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A-LEVELS > ENVIRONMENTAL(AGRICULTURE) > Flashcards

ENVIRONMENTAL(AGRICULTURE) Flashcards

1
Q

what is agriculture?

A

involves the control of terrestrial ecosystems to divert energy and nutrients to the human food chain

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2
Q

what are key principles of agriculture?

A

selection of species

control of abiotic and biotic factors to control production

manipulation of food species to improve productivity

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3
Q

what 3 factors depend upon the choice of which species is selected?

A

> market demand and access

> whether environmental conditions are within the range of tolerance of that species

> whether environmental condition can be controlled

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4
Q

what are some abiotic factors

A

> TEMPERATURE
LIGHT
WATER
SOIL FERTILITY
AERATION

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5
Q

3 reasons for the importance of temperature in agriculture

A

> LENGTH OF THERMAL GROWING SEASON = must be warm enough or the plants to grow. eg grass can survive in very low temperatures, but will not grow below 5 degrees.

> FROST-FREE PERIOD = some crops are damaged by frost. eg maize cannot be grown in areas where late frost is likely

> BIOCHEMICAL REGULATIONS
rate of biochemical reactions, such as photosynthesis, increases in higher temperatures

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6
Q

what are some ways of controlling temperature in agriculture?

A

-low lying areas should be avoided, such as valley bottoms, as they are more likely to have frost because cold air collects here

-south facing slopes in the northern hemisphere receive more solar radiation and tend to be warmer

-greenhouses may be heated in cold weather by burning fuel, such as gas

-frosts in orchards during flowering season can destroy the flowers. this can be controlled by dispersing the cold air with large fans

-POLYTHENE CLOCHES KEEP INDIVIDUAL ROWS OR CROPS WARM

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7
Q

what is the importance of light in agriculture?

A

intensity of light affects rate of photosynthesis. day length affects growth and development. eg oats require longer periods of light each day, whereas maize requires shorter periods.

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8
Q

how does light affect livestock?

A

longer days increase milk production

sheep mate when days are getting shorter in autumn, lambs are born in spring.

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9
Q

how can we control light?

A

artificial lighting can be used to extend the growing season

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10
Q

what is the importance of water in agriculture?

A

-nutrient absorption, nutrients are absorbed from soil as ions dissolved in water

-water is used to transport materials such as glucose and oxygen.

-needed to replace water lost during transpiration. causes water to be drawn upwards to leaves, and the nutrients from the roots are brought with it.

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11
Q

how does water supply affect crops?

A

some crops have high water requirement. eg most rice varieties must be flooded in early stages of growth.

> RELIABILITY = difficult for farmers to plan activities if they do not know how much water will be available. particular problem in areas with unreliable seasonal rainfall.

> AMOUNT = amount of water available is affected by precipitation rates

> QUALITY = substances dissolved in irrigation water can cause problems. eg HIGH SALT CONTENT can cause salivation, which leads to osmotic dehydration of the crop. HEAVY METALS can bioaccumulate in crops, and pose as a threat to the health of humans who eat it

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12
Q

what are some problems caused by WATERLOGGED SOILS?

A

increased risk of fungal diseases

soils become anaerobic and create ideal conditions for denitrifying bacteria, but not nitrifying. this reduces soil fertility as nitrates are lost from the soil more rapidly and replaced more slowly

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13
Q

how can we reduce the water level and improve waterlogged soils?

A

deep ploughing

avoidance of compacting by livestock or macinehery

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14
Q

what are some problems caused by water shortages for crops?

A

plants loose water by transpiration during dry weather. this is reduced by closure of stomata in their leaves, however this also stops the absorption of carbon dioxide, so photosynthesis and growth stop.

a sever water shortage will kill plants as cell dehydration inhibits cellular biochemical reactions such as photosynthesis.

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15
Q

how do water shortages affect livestock?

A

they may die in semi-arid areas where there is a water shortage. shortages can increase trampling as livestock have to travel further for water. this increases the risk of erosion and desertification

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16
Q

what are some methods to increase the water availability?

A

crop irrigation

soil mulching to reduce evaporation losses from the surface

reducing soil compaction from livestock to increase infiltration

provision of suitable habitats for worms to increase infiltration through their tunnelling

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17
Q

what is soil fertility?

A

measure of the ability of the soil to support plant growth. it is a combination of properties including availability of nutrients and water, aeration, texture and structure

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18
Q

what are two ways nutrients can be made available naturally?

A

> LEGUMES = have nitrogen fixing root nodules

> CROP ROTATION= gives time for weathering to release more nutrients and to even out the demands for particular nutrients by different crops

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19
Q

what are the two types of fertilisers?

A

> ORGANIC FERTILISER = animal and plant materials that release nutrients as they decompose. eg manure and sewage sludge, or animal food product waste such as bonemeal

> INORGANIC FERTILISER = man made

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20
Q

what are the advantages of organic fertiliser?

A

many are waste products

may be locally available

increase hummus content

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21
Q

what are disadvantages of organic fertilisers?

A

nutrients are released slowly, so must be used as part of a long term cultivation plan.

cannot be added to a growing crop

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22
Q

what are advantages of inorganic fertilisers?

A

nutrients are released rapidly

nutrient composition can be controlled to meet specific crop requirements

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23
Q

what are disadvantages of inorganic fertilisers?

A

require large amounts of energy to manufacture

some are toxic to worms

high solubility and may be leached after application

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24
Q

what is hydroponics?

A

refers to the growth of a plant in a nutrient solution. usually carried out in greenhouses as part of intensive system. controls limiting factor as much as possible to increase productivity.

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25
Q

what are the advantages of hydroponics?

A

there is no soil to hold pathogens

nutrient supply is optimal

there are no weeds

harvested crops are attractive to consumers as there is no soil.

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26
Q

what are disadvantages of hydroponics?

A

intensive production involves high inputs of nutrients and energy.

high level of technical knowledge needed

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27
Q

what is aeration and why is it important ?

A

UNCOMPACTED SOILS have larger spaces in-between the soil particles which increase aeration. this is important for many aerobic processes such as root respiration and decomposition

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28
Q

what are some farming practices that increase soil compaction?

A

1)weight of farm machinery or livestock trampling
2)farming methods often reduce soil organic matter and therefore reduce worm populations
3)ploughing can kill soil organisms by moving them to depths that they cannot survive at

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29
Q

how to control compaction of soil

A

ploughing turns over and aerates surface soil layers, but not deep layers

adding organic matter provides food for the soil biota that increase aeration

removing livestock from fields when the soil is wet reduces compaction

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30
Q

how does wind velocity affect agriculture?

A

high wind velocity causes severe problems. eg it increases soil erosion, increases evaporation rates and drying of soils.

crop damage = eg the ‘lodging’ of cereal crops when they are flattened by strong winds

31
Q

how to control wind velocity effects?

A

windbreakers such as hedgerows or rows of trees

32
Q

what are biotic factors controlled in agriculture ?

A

> PESTS
POLLINATORS
MAINTENANCE OF SOIL BIOTA

33
Q

what are pests and how are they a problem?

A

organisms that reduce the productivity or quality of a product. they do this by either:
>being a predator and eating the crop/livestock
>being a pathogen and causing disease/carrying a disease
>competing for water and nutrients

34
Q

how are insects a pest?

A

eat the crop, spoil appearance of the harvested. they can act as vectors and spread pathogens

eg aphids suck the sap and reduce growth. they also carry pathogenic diseases such as potato blight

35
Q

how is fungi a pest?

A

causes growing plants to rot. eg leaf smut for rice

36
Q

how is bacteria a pest?

A

reduce harvest by causing diseases. eg bacteria wilt for potatoes

37
Q

what is the difference between endemic pests and epidemic pests?

A

endemic pests are always present, usually in small numbers whereas epidemic pests are not normally present but there may be ‘outbreaks’.

38
Q

what is cultural pest control and some examples

A

involves non-pesticide methods, where crops or livestock are cultivated in a way that reduce risk of pest damage.

EG
>PREDATOR HABITATS
>COMPANION CROPS
>CROP ROTATION
>BIOLOGICAL CONTROL
>PHEROMONE TRAPS
>GENETIC RESISTANCE TO DISEASE
>GM CROPS

39
Q

what are predator habitats?

A

increase the pests’ predators by providing them suitable habitats. eg beetle banks for black ground beetles tat eat aphids.

40
Q

what are companion crops ?

A

crops that are more productive when grown together. inter species relationships include:
>BARRIER CROPS = eg the smell of onion can mask the smell of carrots to reduce damage caused by carrot root flies

> SUPPORT OF POLLINATORS = flowering plants that support bees which are important for the pollination of fruit crops

> NUTRIENT SUPPLY = legumes intercropped to increase nitrate availability in the soil.

41
Q

what is crop rotation?

A

cultivation of different crops usually on a 4-5 year cycle. pests remaining after the end of the first year will have died off before that crop is grown again.

42
Q

what is biological control ?

A

predator or pathogen species is introduced to control pests. they should be specialised feeders that will eat the pests. if they have a wider diet, they may eat beneficial species.

WHITEFLIES in greenhouses controlled by the introduction of PARASITIC ENCARSIA WASPS

43
Q

what are pheromone traps ?

A

release artificial scent that attracts pests. used to either kill all individuals, or enough of one gender.

or used to show that the pest is present so pesticides can be used

44
Q

what is genetic resistance to disease in crops?

A

within any species, there is a range of genetic characteristics for every environmental condition. selective breeding may enhance the resistance to a variety of pests and diseases. pathogens evolve to overcome crop disease resistance, so commercially cultivated crops must focus on wild varieties, CWR (CROP WILD RELATIVE)

45
Q

what are GM crops for pest control ?

A

DNA of a crop can be modified to control pests more effectively by reducing their susceptibility.

46
Q

what is pest control using chemical pesticides?

A

properties of pesticides influence effectiveness and environmental impacts, eg :
>TOXICITY = increased toxicity means that it can be used in smaller volumes. most act by inhibiting enzyme action
>PERSISTENCE = persistent are more chemically stable so degrade slowly. this means they require less frequent application but may spread and harm not target species
>SOLUBILITY = water soluble pesticides can be washed off by rain and need reapplication

47
Q

what are 2 modes of actions by which chemical pesticides kill pests ?

A

CONTACT ACTION
contact herbicides kill plants by damaging the tissue they are sprayed onto. contact insecticides kill insects they are sprayed onto directly, or come into contact with pesticide on protected plant

SYSTEMATIC ACTION
absorbed by crop and translocated throughout plant, it also protects new growth. cannot be washed off by rain but can be retained in harvest and eaten by humans.

48
Q

what are 2 biotic factors in agriculture and their importance?

A

> POLLINATORS
many crops are pollinated by bees, moths and beetles.

> MAINTENANCE OF SOIL BIOTIA
important for soil fertility and crop productivity, especially detritivores and decomposers. increase nutrient availability through breakdown of dead organic matter and nitrogen fixation.

49
Q

how can pollinators service be aided in agriculture?

A

> provision of food supplies by growing plants that provide nectar
restricting use of pesticides that harm pollinators
introduction of bee hives.

50
Q

what are 2 ways to manipulate food species?

A

1)POPULATION CONTROL
2)CONTROL OF GENETICS

51
Q

what are 2 ways of controlling population?

A

> OPTIMUM LIVESTOCK/CROP DENSITY
MONOCULTURE

52
Q

what is optimum livestock/crop density?

A

increased population density can increase the total yield, although yield per individual may be reduced due to inter-species competition. increased population density can increase the risk of the rapid spread of disease.

53
Q

what is monoculture?

A

cultivation of a single species, often over a large area. makes cultivation easier as it allows the use of larger machinery but pests and diseases can spread rapidly if they colonise a field.

54
Q

what are two 3 ways to control genetics

A

> ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION
GENETIC ENGINEERING/TRANSGENICS/GM

55
Q

what is asexual reproduction? (in plants and animals)

A

PLANTS
involves cuttings where new plants are produced from sections of lead from parent plant. offspring are genetically identical, so their characteristics are predictable, but there is no genetic variation so characteristics can’t be improved

ANIMALS
CLONING = aim to produce offspring that are genetically identical to selected individual with desirable characteristics (donor). cells are removed from donor and grown in culture. egg from a female is removed, and the nucleus of the female egg is replaced with the nucleus from the donor cell. egg then implanted into female surrogate.

56
Q

how is asexual reproduction useful in agriculture?

A

large numbers of individual with desirable characteristics can be produced

valuable animals that die can be replaced with genetically identical individuals

57
Q

what is sexual reproduction?

A

offspring combine genes from 2 parents, so their characteristics cannot be predicted accurately. producing breed with particular characteristics, without unwanted ones, can take many generations.
two types of sexual reproduction include
>SELECTIVE BREEDING
>CROSSBREEDING

58
Q

what is selective breeding?

A

production of offspring from parents that were chosen based on genetic characteristics. breeding between genetically similar individuals may produce offspring with similar characteristics but there is an increased chance of inbreeding.

EG HIGHLAND CATTLE = even temper

59
Q

what is crossbreeding?

A

between 2 different parental breeds may produce combination of desirable characteristics with “hybrid vigour” and lower risk of inbreeding. EG ZEBU CATTLE are reared in hot climates, but produce a lower milk yield.

60
Q

what are 2 improved breeding technologies

A

> EMBRYO TRANSFER
ARTIFICIAL INSEMINATION

61
Q

what is genetic engineering/transgenics/GM?

A

GM allows the introduction of single characteristics from one species to another, or between varieties of the same species.

62
Q

what are 2 examples of GM?

A

> ROUNDUP READY SOYA = agrobacterium is resistant to herbicide roundup. gene that produces this resistance is introduced to soybean. decreases weed problems as soya is unaffected by spraying of roundup

> GOLDEN RICE = rice contains vitamin A but is often in the husk that is removed for storage. genes have been transferred from the daffodil, so vitamin A is produced in the rice grains

63
Q

what are advantages of GM crops?

A

individual, desirable characteristics can be introduced without undesirable associated characteristics.

genes may be introduced from species that could have never been achieved by normal selective breeding

increased pathogen resistance decreases risk of disease

64
Q

what are disadvantages of GM crops?

A

GM crops can increase food allergies

increased cost to farmers, especially in LEDCs as many GM crops require new seeds to be purchased every year.

transfer through the food chain

65
Q

how is intensity in agriculture measured?

A

measure of the amount of artificial inputs and exact yield produced

66
Q

what is extensive agriculture?

A

aim is to maximise total yield by spreading available inputs over a large area

67
Q

intensive agriculture?

A

large inputs available but shortage of land. may be productive but not very efficient.

68
Q

what are energy subsidies?

A

any input that aids productivity but requires use of energy. EG = manufacture of nutrient fertilisers/pesticides, pumping of irrigation water, fuel for machinery(such as ploughing) and transport of harvested crop to consumers etc.

69
Q

what is energy ratio?

A

measure of efficiency by comparing energy inputs and outputs, then expressing this as the number of units of food energy produced per energy input.

70
Q

what is food conversion ratio?

A

measure of the mass of food needed to produce a given mass of livestock growth. lower the ratio, the better the conversion of food to animal biomass

71
Q

what is autotrophic nutrition?

A

organisms need chemical energy to drive biological metabolic processes.

chemicals that are broken down to release this energy are not generally available in the environment, but can be built up from simpler molecules by autotrophs.

photoautotrophs, such as plants and algae capture sunlight during photosynthesis.

chemo-autotrophs such as bacteria, harness energy by oxidising methane etc.

autotrophs do not rely on any other organism for their energy supply

72
Q

what is heterotrophic nutrition?

A

must gain energy from other living organisms. much energy captured by autotrophs is used in their metabolic processes and then released back into the environment as low energy density heat. amount of energy available to heterotrophs is much less than what was harnessed. in food chains with many trophic levels, less energy is passed onto the next level.

73
Q
A

A-LEVELS (9 decks)

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