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YEAR 2 BIO > population size and ecosystems > Flashcards

population size and ecosystems Flashcards

1
Q

define ecology

A

study of the ecosystem

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2
Q

define ecosystem

A

a definable area with its own community of organisms and physical environment, all interacting as a relatively self sustaining unit

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3
Q

define community

A

all the populations of all the species that live together in a particular ecosystem

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4
Q

define habitat

A

the part of an ecosystem in which particular organisms live

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5
Q

define population

A

all the interbreeding organism of one species living in a particular habitat at the same time

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6
Q

define environment

A

term used for surroundings. term for the external conditions affecting the existence of organisms

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7
Q

define biotic factor

A

effects of the activities of living organisms on other organisms e.g. food availability

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8
Q

define abiotic factors

A

non living, physical conditions in an ecosystem e.g. temp,light,soil

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9
Q

define niche

A

how it feeds and where it lives

the role that each species plays in an ecosystem

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10
Q

what is the carrying capacity

A

as a population increases it begins to experience environmental resistance as space and resources are reduced and so competition increases
population stabilised at a level which ecologists call the carrying capacity

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11
Q

what is the lag phase

A

little or no pop growth. period of adaptation for preparation for breeding

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12
Q

what is the log phase

A

exponential growth. a period of no constraint on pop growth with adequate supplies

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13
Q

what is the linear phase

A

a decelerating phase when growth rates become limited

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14
Q

what is the stationary phase

A

the population size is maintained at a constant level

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15
Q

what are some factors affecting population

A
  • immigration
  • emigration
  • variation in birth or death rate
  • sudden physical or chemical environment change
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16
Q

when will a population increase

A

when birth and immigrants > death and emigrants

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17
Q

what are density dependant factors

A

factors that increase as the size of population increases = biotic factors

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18
Q

what are density independent factors

A

unrelated to the size of the population = abiotic factor

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19
Q

describe a brine shrimp ecosystem

A 
algae - for photosynthesis 
brine shrimp - for respiration 
competition for space 
competition for resources 
mineral in sand
reproduction 
competition for a mate
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20
Q

what does a food chain show

A

how energy is transferred from one living organism to another

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21
Q

what is a trophic level

A

the level at which an organism feeds

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22
Q

what is energy transfer measured in

A

KJ m^-2 year

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23
Q

how is energy lost

A

lost from each trophic level as heat and some remains stored in dead organisms

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24
Q

what does a pyramid of biomass show

A

area of bars is proportional to the dry mass of all organisms at the level but different organisms may release difference amounts of energy per unit mass

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25
what is a pyramid of energy
burning the organisms to measure calories and work out heat energy release per unit mass
26
what is photosynthetic efficiency
measure of the ability of a plant to trap light energy
27
how can light energy be lost and what %
due to reflection conversion inefficiencies | 20-40% exuded into soil to feed the microbes
28
what is gross primary productivity
the rate at which plants convert light energy into chemical energy as energy is lost when the plant respires, less energy is available to the primary consumer the energy remaining is called the net primary productivity (NPP)
29
how much GPP is lost to respiration
60%
30
how much GPP is used for growth and respiration (NPP)
40%
31
what do consumers have a conversion efficiency of
10%
32
how can energy transfer between each trophic level be calculated
(energy available after transfer)/(energy available before transfer) X 100
33
why does life require nitrogen
protein and nucleic acids
34
what is the major reservoir of nitrogen
79% in the air (inert in this form )
35
how must plants reserve nitrogen and where do they get it from
in a fixed form nitrate ions (NO3^2-) ammonia (NH3) ammonium (NH4+)
36
where do animals get nitrogen from
plants | they digest absorb and assimilate different forms of nitrogen from their food
37
what four biological processes participate in the cycling of nitrogen
- nitrogen fixation - decomposition - nitrification - denitrification
38
what is nitrogen fixation
the nitrogen molecule is inert and uses substantial amounts of energy to break it apart three processes -biological fixation by certain microbes -atmospheric fixation by lightning -industrial fixation by the haber process
39
what is biological fixation
-free living bacteria such as AZOTOBACTER -symbiotic bacteria RHIZOBIUM in root nodules of legumes contain an enzyme called nitrogenase that converts nitrogen and hydrogen into ammonia -the ammonia is used to make amino acids which the legume can use to make proteins in return for supplying the bacteria with carbs
40
what is decomposition
the proteins made by plants enter and pass through food webs just as carbs do at each trophic level their metabolism produces organic nitrogen compounds that return to the environment chiefly in excretions the final beneficiaries of these materials are microorganisms of decay they break down the molecules in excretions and dead organisms into ammonia
41
what is nitrification
ammonia can be taken up directly by plants usually through their roots most of the ammonia produced by decay is converted into nitrates 1) bacteria of the genus NITROSOMONAS oxidise NH3 to nitrites N02- OR 2)nitrobacter oxidise the nitrites to nitrates (NO3-)
42
what is denitrification
reduced nitrates to nitrogen gas, replenishes the atmosphere and closes the nitrogen cycle bacteria =PSEUDOMONAS live deep in soil and in aquatic sediments where conditions are anaerobic use nitrates instead of 02 for final electron acceptor
43
why do we need fertilisers
contain nitrogen nd other mineral ions - obtain from the soil, if farming is intensive then minerals are lost from the soil nitrogen and mineral ions increase growth and yield
44
what are the different types of fertilisers
NATURAL - dead and decaying plants ARTIFICIAL - mined from rocks and blended to give the right mix of nutrients NPK - nitrogen, phosphorous and potassium
45
what are the consequences of using fertilisers
reduced species diversity - NPK fertilisers favour the growth of grass and nettle species leaching - excess nitrogen in soil due to excess fertilisers and causes leaching in rivers eutrophication - excess fertilisers in lakes cause increase in algae and decreases the amount of sunlight
46
advantages of organic fertilisers
``` steady supply go nutrients contain macro and micro nutrients add structure to soil use for disposing farm waste nutrients not readily leached from soil l ```
47
disadvantages of organic fertilisers
offensive smells difficulty spreading mineral release low
48
advantages of inorganic fertilisers
``` nutrients in concentrated form can be in smaller amounts nutrients released rapidly easy to apply clean chemicals lack odour ```
49
disadvantages of inorganic fertilisers
readily leached increased eutrophication expensive risk of spreading to other areas
50
what happens during eutrophication
``` plants and animals die saprotrophs secrete hydrolytic enzymes enzymes digest organic molecules saprotrophs absorb amino acids and sugars sugars are respired for energy and release co2 into the atmosphere amino acids used for growth excess amino acids are respired carbon is returned to the carbon cycle ```
51
what is succession
gradual change in species at a defined location over time
52
what happens to a community during succession
constantly changing and dynamic unit which passes through a number of stages from its origin to its climax the transition from one stage to the next is called succession
53
what is primary succession
plants grow where no plants have grown before
54
what is secondary succession
plants grow where there has been a previous population. these will have been destroyed
55
what are pioneer species
the first species to colonise | often opportunistic species which are able to rapidly exploit a sudden new opening in ground plant cover
56
what is the climax community
the ultimate species to colonise
57
what is bare rock succession
weathering will start to erode the rock forming crevices and breaking down mineral particles no plant competition soil mobile and liable to erosion
58
what is a sere
the sequence of communities with the different species and structures
59
what is a xerosere
a sere in a dry environment
60
what is global warming
he increase of average global temp in excess of the greenhouse gas effect caused by the atmospheres conc of co2
61
what causes an increase in co2
= burning fossil fuels | =deforestation
62
what is the greenhouse effect
carbon dioxide, methane, nitrous oxides, cdc's, ozone and water vapour allow high energy short wave length solar radiation to pass through earths surface re-emits lower energy longer wavelength infrared radiation so the surface warms up
63
what is global warming caused by
high concentrations of greenhouse gases
64
consequences of global warming
``` melting polar ice increased frequency of extreme weather increased forest fires decrease in availability of water world food production may decrease increase in CO2 in oceans will decrease pH which threatens organisms. ```

YEAR 2 BIO (11 decks)

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