Topic 5: Photosynthesis Flashcards
Definition of an ecosystem
All the organisms living in a particular area + Abiotic (non-living) factors
Definition of a niche
The role and organism plays in an environment at a certain point in time. No two species can occupy the same niche but they cant compete for it
Definition of a community
All of the organisms OF A PARTICULAR SPECIES living in a particular habitat at a time
Definition of a habitat
The place where an organism lives
Definition of a population
All of the organisms of one species in a habitat
Examples of Abiotic factors
Light
Oxygen
Moisture levels
Temperature
Examples of biotic factors
Predators
Food availability
Parasitism
Disease
Definition of distribution
Definition of Abundance
Distribution = How spread out everything is
Abundance = Number of something
Difference between primary and secondary succession
In primary succession, the pioneer species is less complex and starts with nothing where as in secondary succession the pioneer species is more complex and already has nutrients in the soil
Explain the process of succession
- The area is first colonised by the pioneer species e.g. lichens which are adapted to survive in harsh conditions
- As organisms die, they are decomposed by microorganisms, thus adding humus (the organic component of soil). This leads to the formation of soil, which makes the environment more suitable for more complex organisms
- As more organisms are decomposed overtime, the soil becomes richer in minerals, thus enabling larger, more varied and more productive plants such as shrubs to survive.
- -Eventually, a climax community is established - the most productive, self-sustaining and stable community of organisms the environment can support, usually with only one or two species.
Outline cyclic phosphorylation
- Photon hits chlorophyll in photosystem I (PSI).
- Electrons are excited.
- Electrons taken up by an electron acceptor.
- Electrons pass along an electron transport chain. Energy is released, and ATP is synthesised.
- Returns to chlorophyll in PSI.
Outline non-cyclic phosphorylation
- Photon hits chlorophyll in photosystem II (PSII).
- Electrons are excited.
- An electron acceptor takes up electrons and passes along an electron transport chain to PSI. Energy is released, ATP is synthesised.
- Photolysis: light energy breaks apart the strong bonds in water molecules - forming hydrogen and hydroxide ions. Electrons released replace lost electrons in the chlorophyll of PSII. Hydroxide ions react together to form water and oxygen.
- Photon hits chlorophyll in Photosystem I.
- Electrons are excited.
- Electrons are taken up by an electron acceptor and passed along an electron transport chain to NADP.
- NADP takes up an H+ ion from dissociated water and forms reduced NADP.
Definition of evolution
Evolution is a change in the heritable traits of biological populations over successive generations. It occurs as a result of a change in allele frequency which in turn is affected by changing selection pressures.
Outline the process of evolution via natural selection
- A variety of phenotypes exist within a population due to random mutation.
- An environmental change occurs and as a result of the selection pressure changes
- Some individuals possess advantageous alleles which give them a selective advantage and allow them to survive and reproduce.
- The advantageous alleles are passed on to their offspring.
- Overtime, the frequency of alleles in a population changes.
Where do the light-independent reactions take place?
Where do the light-dependent reactions take place?
Light-independent = Stroma
Light-dependent = Thylakoid membrane
Explain the light-dependent reaction of photosynthesis
-Light energy excites chlorophyll in PS2 causing it to release electrons
-Electrons are then passed down the electron transport chain from one electron carrier to the next and this process generates ATP in a process called photophosphorylation.
-Phosphorylation can be cyclic or non-cyclic. The final electron acceptor is NADP. When it accepts an electron it forms reduced NADP. Both ATP and reduced NADP from the light-dependent reactions are used in the light-independent stages of photosynthesis.
Define net primary productivity
Define gross primary productivity
NPP - The rate at which energy from the sun is converted into the organic molecules that make up new plant biomass.
GPP - Energy transferred to primary consumers
Therefore NPP = GPP - R
Reasons why energy is lost at different trophic levels
- Undigested matter
- Respiration (exothermic, transfers thermal energy to surroundings)
- Metabolic waste products like urea
What is GP used to produce?
-Amino acids which can be used in protein synthesis for building polypeptides
-Fatty acids which form the tails of lipid molecules such as triglycerides and phospholipids
What is GALP used to produce?
-Hexose sugars e.g. glucose
-Hexose sugars can be joined to make polysaccharides such as starch and cellulose
-Glycerol can be used for building lipid molecules such as triglycerides and phospholipids
-Nucleic acids form the basis of DNA and RNA
Explain the Calvin cycle
-RUBISCO catalyses the reaction between Rubulose bi-phosphate (5-carbon compound) and a single Carbon dioxide atom to form an unstable 6-carbon compound which is unstable and splits immediately, to form 2xGP (glycerate 3-phosphate)
-GP is reduced to GALP in a reaction involving reduced NADP and ATP. Energy from ATP and hydrogen from reduced NADP, both produced during the light-dependent reactions, are used to reduce the two molecules of GP to two 3C molecules of GALP. Some of the carbons in GALP go towards the production of useful organic molecules such as glucose, while the rest allow the regeneration of RuBP
-RuBP is regenerated from GALP in reactions that use ATP
Carbon dioxide and RuBP are combined
Describe the role of the products of the light-dependent reactions in the Calvin cycle (3)
-Products are ATP and reduced NADP
-ATP is used to convert GP to GALP and GALP to RuBP
-Reduced NADP used to convert GP to GALP
Explain the importance of RUBISCO to the productivity of an ecosystem (2)
- Carbon fixation
- Allowing the formation of organic molecules by the Calvin cycle
-These organic molecules allow the transfer of energy to the next trophic level
Describe how GP is produced by carbon fixation (2)
-Rubisco combines carbon dioxide with RuBP
-Unstable 6C molecule breaks down into 2xGP
