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Biology - Module 6 > ecosystems > Flashcards

ecosystems Flashcards

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1
Q

community

A

All the populations of diff species who live in some place at a given time, who can interact w/ each other

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2
Q

ecosystem

A

all interactions between the living and non-living components in a defined area

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3
Q

simple + complex ecosystem

A

Simple ecosystem = desert

Complex ecosystem = tropic rainforest

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4
Q

biotic

A

Living = influences the populations within a community

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5
Q

examples of biotic factors

A

Predation

Competition (inter-specific) for space, food, water, light etc.

Cooperation between organisms (can be between the same species or different species)

Parasitism

Disease

Camouflage

Mimicry
o A hoverfly is harmless, yet it has evolved body colouring like that of a wasp. This deters potential predators into thinking that it is a wasp and could deliver a harmful sting

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6
Q

abiotic factors

A

any physical or chemical factor (non-living) that influences the populations within a community

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7
Q

examples of abiotic

A
  • Availability of water
  • Light
  • Temperature
  • Humidity
  • Atmospheric composition
  • pH
  • Salinity
  • Soil composition
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8
Q

biomass

A

mass of living material of the organism or tissue

chemical energy that is stored within the organism or tissue

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9
Q

niche

A

Role of a particular species

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10
Q

How does low light intensity affect the ecosystem

A

Plants develop photosynthetic pigments that require less light
Grow larger leaves
Reproductive systems that only work in optimum light intensities

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11
Q

How does temp affect the ecosystem

A

Temp has the biggest effect on enzymes in the organisms that live in the ecosystem
May trigger migration/ hibernation
Dormancy/ leaf fall/ flowering in plants

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12
Q

Biomass can be measured in terms of:

A

The dry mass of an organism or tissue (in a given area)

The mass of carbon that an organism or tissue contains

The chemical energy content of the organism when burned in pure oxygen

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13
Q

dry mass

A

mass of the organism or tissue after all the water has been removed

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14
Q

how can biomass change

A

biomass of deciduous trees decreases over autumn = lose leaves

biomass sometimes given with units of time as well

shows the average biomass of an organism within a given area over that time period

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15
Q

How are ecosystems organised

A

trophic levels

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16
Q

Producers in an ecosystem

A

organism that converts light energy into chemical energy by photosynthesis

autotrophs, chemotrophs and photoautotrophs

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17
Q

Autotrophs

A

Convert energy from environment into complex organic matter, then are used as respiratory substrates or for growth

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18
Q

Chemo/photoautotrophs

A

Use light/ chemicals to convert small inorganic molecules into complex organic ones

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19
Q

consumers

A

Higher/est trophic levels
Feed on complex organic matter made by autotrophs and other organisms and use the products of digestion as respiratory substrates or for growth

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20
Q

why is there max trophic levels

A

rarely have more trophic levels than quaternary as there isn’t sufficient biomass and stored energy left to support further organisms.

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21
Q

Decomposers

A

Feed on waste or dead organsims to gain energy by digesting and respiring organic matter

Recycling - returns inorganic ions to the air/soil

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22
Q

Why are ecosystems dynamic

A

Always changing due to many interlaced intearctions that any small change causes several others–> alters flow of biomass

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23
Q

pyramid of numbers

A
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24
Q

pyramid of numbers good

A
  • Easy method
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25
Q

pyramid of numbers bad

A
  • No consideration of size
  • Almost impossible to draw to scale
  • Does not take into account seasonal
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26
Q

pyramids of biomass

A
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27
Q

units of biomass

A
  • g/m2 or g/m3
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28
Q

limitations of pyramids of biomass

A
  • Have to kill organism to get dry mass
  • Sample small = not representative
  • Does not take into account seasonal differences
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29
Q

units for pyramids of energy

A
  • KJ / m2 / yr
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30
Q

pyramids of energy good

A
  • More reliable – measures energy
  • Allows analysis of energy transfers and losses
  • Pyramid shape always same
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31
Q

pyramids of energy bad

A
  • Difficulty + complex to collect energy data
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32
Q

ecological efficacy

A

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

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33
Q

why is a very large proportion of the suns energy not available to producers

A

Light falls away from plants

Light passes through leaves or is reflected away

Light is a mixture of wavelengths, and only certain wave lengths stimulate photosynthesis

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34
Q

why does only a small percentage of plant biomass become biomass in a primary consumer

A

Not all the plant’s biomass is eaten by the primary consumer - THORNS / BONES

Not all the consumer’s biomass intake is digested - faeces

primary consumer converts a lot of chemical energy to movement and heat, and only a small amount to new biomass in its own body

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35
Q

rough efficacy of biomass transfer

A

10%

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36
Q

formula for efficiency of biomass transfer between trophic levels

A

Efficiency of transfer = (biomass transferred / biomass intake) x 100

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37
Q

Net primary productivity (NPP)

A

the rate at which plants convert light energy into biomass.

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38
Q

Gross primary productivity (GPP

A

the rate at which plants convert light energy into chemical energy via photosynthesis.

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39
Q

Why are there fewer consumers at higher levels

A

Energy (biomass) is lost at each trophic level so unavailable to organism at next trophic level, therefore there’s less energy available to sustain living tissue

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40
Q

How is biomass lost

A

A
Cellular respiration - conversion to inorganic molecules such as CO2 and H2O
Excretory materials
Indigestible matter
Not everything is fit for consumption e.g. bones
Transferred at metabolic heat (movement)

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41
Q

Loss of biomass in endotherms vs ectotherms

A

Ectotherms use less energy in maintaing body heat so there is more biomass availabe

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42
Q

How human activities can manipulate the transfer of biomass through ecosystems

A

usually to maximise it in the context of maximising agricultural productivity

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43
Q

how can arable farmers max efficiency of transfer

A

Providing artificial light in greenhouses on overcast days

Optimising planting distances between crops

Irrigation to maximise growth in dry weather

Use of fertilisers

Selective breeding for fast growth

Use of fungicides/pesticides

Fencing to exclude grazers

Ploughing and herbicides to kill weeds

Plant crops that store energy in edible form e.g. seeds, fruit, tubers

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44
Q

how can livestock farmers max efficiency of transfer

A

Use of good quality feeds / food supplements

Use antibiotics and vaccines to reduce disease

Control predation with fencing or with indoor animal husbandry

Reduce competition for grazing e.g. rabbits, deer

Indoor husbandry to reduce energy loss from movement or from getting cold outside

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44
Q

role of nitrogen fixing bacteria

A

convert nitrogen gas into nitrogen containing compounds

contains the enzyme nitrogenase – combines atmospheric nitrogen with hydrogen

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44
Q

write out the nitrogen cycle

A

Nitrogen in the air is fixed via azotobacter, rhizobium or lightning

azotobacter results in nitrates in the soil which are actively transported into plants for proteins

Plants digested by animals to form animal proteins

both plant protein + animal protein released into soil by death or excretion

decomposers break these down into amino acids

ammonifying bacteria -e.g. saprobrionts – convert amino acids into ammonia

Nitrosomonas bacteria convert ammonia into nitrites

Nitrobacter converts nitrites into nitrates

Denitrifying bacteria release the nitrogen into the air and convert some back into nitrites + ammonia

44
Q

rhizobium - nitrogen fixing bacteria

A

Mutualistic bacteria

Live in root nodules in peas + beans (leguminous plants)

Obtain carbohydrates from plants + gives amino acids to plant

44
Q

azobacter - nitrogen fixing bacteria

A

Free living bacteria in soil

44
Q

Nitrobacter

A

Requires oxygen

Soil with air pockets – aerated soil

Nitrite ions -> nitrate ions (highly soluble)

Oxidation

44
Q

draw the nitrogen cycle

A
44
Q

Ammonifying bacteria

A

Saprobrionts

Come from fungi + bacteria kingdoms

Extracellular digestion of DOM= saprobiotic nutrition

Releases nitrogen-containing compounds into the soil

Carries out ammonification

44
Q

nitrifying bacteria

A

nitrosomonas

nitrobacter

44
Q

when does denitrifying bacteria occur

A

Occurs when soil becomes waterlogged – short of oxygen

44
Q

draw out the carbon cycle

A
45
Q

Nitrosomonas bacteria

A

Get energy from reactions involving inorganic ions

Ammonium ions -> nitrite ions

Oxidation + releases energy

Requires oxygen

45
Q
A
45
Q

what carries out denitrification + what are its effects

A

Anaerobic bacteria

Soil nitrates -> nitrogen in atmosphere

Uses nitrates in respiration – releasing nitrogen gas

45
Q

carbon stores

A

In the atmosphere (as CO2)

In sedimentary rocks

In fossil fuels like coal, oil, and gas; coal is almost pure carbon

In soil and other organic matter

In vegetation (e.g. as cellulose)

Dissolved in the oceans (as CO2)

45
Q

Photosynthesis

A

Autotrophs – fix carbon dioxide

Removes from atmosphere

45
Q

sedimentation

A

Plants that die – not fully decomposed

Bodies form layers of sediment + lock carbon into ground

Aquatic organisms – form sediments on sea bed – form fossil fuels

45
Q

physical and chemical effects in the cycling of carbon within ecosystems

A
45
Q

Succession

A

ecosystem changes from simple to complex

45
Q

each stage in succession

A

seral stage

45
Q

Primary succession

A

process that occurs when newly formed or newly exposed land is gradually colonised by an increasing number of species

45
Q

describe primary succession

A

Seeds + spores carried by wind land on exposed rock + begin to grow

Pioneer species change abiotic conditions – less hostile

die + decompose DOM / humus – form basic soil

Break apart top surface of rock

Fragmented rock + humus broken down – basic soil

Seeds of small plants / grasses – carried by wind/ bird faeces land on basic soil + grow

Secondary colonisers

adapted to survive in shallow / nutrient-poor soils

these die + decompose - new soil deeper / more nutrient-rich

lichens cant grow on soil – die out

roots of these form a network that helps to hold the soil in place + prevent it from being washed away

Larger plants and shrubs + small trees = require nutrient-rich soil now grow

more water, which can be stored in deeper soils – ferns

final species to colonise the new land

complex ecosystem

outcompete shrubs / smaller plants for light

climax community

45
Q

Pioneer species

A

Species that begin the process of succession, often colonising an area as the first living thing there

lichens

45
Q

adaptations of pioneer species

A

adaptations

produce large number of seeds + spores

seeds that germinate rapidly

ability to photosynthesis

tolerance to extreme environments

ability to fix nitrogen from air – add to mineral content of soil

45
Q

Climax community

A

Final, stable community that exists after the process of succession has occurred
Usually woodland communities

45
Q

secondary succession

A

Does not start from bare ground

Takes place on a previously colonised but damaged/disturbed habitat

45
Q

Why are sand dunes helpful in terms of succession

A

Shows us the stages of succession in order of occurrence whereas usually we only see the current stage

46
Q

How does succession affect species diversity

A

Increases it however dominant species may outcompete the smaller species killing whole species off

47
Q

How does weathering contribute to succession

A

Decomposition of rock increases soil depth/ changes soil composition
Favouring new species

48
Q
  • Gross primary productivity (GPP)
A

the rate at which plants convert light energy into chemical energy via photosynthesis.

49
Q

NPP equation

A

Therefore: NPP = GPP – R

R = respitory losses

50
Q

The net productivity of consumers can be calculated using the following equation

A

N = I - (F + R)

Where:

I = the chemical energy store in ingested food

F = the chemical energy lost to the environment in faeces and urine

R = the respiratory losses to the environment

51
Q

deflected succession

A

activity of humans by which the resulting stable community is different to the climax community that would have occurred via natural selection

52
Q

Plagioclimax

A

Sub-climax community when succession has been deflected

53
Q

Ways to deflect succession

A

Mainly agriculture and human activity e.g. Grazing

Burning

Application of fetilisers

Application to herbicide

Exposure to excessive amounts of wind

54
Q

How does succession affect biomass

A

Increases it due to more organisms in the ecosystem

55
Q

Why should sub-climax communities be conserved

A

Higher species diversity than climaxx communities - still contain some sub-climax species and climax species

Results in conserving a much wider range of plants and animals that dont live in the climax community

56
Q

Pioneer species on sand dunes

A

Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket

57
Q

Pioneer species on bare rock

A

Algae and lichens as they don’t need to be anchored into the soil

58
Q

secondary colonisers

A

moss

59
Q

Increasing primary productivity

A

Some crops are planted early
Irrigating crops
Drought resistant crops
Using greenhouses
Crop rotation
Fertilisers (provides inorganic ions)
Pesticides/ pest resistant crops

60
Q

How does planting some crops early increase primary productivity

A

Provides a longer growing season to harvest more light

61
Q

How does irrigating crops increase primary productiviy

A

Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average

62
Q

How does growing crops in a greenhouse increases primary productivity

A

Provides a warmer temp —> increases the rate of photosynthesis

63
Q

Crop rotation

A

Growing a diff. crop in each field on a rotational cycle

64
Q

How does crop rotation increase primary productivity

A

Stops reduction in soil levels of inorganic ions e.g. K^+ or NO3^-

65
Q

How does use of pesticides increase primary productibity

A

Prevents loss of biomass and lowering yield of plant

66
Q

Why do plants need NH4+

A

Maintains pH

67
Q

Why do plants need NO3-

A

Part of the nitrogen cycle

68
Q

Function of K+ in plants

A

Improves growth of leaves

69
Q

Function of PO4 3- in pants

A

Improves growth of roots

70
Q

Increasing secondary productivity

A

Harvesting animals before adulthood
Selctive breeding
Animals treated w/ antibiotics
Zero grazing
Keeping environmental temp constant - prevents energy loss through homeostasis

71
Q

How does harvesting animals before adulthood increase secondary productivity

A

Minimises loss of energy as younger animals invest a larger proportion of energy into their growth

72
Q

How does selective breeding increase secondary productivity

A

Produces improved animal breeds w/ faster growth, increased egg production and increased milk production

73
Q

Zero grazing

A

Bringing food directly to animals

Maximises energy allocated to developing muscle by reducing need to move

74
Q

Assimilation

A

Nitrates in the soil are absorbed from the soil by plants and algae. Animals then eat plants and assimilate nitrogen compounds too

75
Q

Human activities affecting the nitrogen cycle

A

Use of fertiliser - neutrification, algae use up all the oxygen

76
Q

Processes removing atmospheric nitrogen

A

Nitrogen fixation by bacteria
Atmospheric fixation
Haber process

77
Q

sampling

A
  • method of investigating the abundance and distribution of species and populations
78
Q

random

A

positions of sampling points are due to chance

no sampling biases

79
Q

systematic

A

sampling points chosen

possible bias

unrepresentative

80
Q

sampling method to estimate size of population

A

Quadrats - for non-motile or slow-moving species

Transects - for non-motile or slow-moving species

Mark-release-recapture - for motile species

81
Q

Species frequency

A

probability that species will be found within any quadrat in the sample area

number of quadrats that the species was present in is divided by the total number of quadrats and then multiplied by 100

82
Q

calculate percentage cover

A
83
Q

transects

A

show how the distribution or abundance of a species changes with the different physical conditions in the area

84
Q

mark-release capture method

A

large first sample taken

marked – not in a way that will effect survival

returned to habitat.

After time – another large sample captures

Count number of marked + unmarked

85
Q

mark-release capture equation

A
86
Q

Assumptions - mark capture release

A

marked individuals are given sufficient time to disperse and mix back in fully with the main population

marking doesn’t affect the survival rates of the marked individuals

marking remains visible throughout the sampling and doesn’t rub off

population stays the same size during the study period

there are no significant changes in population size due to births and deaths

there are no migrations into or out of the main population

87
Q
A
88
Q

Deciding how many samples to take

A

In a pilot study take random samples looking at species distribution

Plot quadrat number against cumulative frequency

When curve levels off use that number of quadrats

Biology - Module 6 (6 decks)

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