a level biology > Ecosystems > Flashcards

Ecosystems Flashcards

(200 cards)

Study These Flashcards
1
Q

ecology

A

name given to the study of the relationships between organisms and their environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why is it important that we study ecology

A
  • understand the natural world
  • understand the variety of life which exists
  • understand interdependence of living organisms
  • help ensure the independence of living organisms
  • to help the survival of as much of Earths biodiversity as possible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

ecosystem

A
  • made up of all the living things that interact with one another
  • in a defined area
  • also the physical factors present in that region
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how are the boundaries of a particular ecosystem chosen

A
  • by the person / team carrying out the study on that ecosystem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

dynamic

A

constantly changing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why are all ecosystems dynamic

A
  • there are living organisms present
  • environmental conditions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how can the factors affecting ecosystems be divided

A
  • biotic
  • abiotic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

biotic factors

A
  • living factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

biotic factors - example

A
  • animals
  • plants
  • population size
  • competition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

abiotic factors

A
  • non living / physical factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

abiotic factors - examples

A
  • water availability
  • temperature
  • light
  • oxygen availability
  • edaphic factors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

examples of things animals compete for

A
  • food
  • space
  • breeding partners
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

abiotic factor - light

A
  • plants affected by light availability
  • needed for photosynthesis
  • greater light availability = greater success of plant species
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do plants have different strategies to cope with different light intensities

A
  • areas of low light = larger leaves
  • develop photosynthetic pigments that require less light
  • reproductive systems that only operate when light availability is at an optimum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

abiotic factor - temperature

A
  • effects the enzymes controlling metabolic reactions
  • plants + ectothermic animals develop more rapidly in warmer conditions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what can changes in temperature do to an ecosystem

A
  • e.g changing seasons
  • trigger migration
  • hibernation
  • leaf fall
  • dormancy
  • flowering
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

abiotic factor - water availability

A
  • lack of water = water stress = death
  • required for photosynthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what will lack of water do to a plant

A
  • most plants to wilt
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

why do plants wilt when they have a lack of water

A
  • water keeps cells turgid
  • keeping the plant upright
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

abiotic factor - oxygen availability in acquatic ecosystems

A
  • good to have fast flowing cold water
  • as this has high O2 concentrations
  • if water becomes too warm / flow too slow
  • less O2 concentration
  • could lead to suffocation of organisms
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

oxygen availability - soil

A
  • waterlogged soil
  • air spaces between soil particles are filled with water
  • reducing oxygen available for plants
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

abiotic factors - edaphic (soil) factors

A
  • different soil types have different particle sizes
  • has an effect on organisms which can survive in them
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

3 main soil types

A
  • clay
  • loam
  • sandy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

clay soil

A
  • fine particles
  • easily waterlogged
  • forms clumps when wet
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
loam soil
- different sized particles - retains water - does not become waterlogged
26
sandy soil
- coarse, well separated particles - allow free draining - does not retain water - easily eroded
27
what is the main energy source all organisms and ecosystems use
- sun
28
what happens to the suns energy during photosynthesis
- converted into chemical energy in plants - chemical energy is then transferred to non-photosynthetic organisms as food
29
food webs
- systems of interlinked food chains - diagrams used to show transfer of biomass and energy through the organisms in an ecosystem
30
biomass
- mass of living material
31
trophic level
- each stage in the food chain/ web
32
what is the first trophic level
producer
33
producer
- organism that converts light energy into chemical energy - via photosynthesis
34
what are the trophic levels after producer
consumers
35
consumer
organism that obtains their energy by feeding on other organisms
36
second trophic level
primary consumer
37
primary consumer
animal that eats a producer
38
trophic levels - first 5
- producer - primary consumer - secondary consumer - tertiary consumer - quaternary consumer
39
why do food chains rarely have more than 5 trophic levels
- there is not sufficient biomass and stored energy left - to support any further organisms
40
decomposers
- break down dead organisms - releasing nutrients back into the ecosystem
41
how are food chains represented
- diagrammatically - as a pyramid of numbers - each level represents the number of organisms at each level
42
in pyramid of numbers, where are the producers shown
at the bottom
43
why is it important to measure biomass
- in study of food chains/webs - as it can be equated to energy content
44
how to calculate biomass at each trophic level
biomass present in each organism x total number of organisms at that level
45
how do we measure biomass
- measure mass of fresh material present - water content needs to be discounted
46
why is measuring biomass unreliable
- varying amounts of water in different organisms - unless large samples are used
47
best way to measure biomass
- measure the dry mass
48
issues with measuring dry mass
- organisms must be killed to be dried - placed in 80 C oven - until all water is evaporated - only a small sample is taken to minimise destruction - sample may not be representative of whole population
49
biomass metrics
grams / square metre = land areas grams / cubic metre = water areas
50
how can biomass be equated to energy content
- carbon compounds are a store of energy
51
why is the biomass in each trophic level nearly always less than the trophic level below -
- when animals eat only a small proportion of the food they ingest is converted into new tissue - it is only this part of biomass which is available for the next trophic level to eat
52
metric - energy available at each trophic level
kilojoules / metre squared
53
ecological efficiency
- the efficiency with which biomass or energy is transferred - from 1 trophic level to the next
54
how can the amount of biomass or energy converted to new biomass by each trophic level in a food chain be represented
pyramid of energy
55
how much sunlight energy which producers receive do they convert into chemical energy and biomass
1-3%
56
why do producers only convert 1-3% of the sunlight energy they recieve into chemical energy
- not all solar energy available is used for photosynthesis - 90% is transmitted through leaf - some is of unusable wavelength - other limiting factors of photosynthesis - some energy is lost as it is used in photosynthesis
57
gross production
the total solar energy that plants convert to organic matter
58
how much solar energy that the plants get is used in respiration
20-50%
59
what do plants do with remaining solar energy
- convert to biomass - this is the energy available to the next trophic level
60
net production
the energy available to the next trophic level
61
how do we calculate net production
gross production - respiratory losses
62
primary production
- the generation of biomass in a producer
63
how much biomass do all consumers convert in their food to their own organic tissue
10%
64
why do consumers only convert 10% of the biomass in their food to their own organic tissue
- not all the biomass is eaten - some energy is transferred to environment as metabolic heat due to movement/respiration - some parts of an organism are eaten but indigestible - these parts egested as faeces - some energy is lost from animal in excretory materials such as urine
65
how much of the energy which was originally present in the sunlight is embodied as biomass in the tertiary consumer
0.001%
66
how do we calculate the efficiency of the energy transfer between each level of a food chain
ecological efficiency
67
ecological efficiency calculation
energy or biomass available after transfer / energy or biomass available before the transfer x100
68
how can human activities manipulate biomass through ecosystems
- human civilisation depends on agriculture
69
agriculture
- involves manipulating the environment to favour plant species which we can eat - and rear animals for their produce - plants and animals are provided with abiotic conditions they need to thrive - competition from other species is also removed
70
example of abiotic conditions provided to plants and animals - agriculture
- warmth - adequate watering - greenhouse use - stabling of animals
71
example of how competition from other species is removed for plants and animals - agriculture
- use of chemicals, e.g pesticides - removing predators by creating barriers to exclude wild herbivores/predators
72
in a natural ecosystem, which trophic level would humans occupy
- 3/4th - where only a tiny proportion of energy is available - which is turned into biomass for consumption
73
what does agriculture do to food chains
- create simple food chains - animals farmed for human consumption - only 3 trophic levels present (animals) - only 2 trophic levels present (plants) - causing minimum energy loss - due to fewer trophic levels present - as much energy as possible is transferred into biomass which can be eaten by humans
74
why do nutrients have to be recycled within an ecosystem
- so plants and animals can grow - as they are used up by living organisms - there is no large external source replenishing nutrients
75
decomposition
- chemical process - in which a compound is broken down into smaller molecules / constituent elements - organic material needs to be processed into inorganic elements and compounds - then returned to environment
76
give examples of essential elements that can be used directly by organisms in their organic form, dead, waste matter
- carbon - nitrogen
77
decomposer
- organism that feeds on and breaks down dead plant/animal matter - thus turning organic compounds into inorganic ones - available to photosynthetic producers in the ecosystem
78
examples of decomposers
- microscopic fungi (primarily) - bacteria (primarily) - can be larger fungi, e.g toadstools
79
why are decomposers saprotrophs
- they obtain their energy from dead or waste organic material - they digest food externally - by secreting enzymes onto dead organisms or organic waste matter
80
how do decomposers digest their food externally through enzyme use
- secreting enzymes onto dead organisms - enzymes break down complex organic molecules - into simple soluble molecules - through this, decomposers release stored inorganic compounds and elements back into environment
81
detritivores
- class of organism involved in decomposition - they help to speed up decay by feeding on detritus
82
detritus
dead and decaying material
83
how do detritivores help speed up decomposition
- break detritus down into smaller pieces of organic material - increasing the surface area for decomposers to work on
84
examples of detritivores
- woodlice - break down wood - earthworms - break down dead leaves
85
what kind of digestion to detritivores perform
internal digestion
86
why is nitrogen an essential element
- making amino acids - making nucleic acids - in plants and animals
87
how do animals obtain nitrogen
through the food they eat
88
how do plants obtain nitrogen
from their environment
89
how is nitrogen abundant in the atmosphere
- 78% air is nitrogen gas - but this form of nitrogen cannot be taken up by plants
90
how can nitrogen be in the correct form to be taken up by plants
- it needs to be combined with other elements - e.g oxygen or hydrogen
91
what helps to convert nitrogen into a useable form to plants
- bacteria - without, nitrogen would become a limiting factor in many ecosystems
92
nitrogen fixation
- nitrogen fixating bacteria contain nitrogenase enzyme - which combines atmospheric nitrogen with hydrogen - producing ammonia - this form of nitrogen can be used and absorbed by plants
93
nitrogen fixing bacteria
- Azotobacter - Rhizobium
94
Azotobacter
- free living soil bacterium
95
Rhizobium
- live inside root nodules - which are growths on the roots of leguminous plants - e.g peas, beans, clover
96
what kind of relationship to Rhizobium and Azotobacter have with the plants
- symbiotic mutualistic relationship - as both organisms benefit
97
why do Rhizobium and Azotobacter have a symbiotic mutualistic relationship
- plant gains amino acids from Rhizobium - which are produced by fixing nitrogen gas in the air into ammonia in the bacteria - bacteria gains carbohydrates produced by the plant in photosynthesis = energy source
98
what does other bacteria do to the ammonia that is produced by nitrogen fixation
- convert it into other organic compounds - which can be absorbed by plants
99
nitrification
- the process by which ammonium compounds in the soil - are converted into nitrogen containing molecules that can be used by plants
100
what type of bacteria is involved in nitrification
- nitrifying bacteria - this is free living bacteria in the soil
101
what type of reaction is nitrification
- oxidation reaction - only occurs in well aerated soil
102
steps of nitrification -
- nitrifying bacteria oxidise ammonium compounds into nitrites (NO2-) - nitrobacter oxidises nitrites into nitrates (NO3-)
103
example of nitrifying bacteria
- Nitrosomonas
104
Nitrobacter
genus of nitrifying bacteria
105
why are nitrate ions the form in which most nitrogen enters the plant
- they are highly soluble
106
dentrification
- dentrifying bacteria converts nitrates in the soil back to nitrogen gas - this happens in the absence of oxygen
107
give an example of an environment which would have no oxygen
waterlogged soils
108
what conditions does denitrification occur under
- anaerobic - bacteria uses nitrates as a source of energy for respiration - nitrogen gas is released
109
ammonification
- process by which decomposers convert nitrogen containing molecules in dead organisms, faeces, urine - into ammonium compounds
110
nitrogen cycle
- process of nitrogen fixation - denitrification - ammonification
111
importance of carbon
- component of all the major organic molecules present in living organisms: - fats - carbohydrates - proteins
112
what is the main source of carbon for land living organisms
- atmosphere - despite only 0.04% of CO2 in atmosphere
113
how is carbon constantly used despite there only being 0.04% in the atmosphere
- it is constantly cycled between the atmosphere, land and living organisms
114
carbon cycle - process
- CO2 in atmosphere and dissolved in seas provides source of inorganic carbon for plants - photosynthesis - CO2 converted into small carbon containing organic molecules by photosynthesis in plants, carbon then used in production of macromolecules - respiration - feeding /death - feeding = carbon macromolecules are passed from producers into primary consumers when producers are eaten and gradually passed up food chain - respiration - death - when organisms die carbon compounds in bodies are released through decomposition and carbon is released into the atmosphere as CO2 when decomposers respire - decomposition - if dead organic matter accumulates in areas without decomposers e.g bottom of ocean the carbon they contain becomes trapped and over millions of years form fossil fuels - fossil fuels - combustion
115
carbon cycle
- LEARN USING POSTERS
116
how does CO2 fluctuate throughout the day
- photosynthesis only occurs in light - so in the day removes CO2 from atmosphere - respiration is carried out all the time - releasing CO2 at a constant rate - atmospheric CO2 levels are higher at night
117
how do CO2 levels fluctuate seasonally
- CO2 levels are lower on a summers day than a winters day - as photosynthesis rates are higher in the summer
118
why have atmospheric CO2 levels increased significantly over the past 200 years
- combustion of fossil fuels - deforestation
119
combustion of fossil fuels - increase in CO2
- released carbon dioxide back into the atmosphere - from carbon that has previously been trapped for millions of years - below Earths surface
120
deforestation - increase in fossil fuels
- removed significant quantities of photosynthesising biomass from Earth - so less carbon dioxide is removed from atmosphere - therefore cleared forest is burnt - releasing more CO2 into atmosphere
121
how do increased CO2 levels contribute to global warming
- trap more thermal energy in atmosphere - as it is a greenhouse gas
122
- in oceans the higher the temperature, the less gas is dissolved - what does this mean for CO2 in oceans due to global warming
- global warming has reduced the carbon bank in he oceans - releasing more into the atmosphere - further contributing
123
how can atmospheric CO2 levels be measured
- samples are taken from deep within a glacier - when ice formed, air bubbles were trapped in the ice - these bubbles reflect composition of the atmosphere at that time - analysis of the gases present within these bubbles reveals the composition of the atmosphere at that point in time - temperature of atmosphere directly relates to level of CO2 present
124
succession
a process by which ecosystems change over time
125
why does succession occur
- as a result of changes to the environment - causing animals and plant species present to change
126
types of succession
- primary succession - secondary succession
127
primary succession
- occurs on an area of land that has been newly formed or exposed - there is no soil or organic material present to begin with
128
example of an area of primary succession
bare rock
129
secondary succession
- occurs on areas of land where soil is present but contains no plant or animals species
130
example of an area of secondary succession
- bare earth that remains after a forest fire
131
where does primary succession occur
- when volcanos erupt depositing lava = igneous rock created - sand is blown by the wind or deposited by sea to create new sand dunes - silt and mud are deposited at river estuaries - glaciers retreat depositing rubble and exposing rock
132
what are the stages of succession known as
seral stage (or sere)
133
what happens at each seral stage
- key species can be identified that change abiotic factors - especially the soil - to make it more suitable for the subsequent existence of other species
134
list the seral stages
- pioneer community - intermediate community - climax community
135
process - primary succession
slow process
136
process - secondary succession
rapid process
137
when does primary succession begin = pioneer community
- by the colonisation of an inhospitable environment - by organisms called pioneer species
138
how do pioneer species arrive
- as spores/seeds - carried by wind from nearby land masses /droppings of birds/ animals
139
examples of pioneer species
- algae - lichen
140
what adaptations to pioneer species have which enables them to colonise a bare environment
- ability to produce large quantities of seeds/spores which are blown by wind and deposited on new land - seeds that germinate rapidly - ability to photosynthesise and produce their own energy - tolerance to extreme environments - ability to fix nitrogen from the atmosphere = adding to mineral content of soil
141
intermediate community
- over time weathering of bare rock produces particles that from basis of a soil - on its own this cannot support other species - however when organisms of pioneer species die and decompose - small organic products are released into the soil
142
humus
the organic component of the soil
143
when humus is formed, what can the land area now do
- soil can support the growth of a new species of plant - as it contains minerals including nitrates - has ability to retain some water
144
what species of plant is the humus soil able to support
secondary colonisers
145
what do the secondary colonisers arrive as
- spores or seeds
146
example of secondary coloniser species
mosses
147
in an intermediate community what can pioneer species be used for
- provide a food source for consumers - so some animal species may start to colonise the area
148
in the intermediate community, what happens as the environmental conditions continue to improve
- new species of plant arrive - known as tertiary colonisers
149
tertiary coloniser example
ferns
150
tertiary colonisers
- plants have a waxy cuticle protecting them from water loss - these species can survive in conditions without an abundance of water - however need to obtain most of their water and mineral salts from soil
151
intermediate community - rock progress
- at each stage rock continues to be eroded - mass of organic matter increases
152
intermediate community - when organisms begin to decompose what happens
- they contribute to a deeper nutrient rich soil - which retains more water - making the abiotic conditions more favourable for small flowering plants - initially grasses - later shrubs - then small trees
153
intermediate community
- multiple seral stages evolve during this period - until climax conditions are attained
154
at each seral stage how does competition occur
- different plant and animal species are better adapted to the current ecosystem conditions - these organisms outcompete many of the species that were previously present - become the dominant species
155
dominant species
- the most abundant species present in the ecosystem at a given time
156
climax community
- final seral stage - community is then in a stable state - will show very little change over time - usually a few dominant plant and animal species - which species make up the climax community depends on the climate
157
in a mild climate with plenty of water, what will the climax community consist of
large trees
158
in a sub arctic climate what will the climax community consist of
herbs and shrubs
159
when is biodiversity the highest during succession
- mid succession
160
why does biodiversity decrease after mid succession
- dominant species out-compete pioneer and other species - resulting in their elimination
161
more successful the dominant species ...
the less biodiversity in a given ecosystem
162
animal succession - primary consumers
- insects - worms - first to colonise an area - as they consume and shelter in moss and lichens present
163
why is animal succession slower than plant succession
- they must move from neighbouring areas - especially if the land is geographically isolated
164
when do secondary consumers arrive in succession
- once a suitable food source has been established - existing plant cover will provide them with suitable habitats - these species have to move from neighbouring areas - eventually larger organisms come in - when biotic conditions favourable
165
what can human activites do to succession
- halt its natural flow - prevent an ecosystem from reaching climax community
166
plagioclimax
- when succession is stopped artificially this final stage is formed
167
what is the main reason for deflected succession
agriculture
168
why is agriculture the main reason for deflected succession
- grazing and trampling vegetation by domesticated animals - removing existing vegetation to plant crops - burning as a means of forest clearance
169
why does grazing and trampling deflect succession
- large areas of land remains as grassland
170
why does removing vegetation deflect succession
- crop becomes the final community
171
why does burning as a means of forest clearance deflect succession
- this leads to an increase in biodiversity - as it provides space - provides nutrient rich ash for other species to grow, e.g shrubs
172
why is deflected succession an important conservation technique
- preserving a species habitat in its current form - ensures their survival
173
why do scientists study the distribution and abundance of organisms within an ecosystem
- to measure and observe biodiversity present in an ecosystem - study how organisms present change during succession
174
distribution of organsism
- where individual organisms are found within an ecosystem - usually uneven throughout the ecosystem
175
where are organisms in an ecosystem generally found
- where biotic and abiotic factors favour them - so survival rate is high - as resources they need are available - predation/pressure from consumers is low
176
what is used to measure distribution
- line/belt transect
177
line transect
- laying a line/surveyors tape along the ground - taking samples at regular intervals
178
belt transect
- provides more information than line transect - 2 parallel lines are marked - samples are taken of the area between these specified points
179
what type of sampling is using belt and line transects
- systematic - non random
180
systematic sampling
- different areas within an overall habitat are identified - then sampled separately
181
strengths - systematic sampling
- allows scientists to discover how different abiotic factors in different areas of the habitat affect the distribution of a species - can be used to look at successional changes
182
abundance of organisms
- the number of individuals of a species present in an area at any given time
183
what can increase the abundance of organisms
- immigration - births
184
what decreases the abundance of organisms
- emigration - deaths
185
population
- group of similar organisms living in a given area at a given time
186
why are populations difficult to count
- time consuming - damaging to environment - (e.g if you use capture recapture methods)
187
how is population estimated
sampling techniques
188
disadvantages of samples
- never entirely representative of organisms present in a habitat
189
how do we increase accuracy of samples
- use a large sample - greater number of individuals studied, - lower the probability chance will influence results - random sampling to remove bias
190
what equipment do we use to measure abundance
- quadrats - counting the number of individual plants contained within the quadrat
191
calculation for abundance (m-2)
number of individuals in sample / area of sample
192
why can't we use quadrats to measure animal abundance
- animals move
193
what method do we use to measure animal abundance
capture-recapture
194
capture recapture - steps
- capture as many individuals as possible in an area - mark/tag each individual - release the tagged individuals back into sample area - allow time for them to redistribute themselves within the habitat - recapture as many individuals as possible in the original sample area - record the number of marked and unmarked individuals present in sample - release all individuals - use Lincoln index to estimate population size
195
estimated population size / Lincoln index
number of individuals in first sample x number of individuals in second sample / number of recaptured tagged individuals
196
once abundance of organisms has been determined scientists will calculate the biodiversity present in a habitat, using what -
Simpsons index of diversity
197
Simpsons index of diversity
D = N(N-1) / En(n-1)
198
Simpsons index of diversity - key :
D = diversity index N = total number of organisms in the ecosystem n = number of individuals of each species
199
Simpsons index of diversity - values
- between 0 & 1 - 0 = no diversity - 1 = infinite diversity
200
the higher the value of Simpsons index of Diversity ...
the more diverse the habitat
a level biology
flashcards
Decks in class (33)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions