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edexcel igcse biology > section d: ecology and environments > Flashcards

section d: ecology and environments Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

ecology

A

study of an organisms environment and the factors that determine it’s distribution and abundance.

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2
Q

environment

A

abiotic factors of ecosystem

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3
Q

population

A

all the organisms of a particular species living in an ecosystem at a particular time

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4
Q

community

A

all of the populations of living organisms living in an ecosystem at a particular time

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5
Q

habitat

A

place where specific organisms live

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6
Q

ecosystem

A

self supporting system of organisms interacting with each other and with their physical environment

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7
Q

quadrats

A

used to sample the distribution of organisms in their habitats, and to estimate the population size of an organism in different areas

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8
Q

what does biotic mean

A

living (factors)

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9
Q

what does abiotic mean

A

non-living (factors)

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10
Q

what is the word equation for photosynthesis

A

water + CO2 (+light) –> glucose + O2

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11
Q

what is the chemical equation for photosynthesis

A

6CO2 + 6H2O ——-> 6O2 + C6H12O6

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12
Q

how much energy is passed from one trophic level to the next

A

10%

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13
Q

what are the different trophic levels of a food chain/web

A

producers, primary, secondary and tertiary consumers and decomposers

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14
Q

where is the ORIGINAL source of energy in food chains/webs

A

the sun, producers convert this light energy to chemical energy through photosynthesis and consumers gain it through consumption.

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15
Q

producer

A

an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

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16
Q

consumer

A

an organism that gets its energy by feeding on other organisms. also known as heterotrophs

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17
Q

what is a trophic level

A

position of an organism in a food chain or food web

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18
Q

decomposer

A

an organism that gets its energy from dead waste or organic matter

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19
Q

what is a food chain

A

a chart showing the flow of energy/food from one organism to the next beginning with the producer

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20
Q

what is a food web

A

a network of interconnected food chains showing the energy flow through that part of the ecosystem

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21
Q

what do arrows represent in a food web

A

the flow of energy

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22
Q

how much energy is lost from the sun to the producer

A

99%

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23
Q

where does the 99% of energy lost from the sun to the producer go to

A

over 90% is reflected by the atmosphere
not all sunlight will fall on a producer
some sunlight will pass through leaves without hitting a chloroplast (transmission)
some light is the wrong wavelength (green light is converted)
some light is converted to heat during photosynthesis and respiration
some light energy is used to evaporate water from leaves

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24
Q

where does the 90% of energy lost from one trophic level to the next go to

A

not all of organism is eaten, e.g. bones
some of the organism may not be digested and will be lost in digestion e.g. humans dont digest cellulose
much energy is lost as heat in cellular respiration to carry out MRSGRENC

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25
Q

why are food chains not super long

A

the continual energy loss puts a limit on the number of trophic levels that can be supported with enegry through a food chain

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26
Q

what is a quadrat

A

it is a square that marks off an exact area so that plants in that area can be identified and counted

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27
Q

what are decomposers

A

organisms such as bacteria and fungi that break down and decompose dead material and waste products to recycle the nutrietns

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28
Q

what is the population size of the organisms in an ecosystem affected by

A

the physical environment such as temperature, rainfall and amount of sunshine

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29
Q

what does the water cycle involve

A

evaporation, transpiration, condensation, and precipiation

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30
Q

how much carbon dioxide is in the air

A

around 0.04%

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31
Q

what is the equation for combustion

A

fuel + O2 –> CO2 + H2O

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32
Q

biodiversity

A

amount of variation of species in an ecosystem

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33
Q

how do you measure biodiversity

A
  1. number of different species (species richness)

2. abundance of each species

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34
Q

types of interactions in ecosystems

A
  1. feeding between trophic levels
  2. competition between organisms (e.g. for light, water or nesting sites)
  3. interaction with abiotic factors (e.g. animals using materials to build shelters
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35
Q

examples of abiotic factors

A 
amount of nitrogen in soil
pH of soil
temperature
wet or dry soil
pollutants
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36
Q

examples of biotic factors

A

change in amount of predators
decreased food availability
disease (e.g bacteria, viruses)

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37
Q

what does nitrifying bacteria do

A

turn ammonia into nitrates

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38
Q

what does denitrifying bacteria do

A

turn nitrates into N2 or nitrogen in the air

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39
Q

what does nitrogen fixing bacteria do

A

turn nitrogen in the air into nitrates. (there is one type in the roots of legumes and one type in the soil)

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40
Q

what is the role of decomposers in the nitrogen cycle

A

recycling proteins

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41
Q

are nitrates soluble

A

yes

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42
Q

name two things we need nitrogen for

A

DNA

proteins / enzymes

43
Q

what are the three ways nitrogen can get back into the soil

A 
lightning (there is enough energy to react the hydrogen and oxygen)
nitrogen fixing bacteria (the two types)
artificial fertilisers (Haber process)
44
Q

what are legumes, give examples

A

anything with a pod e.g peas, beans, clovers

45
Q

what is the symbol for ammonia

A

NH3

46
Q

how are soil ions controlled by farmers and why

A

by adding fertilisers to the soil or growing it in a hydroponic culture to make proteins and other compounds for growth

47
Q

how is soil structure controlled by farmers and why

A

ploughing fields to break up compacted soil; adding manure to improve drainage and aeration of heavy, clay soils. this is for better uptake of mineral ions by active transport and water

48
Q

how is soil pH controlled by farmers and why

A

adding lime to acidic soils; few soils are too alkaline to need treatmenet. this is because soil pH can affect crop growth as un unsuitable pH reduces uptake of mineral ions

49
Q

how is carbon dioxide, light and heat controlled by farmers and why

A

not in a field but in a greenhouse, they can all be altered to maximise crop yield. burning fuels produce heat and carbon dioxide. these limit the rate of photosynthesis and production of organic substances needed for growth, so farmers want to control them.

50
Q

why would a farmer use a greenhouse

A

they can control factors to maximise crop yield:
high humidity for low water loss
heaters produce CO2 needed for photosynthesis
transparent walls allow for natural light
optimum temperature

51
Q

NITROGEN AND CARBON CYCLE

A

.

52
Q

what are organic fertlisers made of

A

faeces of farm animals mixed with straw

53
Q

what are inorganic fertilsers made of

A

inorganic compounds such as potassium nitrate or ammonium nitrate formulated to give plants a specific amount of ion like nitrate

54
Q

how would a farmer increase nitrataes in his soil

A

inorganic fertlisers or grow a legume crop like clover in a field one year in four. legumes have nitrogen fixing bacteria in odules on their roots which convert nitrogen gas to ammonium ions. theyre ploughed back into the soil and by next year it has been oxidised to nitrate by nitrifying bacteria

55
Q

how can a pest harm a crop

A

lowering yield by reducing the growth

affecting the appearance or quality of crop making it unsellable

56
Q

why does a farmer use pesticides

A

improve yield

57
Q

problems with pesticides

A

slow to decompose
bioaccumulation
biomagnefication
kill other harmless insects

58
Q

an ideal pesticide should

A 
control the pest effectively
be biodegradable
be specific so only pest is killed
not cause bioaccumulation
be safe to transport
be easy to apply
59
Q

why was DDT banned

A

it remained active in the environment for many years and didn’t fully decompose for over 10 years
insects became immune to it
kills any type of insect
very soluble in fats

60
Q

what is biological control

A

it uses another organism to reduce the numbers of a pest

61
Q

examples of biological control

A 
introducing a natural predator
introducing a herbivore
introducing a parasite
introducing a pathogen
introducing sterile males
using pheromones
62
Q

pollution def

A

the contamination of the environment by harmful substances that are produced by the activities of humans.

63
Q

how has CO2 increased

A

burning fossil fuels and gas.

deforestation

64
Q

what are the greenhouse gases

A 
CO2
water vapour
methane
nitrous oxide
chloroflurocarbons
65
Q

greenhouse effect

A

short-wavelength infrared radiation strikes the earth, some energy is absorbed. the radiation is re-emitted as longer wave radiation.
some long wavelength IR radiation from earth escapes into space.
some short-length IR radiation from earth is absorbed by the greenhouse fases and re-emitted back to earth.

66
Q

impacts of global warming

A

polar ice caps melt and sea levels rise
change in major ocean currents
change in global rainfall patterns
change the nature of manty ecosystems e.g. migration of birds
changes in farming practices necessary as pests became more abundant.

67
Q

when is carbon monoxide formed

A

when substances containg carbon are burned in a limited supply of oxygen.

68
Q

why is carbon monoxide dangerous

A 
colourless
odourless
tasteless
can be fatal
haemoglobin binds more strongly with it than oxygen (carboxyhaemoglobin), reducing the blood's capacity to carry oxygen.
69
Q

when is SO2 formed

A

when fossil fuels are burnt and combines with water droplets in the air

70
Q

danger of SO2

A

it can be carried as acid rain which leads to acidifcation of lakes, soil and the death of conifers.

71
Q

what organism indicates levels of sulfur dioxide pollution

A

lichen

72
Q

DEFORESTATION

A

PAPER 2

73
Q

what is sewage

A

wet waste from houses, factories and farms.

74
Q

if sewage is discharged untreated into waterways what problems does it cause

A

aerobic bacteria polluted so the lack of oxygen causes animals in freshwater to die.
contains pathogenic bacteria, which are a danger to human health

75
Q

aim of sewage treatment

A

to remove solid and suspended organic matter and pathogenic microorganisms so that cleaner waste can be discharged into waterways

76
Q

what is eutrophication ususally caused by

A

an inorganic mineral ion, nitrates or phosphates from sewage or fertilisers

77
Q

eutrophication

A

artifical fertlisers containing nitrates or phosphates are washed out of soil by rain (leaching) into waterways. the excess mineral ions stimulate the growth of all plants but paticularly algae, (algal bloom). the algae soon start to die and are decomposed by the aerobic bacteria. this uses so much oxygen in the water (and they have no light due to the algae) that fish and other aerobic animals die.

78
Q

what is biodiversity a measure of

A

the number of different species present (species richness)

the relative abundance of each species (their evenness ofnumbers)

79
Q

is biodiviersity a good thing for the environment

A

generally yes because they are often more stable, as an ecological disaster will not affect the entire ecosystem

80
Q

example of ecological disaster

A

disease (could wipe out food sources but a ecosystem rich with biodiversity would not lose all food)

81
Q

where is nitrogen present

A 
many biological compounds:
proteins
amino acids
most vitamins
DNA and ATP
82
Q

what does the nitrogen cycle involve

A

feeding, assimilation, death and decay.

83
Q

why are photosynthesis and respiration not involved in the nitrogen cycle

A

they contribute to the carbon cycle

84
Q

how does feeding and assimilation contribute to the nitrogen cycle

A

pass nitrogen atoms already in organic compounds along food chains

85
Q

how does decomposition contribute to the nitrogen cycle

A

fungi and bacteria produce ammonia from the nitrogen in compounds like proteins, DNA and vitamins

86
Q

how does nitrification contribute to the nitrogen cycle

A

the ammonia is first oxidised to nitrite and then to nitrate by nitrifying bacteria.

87
Q

how do plants contribute to the nitrogen cycle

A

their roots can absorb the nitrates. they are combined with carbohydrates (from photosynthesis) to form amino acids and then proteins, as well as other nitrogen-containing compounds

88
Q

how does denitrification contribute to the nitrogen cycle

A

denitrifying bacteria use nitrates as an energy source and convert them into nitrogen gas. denitrification reduces the amount of nitrate in the soil.

89
Q

how do nitrogen-fixing bacteria in soil contribute to the nitrogen cycle

A

they convert nitrogen gas to ammonia. this is used by bacteria to make amino acids and proteins. when bacteria die, their proteins decompose, releasing ammonia back into the soil.

90
Q

how do nitrogen fixing bacteria in root nodules contribute to the nitrogen cycle

A

make ammonia but this is converted by the plant into amino acids and other organic nitrogen compounds. death and decomposition of the plant returns to the nitrogen to the soil as ammonia

91
Q

how does lightning contribute to the nitrogen cycle2

A

it converts nitrogen gas in the air into oxides of nitrogen. these dissolve in rainwater, enter the soil and are converted to nitrates by nitrifying bacteria

92
Q

how do humans contribute to the nitrogen cycle

A

we make nitrates industrially from nitrogen gas. these are mainly used as fertilisers because they increase the rate of growth of crops.

93
Q

why do carbon levels in the environment fluctuate

A

in the winter, trees do not have leaves and so cannot photosynthesise. they still respire which produces carbon dioxide. so in the winter months they give out more carbon dioxide then they take in. in the summer months, they have many leaves and can photosynthesise, therefore taking in more carbon dioxide than they produce. (altough still respiring) howver because there are fewer trees overall, it does not fully return to that level of last summer.

94
Q

when is methane produced

A

when microorganisms ferment larger organic molecules to release energy.

95
Q

most significant sources of methane

A

decomposition of waste buried in the ground (landfill sites) by microorganisms
fermentation by microorganisms in the rumen (stomach) of cattle and other rumeninants
fermentation by bacteria in rice fields

96
Q

which molecule is contributes to the greenhouse effect more, methane or carbon dioxide

A

methane. although there is less in the atmosphere, each molecule has a much bigger greenhouse effect.

97
Q

where do tropical rainforests form

A

around the equator, south america, central africa and indonesia

98
Q

what is slash and burn

A

the method where trees are cut down and burned

99
Q

why does deforestation occur

A

to provide wood (timber) for furniture or buiding etc, and to clear land for farming.

100
Q

effects of deforestation

A

destruction of habitats and reduced biodiversity. 50-70% of species live in rainforests.
reduced soil quality. no trees and other plants to return minerals to the soil when they die, and no tree roots to hold the soil together. crops planted in deforested areas rapidly use up the minerals and the rest is leached by rain.
the soil is exposed due to lack of tree cover (canopy) and is blown or washed away.
deforesttion may produce climate change. trees reuturn water vapour from soil to the air by transpiration through thier leaves. cutting down the forests will upset the water cycle.
rainforests a valuable source of medicinal drugs and plants cultivated as crops. unknown ones will belost

101
Q

what is sustainable production

A

replacing the trees that have been removed and ensuring that there is no ecological damage.

102
Q

examples of controlled replanting schemes

A

reforestation or re-afforestation

103
Q

why is tackling the farming on this land a complex issue

A

large scale cattle farming and palm oil for cosmetics could be stopped.
however smaller farmers may depend on this for their and their families livelihood - one solution is to give them m financial help to establish farms in other areas.

edexcel igcse biology (5 decks)

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