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A Level Biology Edexcel: Topic 5 - 8

This flashcard set covers the whole of topics 5- 8 by spec point. This is mainly for memorization of the key aspects in each topic. It is recommended to learn these facts well before attempting practice question as you will have a general idea of possible answers and questions that could be asked. Hope it helps :)


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outline the light dependent reaction
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light energy is absorbed by the chlorophyll in PSII causing electrons to be excited and boosted to a higher energy level the electrons are picked up by an electron acceptor the electrons move down an ETC through a series of redox reactions to PSI as the electrons move down the ETC, they release energy which is used for chemiosmosis The electrons lost in PSII are replaced by the photolysis of water oxygen is given off as a waste gas and H+ ions and electrons are used to form NADPH and ATP

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A Level Biology Edexcel: Topic 5 - 8 - Details

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GPP
Gross primary productivity the energy transferred to primary consumers
Outline the light dependent reaction
Light energy is absorbed by the chlorophyll in PSII causing electrons to be excited and boosted to a higher energy level the electrons are picked up by an electron acceptor the electrons move down an ETC through a series of redox reactions to PSI as the electrons move down the ETC, they release energy which is used for chemiosmosis The electrons lost in PSII are replaced by the photolysis of water oxygen is given off as a waste gas and H+ ions and electrons are used to form NADPH and ATP
Ecosystem
All the organisms living in a particular area, known as the community, as well as all the non-living elements of that particular environment
Community
All of the populations of all the organisms living in a particular habitat at a particular time
Where does the light dependent reaction occur?
Happens in the thylakoid membrane
Population
All the organisms of a particular species living in a particular habitat at a particular time
Outline chemiosmosis
Hydrogen ions from the stroma are actively pumped into the thylakoid lumen energy from the electron transfer chain is used to do this this forms an electrochemical gradient because of the difference in concentration of H+ ions the H+ ions in the lumen flow through ATP synthase by facilitated diffusion forming ATP and NADPH which will be used in the light independent reaction
Habitat
The place where an organism lives
Outline the Light independent reaction
RUBP and CO2 combine to form a 6 carbon intermediate that immediately divides to form GP (3C) the RUBP + CO2 reaction is catalysed by rubisco NADPH and ATP are then used to catalyse the conversion of GP into GALP (3C) some molecules of GALP combine to form glucose (6C) whilst the rest are used to regenerate the RUBP using ATP
Photosynthesis
The biological process that occurs in plants which convert carbon dioxide and water into glucose and oxygen in the presence of sunlight
Light independent reaction
Also known as the Calvin cycle occurs in the stroma of the chloroplast uses CO2, NADPH and ATP products are glucose, NADP+ and ADP+Pi has three stages: carbon fixation, reduction and regeneration
Two stages involved in photosynthesis
Light dependent reaction and Light independent reaction (Calvin Cycle)
Structures of the chloroplast
Thylakoid stroma lamellae grana/granum inner membrane outer membrane intermembrane space
Structures of the thylakoid
Thylakoid lumen thylakoid membrane photosystems I and II chlorophyll ATP synthase electron carrier proteins
Photophosphorylation
The conversion of ADP into ATP using energy from sunlight
Ecosystem
All the living organisms in a particular area, known as the community and all the non-living elements of that particular environment
Community
All of the populations of all the organisms living in a particular habitat at a particular time
Population
All of the organisms of a particular species living in a particular habitat at a particular time
Habitat
The place where an organism lives
Succession
The change in species inhabiting an area over time
Primary succession
Occurs when an area previously devoid of life is first colonised by communities of organisms
Secondary succession
Occurs with existing soil that is clear of vegetation
Abiotic
Non living factors of a habitat
Biotic
Living factors of a habitat
Niche
The role of an organisms in its habitat
Niche concept
States that only one organism can occupy each niche in a given habitat at a given time if two or more species have a niche that overlaps, the best adapted will out-compete the others to survive and reproduce
What does a niche consist of?
Biotic and abiotic interactions with the environment
What does species distribution and abundance depend on?
The number and type of ecological niches available within the habitat
What is succession brought about by?
It is brought about by changes to the environment made by organisms colonising it themselves
Humus
The organic component of soil
Process of photolysis
Energy from sunlight is used to break the bonds between the hydrogen atoms and the oxygen atom in a water molecule hydrogen is then further split into H+ ion and electrons
What is NPP?
Net primary productivity the difference between energy fixed by autotrophs and their respiration
What is GPP?
Gross primary productivity the energy transferred to primary consumers
Define primary productivity
The rate at which energy is converted into organic substances by photosynthetic and chemosynthetic autotrophs
Define ecosystem
All the biotic and abiotic factors of a particular area
Define community
All of the populations of all the organisms living in a particular habitat at a particular time
Define population
All of the organisms of a particular species living in a particular habitat at a particular time
Define habitat
The place where an organism lives
Define biotic
The living elements of a habitat
Define abiotic
The non-living elements of a habitat
Define niche
The particular role of a species in a habitat
What does a niche consist of?
Biotic and abiotic interactions with the environment
What does species distribution and abundance in a habitat depend on?
The number and type of ecological niches available within the habitat
What is the niche concept?
States that only one organism can occupy each niche at a given time if two or more species have a niche that overlaps, the best adapted will outcompete the others to survive and reproduce
Define succession
The change in species inhabiting an area over time
What is succession brought about by?
Changes to the environment made by organisms colonising it by themselves
What is primary succession?
Occurs when an area previously devoid of life is first colonised by communities of organisms
What secondary succession?
Occurs with existing soil that is clear of vegetation
What is humus?
The organic component of soil
What are pioneer species?
Species that first colonise an ecosystem they are adapted to survive in harsh conditions they can break down rocks and hold together sands
What happens when organisms die?
They are decomposed by microorganisms this adds humus leading to soil formation over time more decomposed organisms adds more minerals to the soil this allows for more varied and complex organisms to survive
What is a climax community?
The most productive, self-sustaining and stable community that an environment can support, usually with only one or two species
Stages of succession
Pioneer species primary succession secondary succession climax community
Calculate efficiency of biomass and energy transfers between tropic levels
% efficiency = (energy from a lower trophic level/energy from a higher trophic level) X 100
Define climate
The average weather conditions over a long period of time
Define climate change
The long term shift or change in average weather patterns in a place over time
Define anthropogenic
Man made GHG emissions
Define weather
The term used to describe daily conditions
Define global warming
The gradual increase in the average temperature of the Earth's atmosphere and surface
Evidence for climate change
Pollen in peat bogs CO2 emissions and temperature levels records dendrochronology
Results of climate change
Reduction in species more flooding, storms and droughts ice caps melting sea levels and temperatures rising
What are peat bogs?
Partially decomposed organic matter has anaerobic and acidic conditions that prevent bacteria decomposing the organic matter
Pollen in peat bogs
Very resistant to decay they are varied and unique are only produced when the plant is matured their abundance in each layer of the peat bog can be used to analyse climate change their DNA can be analysed to see what conditions the plant they came from grew in
CO2 emissions and temperature level records
Temperature level records as far back as 1850 CO2 records can be obtained as far back as 10 - 15 million years ago these are both important factor and contributors to climate change
What is dendrochronology?
Study of trees the width of tree rings can be studied to determine climate change
The greenhouse gases
CO2, water vapour, methane, N2O they absorb heat energy and reflect it back to the earth
Greenhouse effect
The sun emits heat energy through radiation most of the radiation is absorbed by the earth whilst the rest is reflected back into space short wavelength UV radiation passes through the earth's atmosphere and is reflected from the surface the reflected rays are of a longer wavelength (infrared radiation) and are trapped by GHGs this leads to an increase in the temperature of the Earth's surface and atmosphere
What is the greenhouse effect?
The trapping of UV radiation in the Earth's atmosphere and reflecting the heat back down to the Earth's surface
Why do models for climate change have limitations?
There is not enough knowledge about the initial conditions of the climate system
What are the effects of climate change on plants and animals?
Change in distribution of species change in development of organisms change in the life cycles of species
How does climate change affect the distribution of species?
Species will have to migrate to cooler places this will cause competition in that area eventually leads to extinction due to lack of food and space
How does climate change affect species development?
The sex of some species is determined by the temperature an increase in temperature may effect the sex ratio of these species this leads to extinction because the sex ratio is imbalanced
How does climate change affect life cycles?
Increased temperature increases enzyme activity so more enzyme-substrate complexes are formed increasing the rate of reaction however at temperatures above the optimum rate of reaction decreases as enzymes denature
Evolution
The change in allele frequency of a population over time as a result of natural selection
Natural selection
The process where organisms are better adapted to an environment to survive and reproduce advantageous alleles are passed down to the offspring leads to evolution
Gene mutation
Change in bases sequence on DNA could cause a change in amino acid this may lead to a different protein structure
How can evolution come about through gene mutation and natural selection?
Selection pressure changes alleles change in some of the species the allele is advantageous for them to survive in the environment they can pass down the allele to their offspring those without the allele die as time goes on the frequency of the advantageous allele increase in the species
Selection pressure
External agents which affect an organism's ability to survive in a given environment
Speciation
The evolution of new species from existing ones occurs when there is a lack of gene flow between two populations of species resulting in each population evolving differently
Gene flow
The transfer of alleles between organisms
Two types of speciation
Allopatric and sympatric
Allopatric speciation
Population is isolated by geographical features prevents them from breeding they are reproductively isolated
Reproductive isolation
The inability of a species to breed successfully with related species due to geographical, behavioural, physiological or genetic barriers/differences
Sympatric speciation
Same species found in the same location/habitat evolve differently due to other factors so can no longer produce fertile offspring
What can sympatric speciation occur from?
Ecological isolation temporal isolation behavioural isolation physical incompatibility hybrid inviability hybrid sterility
Ecological isolation
Species occupy different areas of the habitat
Temporal isolation
Species reproduce at different times but within the same area
Behavioural isolation
Species do not respond to the courtship behaviour but are found in the same area
Physical incompatibility
Species can co-exist but physical reasons stop them from mating
Hybrid inviability
Offspring is produced but they don't survive
Hybrid sterility
Offspring can survive to the reproductive age but do not reproduce
Investigate photosynthesis using isolated chloroplasts (the Hill Reaction)
Grind leaves with ice cold sucrose solution in a mortar and pestle strain the liquid into a cooled centrifuge tube and centrifuge for 5 mins at medium speed pour the supernatant into another cooled centrifuge tube and centrifuge for 10 mins at high speed decant and discard the supernatant add ice cold sucrose solution and ice cold pH 7 buffer solution to the left over sediment and mix gently pour equal volumes of the mixture into test tubes A, B and C, also add the same volume of DCPIP to test tube D only boil tube C over a Bunsen burner then cool it under a tap add some DCPIP to test tubes A, B and C leave tubes A, C and D under a lamp and place B in a cupboard observe until all the colour in tube A has disappeared
What does the Hill Reaction prove?
Isolated chloroplasts can still produce oxygen in the presence of light providing evidence for the light dependent reaction
Investigate the effect of temperature on the initial rate of an enzyme-catalysed reaction
5 different temperatures of water baths between 10°C - 50°C put some hydrogen peroxide into a conical flask put the conical flask in the water bath to acclimatise for 2 minutes add some yeast to the conical flask and immediately bung up the conical flask take readings from the gas syringe every 30 seconds for about 3 mins repeat this at each temperature 3 times
Q10
The temperature coefficient measures the rate of change of a reaction when the temperature is increased by 10°C Q10 = rate at higher temperature / rate at lower temperature
Investigate the effect of temperature on brine shrimp
5 different temperatures of water baths between 10°C -30°C add some sea salt to the water in a beaker and stir till it has all dissolved pour out some eggs onto some paper dip some paper in the saltwater to pick up about 40 eggs re dip the wet paper with attached eggs into the saltwater solution place each beaker into the water baths for 24 hours or more count how many eggs hatched out of the 40 eggs repeat to get means
Gel electrophoresis
Used to separate and visualise the amplified sample fragments of DNA are cut with restriction endonucleases the fragments are placed in wells and dye is added so it can glow in UV light DNA is negative so when the current is turned on DNA moves to the anode (the positive electrode) fragments of different sizes move at different speeds so bands appear the bands of each DNA sample will be compared to the DNA ladder that has been prepared already