Biology A2 Topic 5: On the Wild Side

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Part of the Earth and atmosphere where living things are found
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Where organisms interact with each other and their physical environment
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External influences on an organism
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Living factors
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Non-living factors (physical factors)
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Place where an organism lives with distinct characeristics
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Group of organisms of the same species in a habitat
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Different populations in a habitat
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Role of organism in the eco-system and the way it makes use of its resources
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What do environmental factors affect?
The distribution and abundance of the organisms
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Examples of abiotic factors
Climate ; Solar Energy Input ; Topography ; Edaphic factors ; Catastrophes ; Pollution ; Oxygen Availability
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Examples of biotic factors
Competition (inter-specific / intra-specific) ; Grazing ; Mutualism ; Parasitism ; Predation ;
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Factors affecting the organism that arise from human activity
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Examples of anthropogenic factors
Moor-burning ; Deforestation ; Pollution ; Hunting ; Removal of predators
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Why do species survive in a habitat?
Because of their ADAPTATIONS
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Gradual changing over time of a species that inhabit an area until a stable climax community is reached usually dominated by one species of tree
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Stable community usually dominated by one species of tree that exists at the end of succession
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Succession where nothing has ever lived there before
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Succession where the ground has been cleared (ex: fire, ploughed field) but things lived there before and there are minerals etc.
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The first species to colonise an area ; able to cope with the harsh conditions (ex: no soil, no water, temperature extremes) ; change the environment to make it more suitable for other species
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Steps of primary succession
Wind/animals spread seed ---> Pioneer species colonise ---> Change the environment (ex: add nitrate with dead matter, stabilise soil with roots) ---> Conditions suitable for more species, which outcompete the pioneer species
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Steps of primary succession
Environment continues to be changed and bio-diversity increases ---> Taller shrubs outcompete shorter plants, which die ---> Trees grow and outcompete shrubs ---> Area is inhabited by dense forest ---> Stable climax community
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What is the pioneer species in secondary succession?
The fastest growing plants
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What is the pioneer species outcompeted by in secondary succession?
Slower-growing, taller plants
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Type of succession that does not reach the climax community usually due to human activity
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How can we study succession?
Random sampling on spoil heaps using quadrats ; Studying sand dunes
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What is the primary productivity of an eco-system?
The rate at which energy is change into organic molecules in an ecosystem
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Chemical equation of photosynthesis
6CO2 + 6H20-----> C6H1206 + 602
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Where does the energy for photosynthesis come from?
Light (solar energy from the sun)
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The products have more energy than the reactants so....
Act as an energy store
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What is the waste product of photosynthesis?
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Where does photosynthesis take place?
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Describe the structure of a chloroplast
Outer Membrane ; Stroma (space) ; Thylakoid membrane ; Stacked membrane = Granum ; between = thylakoid space ; DNA loop; Starch grain
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Where do light-dependant reactions take place?
Thylakoid membrane
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What are the reactants of light dependant reactions?
Light ; H20, ADP, NADP
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Where does light shine?
On the chlorophyll in the thylakoid membrane
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What happens to the electrons?
They become excited and escape
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What happens after the electrons escape?
They are passed from carrier to carrier by oxidation and reduction reactions along the ELECTRON TRANSPORT CHAIN
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What happens in the thylakoid space?
Water is split into hydrogen, oxygen and electrons during PHOTOLYSIS
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What is the energy from the electron transport chain used for?
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How is NADP changed to reduced NADP?
Using hydrogen from photolysis and the electrons from the electron transport chain
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What happens to the electrons from photolysis?
They are given back to the chlorophyll to replace lost electrons
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What are the products of light dependant reactions?
Oxygen (waste) ; ATP ; reduced NADP
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Where do the light independant reactions take place?
In the stroma
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What are the reactants of light independant reactions?
ATP ; reduced NADP ; CO2
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What are the light independant reactions called?
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What is the carbon dioxide used for?
CARBON FIXATION ; CO2 combines with RuBP using the enzyme RuBISCO
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What happens to the product of this reaction?
It breaks down immediately into GP as it is very unstable
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What do the ATP and reduced NADP do?
They reduce the GP to GALP ; the ATP is used as energy
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What is GALP used for?
Some is used to make GLUCOSE and other organic molecules ; most is used to make more RuBP (ATP is needed for energy)
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How many times is the Calvin Cycle repeated to make one molecule of glucose?
2 ; GALP is 3C and glucose is 6C
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What are the products of light independant reactions?
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Summarise the light dependant reactions
light shines on chlorophyll in thylakoid membrane , electrons excited and escape, move along electron transport chain, in thylakoid space PHOTOYLSIS, electrons used for PHOTOPHOSPHORYLATION, hydrogen and electrons used to make reduced NADP
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Summarise the light independant reactions
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What are autotrophs/ producers?
Organisms that produce their own organic compounds from inorganic compounds
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What are heterotrophs/ consumers?
Organisms that obtain energy by eating material from other organisms (cannot make their own organic compounds)
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Different types of consumers...
Primary Consumers (herbivores) ; Secondary and Tertiary Consumers (carnivores/omnivores)
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How are feeding relationships shown?
In a food chain
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What is a trophic level?
Position a species occupies in a food chain (producers = 1st trophic level)
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What are detritivores?
Organisms that feed on dead/decaying organic matter and pass it through their digestive system
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What are decomposers?
Organisms that feed on dead/decaying organic material by secreting enzymes and absorbing it
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Why are detritivores and decomposers important?
They are important in the recycling of organic matter from waste
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How is light energy 'lost'?
Reflection off leaf ; Transmission through leaf ; Not the right wavelength so cannot be absorbed
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What are the limiting factors of photosynthesis?
Temperature ; CO2 concentration ; Light intensity
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The rate at which chemical energy is stored by plants
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The rate at which energy is transferred into organic molecules to produce new plant biomass
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How to calculate respiration losses?
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Why is energy transfer from producers to primary consumers not very efficient?
Not all available food is eaten ; Energy is lost in faeces and urine ; Most of the energy absorbed is used for respiration
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Why is energy transfer between primary and secondary consumers more efficient?
Most of the herbivores is eaten ; Less energy is lost in faeces (easily digested)
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What is the energy budget of an animal?
C (consumed) = P (biomass production) + R (respiration) + U (urine) + F (faeces)
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How is the flow of energy shown?
Using energy-flow diagrams
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Evidence for climate change?
Temperature records ; Studying peat bogs ; Tree ring analysis (dendrochronology)
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Problems with temperature records
Records don't go back very far ; Data collection might not have been accurate
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How do you study peat bogs?
Anaerobic conditions = no decay ; Pollen grains are collected and used to identify the plant species ; Find out climate it grows in ; We now know how the climate was
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How are tree rings created?
When xylem are pushed forward
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Describe the vascular bundle
Inside: Xylem (dead) ; Middle: Phloem (alive) ; Outside: Schlerenchyma
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How are tree rings used?
A core sample is taken ;Skeleton diagram created : Wide band = good growth (wet) ; Narrow band = poor growth (dry)
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Describe the green house effect
Sun radiates energy and the earth absorbs some of it ; Earth warms up and radiates it back as infrared ; Some of the infrared is trapped in atmosphere by greenhouse gases so warms up the atmosphere
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Examples of greenhouse gases
CFCs, carbon dioxide, methane
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So does CO2 cause global warming?
Rise in fossil fuels did not equal rise in temperature ; Scientific evidence suggests there is a link but doesn't prove it
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Why is it a controversial issue?
Link to human activity is correlation not causation ; Scientists can't prove a theory ; Date inaccurate ; Economic and political reasons; People have the right to choose how to live their life ; Do we have the duty to protect the planet for future?
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What is an extrapolation?
Extend the line on a graph to predict the future date
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What do we assume when extrapolating?
The trend will continue (predictions are not very accurate because things can change)
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How does climate affect the distribution of species?
Climate change causes the balance between species to shift ( some will be dominant some will be outcompeted) ; Will start growing where they didn't before (due to it being too hot/cold) ; Pests may spread to new areas
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How does climate change alter development?
Higher temperatures = Faster photosynthesis (but enzymes might be denatured)
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How does climate change disrupt development and life cycles?
Animals are affected if temperature acts as an environmental trigger for their behaviour (ex: hatching time)
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What is phenology?
The study of seasonal events in the lives of animals and plants (ex: flowering, egg laying) ; Long term records exist which allow us to see change over time
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What to species due as their environment changes?
Species change over time as they adapt to their changing environment
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What is natural selection?
New alleles arise through random mutations ; Variation exists ; The organisms with favourable alleles to environment survive and reproduce ; Pass on favourable alleles ; Change in allele frequency of organisms over time
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Molecular evidence for evolution: DNA hybridisation
When DNA is heated strands seperate ; Create DNA hybrid by mixing two strands from different species ; Closer related = more bases joined ; When DNA heated up again, the less bases paired up means quicker seperation
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DNA profiling
Compare sequence of bases in DNA/ amino acid sequence in proteins of different species ; Very few differences means they evolved from a common ancestor more recently
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Part of a population is isolated from the rest of the population due to geographical features (ex:river) or mutation leading to reproductive isolation (ex: different behaviour) ; Two groups are exposed to different selection pressures
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By natural selection organisms with favourable alleles will survive, reproduce and pass on their alleles ; Over time the organisms in the two groups become less like each other ; Differences too great to allow breeding to produce fertile offspring
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Eventually can't interbreed; Two groups have become separate species
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Where does carbon dioxide come from in carbon cycle?
Respiration ; Decompositon ; Combustion of fossil fuels
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Why does burning fossil fuels upset the balance in the carbon cycle?
Fossil fuels have been building up for millions of years but we have only started burning them very recently more CO2 is released into the atmosphere than is taken in
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Ways to maintain the balance?
Take in more CO2 (reforestation) ; Burn less fossil fuels (biofuels)
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What are biofuels?
Source of energy produces directly in plants/ indirectly by animals by recent photosynthesis ; RENEWABLE ; CARBON NEUTRAL ; ex: wood, vegetable oil
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How does reforestation maintain CO2 balance?
New trees grow rapidly so respiration is less than photosynthesis (more CO2 taken in than given out) = Net absorber ; As forest gets older , more balanced levels and becomes carbon store (carbon in biomass)
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What are the problems with reforestation?
Long term: More vegetation means more food means more animals means more microbes means more respiration means more CO2 ; Limit to tree growth and land available
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Where organisms interact with each other and their physical environment



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External influences on an organism


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Living factors


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Non-living factors (physical factors)


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