Unit 3.5 PopulationSize & Ecosystems (physics&mathstutorflashcards))
1
Q
population
A
number of individuals (of the same species) within a given area
2
Q
community
A
2 or more populations of (different) species within an ecosystem
3
Q
habitat
A
the physical environment where a particular community of a population lives
4
Q
environment
A
conditions that surround an organism (biotic+abiotic)
5
Q
biotic
A
any living factor which affects another organism/species in any way
6
Q
abiotic
A
non living part of the environment that can affect organisms (chemical+physical)
7
Q
name 4 biotic factors
A
- food competition/availability
- disease
- resource/habitat competition
- predation
8
Q
name 6 abiotic factors
A
- light intensity
- temperature
- pH
- wind+moisture
- salinity
-CO2/O2 conc
9
Q
ecosystem
A
a dynamic biological community that is made up of biotic+abiotic components
10
Q
niche
A
role of an organism in the ecosystem (prey/preditor)
11
Q
dispersion
A
how geographically spaced out organisms are
12
Q
fecundity
A
number of offspring an individual can have in a lifetime
13
Q
name 4 limiting factors
A
- food
- temperature
- mates
- space
14
Q
carrying capacity
A
number of individuals a habitat can sustain
15
Q
growth rate =
A
(births - death)/original pop size
16
Q
what factors alter density
A
births/deaths and immigration/emigration
17
Q
density-dependant
A
effects on population size differ with population density
(larger pop = larger death rate)
18
Q
density-independent
A
not influenced by a species population size
19
Q
define ecology
A
the study of the relationships among organisms and their environments
20
Q
what is a large ecosystem called
A
biome
21
Q
what is a small ecosystem called
A
microhabitat
22
Q
what do population numbers depend on
A
births/deaths and immigration/emigration
23
Q
define birth rate
A
the number of offspring born per thousand of population per year
24
Q
define death rate
A
the number of deaths per thousand of population per year
25
what is immigration
the number of individuals entering a region per thousand of population per year
26
what is emigration
the number of individuals leaving a region per thousand of population per year
27
when do population sizes increase
when
births + immigrants > death + emigrants
28
when do population sizes decrease
when
births + immigrants < death + emigrants
29
what are the 3 phases of population growth
- lag phase
- log phase
- stationary phase
30
define the Lag phase of population growth
period of slow population growth
31
define the Log phase of population growth
period of rapid exponential population growth in which birth rate > death rate
32
define the Stationary phase of population growth
period of stability in which population numbers generally remain constant
33
what are the axis on a graph showing bacterial population growth
side = Log of number of cells
bottom = time (hours)
34
what causes the carrying capacity to vary
biotic + abiotic factors
35
what is competition
when different organisms compete for the same resources in an ecosystem
36
give 3 examples of density-dependant factors
- competition
- predation
- disease
37
give an example of density-independant factors
- climate
38
define distribution
The spread of living organisms in an ecosystem
39
what is sampling
selecting a group of individuals that will represent the whole target population
40
what does sampling allow us to do
allows us to measure the distribution and abundance of organisms
41
suggest 2 methods of assessing abundance and distribution of organisms
1. quadrats
2. transects
42
what is a quadrat
square frames which are placed at random in an area to be investigated
43
what is a transect
a line/belt that runs across the area to be investigated
44
suggest 3 different ways that abundance can be measured
- % area cover
- % frequence
- density
45
what is random sampling
a sampling technique used to avoid bias
(e.g creating a square grid and generating random coordinates)
46
what is systematic sampling
sampling technique used to determine the abundance and distribution of organisms along an area at periodic intervals
(e.g along a belt transect)
47
what is the source of energy for an ecosystem
light energy
48
when is light not the source of energy for an ecosystem
when ecosystems rely on chemosynthesis
49
what is a trophic level
the position that an organism holds in a:
- food chain
- food web
- pyramid of numbers
- pyramid of biomass
50
what is biomass
the total dry mass of tissue
51
state the formula for efficiency of biomass transfer
efficiency = (biomass transferred / biomass intake) x100
52
why is some energy never taken in at each trophic level
- some parts of food are not consumed
- some parts of food are not digestible
- plants can not use all light energy as some is the wrong wavelength
53
why is some energy lost at each trophic level
respiration = lost as heat
54
what is a pyramid of biomass
a table of the dry mass of living material at each trophic level of a food chain
55
define gross primary productivity (GPP)
the chemical energy stored in plant biomass (made during photosynthesis)
measured in kJ m⁻² year⁻¹
56
define net primary productivity (NPP)
the amount of chemical energy that is available to heterotrophs in an ecosystem
57
how is NPP calculated
NPP = GPP - Respiration losses
58
define primary succession
where an area previously devoid of life is colonised by pioneer species
59
what is a pioneer species
species that can survive in hostile environments and colonise bare rock or sand
60
summarise the process of primary succession
1. pioneer species colonise the area
2. pioneer species die + decompose = nutrients are added to ground
3. over time, this allows more complex organisms to survive
61
what are seres
various intermediate stages in succession in an ecosystem progressing towards a climax community
62
define secondary succession
a type of succession in which a habitat is re-colonised after a disturbance
63
what is a climax community
the final stage of succession, where the ecosystem is balanced and stable
64
how can you tell that the climax community has been reached
soil is rich enough to support large trees/shrubs and the environment is no longer changing
65
how does succession affect species diversity and stability of the community
succession INCREASES species diversity and the stability of the community
66
which 2 organisms play an important role in decay
- detritivores
- saprotrophs
67
what does a detritivore feed on
dead and organic matter
68
what does a saprotroph feed by
feeds by extracellular digestion
69
describe extracellular digestion by saprotrophs
release enzymes which catalyse breakdown of dead plant and animal material into simpler organic matter
70
what is the carbon cycle
when carbon (in form of CO₂) moves between living organisms and the environment.
involving:
- respiration
- photosynthesis
- combustion
71
describe the 5 stages of the carbon cycle
1. plants remove CO₂ from atmosphere via photosynthesis
2. eating passes carbon compounds along food chain
3. respiration returns CO₂ into atmosphere
4. organisms die + decompose.
saprotrophs break down dead material and release CO₂ via respiration
5. Combustion of materials (wood, fossil fuels) release CO₂
72
define global warming
the gradual rise in the average temperature of the earth due to increasing atmospheric levels of CO₂ + methane gas
73
define the greenhouse effect
the increase of global temperatures caused by the trapping of solar heat by gases in the atmosphere
74
how might global warming affect the natural world?
- temp, rainfall, light level affect survival
- habitats may be destroyed by deforestation/flooding
- species may need to change their habitat, or face extinction
75
what is the nitrogen cycle
the cycle where nitrogen moves between living organisms and the environment, involving
- ammonification
- nitrification
- nitrogen fixation
- denitrification
76
how do plant roots take up nitrogen
taken up via active transport and facilitated diffusion as ammonium and nitrate ions
77
ammonium
NH4+
78
nitrate ions
NO3-
79
name the 4 types of bacteria involved in the nitrogen cycle
- nitrogen-fixing bacteria
- nitrifying bacteria
- denitrifying bacteria
- decomposers
80
describe ammonification
the production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules
81
describe nitrification
the conversion of
atmospheric nitrogen gas --> ammonia
BY nitrogen-fixing bacteria in the soil/root nodules of legumes
82
give some examples of nitrogen-fixing bacteria
- azotobacter
- rhizobium
83
where does azotobacter live
freely in soil
84
where does rhizobium live
inside the root nodules of leguminous plants
85
describe nitrogen fixation
the conversion of
ammonium ions --> nitrate
BY nitrifying bacteria
86
what are the 2 stages of nitrogen fixation
1. Ammonium ions oxidised to nitrite ions
2. nitrite ions oxidised to nitrate ions
87
name the 2 types of nitrifying bacteria
- nitrosomonas
- nitrobacter
88
what is the function of nitrosomonas
oxidises ammonium compounds into nitrites
89
what is the function of nitrobacter
oxidises nitrites into nitrates
90
describe denitrification
the conversion of nitrate ions to nitrogen gas by denitrifying bacteria
91
what are denitrifying bacteria
anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas
92
explain the economic importance of the nitrogen cycle
maximises plant growth and crop yield, increasing food production
93
name 3 methods farmers can use to increase the nitrate content of soil
- ploughing and drainage to aerate the soil
- application of fertilisers
- growing legumes
94
what are fertilisers
natural or artificial materials which are added to soils to provide essential nutrients and improve plant growth
95
Give some examples of natural fertilisers
- manure
- compost
- treated sewage
96
give an example of an artificial fertiliser
ammonium nitrate
97
what is eutrophication
pollution from nitrogen-containing fertilisers cause algal blooms and oxygen level reduction in water
98
describe the 7 steps of fertilisers causing eutrophication
1. fertilisers run-off into rivers
2. nutrients build-up in water
3. algal bloom blocks sunlight
4. aquatic plants cannot photosynthesis ∴ less oxygen produced
5. they die+decompose
6. decomposers further decrease oxygen levels
7. animals can't respire ∴ die
99
how does digging drainage ditches affect habitats
- habitat loss
- biodiversity reduction
- may cause eutrophication
100
