5 - Energy and ecosystems Flashcards
EQ
How would you calculate percentage efficiency of energy transfer between producers and primary consumers? (2)
Measure bars in?
PE = energy avail after/energy avail before x 100
mm
EQ
The average efficiency of energy transfer between producers and primary consumers in pyramids of energy is around 10 %.
Suggest why the efficiency of energy transfer from producers to primary consumers in this food web is higher than 10 %. (2)
- Single-celled producers are more digestible / contain less cellulose (than plants) / less energy lost in faeces;
- All of producer eaten/parts of plant not eaten;
- Less heat/energy lost / less respiration;
EQ
Energy from the sun may ultimately end up in dead plant matter. Describe how. (2)
- Photosynthesis/light dependent reaction/light independent reaction;
- Carbon-containing substances;
EQ
The gross productivity of the plants in the field was highest in July (highest temp). Use the data in the table to explain why. (2)
- High temperature allows enzymes to work faster/allows more collisions/ allows more e-s complexes to be formed
OR
A lot of light so light not limiting; - Photosynthesis reactions are faster/more photosynthesis;
EQ
Give the equation that links gross productivity and net productivity. (1)
Gross productivity = net productivity - respiratory loss/respiration;
EQ
The net productivity of the plants in the field was higher in August than in July. Use the equation in part (b)(i) and your knowledge of photosynthesis and respiration to suggest why. (2)
- Respiration slower /less respiration;
- Light-dependent reaction/photosynthesis less affected by temperature increase;
- Lower (energy) loss;
EQ
A horse was kept in the field from March to October. During the summer months,
the horse was able to eat more than it needed to meet its minimum daily requirements.
Suggest how the horse used the extra nutrients absorbed. (1)
- Stored as fat/glycogen/biomass;
2. Used for growth/movement/reproduction / process involved in growth/movement/reproduction;
EQ
The horse’s mean energy expenditure was higher in March (colder)than it was in August. Use information in the table to suggest why. (2)
- More heat/energy is lost (in March)/colder (in March);
2. Maintain/regulate body temperature/more heat generated; 3. By respiration/metabolism;
EQ
Suggest appropriate units for gross productivity. (1)
KJm-2year-1
EQ
Explain the decrease in gross productivity as the woodland matures. (2)
- Less light / more shading / more
competition for light; - Reduced photosynthesis;
EQ
Use the information in Figure 3 and your knowledge of net productivity to explain why
biomass shows little increase after 100 years. (2)
1. Net productivity = gross productivity minus respiratory loss; 2. Decrease in gross productivity/photosynthesis / increase in respiration
EQ
Rather than use chemical pesticides or biological agents, farmers often use an integrated system of chemical pesticides and biological agents to control agricultural
pests. Explain the advantages of using an integrated system to control agricultural pests. (6)
(Biological Agents) 1. Only needs one application/ reproduces; 2. Specific; 3. Keeps/maintains low population; 4. Pests do not develop resistance; 5. Can use less chemicals / reduces chemical residues / no bioaccumulation; (Chemical pesticides) 6. Acts quickly; 7. Can apply to specific area; 8. Kills all/most/greater variety of pests;
EQ
Explain how the intensive rearing of domestic livestock increases net productivity. (4)
1. Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue; 2. Fed on concentrate /controlled diet / so higher proportion of food absorbed/digested/assimilated / used for biomass/tissue / lower proportion lost in faeces; 3. Movement restricted so less heat/energy/respiratory loss; 4. Heating/Kept warm/ inside so less heat/energy/respiratory loss/maintain body temperature; 5. Genetically selected / selective breeding (for high productivity);
EQ
In some countries, pigs are reared in intensive units in which the temperature is controlled. Agricultural scientists investigated the effect of temperature on pig growth
and on the efficiency with which the pigs converted food to biomass.
In the investigation, the scientists used pigs of the same breed, with similar genotypes. Explain why. (2)
- Same breed so similar alleles;
- Controls/removes variable/so
genes not a factor / only
temperature affects results /
rate of growth affected by
genes;
EQ
The pigs were allowed to eat as much food as they wanted.
How could this have decreased the reliability of any conclusions drawn from the
investigation? (2)
1. Different growth rates / gained different biomass / grew different amount; 2. Not due to temperature / the independent variable;
EQ
10=0.80
20=0.85
30=0.45
A student concluded from these data that the mean growth rate of the pigs was fastest
at 20 oC. Do you agree with this conclusion? Explain your answer. (2)
1. Temperature may be between 10 and 30/10 and 20/20 and 30; 2. Intervals are 10 C/large/not small/should be smaller/should be intermediates;
EQ
Pigs can survive at temperatures above 35. Use the data to suggest why scientists did not carry out any investigations at temperatures higher than 35 (2)
1. Growth rate decreasing / conversion staying same/ decreasing; 2. (Scientists would be) looking for high growth rate/ conversion / data shows unlikely to improve growth/yield; 3. Wastes time/resources/would not relate to farming conditions;
EQ
The scientists isolated the fungus from the tissue of Hydrilla growing in its country of origin. Suggest two possible advantages of using this fungus as the biological
control agent. (2)
1. Is specific / grows/survives in Hydrilla/habitat; 2. Can reproduce / only one application required; 3. Does not become a pest;
EQ
The treatment in experiment 4 was the most effective. Use your knowledge of integrated pest control systems to suggest why the treatment in experiment 4 was the most effective (2)
1. Fluridone/chemical acts quickly / quickly reduces Hydrilla; 2. Fungus/biological control keeps Hydrilla in low numbers; 3. Fungus/biological control works over a long time/can reproduce 4. Resistance does not develop against fungus/biological control;
Define producer
a (photosynthetic) organism that synthesises complex organic molecules from simple inorganic ones.
Define consumer
4 types?
an organism that obtains its energy by feeding on other organisms.
Primary, secondary, tertiary, quaternary
The efficiency of conversion of food to biomass is lower at 0 oC than it is at 20 oC. Suggest an explanation for the lower efficiency (2)
1. Will lose more heat / not as much energy used to maintain body temperature; 2. Heat resulting from respiration/more respiration; 3. More food used in respiration;
Define decomposer
2 types with examples?
Nutrients released in what form?
An organism that breaks down complex organic molecules into simple organic molecules or ions by secreting enzymes onto them.
Decomposer - fungi and bacteria, detritivore e.g. earthworms
One that can be absorbed by producers
Define food chain
a feeding relationship
Define trophic level
the position of an organism in a food chain.
Food webs:
Most animals?
In single habitat?
Problems? (2)
Rely on multiple food sources.
Many food chains linked together to form food web.
Impossible to show feeding interrelationships of all of species - too many.
Relationships change - time of year, age and population size.
Why is most energy from the Sun not converted? (4)
Reflected back to space by clouds/dust or absorbed by atmosphere
Not all wavelengths absorbed
May miss chlorophyll molecule
Limiting factors of photosynthesis
Why is most energy not transferred between trophic levels? (4)
Some of organism not eaten.
Some parts not digested
Some excreted
Some lost as heat in respiration/radiation
Inefficient transfer between trophic levels means? (3)
Most food chains have no more than 5 trophic levels - insufficient energy to support larger population.
Biomass less at higher levels.
Gross productivity less at higher levels.
Percentage efficiency/energy transfer calculation
Units?
Equation?
Unit = kJm-2year-1
Percentage efficiency/energy transfer = (energy available after the transfer/energy available before the transfer) x 100
Why are ecological pyramids useful?
Provide quantitative information
Pyramids of number:
Problems? (2)
Size of organism not taken into account
Number of individuals may be too great to fit scale
Pyramids of biomass:
Problems: (2)
Seasonal differences not taken into account
Same biomass does not necessarily mean same energy - 1g fat 2x energy as 1g carb
Pyramids of biomass:
Define biomass (3)
Units? (2)
the total mass of living material in a specific area at a given time.
Fresh mass unreliable - varying water content
Dry mass reliable - requires killing organism, small scale, not representative
Area being sampled - grams per square metre (gm-2).
Volume being sampled - grams per cubic metre (gm-3)
Pyramids of energy:
Most?
Unit?
Most accurate
kJm-2year-1.
Problems? (2)
Collecting energy information difficult
Not representative - taken from small area
Define productivity
the rate at which something is produced.
Define gross productivity
total quantity of energy that producers convert to organic matter ( kJm-2year-1)
Define net productivity
Affected by? (2)
Net productivity = gross productivity - respiratory losses
(energy available to next trophic level)
Photosynthetic efficiency
Area of ground covered by crop leaves.
Energy input:
Why do agricultural systems have a higher energy input? (3)
Suppressing climax community requires additional energy (e.g. ploughing, removing weeds) from:
Food - energy expended by farmers comes from food
Fossil fuels - energy used by machinery comes from fuels
Productivity:
Why do agricultural systems have higher productivity? (2)
Competition reduced so effect of limiting factors reduced (e.g. for light, carbon dioxide)
Fertilisers and pesticides
Define pest
an organism that competes with humans for food or space, or could be a danger to health.
Define pesticide
Poisonous chemical that kill pests.
Biological control aims to… not….
Because… due to…
Control so pest has no adverse effect, not eradicate
Predators would die - no food
Biological control:
Advantages (5)
Disadvantages (3)
Adv: Specific Only needs one application/reproduces Keeps/maintains low population Pests do not develop resistance Reduces chemical residues/no bioaccumulation
Disadv:
Acts slowly
Does not kill all pests
May become pest itself
Chemical control:
Advantages (2)
Disadvantages (3)
Adv:
Acts quickly
Kills all pests
Disadv:
Needs multiple applications
Pests develop resistance
Chemical residues/bioaccumulation
How does each reduced productivity?
Weeds?
Insect pests? (2)
Monoculture?
Weeds - compete for limited resources so reduce photosynthesis
Insect pests - predators/damage leaves so reduce photosynthesis
Monoculture - enables pests to spread rapidly
Economics of pest control:
Important to balance?
Often conflicting interests between? why? (4)
Balance cost of pest control with benefits
Farmer - economic (cheap prices but profit)
Conservationists - environmental (food for future)
How does intensive rearing increase productivity? (6)
Movement restricted - less heat lost in respiration
Slaughtered when still growing - more energy transferred to biomass
Fed on concentrate - higher proportion of food absorbed
Heating - less heat lost maintaining body temperature;
Genetically selected
No predation/competition
