as minerals provided in correct amounts - no growth deficiency.

Question 33

Describe how use of pesticides improves yield in intensive farming.

Answer 33

Herbicides prevent competition from non crop plants while insecticides reduces crop damage from pest species’.

Question 34

Describe how appropriate crop spacing improves yield in intensive farming.

Answer 34

Sowing seeds at optimum density ensures reduced competition between adjacent crops whilst maximising land coverage.

Question 35

Describe how livestock confinement improves resp/production ratio.

Answer 35

By reducing moment, in fenced off field or outhouse, less energy used in resp + more used to allow laying down of tissue.

Question 36

Describe how keeping animals inside improves yield in intensive farming.

Answer 36

Keeping livestock inside in warm conditions in barn, especially during winter, reduces energy required to produce heat + maintain body temp.

Question 37

Describe how use of high energy foods improves yield in intensive farming.

Answer 37

Results in increased growth rates in livestock.

Question 38

Describe how killing younger animals improves yield in intensive farming.

Answer 38

Once animal has reached full size, it is slaughtered as keeping them longer wastes resources as no more tissue mass generated.

Question 39

How can the efficiency of secondary productivity be worked out?

Answer 39

Using energy budgets.

P = C - R - F - U

Question 40

What does each symbol in the equation for efficiency of secondary productivity mean?

Answer 40

P = Net secondary Productivity
C = Energy Consumed
R = Energy lost in Respiration
F = Energy lost in Faeces
U = Energy lost in Urine

Question 41

What must be maximised and minimised (letter wise) in intensive farming?

Answer 41

Max C (high energy foods) + reduce R (confinement), U or F increases growth + profit.

Question 42

What are some of the ethical issues raised by intensive farming of domestic livestock?

Answer 42

High stress levels, bone + joint damage, hooves of cattle evolve for slats. Management difficult, disease spreads quickly when close proximity, overuse of antibiotics causes resistance in bacteria, reduced genetic diversity + increased pollution from increased fossil fuel use + farmland waste.

Question 43

Why are tropical swamps + forests the most productive natural ecosystems?

Answer 43

More insolation/incident sunlight so higher GPP. Summer all year long. More sun.

Question 44

Why is it better to farm livestock than crops upland?

Answer 44

Not flat, doesn’t drain well, more peaty, crops less efficient.

Question 45

Explain the shape of a pyramid of biomass?

Answer 45

Less biomass as goes up as less energy available.

Question 46

Why might NPP values for a plant be negative above 30c?

Answer 46

Above 30c, photosynthesis less efficient. Respiration exceeds photosynthesis. Resp exceeds GPP. Temp increases resp.

Question 47

Explain how eutrophication causes high BOD in a river?

Answer 47

Nitrates cause algal bloom, they die and are decomposed by bacteria. Bacteria experience population increase. Bacteria aerobically respire causing huge BOD as O2 used up.

Question 48

When describing a graph, how should you describe the value which is more than a certain point.

Answer 48

Above, not after.

Question 49

What is the average energy transfer between plant and primary consumer?

Answer 49

5 to 20%