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A-level Biology > Population Size And Ecosystems > Flashcards

Population Size And Ecosystems Flashcards

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1
Q

Define the term habitat

A

The place in which the organism lives

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2
Q

Define the term ecology

A

The study of the interrelationships between organisms and their abiotic and biotic environment

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3
Q

Define the term abiotic environment

A

Non-living conditions affecting a community or an organism like temperature and soil ph

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4
Q

Define the term biotic environment

A

The living conditions affecting a community or an organism like competition predation and disease

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5
Q

Define the term population

A

An interbreeding group of organisms of the same species occupying a particular habitat

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6
Q

Define the term ecosystem

A

A characteristic community of interdependent species interacting with the abiotic components of the habitat

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7
Q

Define the term community

A

Interacting populations of two or more species in the same habitat at one times

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8
Q

Define the term niche

A

The role and position a species has in its environment including all interactions with the biotic and abiotic factors of its environment

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9
Q

What are the levels of organisation (from most broad to least)

A

Biosphere, ecosystem, community, population, organism

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10
Q

Explain how ecosystems are dynamic

A
  • the energy flowing through it changes
  • biological cycles vary
  • habitats change over time as succession occurs
  • new species arrive and some die out
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11
Q

What determines the size of a population?

A

Birth rate
Death rate
Immigration
Emigration

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12
Q

Define birth rate

A

The reproductive capacity of a population the number of new individuals derived from reproduction per unit of time

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13
Q

Define immigration

A

The movement of individuals into a population of the same species

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14
Q

Define emigration

A

Individuals or species leaving a habitat to enter and live in a new one.

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15
Q

What is the equation for population number?

A

(Birth rate-death rate)+(immigration-emigration)

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16
Q

Why should we talk about death rate when it comes to bacteria and fungi?

A

They are not born. They are reproduced by binary fission

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17
Q

What is environmental resistance?

A

Any factor which may slow down the growth of a population

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18
Q

List some biotic factors

A 
Predation
Parasitism
Competition
Overcrowding
Disease
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19
Q

List some abiotic factors

A 
Weather
Light intensity
Temperature
Ph
Accumulation of toxic waste
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20
Q

What sort of factors can increase population growth?

A
  • good food and water supply
  • plenty of space
  • resist disease and parasitism
  • small number of predators
  • high reproduction rate
  • favourable light
  • stable abiotic conditions
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21
Q

Factors which cause environmental resistance

A 
Competition for food
Not enough space so toxic waste accumulates
Can not resist disease 
Low reproduction rate
Unfavourable light
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22
Q

What is the carrying capacity?

A

The maximum population number a given environment can support or maintain around which a population fluctuates dependant if the availability of resources

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23
Q

What are the four stages of the population growth curve in order?

A

Lag phase
Exponential phase
Stationary phase
Death phase

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24
Q

Describe the lag phase in the population growth curve

A
  • initially population won’t increase
  • then there is a period of adaptation, preparation for growth and enzyme synthesis
  • intense metabolic activity
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25
Q

Describe the exponential phase of the population growth curve

A
  • no factors limiting reproduction
  • eventually environmental resistance sets
  • cells divide at a constant rate with the population doubling per unit time
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26
Q

Describe the stationary phase of the population growth curve

A

Birth rate = death rate

  • due to certain factor limiting the population growth
  • the population has reached its carrying capacity for that particular environment
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27
Q

Describe the death phase of the population growth curve

A

Death rate is bigger than birth rate

-due to all nutrients being used up or toxic substances like waste building up.

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28
Q

Define intraspecific competition

A

Competition between individuals of the same species

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29
Q

Define inter specific competition

A

Competition between individuals of different species

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30
Q

Define saprobiont

A

A microorganism that obtains it’s food from the dead or decaying remains of other organisms

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31
Q

Define set point

A

The numbers of most species that lie near an equilibrium point

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32
Q

Define what the sigmoid growth curve is

A

An a-shaped graph to show the population growth pattern when the animal occupies a new habitat

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33
Q

Define the term density independant factor

A

The effect of an abiotic factor in the environment that does not depend on the density of a population

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34
Q

Define the term density dependent factor

A

Biotic factors which will affect a greater proportion of the population if the population is denser

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35
Q

What is a limiting factor?

A

And abiotic or biotic factor which restricts the number or reproduction of organisms in an ecosystem is a limiting factor

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36
Q

Give an example of a density dependant factor

A

Depletion if food supply
Disease
Parasitism
Predators

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37
Q

Give examples of density independent factors

A

Flood

Fire

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38
Q

Define the term abundance

A

The measure of how many organisms are in a habitat.

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39
Q

What methods can be used to measure the abundance of animals?

A

Capture mark recapture

Kick sampling

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40
Q

What methods can be used to measure the abundance in plants?

A
  • quadrat to find density
  • estimating % cover
  • estimating % frequency
  • transects (line and belt)
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41
Q

What does a kite diagram enable you to do?

A

Represent percentage cover of plants along a transects

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42
Q

What is the equation to estimate population size using capture recapture?

A

(Total no organisms(sample 1) X total no organisms (sample 2) ) / no marked organisms (sample 2)

*round to nearest whole number

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43
Q

Describe how you would carry out a capture recapture

A

Capture a group of organisms and mark them and count the number of them

Release back into habitat and allow time to mix

Capture a second sample and count the total and count the number of them marked.

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44
Q

What does kick sampling explore?

A

Investigates the biodiversity of streams

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45
Q

Define the term ecosystems

A

A natural unit of living components in a given area as well as the non living factors with which they interact

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46
Q

Define the term ecological energetics

A

The study of the flow of energy through the ecosystem

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47
Q

Define the term trophies level

A

Feeding level

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48
Q

Define the term primary consumer

A

Also known as herbivores. Animals which feed on plants

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49
Q

Define the term carnivores

A

Animals that feed on other animals

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50
Q

Define the term detritivores

A

Organisms such as earthworms that feed on small fragments of organic debris, called detritus, made up of non living organic material like fallen leaves or the remains of dead organisms

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51
Q

Define the term decomposes

A

Microbes such as bacteria and fungi that obtain their nutrients from dead organisms and faeces. They complete the process of decomposition started by detritivores

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52
Q

What is the source of energy in an ecosystem?

A

Sunlight energy trapped by photosynthesis (except for chemosynthesis)

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53
Q

What happens to sunlight energy once absorbed by chloroplasts?

A

Used in photosynthesis to drive the conversion of co2+water into glucose

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54
Q

What are organic substances?

A

Those molecules that contain carbon

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55
Q

What happens to glucose in plants?

A

Used in respiration

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56
Q

What is the name for plants because they manufacture organic substances from light water and carbon dioxide?

A

Producers

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57
Q

Are plants the only producers?

A

No. Some protoctista and bacteria also photosynthesise (photoautotrophs) and some bacteria are chemoautotrophs

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58
Q

What are the possible energy sources on earth?

A

Geothermal
Electrical
Chemical

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59
Q

What are producers in a food chain?

A

Green plants, Cyanobacteria, protoctista
Incorporate the suns energy into carbohydrates and therefore an energy for the next organism in the food chain
Trap solar energy and synthesise sugar from inorganic compounds by photosynthesis
Only a small amount of the total energy that reaches the plant al light is incorporated into the plants tissue

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60
Q

How is energy passed along trophies levels?

A

Material of the previous organism is consumed from the next trophic level
Energy is converted into the molecules of the consumer
Some energy is lost at each level
Therefore energy flowing through the ecosystem reduces the further up you go, ultimately leaving the system as heat

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61
Q

What is a food web?

A

It shows you how the organisms in a community interact with each other through food consumption

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62
Q

What is a food chain?

A

A linear sequence of organisms in a food web

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63
Q

Why can’t a food chain be very long?

A

Because after about 4 or 5 trophic levels there is not enough energy left to support another level

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64
Q

What does the length of a food chain depend on?

A
  • energy entering the chain in the first place (more energy fixed by photosynthesis linger chain)
  • energy transfer efficiency
  • predator prey population fluctuate and relative Abundace affects length
  • larger ecosystems support longer chains
  • 3D environments longer chains
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65
Q

Name ways in which sunlight energy is lost so that it isn’t all absorbed into the leaf

A
  • wrong wavelength for photosynthesis
  • reflected by the leaf
  • passes through the leaf
  • some is lost as heat before being absorbed by chloroplasts
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66
Q

What is the equation used to find the photosynthetic efficiency to find the % of light energy that is converted into glucose?

A

(Quantity of light incorporated into product) / (quantity of energy falling on the plant) X 100 = ……%

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67
Q

What is primary productivity?

A

The rate at which energy is converted by producers into biomass

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68
Q

What is secondary productivity

A

The rate at which the consumers convert the chemical energy of their food into biomass in their cells or tissue

69
Q

Where does secondary productivity occur?

A

Heterotrophs (animals & fungi)
Some bacteria
Some protoctista

70
Q

Why is there a loss of energy at each trophies level?

A
  • energy in molecules which are egested, which is transferred to decomposers (carnivores diet is protein rich so more efficiently digested than herbivores)
  • lost as heat fuelled by energy generated from respiration
  • energy remains in molecules in parts of the animals which cannot be eaten like horns fur and bone.
71
Q

How can you calculate the efficiency of energy transfer?

A

Energy incorporated into biomass after transfer / energy available in biomass before transfer X 100 = …… %

72
Q

What does GPP stand for?

A

Gross primary productivity

73
Q

What is GPP?

A

The rate of production of chemical energy (KJ m-2 y-1) in organic molecules by photosynthesis in a given area in a given time.

74
Q

What does NPP stand for?

A

Net primary productivity

75
Q

What is NPP?

A

Energy in the plants biomass which is available to the primary consumer

76
Q

What is respiration?

A

Process in living organisms involving production of energy - glucose and other substances are broken down to produce ATP

77
Q

What is the relationship between GPP NPP AND R

A

GPP= NPP+respiration

78
Q

Why is plant material difficult to digest?

A

It contains indigestible cellulose and lignin

79
Q

Why are carnivores more efficient at converting their food into body tissue?

A

The diet is rich in protein which is more readily and efficiently digested

80
Q

What determines the number of trophic levels?

A
  • the total producer biomass

- efficiency of energy transfer

81
Q

What are ecological pyramids?

A

A diagram that shows a particular feature of each trophic level in an ecosystem

82
Q

What is always at the bottom of an ecological pyramid?

A

Producers

83
Q

What are the three types of ecological pyramid?

A

Pyramid of number
Pyramid of energy
Pyramid of biomass

84
Q

What is a disadvantage of ecological pyramids?

A

Don’t take into account that some organisms operate at more than one trophic level at the same time

85
Q

What is an advantage of a pyramid of numbers

A

Easy to construct

86
Q

What are some disadvantages of pyramid of numbers

A

Doesn’t take size of organism into account
Doesn’t recognise difference in adult and juvenile forms
Hard to draw to scale when there is a large number range
Can become inverted

87
Q

What are some advantages of pyramids of energy?

A
  • most accurate way to represent feeding relationships
  • never inverted as energy can only be lost at each stage
  • easy to compare efficiency of energy transfer between trophic levels and different communities.
88
Q

Disadvantages of pyramid of biomass

A

Hard to measure accurately
They don’t indicate productivity or amount of energy flowing through the ecosystem
Can be inverted
Not all of one trophic level will transfer to the next
Species with similar biomass may have different life spans

89
Q

Why do we try to use dry biomass and why is it hard?

A

Hard to do and time consuming.

Wet biomass is affected by water uptake and loss so will change where as dry will remain constant.

90
Q

Define the term biomass

A

The mass of living material present at a given time

91
Q

Define the term succession

A

The change in structure and composition of a species of a community over time

92
Q

Define the term climax community

A

A community that has reached equilibrium with its environment and no further changes occur

93
Q

Define the term sere

A

A stage in succession. the sequence of communities with different species and structures.

94
Q

Define the term pioneer

A

The first organism ms to colonise bars rock such as lichens and algae

95
Q

Define the term primary succession

A

The introduction of plants and animals into areas that have not previously supported a community

96
Q

Define the term secondary succession

A

Reintroduction of organisms into a bare habitat previously occupied by plants and animals

97
Q

Define the term xerosere

A

A sere in a very dry environment

98
Q

What sort of human activities interfere with or prevent succession?

A

Sheep grazing
Farming
Deforestation
Soil erosion

99
Q

What are seral stages?

A

Different stages in the sere where there are changes in the environment which makes it suitable for other species.

100
Q

What helps succession to progress?

A

Immigration of a new species.

101
Q

In a climax community what is the equilibrium between?

A

GPP and total respiration
Energy used from sunlight and released by decomposition
Uptake of nutrients from soil and return by decayed remains

102
Q

What would a stable community look like?

A

Good species diversity
Complex food web
Dominated by long lived plants

103
Q

As a xerosere progresses what increases?

A 
Soil thickness
Biomass
Biodiversity
Resistance to invasion from new species
Stability to disruption by new environmental challenges like abnormal weather
104
Q

What adaptations would a pioneer species have?

A 
Vast quantities of wind dispersed seeds or spores 
Rapid seed germination
Ability to photosynthesise
Ability to fix nitrogen from atmosphere 
Tolerance to extreme conditions
105
Q

Define secondary succession

A

The changes in a community following the disturbance or damage to a colonised habitat

106
Q

What is disclimax in a habitat?

A

Human interference can affect a succession and may prevent the development of the climax community

107
Q

What factors affect succession?

A

Immigration (spores and seeds help provide primitive soil with more minerals)
Competition to establish new seral stages

108
Q

How are nutrients cycled through a habitat?

A

Detritivores and decomposers break down remains and waste products of producers and consumers
Minerals return to the soil and plants take them up again

109
Q

What does it mean when we say the energy transfer has a linear fashion?

A

Minerals cycle between biotic and abiotic components of the environment

110
Q

How do microorganisms return nutrients to the soil?

A

Fungi and bacteria secrete enzymes to extracellularly digest the organic matter, the products of which are then absorbed to be used in respiration and waste products are released

111
Q

Give examples of organic molecules

A

Carbohydrates
Lipids
Proteins

112
Q

What are the two main human activities which increase the carbon dioxide levels in the atmosphere?

A

Deforestation

Burning of fossil fuel

113
Q

What are the main processes in the carbon cycle?

A

Respiration
Photosynthesis
Decomposition

114
Q

Define respiration

A

Carbon dioxide is added to the air by respiration of animals plants and microorganisms

115
Q

Define photosynthesis

A

It reuses almost as much carbon dioxide as is released into the atmosphere my respiration

116
Q

Define decomposition

A

Dead remains of animals and plants are acted upon by detritivores and saprobionts in soil releasing carbon dioxide into the atmosphere

117
Q

Define combustion

A

Burning fossil fuels releases carbon dioxide that was previously locked up in them into the atmosphere

118
Q

Define deforestation

A

The removal of trees in large numbers as well as large amounts of photosynthesising biomass so that less carbon dioxide is removed from the atmosphere

119
Q

Define the term fossilisation

A

Geological process of converting biological remains into coal oil and natural gas or peat is decay of biological remains is prevented by anaerobic conditions or acidic conditions

120
Q

How does carbon become a part of chalk stone and marble?

A

There is bicarbonate in shells and exoskeletons of anthropods which sink to the bottom of the ocean when they die.

121
Q

What is meant by the term carbon footprint?

A

A way of measuring the contribution to the greenhouse gases in the atmosphere by an individual, product or service

122
Q

Is the greenhouse effect a natural process?

A

Yes

123
Q

How does deforestation affect the carbon cycle?

A
  • reduces the rate at which co2 it’s taken out of the atmosphere by photosynthesis by cutting down large amounts of photosynthesising biomass
  • once cut down, trees are burned or left to decay which releases co2 into the atmosphere
124
Q

How does climate change affect the carbon cycle?

A

Carbon dioxide is a greenhouse gas meaning it absorbs radiation from earth and if excess is accumulated leads to global warming

125
Q

What are the greenhouse gases

A 
Co2
Methane
Nitrous oxides
CFC 
Ozone
Water vapour
126
Q

How do greenhouse gases cause the earths atmosphere to warm up?

A

Short wavelength radiation from sun passes through to the earths surface
Much is absorbed by the earth so it warms up
Earth retaliated lower energy longer wavelength infra red radiation
It’s absorbed and trapped by greenhouse gases in the atmosphere
This retaliates the energy is many directions

127
Q

What would happen if the greenhouse effect didn’t occur naturally?

A

The earth would be too cold to sustain life.

128
Q

What are the consequences of global warming?

A
  • melting of polar ice leading to flooding in coastal areas
  • increased frequency of extreme weather like droughts and hurricanes
  • increase forest fire frequency
  • desertification in tropical areas
  • world food production decreases
  • ocean acidification as co2 diffuses into the water
129
Q

What is global warming?

A

The increase in average global temperature in excess of the greenhouse effect caused by the atmospheres historical concentration of carbon dioxide

130
Q

How can you reduce your carbon foot print?

A 
Reduce reuse and recycle
Drive less
Less air con or heating
Eat less meat
Avoid food waste-compost
Plant trees in deforested regions
131
Q

What types of biological molecules contain nitrogen?

A

Amino acids
Nucleotides
ATP
chlorophyll

132
Q

What is the nitrogen cycle?

A

The flow of nitrogen atoms between organic and inorganic nitrogen compounds and atmospheric nitrogen gas in an ecosystem

133
Q

How do plants take in nitrogen?

A

Root hair cells actively transport it into the plant by carrier molecules from the soil

134
Q

How do animals take in nitrogen?

A

By eating and digesting plants

135
Q

What are the stages in the nitrogen cycle?

A 
Nitrogen fixation
Assimilation (putrefaction)
Ammonification
Nitrification
Denitrification
136
Q

What does the bacteria nitrosominas do?

A

NH 4+ => NO 2-

Ammonium ions to nitrites

137
Q

What does the bacteria nitrobacter do?

A

NO2- => NO3-

Nitrites to nitrates

138
Q

What does the bacteria pseudomonas do?

A

NO3- => N2

Nitrates to nitrogen gas

139
Q

What does the bacteria rhizobium do?

A

N2 => NH4+

Nitrogen gas to ammonium ions
Root nodules
Using the enzyme nitrogenase
Anaerobic conditions

140
Q

What does the bacteria azotobacter do?

A

N2 => NH4 +

Nitrogen gas to ammonium ions
Free living in the soil
Anaerobic conditions
Enzyme nitrogenase

141
Q

What is nitrogen fixation?

A

The process by which atmospheric nitrogen is converted fixed into nitrogen containing compounds

142
Q

What are the ways in which nitrogen can be fixed?

A

Lightning
Industrial processes (Haber process)
Nitrogen fixation by microorganisms (rhizobium and azotobacter)

143
Q

Describe the first stage of nitrogen cycle (nitrogen fixation)

A
  • fixed by microorganisms like rhizobium (in root nodules) and azotobacter (free living in soil)
  • plant and bacteria have a mutualistic relationship
  • this happens when the plant dies to decompose plant and rhizobium and release them into the soil.
144
Q

Where can you find rhizobium?

A

In the root nodules of leguminous plants like beans

145
Q

Describe the second stage of the nitrogen cycle (assimilation)

A

Bacteria convert nitrogen gas from soil into ammonium compounds in the legume root
Plant absorbs ammonium compounds and convert them into amino acids

146
Q

Describe the third stage of the nitrogen cycle (ammonification (putrefaction))

A

The process by which decomposers break down dead plants/animals/faeces into ammonium.
Decomposers (fungi and bacteria) secrete enzymes to exracellularly digest matter

147
Q

Describe the 4th stage in the nitrogen cycle (nitrification)

A

The process by which bacteria convert ammonium compounds into nitrites and nitrates in the soil
Step 1: oxidation of ammonium ions into nitrite by nitrosomonas (NH4+=>NO2-)
Step 2: oxidisation of nitrites into nitrates by nitrobacter (NO2-=>NO3-)
AEROBIC conditions
Ploughing

148
Q

Describe the 5th stage of nitrogen cycle (denitrification)

A 
The process by which bacteria convert nitrates in soil into nitrogen gas in the atmosphere
ANAEROBIC conditions (reduction) 
Pseudomonas converts NO3- => N2
149
Q

Why is denitrification a problem for waterlogged soils?

A

It’s favoured by anaerobic conditions so happens easily.

150
Q

What is a consumer?

A

Animals that feed on another food source like plants or other animals

151
Q

What is a decomposer?

A

Organisms, fungi, and bacteria that break down dead organic matter to obtain nutrients.

152
Q

What is an excretory product?

A

The waste products that have been produced as a result of metabolic processes in an organism

153
Q

What is a legume?

A

A dicotyledonous plant that forms a mutualistic relationship with nitrogen fixing bacteria found in root nodules. These plants improve soil fertility and are used in crop rotations
Eg prawns beans and clover

154
Q

What does mutualistic mean?

A

A relationship between two species which result in benefit to both

155
Q

What is a producer?

A

An autotrophic organism that converts light energy into chemical energy by photosynthesis

156
Q

What is a root module?

A

A small swelling on the root of a leguminous plant which results from infection with nitrogen fixing bacteria like rhizobium.

157
Q

What does saprobiontic mean?

A

An organism that obtains its nutrients from dead or decaying organic matter. They secrete digestive enzymes onto the surface of their food. The breakdown of complex organic molecules into simple inorganic products which are then absorbed by the bacteria or fungi or recycled as nutrients

158
Q

What is translocation?

A

The transport of amino acids form one part of the plant to the other.

159
Q

What is eutrophication?

A

The artificial enrichment of aquatic habitats by excess nutrients often caused by run off fertilisers

160
Q

What human activities can improve the circulation of nitrogen in fields?

A 
Ploughing
Draining land
Treated sewage sludge
Planting legume fields
Artificial nitrogen fixation
Slurry
Animal waste as brown manure
161
Q

How does ploughing fields improve circulation of nitrogen in soils?

A

Improves aeration which favours:

  • aerobic organisms like free living nitrogen fixers
  • nitrifying bacteria
  • plant roots respire aerobically and generate ATP
162
Q

How does draining land improve circulation of nitrogen in soils?

A

Allows air to enter the soils which reduces anaerobic conditions, favouring denitrifying bacteria so loss of nitrates reduces

163
Q

How does treated sewage improve circulation of nitrogen in soils?

A

Sustainable alternative to inorganic fertiliser

164
Q

How does planting legume fields improve circulation of nitrogen in soils?

A

Like alfalfa or clover to enhance nitrogen fixation and when the crops die it’s ploughed back into soil as green manure supplying Hugh nitrogen content to soil

165
Q

How does artificial nitrogen fixation improve circulation of nitrogen in soils?

A

Like the haber process converts oxygen into fertilisers to produce high volumes of good quality food

166
Q

What problems are caused by excess nitrate in soil?

A

More fertiliser used on agricultural land and decreased diversity in grassland

Fertilisers increase growth of grasses and plants like nettles which reduce light intensity for smaller plants

167
Q

What problem is caused by nitrates in rivers?

A
  • salt concentrations increase

- eutrophication

168
Q

Outline the process of eutrophication

A
  • nitrates from fertilisers leached from soil into lake and rainfall
  • algal bloom turns surface water green in response to the fertiliser
  • reduces light intensity for aquatic plants. So reduces photosynthesis leading to plants dying
  • aerobic decomposing bacteria decompose dead plants using the o2 in water to respire leading to reduced oxygen levels
  • water becomes deoxygenated so all oxygen requiring species die

A-level Biology (13 decks)

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