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population size and ecosystems Flashcards

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1
Q

how are ecosystems dynamic?

A
  • intensity of energy flowing through varies
  • biological cycles vary mineral availability
  • habitats change as succession occurs
  • species arrive and leave
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2
Q

what determines population size?

A
  • birth rate (hatching, binary fission)
  • death rate
  • immigration
  • emigration
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3
Q

fugitive species

A
  • poor at competition
  • rely on large scale reproduction and dispersal
  • invade new environments rapidly
    e.g. algae colonising bare rock
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4
Q

equilibrium species

A
  • control population by competition in a stable habitat
  • sigmoid (s-shaped) curve of growth = one-step growth curve
    e.g. bacteria in fresh nutrient solution
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5
Q

lag phase

A
  • period of slow growth, adaption or preparation for growth
  • cells adjust to new conditions
  • intense metabolic activity for enzyme synthesis
  • the time to reach sexual maturity, find a mate and gestate young in sexually reproducing organisms
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6
Q

log/exponential phase

A
  • numbers increase, more individuals available for reproduction
  • no factor limiting growth
  • bacterial population doubles per unit time
  • cell numbers increase logarithmically
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7
Q

stationary phase

A
  • birth rate = death rate
  • maximum population, fluctuates around carrying capacity in response to environmental changes
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8
Q

death phase

A
  • factors that slow population growth become more significant
  • negative gradient
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9
Q

environmental resistance

A

environmental factors that slow population growth

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10
Q

environmental resistance examples

A
  • food availability
  • overcrowding (not enough space or nesting sites)
  • competition
  • accumulation of toxic waste
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11
Q

biotic

A

a part of the environment of an organism that is living

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12
Q

biotic factors examples

A
  • predation
  • parasitism, disease (infection spreads rapidly)
  • competition for other species for nesting sites and food
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13
Q

abiotic

A

a part of the environment of an organism that is non-living

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14
Q

abiotic factors examples

A
  • temperature
  • light intensity
  • oxygen availability
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15
Q

predator prey relationships

A
  • negative feedback
  • abundance of prey limits the number of predators that can survive, and the number of predators controls the number of prey
  • e.g. snowshoe hare and lynx
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16
Q

density dependent factors

A

environmental factors that affect a greater proportion of the population if the population is denser
- biotic factors (disease)
e.g. parasites are transmitted more efficiently so a larger number are effected
e.g. higher prey density = predators encounter more prey = more prey eaten

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17
Q

density independent factors

A

abiotic factors (suddenly change) in the environment that don’t depend on population density
same effect regardless of population size
e.g. flood, fire

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18
Q

carrying capacity

A

the maximum number around which a population fluctuates in a given environment.
around a set point

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19
Q

why are physical features in a habitat described first?

A

physical features (soil type, temp) determine the number and types of plants
animals present depend on the types of plants

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20
Q

abundance

A

the number of individuals in a species in a given area or volume
a measure of how many individuals exist in a habitat

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21
Q

measuring animal abundance

A
  • capture-mark-recapture for moving organisms, using lincoln index
  • kick sampling in a stream and counting invertebrates. unreliable if misidentified, escaped or miss the net
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22
Q

capture mark recapture assumptions

A
  • few/no deaths or births
  • no immigration or emigration
  • marked individuals redistribute themselves evenly among the population
  • all organisms have equal chance of capture/recapture
  • marking method is not toxic / doesn’t make more conspicuous to predation
  • marking is not lost
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23
Q

measuring plant abundance

A
  • quadrat. calculate mean no. individuals in known area to find density
  • estimate % cover with individuals hard to recognise
  • estimate % frequency
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24
Q

distribution

A

the area or volume of which the organisms of a species are found

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25
Q

line transect

A

shows the organisms that lie on a line, at measured intervals

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26
Q

belt transect

A

shows abundance data for a given area at measured distances along the transect.
a quadrat is placed at each coordinate
e.g. shown in a kite diagram but rounded numbers reduce accuracy

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27
Q

readings taken from a belt transect

A
  • density of chosen species
  • % frequency of chosen species
  • % area cover for all species
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28
Q

what can’t be measured by a transect

A

motile animals as they move
instead done by direct observation of individuals or nests, faecal deposits or vegetation markings

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29
Q

ecosystem

A

a characteristic community of interdependent species interacting with the abiotic (soil, air) components of their environment
components linked by energy flow and nutrient cycling

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30
Q

community

A

many species living and interacting together

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31
Q

types of ecosystems

A
  • small (human large intestine)
  • large (ocean)
  • temporary (puddle)
  • permanent (lake)
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32
Q

energy

A

the ability to do work
allows changes to occur

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33
Q

law of thermodynamics

A

a sequence of energy changes allow the functioning of an ecosystem
energy flows through the components of the ecosystem

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34
Q

habitat

A

the place in which an organism lives
an ecological or environmental area inhabited by a living organism
provides the means of survival (food, water, soil, temp, pH)
may be inside an organism

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35
Q

microhabitat

A

a very small area that differs from its surroundings
features suitable for a particular species

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36
Q

community

A

interacting populations of 2+ species in the same habitat at the same time
- relates to distribution, abundance, genotypic/phenotypic differences, food web structure, predator-prey relationships

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37
Q

biomass

A

the mass of biological material in living / recently living organisms

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38
Q

ultimate source of energy for ecosystems

A

photosynthetic organisms convert sunlight energy into chemical energy, passes down organisms through a food chain

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39
Q

trophic level (feeding level)

A

the number of times that energy has been transferred between the Sun and successive organisms along a food chain

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40
Q

food chains

A

a means of transferring biomass
shown as a linear sequence of organisms in a food chain

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41
Q

food chain steps

A
  • producers (simple inorganic compounds to complex organic molecules) incorporate sun’s energy into carbs
  • they trap solar energy and synthesise sugars by photosynthesis
  • little incorporated into plant tissues
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42
Q

decomposition

A

when producers and consumers die energy remains in the organic compounds
dead tissues breakdown and are converted into simpler organic compounds

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43
Q

saprobiont

A

microorganism that obtains its food from the dead / decaying remains of other organisms
detritivores and decomposers feed as saprobionts
- contribute to recycling of nutrients

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44
Q

detritivores

A

organisms which feed on small fragments of organic debris (remains of dead organisms and fallen leaves - detritus)
e.g. earthworm, woodlice

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45
Q

decomposer

A

microbes that obtain nutrients from dead organisms and animal waste
complete process of decomposition started by detritivores
e.g. bacteria, fungi

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46
Q

food web

A

shows how organisms in a community interact with each other through the food they eat

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47
Q

why are food chain lengths limited?

A

no more than 4 or 5 trophic levels
energy is lost at each link and there is not enough to support another
inefficient transfers due to undigestible material (bones), lost as heat, lost via respiration

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48
Q

factors determining the length of a food chain

A
  • the more energy entering the 1st trophic level = longer, e.g. tropical (light all year round) food chains longer than Artic
  • energy transferred more efficiently = longer
  • predator prey populations fluctuate, so relative abundance affects length
  • larger ecosystem = supports longer chain
  • 3D environment (aquatic, forest canopy) = longer than 2D (grassland)
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49
Q

why does 60% of light energy falling on a plant not be absorbed by photosynthetic pigments?

A
  • wrong wavelength
  • reflected
  • transmitted through leaf
  • strikes non-photosynthesising parts
  • only small % utilised
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50
Q

photosynthetic efficiency (PE)

A

measure of ability to of plant to trap light energy
higher in crop plants
- depends on: plants genotype, environmental factors, if selectively bred for high productivity

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51
Q

PE equation

A

quantity of light energy incorporated into product (divided by )
quantity of energy falling onto plant
(times 100)

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52
Q

gross primary productivity (GPP)

A

amount of chemical energy stored in the carbohydrates within plants
-the rate of production of chemical energy in organic molecules by photosynthesis, in given area and time
- large proportion released by respiration of plant (for protein synthesis)
- 1%

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53
Q

net primary productivity (NPP)

A

energy in the plants biomass available to primary consumers
- food available to primary consumers / crop yield
- GPP - respiration
- 0.5%

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54
Q

primary productivity

A

the rate at which energy is converted by producers into biomass
10% efficiency

55
Q

secondary productivity

A

rate at which consumers convert chemical energy of food into biomass
- accumulation of assimilated food in biomass in cells/tissues
- occurs in heterotrophs (animals, fungi, bacteria, Protoctista)
20% efficiency

56
Q

how is energy lost along a food chain?

A
  • energy in egested molecules.
  • energy lost as heat. after processes fuelled by energy generated in respiration (muscle contraction)
    -energy remains in molecules uneaten (horns, bones, fur)
57
Q

herbivore vs carnivore energy transfer

A
  • cows feed on plants (cellulose) digested by mutualistic micro-organisms, remains pass out as faeces (undigested material), provides energy for decomposers. 60% energy lost as waste products.
  • carnivore protein-rich diet is readily and efficiently digested. 20% energy lost as waste products.
58
Q

efficiency down food chain

A
  • herbivores have 10% conversion efficiency of ingested energy into biomass and they don’t eat all the vegetation
  • carnivores have 20% efficiency, food easier to digest
59
Q

efficiency of energy transfer equation

A

energy incorporated into biomass after transfer
(divided by)
energy available in biomass before transfer
(times 100)

60
Q

ecological pyramid

A

a diagram that shows the a particular feature of each trophic level in an ecosystem
but don’t take into account some organisms operate at multiple levels

61
Q

pyramid of numbers

A
  • how many organisms at each level
  • easy to construct
  • but: doesn’t consider organism size, difference between old and young, large number range (scale issue), may be inverted
62
Q

pyramid of energy

A
  • shows how much energy is transferred between levels (organisms burned in calorimeter)
  • most accurate
  • as material passes up, energy is lost, so bars decrease
  • never inverted
  • easy to compare efficiency of energy transfer between levels
63
Q

pyramid of biomass

A
  • mass of living material at each level
  • but: difficult to measure accurately (plant roots), don’t indicate productivity, may be inverted, not representative (not all mass transferred like bones), species with similar biomass may have different life spans (not comparable)
64
Q

standing crop

A

the mass of individuals present at a given time

65
Q

succession

A

the change in structure and species composition of a community over time
- over decades (after wildfire)
- over 10000s years (after mass extinction)

66
Q

(climatic) climax community

A

a stable, self-perpetuating community that has reached equilibrium with its environment, no further change
- stable community
- complex food web
- species diversity

67
Q

primary succession

A

change in structure and species composition of a community over time in an area not previously colonised
- sequence of changes following introduction of new species

68
Q

primary succession stages

A
  • pioneer species colonise bare rock
  • plants change the environmental conditions
  • better adapted plants colonise
  • rock weathering / erosion / decaying matter = primitive soil forms
  • animals can survive (ants, spider)
  • wind-blown spores allow moss growth
  • outcompeted by small plants / grasses
  • tall grass = shade-tolerant species established
  • death/decay = thick soil, minerals, humus
  • effectively holds water
  • soil builds = deep rooted plants (shrubs, trees)
  • soil deepens
  • large trees outcompete small ones = stable, climax community
  • tree canopy limits light = floor diversity decreases
69
Q

pioneer species

A

the first species to colonise a new area in an ecological succession, e.g. algae, lichen
form a pioneer community

70
Q

sere

A

sequence of communities, with different species and structures

71
Q

xerosere

A

sere in a very dry environment

72
Q

seral stages

A

stages in succession when particular species dominate
each change the environment = more suitable for other species

73
Q

climax community is balanced with equilibrium between:

A
  • GPP + total respiration
  • Energy used from sunlight + released by decomposition
  • soil nutrient uptake + return by plant / animal decay
  • new growth + decomposition
74
Q

as xerosere progresses, the following increases:

A
  • soil thickness
  • water availability
  • humus
  • minerals
  • biomass
  • biodiversity
  • resistance to new species invasion
  • stability to disruption by environmental challenges
75
Q

secondary succession

A

changes in a community following disturbance/damage to a colonised habitat.
rapid recolonisation of a habitat after fire/tree felling
- seeds/spores may remain in soil

76
Q

disclimax

A

prevention of development of a climatic community due to human interference

77
Q

causes of a disclimax

A
  • grazing sheep / cattle, good for grass but prevents tree growth
  • farming removes species
  • deforestation removes tree communities
78
Q

factors affecting succession

A
  • migration
  • competition (inter/intraspecific)
79
Q

migration affecting succession

A

arrival of new species (spores, seeds, animals) is vital
- non-native species affect community and soil

80
Q

competition affecting succession

A
  • plant compete for light, space, water, nutrients. animals for food, shelter, space, mates.
  • operates at seral stages
  • species with competitive advantage survive
81
Q

intraspecific competition affect on succession

A

individuals of same species, density dependent
- higher population = higher competition
- organisms produce more offspring than habitat can support = regulates numbers
- best suited alleles = successfully reproduce

82
Q

interspecific competition affect on succession

A

different species
- each has own niche
- occupy a particular area and a particular role in community
- less competitive species replaced

83
Q

niche

A

describes an organisms way of life
- the role/position a species has in an environment
- all interactions with biotic and abiotic factors

84
Q

competitive exclusion principal

A

when 2 species occur in the same niche, 1 will outcompete the other

85
Q

facilitation

A

to enable something to happen
- positive interactions
- significant as succession progresses = complex communities
- provides better resource availability
- provides refuse from physical stress, predation, competition
e.g. mutualism, commensalism

86
Q

symbiosis

A

the association between individuals of 2 species.
highly interdependent or loose association

87
Q

mutualism

A
  • an interaction between 2 species, beneficial to both
    e.g. flowing plants + pollinators, close association of fungi + plant roots
88
Q

commensalism

A
  • interaction between 2 species, 1 benefits, 1 unaffected
    e.g. squirrel sheltered in a tree ( tree not affected)
  • over time species evolve = relationships change, e.g. parasite may become useful, providing nutrients = commensal
89
Q

why has carbon dioxide concentration increased in the atmosphere?

A
  • burning fossil fuels releases locked up CO2
  • deforestation removes photosynthesising biomass, so less CO2 is removed
90
Q

3 major biological processes in the carbon cycle

A
  • respiration: CO2 added to atmosphere by living organisms and combustion of fossil fuels
  • photosynthesis: takes in CO2 from atmosphere, large scale
  • decomposition: decomposers break down detritus releasing CO2.
91
Q

compression of carbon in consumers in the sea

A
  • in aquatic ecosystems CO2 (as bicarbonate) is combined with minerals, = calcium carbonate shells and sea creature exoskeletons (sink after death)
  • carbonates become components of chalk, limestone, marble. lost from the biosphere. if exposed to atmosphere = eroded = release CO2
92
Q

human impact on carbon cycle

A
  • deforestation
  • climate change
  • greenhouse effect
  • global warming
93
Q

deforestation and carbon cycle

A
  • rate of CO2 atmospheric removal by photosynthesis reduced
  • global scale = massive reduction, contributes to global warming
  • trees felled = burned or decayed = releases CO2
  • increases CO2
94
Q

climate change (temp ,rain, wind) and carbon cycle

A
  • rise in CO2 and greenhouse gases
  • burn fossil fuels: increased industrialisation and global transport = steep increase in emissions
  • deforestation: forests affects maintenance of CO2 balance
  • more greenhouse gases absorbing radiation = global warming
95
Q

global warming

A

the increase of average global temps in excess of greenhouse gas effect cause by atmospheres historical CO2 concentration

96
Q

greenhouse effect and carbon cycle

A
  • gases include: CO2, methane, water vapour, nitrous oxide)
  • allow high energy, short wavelength solar radiation to reach earth surface
  • absorbed by earth = warms up, re-radiates low energy, low wavelength IR radiation, then absorbed and trapped by gases = then reabsorbed = warming
  • natural process to sustain life
97
Q

global warming and carbon cycle

A

enhanced greenhouse effect caused by high CO2 due to human activities
consequences:
- polar ice melt = coastal flooding
- increased extreme weather and forest fire frequency
- decreased water in tropical areas = deserts expand/form
- animals move (slow to adapt), plants move slower = extinction = extinct animals depending on plants = ecosystems collapse
- fishing / crop-growing belts move
- increased crop yields, higher photosynthesis
- decreased food production = economic issues
- higher ocean CO2 = lower pH = threatens organisms. coral reefs soluble in acid.

98
Q

farming and global warming

A

affected by temp changes and timing/quantity of rain.
more flooding/droughts, less water to sustain production
reduced water supply depletes yields

99
Q

how to improve soil quality

A
  • conservation tillage: leave crop residue on soil surface, reduces erosion. improve water use.
  • add organic matter to top soil
  • cover crops: enhances soil structure.
  • crop rotation: reduce pests and mineral repletion
100
Q

how to reduce effects of methane from dairy/meat farming

A
  • reduce meat / dairy dietary intake
  • high-sugar grass, oats in cow diet reduces methane release
101
Q

how to reduce methane release from decomposition of wet soils (rice paddies)

A
  • use rice varieties that grow in drier conditions
  • ammonium sulphate added favour non-methane producing microorganisms
102
Q

how to reduce nitric/nitrous oxide released from anaerobic and waterlogged soils

A
  • improve drainage
  • remove water
  • aerate soil (ploughing)
103
Q

how to improve water supply due to low rain and high temps

A
  • use drought tolerant crops
104
Q

carbon footprint

A

the total amount of CO2 generated by an individual, product or service in 1 year.
measures a contribution to greenhouse gases in atmosphere

105
Q

indirect sources of greenhouse gases from crop farming

A
  • farming tools production
  • insecticide, herbicide, fertiliser production
  • farm machinery powered by fossil fuels
  • transport of produce
106
Q

how to reduce greenhouse gas production

A

3 Rs: reduce, reuse, recycle
- recycle packing material
- drive less
- use less air conditioning and heating (dress appropriately)
- reduce animal protein, rice, imported food, packed/processed food intake
- avoid food waste (compost)
- plant trees in deforested regions

107
Q

the nitrogen cycle

A

the flow of nitrogen atoms between organic and inorganic compounds, and atmospheric nitrogen gas in an ecosystem

108
Q

nitrogen fixation steps

A
  • nitrogen = triple bond = stable. few have the enzyme to break bond.
  • reduction of nitrogen molecules (N2 gas) in atmosphere) to ammonium ions
  • azotobacter (to ammonium ions) and rhizobium (to ammonia used by plants)
  • N2 gas diffuses into legume root nodule, nitrogenase catalyses reduction to ammonium ions (ATP, aerobic)
  • poisoned by oxidising conditions
  • root nodules contain leg-haemoglobin = pink
  • ammonium ions to organic acids to amino acids (incorporated into proteins), some used for plant metabolism
109
Q

azotobacter

A

free living nitrogen fixing bacteria in soil
- atmospheric nitrogen to ammonia, taken up by plants

110
Q

rhizobium

A

bacteria in roots of legumes, symbiotic with plants
- atmospheric nitrogen to ammonium ions in soil

111
Q

ammonification / putrefaction steps

A
  • decomposers secrete enzymes to decay dead organisms / animal products
  • proteases digest proteins into amino acids
  • deaminases remove NH2 group from amino acids = reduced to ammonium ions
    -Nitrogen compounds in waste products (e.g. urine and faeces) and dead organisms are converted into ammonia by saprobionts (a type of decomposer including some fungi and bacteria)
    This ammonia forms ammonium ions in the soil
112
Q

how are nitrogen fixing bacteria symbiotic with plants?

A
  • bacteria provide plants with nitrogen containing compounds
  • plants provide bacteria with organic compounds (carbohydrates)
113
Q

nitrification steps (addition of nitrogen to soil)

A
  • ammonium ions converted to nitrites, then nitrates
  • nitrifying bacteria require aerobic conditions for oxidation reactions
  • nitrosomas and nitrobacter
114
Q

nitrosomonas

A

convert ammonium ions to nitrites

115
Q

nitrobacter

A

convert nitrites into nitrates

116
Q

denitrification steps (loss of nitrogen from soil)

A
  • Denitrifying bacteria (anaerobic bacteria - pseudomonas) use nitrates in the soil during respiration
  • producing nitrogen gas, which returns to the atmosphere
  • occurs in anaerobic conditions (little or no oxygen available, waterlogged soil)
117
Q

nitrogen fixation definition

A

reduction of nitrogen atoms in nitrogen molecules to ammonium ions, by prokaryotic organisms

118
Q

non-biological processes that impact the nitrogen cycle

A
  • agricultural fertilisers add nitrogen to soil
  • lightning adds nitrogen to soil
  • leaching of minerals removes nitrogen from soil
119
Q

ways to improve nitrogen circulation

A
  • ploughing
  • drainage
  • artificial nitrogen fixation
  • animal waste
  • slurry
  • treated sewage sludge
  • planting legumes
120
Q

how does improve ploughing nitrogen circulation?

A

improves soil aeration, favouring:
- aerobic organisms (nitrogen fixers) enhancing NH3 formation
- nitrifying bacteria, enhances NH3 to nitrites + nitrates
- roots respiring aerobically = ATP, fuels uptake of minerals

121
Q

how does drainage improve nitrogen circulation?

A

removal of water = air enters soil
reduces anaerobic conditions = inhibits denitrifying bacteria
reduces nitrate loss

122
Q

how does artificial nitrogen fixation improve nitrogen circulation?

A

e.g. Haber process (forms ammonia)
- industrial processes convert nitrogen to fertilisers to produce food.
- fertilisers contain NH3 and nitrate ions = increases ions produced by nitrogen fixing and nitrifying bacteria

123
Q

how does animal waste (collected from farms) improve nitrogen circulation?

A
  • manure contains nitrogen and nutrients for plant growth
  • improves soil structure = holds more nutrients and water = more fertile
  • encourages microbial activity = promotes mineral supply = improved plant nutrition
  • nitrogen compounds gradually released to soil
124
Q

how does slurry (manure + water) improve nitrogen circulation?

A
  • produced by livestock rearing systems
  • injected into soil
  • preserves soil structure
    but smelly (herbivore manure less so)
125
Q

how does treated sewage sludge improve nitrogen circulation?

A
  • biosolids
  • sustainable alternative to inorganic fertilisers
126
Q

how does planting legumes improve nitrogen circulation?

A
  • enhances nitrogen fixation
  • crops die = ploughed back into soil as green manure (high nitrogen content)
127
Q

oligotrophic

A

few dissolved minerals in upland streams

128
Q

eutrophic

A

water enhanced with minerals

129
Q

dystophic

A

mineral concentration so high that organisms die

130
Q

eutrophication

A

processes / artificial enrichment of aquatic habitats by excess nutrients, caused by fertiliser run off
- nitrogen containing fertilisers leach from agricultural land, increasing mineral content of water

131
Q

eutrophication stages

A
  • mineral ions (nitrates) from excess fertiliser leach into waterways
  • causes rapid growth of algae = algal bloom
  • blocks sunlight and water becomes green. light can’t penetrate
  • plants below the surface die as can’t photosynthesise
  • algae die when competition for nutrients increases
  • aquatic plants and algae die = decomposing bacteria feed on dead organic matter
  • animal species diversity decreases
  • decomposers respire aerobically using up dissolved oxygen
  • dissolved O2 content in water decreases
  • aquatic organisms die
  • anaerobic bacteria release gases
132
Q

biochemical oxygen demand (BOD)

A
  • created by decomposers
  • represents the amount of oxygen consumed by bacteria / microorganisms while they decompose organic matter under aerobic conditions
133
Q

how to reduce the quantity of nitrogen entering waterways

A
  • restrict amount of fertiliser applied
  • only apply fertiliser during growing season = readily used, not leached
  • leave area 10m from water untouched
  • dig drainage ditches (mineral concentrate in them and undergo eutrophication = protects natural watercourse)

Biology eduquas (11 decks)

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