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level: Ecosystems and Photosynthesis

Questions and Answers List

level questions: Ecosystems and Photosynthesis

QuestionAnswer
outline the light dependent reactionlight 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
where does the light dependent reaction occur?happens in the thylakoid membrane
outline chemiosmosishydrogen 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
Outline the Light independent reactionRUBP 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
Light independent reactionalso 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
structures of the chloroplastthylakoid stroma lamellae grana/granum inner membrane outer membrane intermembrane space
structures of the thylakoidthylakoid lumen thylakoid membrane photosystems I and II chlorophyll ATP synthase electron carrier proteins
photophosphorylationthe conversion of ADP into ATP using energy from sunlight
process of photolysisenergy 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
equation combining GPP, NPP and respirationNPP = GPP - R
define primary productivitythe rate at which energy is converted into organic substances by photosynthetic and chemosynthetic autotrophs
define ecosystemall the biotic and abiotic factors of a particular area
define communityall of the populations of all the organisms living in a particular habitat at a particular time
define populationall of the organisms of a particular species living in a particular habitat at a particular time
define habitatthe place where an organism lives
define bioticthe living elements of a habitat
define abioticthe non-living elements of a habitat
what is the distribution and abundance of a habitat controlled by?biotic and abiotic factors
define nichethe 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 successionthe 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 successionpioneer 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