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A Level Biology Edexcel A > On the Wild Side > Flashcards

On the Wild Side Flashcards

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1
Q

Define ecosystem

A

A community of living organisms (biotic) and their physical environment (abiotic) in an area, which is self sustaining.

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2
Q

Define habitat

A

The environment with a distinct set of conditions where a species or a group of species live.

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3
Q

Define community

A

Populations of living things interacting with each other in a habitat or ecosystem.

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4
Q

Define population

A

A group of interbreeding organisms of the same species living together in the same area at the same time.

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5
Q

Define abiotic

A

Non-living factors

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6
Q

Define biotic

A

Living factors

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7
Q

List abiotic factors.

A
  • Oxygen concentration
  • soil pH
  • Temperature
  • soil texture
  • light intensity
  • Catastrophes: fire, disease, volcanic eruption
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8
Q

List biotic factors.

A
  • Animals
  • Plants
  • Fungi
  • Bacteria
  • Grazing
  • Intraspecific competition
  • Predation
  • Grazing
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9
Q

What are anthropogenic factors?

A

Changes in the environment due to human influence which can be biotic or abiotic factors arising from human activity. e.g. deforestation, grazing.

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10
Q

Define niche.

A

The role that an organism plays in a habitat. If two individual species share the same niche they will compete until one out-competes the other.

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11
Q

Define succession.

A

A gradual sequence of changes in a community/ ecosystem or in organisms/ species/ plants over a period of time.

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12
Q

Define climax community.

A

The final stage of succession which is self sustaining and stable, usually with one dominant species. It remains stable if there are no changes in abiotic or biotic conditions.

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13
Q

When does primary succession take place?

A

In a newly formed habitat where there has never been a community before.

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14
Q

Describe the pioneer phase in primary succession.

A
  1. Process starts on newly formed habitats where there has never been a community before
  2. Pioneer species such as lichen and algae start to grow
  3. These species can live in the harsh conditions etc
  4. They add organic matter (humus) and with the substrate (rock/ash) start to produce a thin soil - change in abiotic conditions
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15
Q

Describe the development stage in primary succession.

A
  1. Mosses can now grow - change in biotic conditions. They add more organic matter to the soil so it can hold more water and mineral ions.
  2. Small shallow-rooted plants can now grow.
  3. As abiotic conditions in the habitat improves, larger tall plants can grow. These eventually outcompete the short plants and replace the previous community.
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16
Q

Describe the climax community stage in primary succession.

A
  1. A community dominated by trees (normally) is established.
  2. Remains unchanged/ stable unless abiotic or biotic conditions in the habitat change. It is self-sustaining
  3. Many different types of species and niches (high biodiversity).
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17
Q

Where does secondary succession take place?

A
  1. On bare soil where an exisiting community has been cleared.
  2. This can be after events such as ploughing, fires, hurricane, flooding or if grazing has stopped.
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18
Q

What is deflected succession?

A

When human activities prevent succession from running its course.

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19
Q

What is interspecific competition?

A

Competition between species

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20
Q

What is intraspecific competition?

A

Competition within a species

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21
Q

What are edaphic factors?

A

Factors related to soil

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22
Q

What is topography?

A

Altitude, slope, aspect and drainage

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23
Q

What is Plagioclimax?

A

A climax community which is partly the result of human intervention.

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24
Q

Write the balanced chemical equation for photosynthesis.

A

6CO2 + 6H2O —> C6H12O6 + 6O2

above arrow should say energy from sunlight in the presence of chlorophyll.

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25
Q

What is photolysis?

A

The splitting of water using energy from sunlight. Hydrogen ions, electrons and oxygen are released.
6CO2 + 6H2O —> C6H12O6 + 1/2O2

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26
Q

How is the hydrogen from the water stored?

A

The hydrogen reacts with the carbon dioxide. The carbon dioxide is reduced to form the carbohydrate glucose.

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27
Q

How is glucose used?

A
  • It can be used immediately in respiration to provide energy.
  • It can be converted into sucrose for transport around the plant.
  • It can be stored as starch (amylose & amylopectin) or converted into cellulose and other organic compounds (lipids, amino acids and nucleic acids)
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28
Q

Describe the structure and function of the thylakoid membranes.

A

System of interconnected fluid filled sacs with proteins embedded in the membranes. Site of light dependent reactions. Holds proteins (pigments and electron carriers). Site of ATPsynthase enzymes which make ATP by phosphorylation of ADP.

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29
Q

Describe the structure of the granum.

A

Stack of thylakoid membranes.

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30
Q

Describe the structure and function of the starch grain.

A

Small organelles in stroma which store starch.

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31
Q

Describe the structure and function of the thylakoid space.

A

Fluid in the thylakoid sacs which is the site of photolysis and contains enzymes for the reaction.

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32
Q

Describe the structure and function of the stroma.

A

Fluid which is the site of the light independent reactions - contains enzymes for this.

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33
Q

Describe the structure and function of the inner membrane.

A

Contains transport proteins which regulate movement of sugars and proteins in/ out of chloroplast.

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34
Q

Describe the structure and function of the loop of DNA.

A

Contains genes for making chloroplast proteins.

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35
Q

Where does the light dependent reaction take place?

Photosynthesis

A

Thylakoid membranes.

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36
Q

What is stage 1 of photosynthesis?

Photosynthesis

A

Light-dependent stage

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37
Q

Describe light-dependent photosynthesis.

Photosynthesis

A

Occurs in the thylakoid membrane.
Light energy excites two electrons per chlorophyll to an excited energy state.
Electrons travel down the electron transport chain via a series of redox reactions.
Energy is lost to synthesis of ATP in photophosphorylation. Electrons from PSII replace those from PSI using ATP synthase. Photolysis occurs, producing oxygen gas, H+ ions and electrons. The electrons combine with NADP to form NADPH.

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38
Q

What is it called when ADP and phosphate join together?

A

phosphorylation

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39
Q

What is the structure of ATP?

A

adenine, ribose, 3 phosphate groups.

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40
Q

Give the equation for the reversible reaction of ATP and ADP.

Photosynthesis

A

ATP ——> ADP + Pi

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41
Q

What is it called when ADP and phosphate break apart?

Photosynthesis

A

Hydrolysis
Dephosphorylation.

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42
Q

What is stage 2 of photosynthesis called?

Photosynthesis

A

Light independent reactions/ Calvin cycle

43
Q

Where does the calvin cycle take place?

Photosynthesis

A

inside the stroma

44
Q

Describe light-independent photosynthesis.

Photosynthesis

A
  • 6xCO2 and 6xRuBP (5C) are catalysed by RuBISCO to form 12xGP (3C). This is known as carbon fixation.
  • 12xGALP are produced by reduction of GP using hydrogens from the oxidation of NADPH and energy is provided by dephosphorylation of ATP into ADP and Pi.
  • 2xGALP are removed to form Glucose (6C) which can be converted into many other organic molecules.
  • The remaining 10 GALPs are used to regenerate the 6 RuBP. The GALP is phosphorylated. The energy and phosphate for this is provided by the hydrolysis / dephosphorylation of ATP into ADP and Pi.
45
Q

What happens to the hexose sugar from the 2 GALPs?

A

Converted into:
* a-glucose to be used in respiration or converted into sucrose for transportation to be stored as starch (amylose & amylopectin)
* b-glucose to form cellulose
* amino acids, lipids and nucleic acids.

46
Q

Define productivity.

A

The rate of generation of a biomass in an ecosystem. It depends on how much energy is absorbed by the producers and how much energy is transferred to higher trophic levels.

47
Q

Define GPP (Gross Primary Productivity).

A

The rate at which chemical energy is incorporated/ stored into organic molecules (biomass) by plants (photosynthesis) in an ecosystem in a given area or volume. It is expressed as energy per unit area per year - kJ m-2y-1, MJ ha-1y-1.

48
Q

Define NPP (Net Primary Productivity).

A

The rate at which chemical energy is incorporated/ stored into organic molecules (biomass) by plants (photosynthesis) in an ecosystem in a given area or volume after respiratory losses to the environment have been taken into account. Expressed as energy per unit area per year: kJm-2y-1.

49
Q

Define biomass.

A

The mass of carbon or dry mass of tissue per given area. The chemical energy store in dry biomass can be estimated using calorimetry.

50
Q

List the reasons as to why 100% of light energy falling on a leaf is not converted to biomass.

A
  1. Light is reflected off of the leaf’s surface
  2. Light is transmitted straight through the leaf (does not hit a chlorophyll molecule).
  3. Light is incorrect wavelength/ colour
  4. Light is in excess - already at maximum photosynthesis
  5. Light energy used in evaporation
51
Q

Give the expression for the % efficiency of photosynthesis.

A

GPP/ quantity of light energy striking the plant * 100

52
Q

Give the expression that links NPP and GPP.

A

NPP = GPP - R where R is respiration

53
Q

How is energy lost between producers and primary consumers?

A
  1. Plants respire
  2. Not all of the plant gets eaten
  3. Some energy is lost in faeces and urine
  4. Energy is lost to environment as heat
54
Q

Why is the transfer of energy more efficient between primary and secondary consumers?

A
  1. Most of the herbivore is eaten by the carnivore
  2. Most of the herbivore is protein rich so more easily digested
55
Q

Define the term correlation.

A

When a change in one variable is associated with a change in another variable.

56
Q

Define the term causation.

A

When a change in one variable is responsible for a change in another variable.

57
Q

Describe how peat bogs can provide evidence for climate change.

A

Anaerobic and acidic conditions stop the decomposition of plants by inhibiting the growth and survival of microorganisms which are responsible for decay and so preserve organic matter.

58
Q

Describe how dendrochronology can provide evidence for climate change.

A

Trees grow new layers of xylem vessels. New vessels grow in accordance to climate e.g. abundance of water and optimum temperature is better for tree growth. Wide tree rings indicate warm and wet conditions.

59
Q

Describe how pollen analysis (indicator species) can provide evidence for climate change.

A
  1. Plants produce vast quantities of pollen
  2. Tough outer layer which is decay resistant
  3. Each pollen has a distinctive shape for each tree.
  4. The deeper the pollen in a bog, the further in the past it was deposited.
  5. Pollen indicates climate of region as each tree has specific ecological growth conditions

But pollen can be dispersed over a wide area so it is uncertain if the plant actually grew there or was blown there.

60
Q

Describe how ice cores can provide evidence for climate change.

A

As water freezes, bubbles of air become trapped within the ice. The ratio of different oxygen isotopes is measured and this gives an estimate of the average temperature when the ice was formed. The CO2 concentration can also be measured in the bubbles.

61
Q

Define global warming.

A

The gradual increase in mean temperature of the Earth’s atmosphere and oceans.

62
Q

Define climate change.

A

A significant change in the weather of a region over a period of at least several decades.

63
Q

Define CO2 source.

A

rate of production of CO2 is greater than rate of CO2 use e.g. burning fossil fuels.

64
Q

Define CO2 sink.

A

rate of production of CO2 is less than the rate of CO2 use. e.g. oceans

65
Q

Describe the greenhouse effect.

A
  • Greenhouse gases are released into the atmosphere and accumulate.
  • UV light can pass through the greenhouse gases but IR cannot.
  • They trap/ absorb infrared radiation from the Sun so heat cannot escape and as a result the Earth’s mean temperature increases.
66
Q

Give sources of CO2

A
  • combustion of fossil fuels
  • deforestation
67
Q

Give sources of methane

A
  • decay of organic matter in water-logged conditions.
  • incomplete combustion of fossil fuels.
  • digestive systems of cattle.
68
Q

Describe the impact of global warming.

A
  • crop failure
  • ice caps melting
  • rising sea levels
  • extreme weather
  • ocean acidification
69
Q

Define controversial issue.

A

When alternative points on an issue can reasonably be held.

70
Q

Why is climate change controverisal?

A
  1. Science cannot prove theories it can only disprove them
  2. There is incomplete knowledge about how the climate system works. The data sets used in making predictions have their limitations.
71
Q

What is the general consensus on climate change?

A
  • Global temperatures are rising and the climate is changing
  • Greenhouse gases are partly responsible for this
72
Q

Arguments against climate change.

A

Climate change and increase in temperature are due to:
* the natural cycle of climate variations
* changes in the sun’s activity

People can be influenced by their own particular values and viewpoint, political and economic considerations

73
Q

Define extrapolation.

A

an inference about the future (or some hypothetical situation) based on known facts and observations.

74
Q

What does extrapolation allow scientists to do?

A

Make predictions about the future based on assumptions that there has to be enough data to establish the trend accurately and the present trend continues.

75
Q

What are the limitations of extrapolation?

A

The prediction will only be accurate if there is no change in the ‘system’. Models are not expected to predict the future precisely, but to make the best prediction based on the available evidence.

76
Q

Why is modelling climate change difficult and list the factors.

A

Many factors are involved so even if one factor is missed out of a model then its predictive accuracy will be reduced.

Factors which affect climate change include: other greenhouse gases e.g. N2O, aerosols, extent of cloud cover, changes in sun’s radiation, the fraction of the Earth covered with ice and snow, the degree of reflection from parts of Earth without snow/ ice.

77
Q

Why might predictions of climate change be incorrect and how are models continually improving?

A

Incorrect due to limited data, limited knowledge about how the climate system works, limitations in computing resources, failure to include all the factors affecting climate change and changing trends in factors included.

Improving by using bigger data sets, incorporation of more factors and more sophisticated interactions.

78
Q

Define carbon neutral.

A

The amount of CO2 released during combustion is equal to the amount taken up from the atmosphere in recent photosynthesis. There is no net increase in CO2 in the atmosphere.

79
Q

What is the role of microorganisms in the carbon cycle?

A

Recycle plant biomass. Release CO2 during respiration in the decomposition of organic matter. The CO2 is then available for photosynthesis.

80
Q

What are the two main factors likely to be responsible for the carbon cycle being out of balance?

A
  • Combustion of fossil fuels
  • Deforestation
81
Q

What other factors can upset the carbon balance?

A

Volcanoes, creation of marine sediments, erosion and chemical weathering (acid rain) of sedimentary rocks, rising global temperatures – e.g. increase in decomposition of peat by microorganisms and warmer oceans can hold less dissolved CO2.

82
Q

Describe the roles of biofuels in maintaining balance in the carbon cycle.

A

Source of energy produced, directly in plants or indirectly in animals, by recent photosynthesis – they are carbon neutral. They are renewable. Must consider how the biofuel is harvested and transported – machinery releases CO2. Disadvantages: destruction of forests & biodiversity to grow crop (not sustainable), less land available to grow food.

83
Q

Describe the roles of reforestation in maintaining balance in the carbon cycle.

A

Young trees grow rapidly – lots of carbon fixation to produce biomass (NPP). Photosynthesis is greater than respiration – net absorbers of CO2. As tree ages, ability to uptake as much CO2 decreases – create carbon sink. Is a limit as to how much trees can take in CO2. Keep growing young trees or algae in the oceans.

84
Q

Define phenology.

A

The study of seasonal events in the lives of animals and plants

85
Q

How do organisms cope with climate change?

A
  • changing species distribution
  • Altered development and life cycles
86
Q

What features enable animal and plant species to change their distribution?

A
  • Animals – ability to fly, swim over long distances, mobile over a large land mass.
  • Plants – good seed dispersal.
87
Q

What are the possible consequences of new species moving to an area?

A

Increased competition for the same niche, change in the dominant species.

88
Q

What are the possible solutions of climate change for a species?

A

Migrate, adapt to a different niche, become extinct if can’t move/nowhere to go.

89
Q

What problems would the migrating animal species face?

A

Lack of normal food supply, competition with existing species for a niche

90
Q

What are the 3 environmental factors likely to effect species?

A

Temperature, if it acts as a cue or trigger for their development or behaviour.

Photoperiod

Plants - Rainfall

91
Q

Why do animals and plant need to be synchronised with each other?

A

The hatching of eggs or the emergence of adults (after hibernation) is synchronised with periods of maximum food availability. A mismatch can seriously reduce survival rates.

91
Q

How is phenology used to provide evidence for climate change?

A

The timing of developmental events are used as biological indicators. Many long-term records exist. Many data sets from different species and different locations are needed. They are compared and tested statistically to improve validity.

92
Q

Define allele frequency.

A

The relative frequency of a particular allele for a particular gene in a {population / gene pool}

93
Q

Define genome.

A

All the genes (coding regions) and non-coding regions of DNA in an organism

94
Q

What have the techniques of molecular biology enabled scientists to gain evidence about?

A

Evolution and the evolutionary history of organisms, i.e. common ancestors

95
Q

What is the study of DNA/the genome called?

A

Genomics

96
Q

What is the study of proteins called?

A

Proteomics

97
Q

Name the 4 molecular techniques.

A
  • DNA hybridisation
  • DNA profiling
  • DNA and protein sequencing
  • DNA molecular clocks
98
Q

Describe DNA hybridisation.

A
  • Heat (95°C) double stranded DNA samples from 2 different species i.e. human and chimp.
  • This denatures the DNA and creates separate strands.
  • Mix the DNA strands from both species together so that they complementary base pair to produce hybrid DNA.
  • Heat the DNA by slowly increasing the temperature.
  • The higher the temperature needed to denature the hybrids, the more closely related the species.
99
Q

Describe DNA profiling

A
  • Use restriction enzymes to cut the DNA at specific sequences.
  • Different sized fragments are produced which can be visualised on a gel
  • Mutations in sequences in different individuals in same species or different species will change the lengths of the fragments so different bands will be seen on the gel.
  • The closer the match in the bands, the closer related the individuals or species.
100
Q

Describe DNA and protein sequencing.

A

Comparing the sequence of bases in DNA or amino acids in proteins between different species. The closer the sequence, the more closely related the species – they evolved from a common ancestor.

101
Q

Describe DNA molecular clocks.

A

As species evolve they accumulate random mutations at a regular rate, becoming more genetically different. For a given gene, the mutation rate is fairly constant. This can be used as a molecular clock. The number of differences between species can be used to calculate how long ago they shared a common ancestor.

102
Q

State the equation for dissolving of CO2 in oceans.

A

CO2 + H20 —> H2CO3 —> HCO3- + H+

A Level Biology Edexcel A (9 decks)

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