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Biology Unit 3 > 3.5 Population size and ecosystems 7 > Flashcards

3.5 Population size and ecosystems 7 Flashcards

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1
Q

define ecology

A

the study of the relationships among organisms and their environment

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2
Q

define ecosystem

A
  • the community of biotic and abiotic components of an area and their interactions
  • vary from very large e.g. biome to very small e.g. microhabitat
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3
Q

describe biotic and abiotic factors, giving examples

A

-biotic- living features of an ecosystem e.g. predators, disease
-abiotic- non-living features of an ecosystem e.g. light, temperature

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4
Q

define community

A

all of the population of diff species living together in a habitat

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5
Q

what is a habitiat?

A

the region where an organism normally lives

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6
Q

define population

A

all organisms of the same species living with one another in a habitat at the same time

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7
Q

define niche

A

describes how an organism ‘fits’ into an ecosystem and its role in that environment

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8
Q

what do population numbers depend on?

A

birth rate
death rate
immigration
emigration

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9
Q

define birth rate and death rate

A

birth rate- number of offspring born per thousand of population per year
death rate- number of deaths per thousand of population per year

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10
Q

what is immigration?

A

number of individuals entering a region per thousand of population per year

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11
Q

what is emigration?

A

number of individuals leaving a region per thousand of population per year

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12
Q

when do population sizes increase?

A

when births and immigrants are greater than deaths and emigrants

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13
Q

when do population sizes decrease?

A

when deaths and emigrants are greater than births and immigrants

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14
Q

describe the phases of population growth:

A

lag phase- period of slow population growth
log phase- period of rapid exponential population growth in which birth rate exceeds death rate
stationary phase- period of stability in which population numbers generally remain constant
death phase

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15
Q

what is carrying capacity?

A

the average size of a population that can be supported by an ecosystem over extended periods of time, varies depending on biotic and abiotic factors

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16
Q

what is competition?

A

when different organisms compete for the same resources, light, water, mates, territory in an ecosystem
limits population sizes

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17
Q

describe density-dependent and density-independent factors giving examples

A

density-dependent factors- factors whose effects on pop size differ with pop density e.g. comp, predation, disease
density-independent factors- factors whose effects on pop size remain same regardless of pop density e.g. climate

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18
Q

what is abundance?

A

number of individuals per species in a specific area at any given time

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19
Q

what is distribution?

A

the spread of living organisms in an ecosystem

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20
Q

what is sampling?

A

selecting a grp of individuals that will represent the whole target pop, allows us to measure the distribution and abundance of organisms

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21
Q

suggest methods of assessing abundance and distribution of organisms

A

quadrats- square frames placed at random in area to be investigated
transects- line or belt that runs across the area to be investigated

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22
Q

suggest diff ways abundance can be quantified

A

percentage area cover
percentage frequency
density

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23
Q

what is random sampling?

A

a sampling technique used to avoid bias, e.g. creating a square grid and generating random coordinates

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24
Q

what is systematic sampling?

A

sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals e.g. along a belt transect
commonly used in ecosystems where some form of gradual change occurs

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25
what is the source of energy for an ecosystem?
light energy
26
what is a trophic level?
the position that an organism holds in a food chain, food web, pyramid of numbers or pyramid of biomass
27
what is biomass and how is it transferred? how can we measure this?
the total weight of living matter in a certain area transferred up trophic levels through consumption measured in terms of mass of carbon or dry mass of tissue
28
formula for the efficiency of biomass transfer:
efficiency = biomass transferred/ biomass intake x100
29
why is some energy never taken in at each trophic level?
some parts of food arent consumed some parts of food are indigestible plants cant use all light energy as some is the wrong wavelength or reflected by waxy cuticle
30
why is some energy lost at each trophic level?
respiration, lost as heat
31
what is a pyramid of biomass?
a table of the dry mass of living material at each trophic level of a food chain, forms the shape of a pyramid
32
what is meant by net and gross primary productivity?
GPP- the rate of chemical energy fixture during photosynthesis by all producers in an ecosystem, measured in kJm-2yr-1 NPP- the amount of chemical energy available to heterotrophs in an ecosystem
33
How is NPP calculated?
by subtracting chemical energy generated in respiration from GPP NPP=GPP-R
34
Primary succession?
where an area previously devoid of life is colonised by pioneer species
35
Pioneer species?
species that can survive in hostile environments and colonise bare rock/sand e.g. lichens
36
summarise the process of primary succession
pioneer species colonise the area they die decompose adding nutrients to ground overtime allowing more complex organisms to survive
37
Seres?
various intermediate stages in succession in an ecosystem progressing towards a climax community
38
Secondary succession?
type of succession in which a habitat is re-colonised after a disturbance
39
what is climax community and how is it reached?
the final stage of succession where ecosystem is balanced reached when soil is rich enough to support large trees/ shrubs and the environment is no longer changing
40
how does the succession affect species diversity and the stability of a community?
succession increases species diversity and the stability of a community
41
examples of organisms that play an important role in decay
detritivores - feed on dead organic matter saprotrophs - feed by extracellular digestion
42
describe extracellular digestion by saprotrophs:
they release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter
43
carbon cycle?
cycle thru which carbon (CO2) moves between living organisms and the environment involving respiration photosynthesis and combustion
44
describe stages of carbon cycle?
1. photosynthesising plants remove co2 from atmosphere 2. eating passes carbon compounds along food chain 3. respiration in plants and animals returns co2 to atmosphere 4. organisms die and decompose, saprotrophs break down dead material and release co2 via respiration 5. combustion o materials(e.g.wood, fossil fuels) releases Co2
45
describe global warming:
the gradual rise in average temp of earth due to increasing atmospheric levels of co2 and methane gas
46
what is the greenhouse effect?
increase of global temps caused by trapping of solar heat by gases in atmosphere
47
how might global warming affect the natural world?
temp, rainfall, lightlevels etc. affect survival habitats may be destroyed by deforestation or flooding species may need to change habitat or face extinction
48
what is the nitrogen cycle?
cycle thru which nitrogen moves between living organisms and the environment involving ammonification, nitrification, nitrogen fixation and denitrification
49
how do plant roots take up nitrogen?
via active transport and facilitated diffusion as ammonium(NH4+) and nitrate ions (NO3-)
50
four types of bacteria involved in the nitrogen cycle?
Nitrogen-fixing bacteria Nitrifying bacteria Denitrifying bacteria Decomposers
51
describe ammonification:
the production of ammonium compounds when decomposers feed on organic nitrogen containing molecules
52
describe nitrification
conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in soil/ root nodules of legumes
53
examples of nitrogen fixing bacteria
- azotobacter - lives freely in the soil - rhizobium - lives inside the root nodules of leguminous plants
54
describe nitrogen fixation
conversion of ammonium ions to nitrate ions by nitrifying bacteria, takes place in two stages - ammonium ions oxidised to nitrite ions - nitrite ions oxidised to nitrate ions
55
name two types of nitrifying bacteria, state their functions
- nitrosomonas - oxidises ammonium compounds to nitrites - nitrobacter - oxidises nitrites to nitrates
56
describe denitrification
conversion of nitrate ions to nitrogen gas by denitrifying bacteria
57
what are denitrifying bacteria?
anaerobic microorganisms found in waterlogged soils responsible for the reduction of nitrate ions to nitrogen gas
58
describe the economic importance of the nitrogen cycle
maximises plant growth and crop yield increasing food production
59
how can farmers increase the nitrate content of soil?
- ploughing and drainage to aerate the soil - application of fertilisers -growing legumes
60
what are fertilisers?
natural or artificial materials added to soils to provide essential nutrients and improve plant growth
61
some examples of natural fertilisers:
manure compost treated sewage
62
an example of an artificial fertiliser:
ammonium nitrate
63
Eutrophication??
process by which pollution by nitrogen-containing fertilisers result in algal blooms and subsequent oxygen level reduction in bodies of water
64
describe how fertilisers can cause eutrophication:
1. fertiliser run-off into rivers and lakes 2. nutrients build-up in water 3. algal bloom blocks sunlight 4.aquatic plants cannot photosynthesis less oxygen produced 5. die and decompose 6. decomposers further deplete oxygen levels 7. animals can no longer respire aerobically so die
65
how does digging drainage ditch affect habitat?
habitat loss reduction in biodiversity may lead to eutrophication

Biology Unit 3 (8 decks)

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