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Edexcel SNAB A Level Biology > Topic 5 - On the Wild Side > Flashcards

Topic 5 - On the Wild Side Flashcards

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1
Q

What is a habitat?

A

The place where an organism lives

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2
Q

What is a population?

A

All the individuals of one species living in a habitat

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3
Q

What is a community?

A

Multiple populations living and interacting in the same area

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4
Q

What is an ecosystem?

A

A community and its interactions with the non-living parts of its habitat

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5
Q

What is a biotic factor, and what are some examples of these?

A

Living factors which influence populations within their community, come about as a result of the activity of other organisms
EXAMPLES: predation, food availability, inter/intraspecific competition, new pathogens

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6
Q

What is an abiotic factor, and what are some examples of these?

A

Non living factors which influence populations within their community
EXAMPLES: temperature, light intensity, soil moisture, humidity, O2/CO2 conc

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7
Q

What is a niche?

A

The role of a species within its habitat

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8
Q

What is abundance?

A

The number of individuals of a particular species living in a habitat

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9
Q

What is distribution?

A

Where a species lives

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10
Q

Why must two species not occupy the same niche?

A

The two species will be in direct competition with each other for resources, and one of the two species will out-compete the other, causing it to die out in that particular habitat

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11
Q

What are some examples of the role of a species (niche)?

A
  • What it eats
  • Which other species depend on it for food
  • What time of day a species is active
  • Exactly where in a habitat a species lives
  • Exactly where in a habitat a species feeds
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12
Q

What is succession?

A

Succession is the sequence of species/communities replacing each other with time

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13
Q

What is primary succession?

A

The process of ecosystem change over time, beginning with newly formed or newly exposed land

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14
Q

What is colonisation?

A

The arrival of organisms on bare land

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15
Q

How does succession occur?

A
  1. (Colonisation by) pioneer (species);
  2. Change in environment / example of change caused by organisms present;
  3. Enables other species to colonise / survive;
  4. Change in diversity / biodiversity;
  5. Stability increases / less hostile environment;
  6. Climax community;
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16
Q

What are the stages of primary succession?

A

1st seral stage - pioneer species such as moss and lichens colonise the bare rock
2nd sere - dead organic matter from pioneer species creates shallow soil with some water available (less run off) so small plants grow
3rd sere - soil depth increases, more diverse habitat, trees begin to grow
CLIMAX COMMUNITY - equilibrium is reached, stable community

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17
Q

Why does succession change the abiotic and biotic conditions?

A

Often the new colonising species then change the environment in such a way that it becomes less suitable for the previous species - e.g. pioneer species are outcompeted, trees block out smaller shrubs

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18
Q

What is secondary succession?

A

Where a previously occupied area is re-colonized following a disturbance that kills much or all of its community (soil already present)

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19
Q

What is a plagioclimax?

A

An area or habitat in which the influences of the humans have prevented the ecosystem from developing further.

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20
Q

What is gross primary productivity?

A

The rate at which chemical energy is converted into carbohydrates during photosynthesis

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21
Q

What is net primary productivity?

A

The rate at which energy is stored in plant biomass

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22
Q

How do you work out NPP?

A

NPP = GPP - R
where R = plant respiratory losses

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23
Q

What are the units for GPP?

A

Energy per unit area per year
kJ m-2 y-1

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24
Q

What does primary productivity depend on?

A
  • amount of sunlight energy
  • ability of diff types of producers to use energy to synthesise organic compounds
  • availability of other factors needed for growth of producers, e.g. mineral ions
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25
Q

How do you calculate the energy in a trophic level?

A

energy lost in respiration + energy lost in faeces + energy lost in urine + energy in new biomass

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26
Q

What is a trophic level?

A

The stage in a food chain

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27
Q

What are primary consumers?

A

Animals that eat plant material

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28
Q

What are producers?

A

Organisms such as plants that convert light energy into chemical energy stored in biological molecules

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29
Q

Why is the transfer of energy in a food chain not 100% efficient?

A

Energy is lost to the environment at every trophic level

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30
Q

Why is around 90% of the energy lost to the environment between trophic levels?

A
  • not every part of the organism is eaten
  • consumers are unable to digest all of the food that they ingest
  • energy lost via heat in respiration
  • energy is lost when organisms excrete the waste products of metabolism
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31
Q

What is net productivity?

A

The rate at which energy is converted into biomass in the body of a consumer

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32
Q

Why is a large proportion of the sun’s energy not available to producers for building biomass?

A
  • light passes through leaves or reflected away
  • light hits non photosynthetic parts of the plant
  • only certain wavelengths absorbed in photosynthesis
  • energy lost via heat from respiration
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33
Q

What is the equation to calculate the efficiency of energy transfer in a food chain?

A

Energy efficiency = (net productivity/energy received) x100

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34
Q

How can you calculate experimentally the efficiency of biomass transfer from one trophic level to the next in a food chain?

A

Dry biomass is measured by drying a sample of the organism in an oven at a low heat and weighing the sample at regular intervals until the mass becomes constant. Then use efficiency equation for biomass transfer

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35
Q

What is the equation to calculate the efficiency of biomass transfer?

A

Efficiency of biomass transfer = (biomass transferred/biomass intake) x100
Biomass transferred = biomass that has passed to the higher trophic level
Biomass intake = biomass of the lower trophic level that has been consumed

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36
Q

What is the equation for photosynthesis (chemical and word)?

A

6H2O + 6CO2 → C6H12O6 + 6O2
Water + carbon dioxide → glucose + oxygen

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37
Q

What is ATP?

A

Adenosine triphosphate
Universal energy currency used to transfer and supply energy within cells

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38
Q

What is the structure of ATP?

A

It is a nucleic acid, phosphorylated nucleotide consisting of adenine, ribose sugar and a triphosphate group

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39
Q

How is ATP produced in respiration?

A

ADP + Pi → ATP
Phosphorylation

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40
Q

How is ATP hydrolysed/broken down?

A

ATP → ADP + Pi
Dephosphorylation, catalysed by ATPase

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41
Q

What is a chloroplast?

A

The site of a plant cell where photosynthesis occurs

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42
Q

What is the structure of a chloroplast?

A

Double membrane, filled with cytoplasm like fluid known as the stroma, membrane system inside consists of a series of fluid filled flattened sacs known as the thykaloids (several = grana)

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43
Q

How is the structure of a chloroplast related to it’s function?

A

Stroma - contains enzymes that catalyse photosynthesis reaction
Double membrane - encloses components needed for photosynthesis so they are close to each other
Grana - large SA, max number of photosystems and max absorption of light
Thylakoid - compartmentalisation, space for accumulation of H+ ions

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44
Q

What happens in the light dependent reaction of photosynthesis?

A

Light energy excites electrons in chlorophyll. Photolysis of water produces hydrogen ions, oxygens and electrons. Electrons used in ETC to replace those lost in chlorophyll. ATP is generated (photophosphorylation) NADP is reduced

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45
Q

How does the structure of the grana relate to its function?

A

Grana formed from many layers to increase SA for light absorption
Thylakoid membranes contain chlorophyll to absorb light
Electron carrier molecules in thylakoid membrane involved in ATP production

46
Q

What is produced in the photolysis of water?

A

2H+ ions
2 electrons
One atom of oxygen

47
Q

What is the difference between cyclic and non cyclic photophosphorylation?

A

Non cyclic: produces both ATP and NADPH
Cyclic: ATP only

48
Q

What happens in non-cyclic photophosphorylation?

A

Light energy hits photosystem II. Two electrons gain energy and are excited, leaving PSII to travel on the electron transport chain. This enables chemiosmosis. Electrons passed to PSI and then combine with H+ ions from photolysis and coenzyme NADP to form reduced NADP (NADPH), which then passes to the light independent reaction

49
Q

What happens in cyclic photophosphorylation?

A

Light hits photosystem I. Electrons excited and pass down ETC, driving chemiosmosis. At the end of the electron transport chain, electrons re-join PSI in a complete cycle. ATP produced joins light independent reaction

50
Q

How is light energy converted to chemical energy in the light dependent reaction?

A

In the form of ATP and reduced NADP

51
Q

What products of the light dependent reaction are used in the light independent reaction?

A

Reduced NADP and ATP

52
Q

How does chemiosmosis in the light dependent reaction catalyse the production of ATP?

A

H­­+ ions are actively pumped from a low concentration in the stroma to a high concentration in the thylakoid space (conc gradient)
H­­+ ions diffuse back across the thylakoid membrane into the stroma via ATP synthase enzymes embedded in the membrane
The movement of H­­+ ions causes the ATP synthase enzyme to catalyse the production of ATP

53
Q

What are the 3 main steps of the light independent reaction/Calvin cycle?

A

Carbon dioxide is combined with RuBP (5C) - yields two molecules GP (3C)
GP is reduced to GALP (3C) in a reaction involving reduced NADP and ATP
RuBP is regenerated from GALP in reactions that use ATP

54
Q

What happens when CO2 and RuBP are combined? (Calvin Cycle)

A

CO2 combines with 5C sugar RuBP in a reaction catalysed by the enzyme rubisco. Resulting compound is 2 3C compounds known as GP.
CO2 is fixed and has become part of molecule within plant cell

55
Q

How is GP reduced?

A

Energy from ATP and hydrogen from reduced NADP are used to reduce the two molecules of GP to two 3C molecules known as GALP.

56
Q

How much of GALP is used in the generation of organic molecules such as glucose?

A

2 molecules of GALP contain 6 carbon atoms, 5 of which are needed to regenerate RuBP - for every turn of the Calvin cycle, only 1/6 of a molecule of glucose is produced

57
Q

How is RuBP regenerated in the Calvin Cycle?

A

5/6 of GALP molecules are used. This process requires ATP

58
Q

What is GP used to produce?

A
  • amino acids (protein synthesis)
  • fatty acids (lipid molecules)
59
Q

What is GALP used to produce?

A
  • hexose sugars (e.g. glucose)
  • glycerol
  • nucleic acids
    Glucose can be used by the plant in respiration, other biological molecules used to build biomass
60
Q

What is the Hill reaction?

A

Where NADP accepts electrons to become reduced NADP

61
Q

How can the Hill reaction be observed?

A

Using indicators like DCPIP
DCPIP accepts electrons released by light dependent reaction to turn colourless from blue (oxidised to reduced)

62
Q

What is climate?

A

The weather conditions in a region over a long period of time (several decades)

63
Q

What is climate change?

A

When the weather conditions in a region change significantly over a long period of time

64
Q

What evidence is there for climate change caused by human activities increasing the concentrations of greenhouse gases?

A
  • records of atmospheric CO2 levels (gas composition of bubbles in ice cores)
  • records of average global temperatures
  • records of changing plant communities gained from sampling of pollen grains preserved in peat bogs over time
  • records of tree growth (dendrochronology)
65
Q

What does the data for CO2 levels and temperature show?

A

Data shows a correlation between rising atmospheric CO2 levels and temperature. THIS DOES NOT EQUAL CAUSATION, but is strong evidence that CO2 released by human activities since the industrial revolution is causing increasing global temps

66
Q

How can studying pollen grains in peat bogs provide evidence for climate change?

A
  • pollen is preserved in peat bogs
  • a plant species can be identified from its pollen
  • climate affects the type of plants growing
  • depth of peat correlates with period of time since pollen was produced
  • changes in pollen over time indicate changes in climate
67
Q

How does dendrochronology show changes to climate over the years?

A

Tree trunks grow in diameter each growing season as they produce more vascular tissue. Trees grow faster when conditions are warmer - analysis of width of tree rings can provide a measure of climate during each year of growth

68
Q

What is a greenhouse gas?

A

Gas that absorbs re-radiated radiation to trap it into the Earth’s atmosphere so it is not lost in space, contributing to the greenhouse effect

69
Q

What happens in the greenhouse effect?

A

Solar radiation from the sun is either absorbed or reflected back into space. However, whilst some of the infrared radiation reflected away passes into space, some is absorbed and re-emitted by greenhouse gas molecules, warming the Earth’s surface and lower atmosphere.

70
Q

Why are anthropogenic emissions of greenhouse gases affecting the climate?

A

Human activities such as deforestation/burning fossil fuels leads to increased amount of greenhouse gases like CO2 or CH4. Therefore more infrared radiation is trapped in the atmosphere.
Causing a MEAN increase in the surface/atmospheric temperature.

71
Q

How do humans release carbon dioxide into the atmosphere?

A
  • combustion of fossil fuels (e.g. in the Industrial Revolution)
  • when natural stores of carbon (carbon sinks such as peat bogs and trees) are destroyed by human activities
72
Q

How do humans contribute to the release of methane into the atmosphere?

A
  • cattle farming (methane released from guts of ruminant animals)
  • landfill sites (when organic waste decomposes)
  • extraction of underground fossil fuels
  • warming of poles leads to release of methane from natural stores like permafrost
73
Q

What is extrapolation?

A

Using existing data to make predictions about what will happen in the future

74
Q

What can global warming predictions be used for?

A
  • Plan for the future: building flood defences, funding scientific research
  • Encourage people to change their activities: reduce burning of fossil fuels, reduce meat consumption, increase renewables
75
Q

What is the IPCC?

A

Intergovernmental Panel on Climate Change - a group of climate scientists around the world that has used existing data to extrapolate how global temperatures might change in the future under different human activity scenarios

76
Q

What are the limitations to climate change models based on extrapolated data?

A
  • don’t know which scenario for the future is most likely
  • don’t know if future technologies will be successful at removing greenhouse gases
  • global climate patterns are complex and hard to predict
  • unknown other factors: e.g. volcanic eruptions
  • unknown exactly how CO2 affects global temp
77
Q

What effects does climate change have?

A
  • more extreme weather events
  • changes to ocean currents leading to altered local climate
  • changes in patterns of rainfall (warmer air holds more moisture)
78
Q

What is the evidence for changes in climate patterns due to climate change?

A
  • warming climate cause species migration
  • water availability in habitats changing
  • seasonal cycles changing (animals producing young earlier in the year)
  • polar ice and glaciers retreating
  • sea levels rising
79
Q

What effect does changing air temperature have on organisms and why?

A

Impacts on metabolism of living organisms due to effect of temperature on enzyme activity

80
Q

What effects do lower and higher temperatures have on enzyme reactions?

A

Lower temps = prevent reactions from happening or slow them down (molecules move relatively slowly with less kinetic energy)
Higher temps = reactions speed up (molecules move more quickly as have more kinetic energy) until DENATURATION

81
Q

What happens when an enzyme is denatured?

A

The increased kinetic energy and vibration of an enzyme puts a strain on its bonds, causing the weaker hydrogen and ionic bonds to start to break. This changes tertiary structure, permanently damaging the active site and preventing the substrate from binding

82
Q

How can changes to enzyme activity due to changing global temperatures affect living organisms?

A

Some chemical reactions take place faster at higher temps, some are slowed down at higher temps. E.G. RUBISCO IN CALVIN CYCLE
Sex of young determined by temperature.
Species may have to change their distribution in response to changing temperatures in order to survive

83
Q

What is the temperature coefficient?

A

Calculates the increase in rate of reaction when the temperature is increased by 10 degrees
Q10 = rate at higher temperature/rate at lower temperature

84
Q

How can you evaluate statements surrounding climate change?

A

Consider how good the evidence is: reliability of data, data from several independent studies, statistical analysis
Consider whether statement comes from trustworthy source: biased/subjective

85
Q

What is the most important factor surrounding the climate change debate?

A

Climate is COMPLEX and can be affected by a number of factors

86
Q

What is the carbon cycle?

A

The many processes by which carbon is transferred and stored

87
Q

Why is carbon important?

A

Found in biomass of living organisms, as well as in the atmosphere, rivers, lakes and oceans.
It regulates temperature, and is the chemical backbone of many important compounds

88
Q

What happens in the carbon cycle?

A

Carbon is present in atmosphere in form of CO2.
Removed by producers via photosynthesis, and then transferred to and between consumers as a result of feeding. Transferred back to atmosphere by respiration, and also after organism death when decomposers feed on tissues and respire to release carbon back into atmosphere. Carbon can also be stored in carbon sinks (fossil fuels, peat bogs), and later released by combustion

89
Q

How can we reduce climate change?

A

Reducing carbon emissions and rate at which fossil fuels are burned.
Increasing carbon removal

90
Q

How can we reduce carbon emissions?

A
  • burning biofuels instead of fossil fuels
  • use of other renewable energy sources
91
Q

What are biofuels and the pros/cons?

A

Fuels made from recently living biomass. Still release CO2 when burnt
FOR - cheaper than oil, ‘carbon neutral’ as only release carbon recently removed from atmosphere, regrown quickly = renewable
AGAINST - still do release CO2, vast amounts of land needed to grow - loss of habitat (biodiversity) and trees

92
Q

What are renewable energy sources (and examples) and what are the pros/cons?

A

Energy derived from natural sources that are replenished at a faster rate than they are consumed e.g. wind, solar, tidal, geothermal
FOR - advancing quickly and becoming more efficient/cheaper, no CO2 released
AGAINST - no single source is perfect, often dependent on natural processes and create visual scar

93
Q

What are the methods of increasing carbon removal?

A
  • potentially carbon capture but technology not advanced enough yet
  • increasing rates of photosynthesis: reforestation, stopping deforestation
94
Q

What is evolution?

A

Changes in the heritable characteristics of organisms over generations

95
Q

What is natural selection?

A

The process by which organisms that are better adapted to their environment survive, reproduce, and pass on their advantageous alleles, causing advantageous characteristics to increase in frequency within a population

96
Q

How does natural selection occur?

A
  1. genetic variation within a population, mutations ocurring
  2. selection pressures affect population
  3. those with advantageous alleles more likely to survive and reproduce
  4. advantageous allele passed down to offspring in reproduction
  5. advantageous alleles become more frequent in the population
97
Q

What is speciation and what must happen for it to occur?

A

The development of new species from pre-existing species over time
Must have 2 populations reproductively isolated from each other so there is no or limited gene flow between the two

98
Q

What is a species?

A

A group of organisms with similar physiology, morphology and behaviour that can successfully interbreed to produce fertile offspring

99
Q

What are the 2 types of speciation?

A

ALLOPATRIC - with a geographical barrier
SYMPATRIC - without a geographical barrier

100
Q

How does allopatric speciation occur?

A

Geographical barrier separates two populations. Prevents populations from interbreeding so no gene flow between them. 2 populations experience different environment and different selection pressures, so different alleles become advantageous. Different alleles are passed on and become more frequent in the populations, over time 2 distinct species form, can no longer interbreed to produce fertile offsprint

101
Q

How does sympatric speciation occur?

A

Group of organisms splits into 2 populations which no longer interbreed (due to mutation causing change in phenotype). No gene flow = different alleles being passed on in each population due to differences in selection pressures. Different alleles become more frequent and eventually 2 populations can no longer interbreed to produce fertile offspring

102
Q

What is a reproductive barrier?

A

Any mechanism that impedes 2 species from producing fertile and/or viable hybrid offspring

103
Q

What are the 2 types of reproductive barrier?

A

PRE-ZYGOTIC: barrier stopping breeding
POST ZYGOTIC: zygote has formed

104
Q

What are the types of pre-zygotic barriers?

A
  • temporal isolation: breeding occurs at different times
  • habitat isolation: species breed in different habitats
  • behavioural isolation: little/no sexual attraction between species
  • mechanical isolation: structure differences prevent gamete exchange
  • gametic isolation: gametes fail to unite
105
Q

What is the evidence for evolution?

A
  • fossil record
  • real life observations e.g. antibiotic resistance
  • molecular evidence: analysis of DNA and proteins show evolution of species from one common ancestor
106
Q

How do genomics and proteomics give evidence for evolution?

A

Genomics - changes in DNA base sequences
Proteomics - changes in amino acid sequences
Can compare similarity even across different species, level of similarity suggests how long since species diverged from each other, can establish relationships between organisms

107
Q

How can the scientific community assess new ideas?

A
  • reading scientific journals (PEER REVIEW)
  • attending scientific conferences (present findings etc)
108
Q

How does carbon dioxide act as a greenhouse gas?

A

It absorbs long wave infrared radiation reflected by the surface of the Earth (causing global warming)

109
Q

What is global warming?

A

The gradual increase in average/mean temperature of the Earth’s surface/atmosphere/oceans

110
Q

Why might keeping cattle indoors in barns lead to a higher efficiency of energy transfer?

A

Less energy lost in heat/maintaining body temp

111
Q

What are the reasons for low efficiency of energy transfer through ecosystems?

A
  • some light reflected
  • some light misses photosynthetic tissue
  • energy lost as heat
  • energy lost via respiration
  • energy lost in faeces
112
Q

What changes occur to bare rock to allow the growth of trees?

A

Pioneer species colonise
Break up the rock
Add organic matter as they decompose
Soil is deeper/has more water

Edexcel SNAB A Level Biology (9 decks)

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