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Biology > 6.3.1 Ecosystems > Flashcards

6.3.1 Ecosystems Flashcards

1
Q

ecosystem definition

A

made up of all the living organisms that interact with one another in a defined area and also the physical factors present in that region

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2
Q

what does all ecosystems are dynamic mean

A

they are constantly changing

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3
Q

biotic factors

A

living factors
- size of their population
- the competition between 2 populations for food source

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4
Q

abiotic factors

A

non - living or physical factors
- rainfall
- temperature
oxygen availability
soil

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5
Q

examples of things which animals compete for

A

food
space / territory
breeding partners

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6
Q

light as an abiotic factor

A

plants require it for photosynthesis so the greater the availability the greater the greater the success of the plant species

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7
Q

Temperature as abiotic factor

A

effects the enzymes controlling metabolic reactions
plants will develop more rapidly if warmer

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8
Q

how can changing temperature of an ecosystem effect it

A

trigger migration of some animal species and hibernation in some
can trigger leaf-fall, dormancy and flowering

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9
Q

what does lack of water availability lead to in most plant and animal populations

A

stress which if severe can lead to death
- cause plants to wilt as cells won’t keep turgid and its required for photosynthesis

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10
Q

how to maintain high oxygen availability for aquatic organisms

A

fast-flowing water cold water
if it becomes to warm or slow flow rate the resulting drop in O2 conc can lead to suffocation

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11
Q

how can water logged soil reduce O2 availability for plants

A

air spaces between soil particles are filled with water

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12
Q

3 main types of soil types

A

clay- fine particles - easily water logged and forms clumps when wet
Loam - has different sized particles- it retains water but doesn’t become waterlogged
Sandy - coarse well separated particles allow free draining - doesn’t retain water - easily eroded

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13
Q

trophic levels

A

diagrams used to show transfer of biomass and therefore energy through organisms in an ecosystem

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14
Q

what is always the first trophic level

A

producer

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15
Q

what is a producer

A

an organism that converts light energy into chemical energy by the process of photosynthesis

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16
Q

consumers

A

organisms that obtain their energy by feeding on other organisms

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17
Q

order of trophic levels after producer

A

primary consumer
secondary consumer
tertiary consumer
quaternary consumer

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18
Q

decomposers

A

break down dead organisms releasing nutrients back into the ecosystem

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19
Q

Biomass

A

mass of living material present in a particular place or in a particular organism

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20
Q

how to calculate biomass at each trophic level

A

(biomass present in each organism) X (total number of organism in that trophic level)

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21
Q

whats the easiest way to measure biomass

A

measure the mass of fresh material present

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22
Q

problems with calculating dry mass of organisms

A

organisms have to be killed in order to be dried
organisms are placed in 80 degree oven until all water is evaporated

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23
Q

what is biomass measured in

A

grams per square metre for land
grams per cubic metre for water

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24
Q

why is the biomass of each trophic level less than the trophic level below

A

as when animal eats only a small proportion of the food they ingest is converted into new tissue

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25
what is energy available at each trophic level is measured in
kilojoules per metre squared per year
26
ecological efficiency
efficiency with which biomass or energy is transferred from one trophic level to the next
27
why do producers only convert 1-3% of the sunlight
as not all of the solar energy is available is used for photosynthesis as approx. 90% is reflected other factors may limit photosynthesis such as water availability proportion of the energy is lost as used for photosynthetic reactions
28
gross production
total solar energy that plants convert to organic matter
29
how to calculate the energy available to the next trophic level
net production= gross production - respiratory losses
30
why do consumers convert at most 10 % of the biomass in their food to their own organic tissue
-not all biomass of organism is eaten - roots or bones may not be eaten - some energy is transferred to the environment as metabolic heat due to movement and respiration - some parts are eaten but indigestible - some energy is lost from the animal in excretory materials
31
ecological efficiency
energy or biomass available after transfer/ energy or biomass available before the transfer X 100
32
human activities an manipulate biomass through ecosystems
agriculture involves manipulating the environment to favour plant species we can eat or animals for food competition is removed agriculture creates very simple food chains
33
decomposition
chemical process in which a compound is broken down into smaller molecules or its elements
34
decomposer
an organism that feeds on and breaks down dead plant or animal matter turning organic compounds into inorganic ones available to photosynthetic producers in the ecosystem
35
what a primarily decomposers
fungi and bacteria
36
why are decomposers saprotrophs
they obtain their energy from dead or waste organic material
37
how do decomposers digest their food
externally by secreting enzymes onto dead organisms enzymes breakdown complex organic molecules into smaller soluble ones they then absorb these molecules
38
detritivores
another class of organisms involved in decomposition as they help speed up decay process by feeding on detritus
39
what does detritivores include
woodlice earthworms
40
what type of digestion do detritivores do
internal
41
what do detritivores do
break down matter into smaller pieces of organic material to increase surface area for decomposers to work on
42
how do plants and animals obtain nitrogen
animals obtain it in the food they eat plants have to take it in from their environment
43
how does nitrogen become useable by plants
combined with other elements such as H or O bacteria converting into a form thats usable
44
nitrogen fixation
bacteria using enzyme to combine atmospheric nitrogen with hydrogen to form ammonia which can be absorbed by plants
45
nitrogen fixing bacteria
contain enzyme nitrogenase which does nitrogen fixation
46
where do nitrogen fixing bacteria live
inside root nodules free living in soil
47
why do bacteria have a symbiotic mutualistic relationship with the plant they live inside the root nodules of
- plant gains amino acids from bacteria which are produced by fixing nitrogen gas in the air to ammonia - bacteria gains carbohydrates produced by the plant during photosynthesis which they use as energy source
48
Nitrification
process by which ammonium compounds in soil are converted into nitrogen-containing molecules that can be used by plants
49
what type of reaction is nitrification
oxidation
50
2 steps of nitrification
nitrifying bacteria oxidises ammonium compounds into nitrites - Nitrobacter oxidises nitrites into nitrates
51
denitrification
denitrifying bacteria converts nitrates in soil back to nitrogen gas
52
when does denitrification occur
under anaerobic conditions when there's no oxygen
53
ammonification
name given to process by which decomposers convert nitrogen-containing molecules in dead organisms, faeces and urine into ammonium compounds
54
nitrogen cycle
55
carbon cycle
56
why do CO2 levels fluctuate in the atmosphere
photosynthesis only occurs during the day so it removes CO2 however all day and through the night living organisms respire releasing CO2 at a relatively constant rate so increases CO2 levels at night
57
why have CO2 levels increased significantly over the last 200 yrs
- combustion of fossil fuels releases CO2 back into the atmosphere from C that's been trapped under earths surface for thousands of yrs - deforestation removed significant quantities of photosynthesising biomass from earth so less CO2 is removed from the atmosphere
58
why is CO2 called a greenhouse gas
as it traps the thermal energy int the atmosphere
59
Primary Succession
occurs on an area of land that has been newly formed or exposed such as bare rock - no soil or organic material present to begin with
60
Secondary Succession
occurs on an area of land where soil is present but contains no plant or animal species - bare earth that remains after a forest fire
61
when does primary succession occur
when volcanoes erupt, deposit lava that solidifies igneous rock is created sand is blown by wind or deposited by the sea to create new sand dunes silt and mud deposited at river estuaries glaciers retreat depositing rubble and exposing rock
62
main seral stages
pioneer community, intermediate community, climax community
63
stages of succession
64
pioneer community
first seral stage species arrive as spores or seeds carried by wind from nearby land masses or dropped by animals or birds passing e.g algae and lichen
65
adaptations of pioneer species
ability to produce large quantities of seeds or spores which are blown by wind and deposited on new land - seeds that germinate rapidly - ability to photosynthesise to produce their own energy - tolerance to extreme environments - ability to fix nitrogen from atmosphere so adding to the mineral content of the soil
66
intermediate community
when pioneer species die and decompose small organic products are released into the soil - called humus soil can then grow new species of plants known as secondary colonisers as it contains the right minerals and can retain some water secondary colonisers arrive as spores and seeds - mosses as more decompose tertiary colonisers form each stage is more adapted to current conditions
67
climax community
stable state- shows very little change overtime which species make up the climax community depends on the climate if mild- plenty of water so community will be large trees - not very diverse as there's dominant species so how successful they are affects the biodiversity
68
Animal succession
slower than plant succession as they must move from neighboring areas primary consumers such as insects are first to colonise an area as they consume and shelter in mosses and lichen secondary consumers only come once suitable food source has been established and habitats are available
69
plagioclimax
the final stage formed when succession is stopped artificially
70
main reason for deflected succession
agriculture
71
why is agriculture main reason for deflected succession
grazing and trampling of vegetation by domesticated animals results in large areas remaining as grassland removing existing vegetation to plant crops causes crop to become final community burning as means of forest clearance - leads to increase in biodiversity as provides space and nutrient rich ash for other species to grow such as shrubs
72
distribution of organisms
where individual organisms are found within an ecosystem - usually uneven throughout ecosystem
73
what's used to measure distribution
line or belt transect
74
line transect
involves laying line or tape along ground and taking samples at regular intervals
75
belt transect
provides more info 2 parrellel lines marked and samples taken of area between these specific points
76
what type of sampling are belt and line transects
systematic sampling type of non-random sampling
77
systematic sample definition
different areas within an overall habitat are identified and then sampled separately
78
why is systematic sampling better than random sampling
allows scientists to study how differing abiotic factors in different areas of the habitat affect the distribution of species
79
Abundance of organisms
the number of individuals of a species present in an area at any given time
80
what is a disadvantage of getting a sample
never entirely representative of the organisms present in a habitat
81
how to increase accuracy of getting a sample to measure abundance
get as big a sample as possible so greater number studied the lower the probability chance will influence the result
82
estimated number of population = plants
Number of individuals in sample / area of sample (m^2)
83
method to measure animal abundance
1. capture as many individuals as possible in sample area 2. mark or tag each one 3. release marked animals back into sample area and allow time to redistribute 4. Recapture as many as possible in original sample 5. record number of marked and unmarked individuals present in sample - release them use Lincoln index to estimate population size
84
Estimated population size = animals
(number of individuals in 1st sample X number of individuals in 2nd sample) / number of recaptured marked individuals
85
Simpson's index of diversity equation
D = 1 -∑ (n/N)^2
86
what value is Simpson's index always between
0 and 1
87
what is diversity is it if Simpson's index is 0
no diversity
88
what is diversity is it if Simpson's index is 1
infinite diversity
89
higher value of Simpson's index =
more diverse the habitat

Biology (25 decks)

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