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23 - Ecosystems Flashcards

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1
Q

What is an ecosystem?

A

-All the interacting living organisms and the non-living conditions in an area
-Dynamic
-Range in size

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2
Q

What is a biotic factor?

A

Living components of an ecosystem

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3
Q

What is an abiotic factor?

A

Non-living components in an ecosystem

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4
Q

What are the biotic factors that affect ecosystems?

A

Interactions between organisms
-Competition (intraspecific/interspecific) for food, territory, breeding partners, etc

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5
Q

What are the abiotic factors that affect ecosystems?

A

-Light: Affects photosynthesis, greater success of a plant species where light availability is greater
-Temperature: Affects enzyme controlled metabolic reactions, both plants and ectotherms develop faster in warmer temps
-Water availability: lack of water leads to water stress, causing wilting as water is required to maintain turgidity of cells, also needed for photosynthesis
-Oxygen availability: necessary for respiration (fast flowing cold water, but not water logged soils)
-Edaphic (soil) factors: CLAY - fine particles, easily waterlogged, clumps when wet / LOAM - particle size varies, retains water, not waterlogged / SANDY - coarse and separated particles, water drains, does not retain water, erodes easily

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6
Q

What is a trophic level?

A

Stage in a food chain

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7
Q

What is a food chain?

A

Diagram showing direction of energy flow

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8
Q

What is a food web?

A

Series of interlinked food chains

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9
Q

What is a producer?

A

Organism that coverts light energy into chemical energy

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10
Q

What is a consumer?

A

Organism that obtains its energy by feeding off another organism

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11
Q

What is biomass?

A

Mass of living material

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12
Q

List the trophic levels/

A

Producer - organism that converts light energy to chemical energy
Primary consumer - animal that eats a producer
Secondary consumer - animal that eats a primary consumer
Tertiary consumer - animal that eats a secondary consumer
Quaternary consumer- animal that eats a tertiary consumer

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13
Q

Why don’t food chains usually have more than five trophic levels?

A

There is not usually sufficient biomass and energy stored left to support any further organisms

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14
Q

What are the 3 types of ‘pyramids’ that represent food chains

A

Pyramid of energy
Pyramid of biomass
Pyramid of numbers

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15
Q

How do you calculate biomass at each trophic level

A

Multiply biomass of each organism by the total number of organisms in that area
BUT water content must be discounted (dry mass) and must be killed to be dried

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16
Q

What is biomass measured in?

A

g/m^2
OR
g/m^3

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17
Q

Why does biomass always decrease between successive trophic levels?

A

Only a small proportion of food ingested is converted into new tissue

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18
Q

What are the units for energy at each trophic level

A

kJ/m^2/yr

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19
Q

What is ecological efficiency?

A

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

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20
Q

What is the efficiency of a producer

A

Convert 1-3% of light energy into chemical energy and hence biomass

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21
Q

Explain the efficiency of a producer

A

-Not all light energy available is used for photosynthesis (90% is reflected)
-Other factors may limit photosynthesis
-Some energy is lost as it is used for photosynthetic reactions

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22
Q

What is gross production?

A

The total light energy that plants convert into organic matter

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23
Q

What is the net production formula

A

Net production = gross production - respiratory losses

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24
Q

What is the efficiency at consumer level?

A

Convert at most 10% of the biomass into their own organic tissue

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25
Explain the efficiency at consumer level
-not all biomass of organism is eaten (eg. Roots, bones) -some energy traversed to environment as metabolic heat due to movement and respiration -some part of organism cannot be digested (are egested as faeces) -some energy lost from animal in excretory materials (eg urine)
26
What is the formula for ecological efficiency?
Ecological efficiency = (Energy or biomass available after the transfer / Energy or biomass available before the transfer) x 100
27
How do human activity manipulate biomass through ecosystems?
Humans would occupy 2nd/3rd/4th trophic level Due to agriculture humans there are only 3 trophic levels, minimises biomass/energy loss
28
What is decomposition?
Chemical process in which a compound is broken down into smaller molecules
29
What is a decomposer?
Organism that breaks down dead organisms realising nutrients back into the ecosystem
30
What are key examples of decomposers?
Microscopic bacteria and fungi
31
What are saprotrophs?
Organisms that acquire nutrients by absorption of decaying material
32
How do saprotrophs digest their food?
Externally Secrete enzymes onto dead organisms Enzymes break down complex organic molecules into simpler soluble molecules Decomposers absorb the small soluble molecules
33
What is a detritivore?
Organism which speeds up decay by breaking down detritus into smaller pieces (Usually small animals?)
34
What is nitrogen necessary for in plants/animals?
Making amino acids and proteins Making nucleic acids
35
What are examples of nitrogen fixing bacteria?
Aztobacter and Rhizobium
36
What is the enzyme present in nitrogen fixing bacteria that combines atmospheric nitrogen to hydrogen?
Nitrogenase
37
What is nitrogen fixation?
Conversion of nitrogen gas into ammonium compounds Requires nitrogen fixing bacteria: Aztobacter and Rhizobium
38
What is nitrification?
Conversion of ammonium compounds into nitrites and nitrates Requires nitrifying bacteria: Nitrosomonas and Nitrobacter
39
What’s denitrification?
Conversion of nitrates to nitrogen gas Only occurs us anaerobic conditions (eg waterlogged soil) Requires Pseudomonas
40
What’s ammonification?
Conversion of nitrogen compounds in dead organic matter or waste into ammonium compounds by decomposers
41
Entire nitrogen cycle
42
Entire carbon cycle
43
Why is there fluctuations in atmospheric carbon dioxide?
Photosynthesis only occurs in presence of light so less CO2 in day Varies seasonally (higher in winter than summer) Global increase due to fossil fuel consumption and deforestation
44
What is succession?
Progressive replacement of one dominant type of species or community by another in an ecosystem until a stable climax community is established
45
What does succession occur as a result of?
Changes to environment causing plant and animal species present to change
46
What are the two types of succession?
Primary succession - occurs on newly formed/exposed area of land, no soil/organic material present initially Secondary succession - occurs in areas of land where soil is already present but there is no plant or animal species
47
When does primary succession occur?
Volcanoes erupt, depositing lava Sand is blown to crease sand dunes Silt and mud deposited at river estuaries Glaciers retreat depositing rubble/exposing rock
48
When does secondary succession occur?
Fire leaving bare earth Land altered Grazing Agriculture
49
What is a seral stage/sere?
Stages in succession
50
What are the seral stages of succession?
Barren land Pioneer community - lichens Intermediate community - mosses, grasses, small trees Climax community - woodland
51
What is a pioneer species?
First organism to colonise an area
52
What is pioneer community?
Colonisation of inhospitable environment by pioneer species Species arrive as spores/seed carried by wind/birds (Lichen and algae)
53
What adaptations does a pioneer species have?
Ability to produce large quantities of seed/spores Seeds that germinate rapidly Ability to photosynthesise Tolerance to extreme environments Ability to fix nitrogen from atmosphere, adding to mineral content of soil
54
How is intermediate community formed?
Over time, weathering of bare rock produces soil When organisms of pioneer species die and decompose, organic products released into soil So soil can support growth of new plants (secondary colonisers - eg mosses) Some animals may colonise area as secondary colonisers may provide food Tertiary coloniser such as ferns eventually colonise as environmental conditions improve
55
What is a climax community?
Final stage in succession where community is said to be in stable state
56
What stage is the most bio diverse in succession?
Mid succession
57
What is a plagioclimax?
Stage in succession where artificial or natural factors prevent the natural climax community from forming
58
What are some reasons for a plagioclimax?
Grazing/trampling of vegetation by domesticated animals - grassland becomes final community Removing existing vegetation to plant crops - crop becomes final community Burning to clear forest - nutrient rich ash allows more biodiversity and species to grow
59
What is the distribution of organisms?
Refers to where individual organisms are found within an ecosystem
60
How do you measure distribution of organisms?
Using a line/belt transect
61
How do you use a line transect?
Lay measuring tape on the ground and take samples at regular intervals
62
How do you use a belt transect?
Two parallel lines marked Samples taken between the specified points
63
What sampling strategy do line and belt transects use?
Systematic sampling (non-random)
64
What is the abundance of organisms?
Number of individuals of a species present in an area at any given time
65
Why might abundance of organisms fluctuate daily?
Immigration and birth rates will increase number Emigration and death rate will decrease number
66
How do you measure plant abundance?
Use quadrats to take random samples in the area Count number of individuals contained within quadrat Use this formula: Estimated number in population (/m^2) = number of individuals in samples / area of sample (m^2)
67
How do you measure animal abundance?
1. Capture as many individuals as possible in a sample area 2. Mark/tag each individual 3. Release marked individuals back into environment and allow time for them to redistribute 4. Recapture as many individuals as possible in the original sample area 5. Record the number of marked and unmarked individuals 6. Use this formula to estimate population size: Estimated population size = (number of individuals in first sample x number of individuals in second sample) / number of recaptured individuals
68
How can you calculate biodiversity in a habitat?
Use simpsons index of diversity 0 = no diversity 1 = infinite diversity
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