Topic 5

• Stroma

  Fluid around thylakoid membranes

  Contains enzyme that catalyses light dependent reaction of photosynthesis
• Chloroplast inner and outer membrane

  Double membrane encloses the chloroplast

  Transport proteins in the membrane control the flow of molecules between the stroma and cytoplasm
• thylakoid space

  fluid within thylakoid membrane that contains enzymes for photolysis
• grana

  Creates a large surface area, maximising the number of photosystems and allowing maximum light absorption

  provides more membrane area for proteins such as electron carriers, which are involved in ATP production using ATP synthase
• thylakoid

  flattened fluid filled sacs

  contain proteins called photosystems that contain chlorophyll
• Lamella

  Connects thylakoids
• Photosystems

  Photosystem I and photosystem II contain different combinations of photosynthetic pigment

  each photosystem absorbs different wavelength
• ATP hydrolysis

  ATP -> ADP + Pi + energy

  uses ATP hydralyse

  releases energy
• ATP phosphorylation

  ADP + Pi -> ATP

  uses ATP synthase

  phosphorylation requires energy
• Temperature

  At low temperatures, the enzyme Rubisco has less kinetic energy so there are less frequent collisions and fewer enzyme-substrate complexes form

  At optimum temperature, rate of photosynthesis is high

  Above optimum temperature, enzyme Rubisco may denature so enzyme-substrate complexes cannot form
• Light intensity

  Increasing light intensity increases the rate of photosynthesis because more light hits the photosystems so more ATP produced

  In low light intensity, light-dependent reactions cannot occur.

  Lower levels of reduced NADP and ATP. Reduced NADP and ATP required for GP and GALP production in light-independent reactions

  Calvin cycle also cannot take place so the rate of photosynthesis decreases
• CO2 concentration

  Increasing CO2 conc increases the rate of photosynthesis

  At high CO2 conc, there is more carbon available for fixation in Calvin cycle so the rate of Calvin cycle increases

  very high CO2 may cause stoma to open wider and so a lot of water is lost

  high amounts of water loss decrease rate of photosynthesis
• Explain how studying pollen grains in peat bogs can provide evidence of climate change

  pollen grains preserved in peat bogs

  pollen grains are specific to species of plant

  Different plant species grow in different climatic conditions

  depth of peat correlates with period of time since pollen was produced

  changes in pollen over time indicates changes in climate over time
•  How do two different species evolve from a common ancestor

  Groups within species separate from each other and become geographically isolated  This leads to reduced gene flow between groups 

  Allopatric speciation occurs  

  The different groups experience different selection pressures leading to natural selection 

  Natural selection occurs

  The species evolves to the point that they become reproductively isolated so they can no longer produce fertile offspring.  
• NPP

  rate at which energy is stored as biomass
• GPP

  the chemical energy stored in plant biomass, in a given area or volume
• Q10

  temperature coefficient

  formula: rate at temperature/rate at temperature - 10
• explain why GPP is lower than the light energy available to the ecosystem

  not all light falls on the leaf

  some of the light is reflected from surface of the leaf

  some of the light misses the chloroplast and is transmitted through the leaf

  some of the light is the wrong wavelength so not absorbed by chlorophyll
• stages of succession

  Colonisation of pioneer species that can tolerate harsh environmental conditions.

  As the pioneer species die and decompose, they change the environmental conditions, which allows for establishment of more diverse species.

  This introduces competition for resources between different species. The less adapted species are out-competed.

  Eventually, pioneer species are replaced by successive species better adapted to new environments. Eventually, a dominant species stabilises the environment and evolves into a climax community.
• succession in rocky land

  Pioneer species colonise bare rock

  Pioneer species break up the rock

  As the plants die and decompose, they add to the organic matter

  eventually, as the soil becomes deeper, trees and climax community is able to grow
• Sympatric Speciation

  • Sympatric speciation takes place with no geographical barrier
  • A group of the same species could be living in the same place but no gene flow occurs between them
  • Ecological separation: Populations are separated because they live in different environments within the same area
  • For example, soil pH can differ greatly in different areas. Soil pH has a major effect on plant growth and flowering
  • Behavioural separation: Populations are separated because they have different behaviours
• where does light dependent reaction take place

  thylakoid membrane
• where does light independent reaction take place

  stroma
• where does photolysis occur

  grana
• explain why respiration affects production of biomass

  NPP = GPP - R

  Respiration requires glucose to provide energy

  because more glucose used in respiration, there is less available to be stored as biomass
• Role of zoos in animal conservation

  description of role in protection = protection from poachers, hunting

  description of role in repopulation = increases population size; reintroduction into wild

  description of role in education = education of conservation of species

  description of role in research = discovering breeding cycles, investigating how to improve health, developing genetic database
• chi-square test rejecting null hypothesis

  If the chi-squared value is greater than, or equal to, the critical value then there is a significant difference between observed and expected results

  • A factor other than chance is causing the difference
  • The null hypothesis can be rejected
• chi square test accepting null hypothesis

  • If the chi-squared value is smaller than the critical value then there is no significant difference between observed and expected values
  • Any differences are due to chance
  • The null hypothesis is accepted
• t-test accepting null hypothesis

  t value less than the critical value

  accept the null hypothesis
• Ice cores

  analysing the gas composition of bubbles formed in ancient ice cores Ice is deposited as water freezes over time, so the deeper into the ice, the older it is
• Dendrochronology

  • Tree trunks grow in diameter as they produce more vascular tissue, which grows in a ring.
  • Light-coloured rings are produced by fast growth during warmer months, dark-coloured rings form as a result of the colder months
  • Trees grow faster when conditions are warmer, so the rings that form during warm years are wider than the rings that form during cool years
  • Analysis of the width of tree rings can provide a measure of climate during each year of growth
  • Taking cores from the trunks of older trees can provide suggest changes in climate over many years
• carbon sinks

  oceans, peat bogs, trees and soil
• addition of carbon dioxide to the environment

  Deforestation, soil degradation, peat harvesting, and ocean warming