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Biology > 6.3.1 Ecosystems > Flashcards

6.3.1 Ecosystems Flashcards

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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
Q

what is energy available at each trophic level is measured in

A

kilojoules per metre squared per year

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26
Q

ecological efficiency

A

efficiency with which biomass or energy is transferred from one trophic level to the next

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27
Q

why do producers only convert 1-3% of the sunlight

A

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

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28
Q

gross production

A

total solar energy that plants convert to organic matter

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29
Q

how to calculate the energy available to the next trophic level

A

net production= gross production - respiratory losses

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30
Q

why do consumers convert at most 10 % of the biomass in their food to their own organic tissue

A

-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

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31
Q

ecological efficiency

A

energy or biomass available after transfer/ energy or biomass available before the transfer X 100

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32
Q

human activities an manipulate biomass through ecosystems

A

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

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33
Q

decomposition

A

chemical process in which a compound is broken down into smaller molecules or its elements

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34
Q

decomposer

A

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

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35
Q

what a primarily decomposers

A

fungi and bacteria

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36
Q

why are decomposers saprotrophs

A

they obtain their energy from dead or waste organic material

37
Q

how do decomposers digest their food

A

externally by secreting enzymes onto dead organisms
enzymes breakdown complex organic molecules into smaller soluble ones they then absorb these molecules

38
Q

detritivores

A

another class of organisms involved in decomposition as they help speed up decay process by feeding on detritus

39
Q

what does detritivores include

A

woodlice
earthworms

40
Q

what type of digestion do detritivores do

A

internal

41
Q

what do detritivores do

A

break down matter into smaller pieces of organic material to increase surface area for decomposers to work on

42
Q

how do plants and animals obtain nitrogen

A

animals obtain it in the food they eat
plants have to take it in from their environment

43
Q

how does nitrogen become useable by plants

A

combined with other elements such as H or O
bacteria converting into a form thats usable

44
Q

nitrogen fixation

A

bacteria using enzyme to combine atmospheric nitrogen with hydrogen to form ammonia which can be absorbed by plants

45
Q

nitrogen fixing bacteria

A

contain enzyme nitrogenase which does nitrogen fixation

46
Q

where do nitrogen fixing bacteria live

A

inside root nodules
free living in soil

47
Q

why do bacteria have a symbiotic mutualistic relationship with the plant they live inside the root nodules of

A
  • 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
Q

Nitrification

A

process by which ammonium compounds in soil are converted into nitrogen-containing molecules that can be used by plants

49
Q

what type of reaction is nitrification

A

oxidation

50
Q

2 steps of nitrification

A

nitrifying bacteria oxidises ammonium compounds into nitrites
- Nitrobacter oxidises nitrites into nitrates

51
Q

denitrification

A

denitrifying bacteria converts nitrates in soil back to nitrogen gas

52
Q

when does denitrification occur

A

under anaerobic conditions when there’s no oxygen

53
Q

ammonification

A

name given to process by which decomposers convert nitrogen-containing molecules in dead organisms, faeces and urine into ammonium compounds

54
Q

nitrogen cycle

A
55
Q

carbon cycle

A
56
Q

why do CO2 levels fluctuate in the atmosphere

A

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
Q

why have CO2 levels increased significantly over the last 200 yrs

A
  • 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
Q

why is CO2 called a greenhouse gas

A

as it traps the thermal energy int the atmosphere

59
Q

Primary Succession

A

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
Q

Secondary Succession

A

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
Q

when does primary succession occur

A

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
Q

main seral stages

A

pioneer community, intermediate community, climax community

63
Q

stages of succession

A
64
Q

pioneer community

A

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
Q

adaptations of pioneer species

A

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
Q

intermediate community

A

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
Q

climax community

A

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
Q

Animal succession

A

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
Q

plagioclimax

A

the final stage formed when succession is stopped artificially

70
Q

main reason for deflected succession

A

agriculture

71
Q

why is agriculture main reason for deflected succession

A

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
Q

distribution of organisms

A

where individual organisms are found within an ecosystem
- usually uneven throughout ecosystem

73
Q

what’s used to measure distribution

A

line or belt transect

74
Q

line transect

A

involves laying line or tape along ground and taking samples at regular intervals

75
Q

belt transect

A

provides more info
2 parrellel lines marked and samples taken of area between these specific points

76
Q

what type of sampling are belt and line transects

A

systematic sampling
type of non-random sampling

77
Q

systematic sample definition

A

different areas within an overall habitat are identified and then sampled separately

78
Q

why is systematic sampling better than random sampling

A

allows scientists to study how differing abiotic factors in different areas of the habitat affect the distribution of species

79
Q

Abundance of organisms

A

the number of individuals of a species present in an area at any given time

80
Q

what is a disadvantage of getting a sample

A

never entirely representative of the organisms present in a habitat

81
Q

how to increase accuracy of getting a sample to measure abundance

A

get as big a sample as possible so greater number studied the lower the probability chance will influence the result

82
Q

estimated number of population =
plants

A

Number of individuals in sample / area of sample (m^2)

83
Q

method to measure animal abundance

A
  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
Q

Estimated population size =
animals

A

(number of individuals in 1st sample X number of individuals in 2nd sample) / number of recaptured marked individuals

85
Q

Simpson’s index of diversity equation

A

D = 1 -∑ (n/N)^2

86
Q

what value is Simpson’s index always between

A

0 and 1

87
Q

what is diversity is it if Simpson’s index is 0

A

no diversity

88
Q

what is diversity is it if Simpson’s index is 1

A

infinite diversity

89
Q

higher value of Simpson’s index =

A

more diverse the habitat

Biology (25 decks)

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