1. Light-Independent Reaction - This reaction is also known as Calvin Cycle or carbon fixation. - It happens in stroma.

- Carbon dioxide combines with RuBP to form two glycerate phosphate (GP), catalyses by ribulose biphosphate (RUBISCO). - ATP then provides energy for the reduction of glycerate phosphate (GP) to two triose phosphate (TP), oxidizing reduced NADP to NADP. - Triose phosphate (TP) or glycerade-3-phosphate (GALP) is then converted into organic compounds such as glucose. - Ribulose biphosphate (RuBP) is then regenerated from TP, using ATP again. - Out of 6 TP, only 1 TP is used to produce organic compound. - Thus, 3 cycles only produce 1 TP. (3C) - 6 cycles are needed to produce glucose (6C).

2. Light-dependent Reaction - Light energy is absorbed by the chlorophyll in photosystem II. - An electron is excited into a higher energy level. - The excited electron is passed along the electron transport system to Photosystem II. - Light energy also splits water into protons, electrons and oxygen. - The electron replaces the excited electron from chlorophyll. - The excited electron reaches Photosystem I and is excited again to a higher energy level. - The excited electrons lose energy as they move along ETC. - The energy is used to transport protons into thylakoid so thylakoid has a higher concentration gradient than the stroma. - Protons then move down concentration gradient into stroma via ATP synthase. - The energy from this movement is used to add inorganic phosphate into ADP, producing ATP. - Light energy is then absorbed by PS1, which excites the electrons to an even higher energy level. - The electrons then are transferred to NADP, along with a proton, forming reduced NADP (NADPH+). - This process produced reduced NADP, oxygen and ATP. - Through cyclic photophosphorylation, the electrons from chlorophyll are not passed into NADP, but to PS1 via electron carriers. - This process does not produce reduced NADP or oxygen, only ATP.

3. Primary Succession - Pioneer species colonise the rocks as they can grow even without soil. - For example, lichens grow on and break down rocks, releasing minerals. - When the lichens die and decomposed, soil is formed, and other species with short roots can grow, eg mosses. - Larger plants that need more water can move in as the soil deepens. Eg. Grass. - As the plants die and decompose to form organic matters, the soil thickens. - Shrubs, ferns and small trees begin to grow. - These begin to compete with grasses and smaller plants to become dominant species. - Finally, the soil is deep and rich enough in nutrients to support large trees. - These become dominant species and climax community is formed. - Climax community is stable as it has high biodiversity and balanced equilibrium of species.

Secondary Succession - Same as primary succession, except that it begins with soil, and pioneer species are the bigger plants such as shrubs.

4. Causes of global warming

- CO2 : fossil fuels (coal, oil, natural gas, petrol) are burnt : destruction of carbon sinks (stores carbon) e.g. trees : when trees are burnt or decomposers break down the organic compounds and release it in the form of CO2 through respiration

- Methane : fossil fuels are extracted, more decaying waste and more cattle which give off methane as waste gas : natural stores e.g frozen ground (permafrost), as TEMP increases, these stores will thaw (melt) and release large amount of methane

5. Effects of Global Warming

a. Rising temperature - Increase in temperature will affect enzyme activity. - If above optimum temperature, enzyme activity increases and speeds up metabolic reactions. - Rate of growth increases. Progress through life cycle faster.

b. Changing Rainfall Patterns c. Changing the Timing of Seasons. - Affect life cycles of some organisms. - Affect distribution of some species.

6. Ways to reduce global warming

a. BIOFUELS - Biofuels are fuels produced from biomass (material that is or was recently living) - Biofuels are burnt to release energy, which produces CO2. - The amount of CO2 produced is the same as the amount of CO2 taken in when the material was growing. - So no net increase in atmospheric CO2 concentrations when biofuels are burnt.

b. REFORESTATION - more trees, more CO2 removed by photosynthesis - CO2 is converted into carbon compounds and stored as plant tissues in trees - more carbon is kept out of atmosphere

7. Geographical Isolation causes Reproductive Isolation - Happens when a physical barrier divides a population of species. - Cannot interbreed. - Gene flows between populations are restricted. - The differences in selective pressures may cause reproductive isolation. - Population will adapt to respective region. - Different characteristics will be advantageous on each side. - So allele frequency changes in each population over time. - Leads to differences between gene pools. - Besides that, there may be random mutations in their genes, leading to diversity in features.

8A. How theory of evolution is supported by DNA evidence - Theory of evolution suggests that all organisms have evolved from shared common ancestors. - Closely related species diverged more recently. - Evolution is caused by gradual changes in the base sequence of organisms DNA. - So organisms that diverged away from each other more recently should have more similar DNA, as less time has passed for changes in DNA sequence to occur.

8B. by PROTEOMICS? - Study of proteins (shape, size, amino acid sequence) - Sequence of amino acids in protein is coded for by DNA sequence in a gene. - Related organisms have similar DNA sequences. - So similar amino acid sequences in proteins. - So organisms that diverged away from each other more recently have more similar proteins.

9. How scientific community check evidence published in scientific journals? - Before published, it must undergo peer review, which is when other scientists who work in that area read and review the work. - The peer reviewer checks the work is valid and supports the conclusions. - Scientific journals also allow other scientists to repeat experiments and see if they get the same results using the same methods. - If the results are replicated over and over again, the scientific community can ensured that the evidence collected is reliable.

10. Transcription - RNA polymerase attaches to the DNA at the beginning of the gene. - The hydrogen bonds between the two DNA strands break, separating the strands, and DNA uncoils. - One of the strands is then used as template to make an mRNA copy, called antisense strand. - Free nucleotides are lined up alongside the template strand via complementary based pairing. - RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand. - Hydrogen bonds between uncoiled strands of DNA reform and coil back into a double-helix. - When RNA polymerase reaches a stop codon, it stops making mRNA and detaches from the DNA. - mRNA moves out of the nucleus through nuclear pore and attaches to a ribosome.

-Before leaving, mRNA undergoes splicing. - Introns are removed and exons joined forming mRNA strands. - Exons can be joined in different orders to form different mRNA strands.

11. Translation - mRNA attaches to the ribosome. - tRNA with an anticodon attaches to the first codon on mRNA via complementary base pairing. - A second tRNA attaches itself to the next codon the same way. - The two amino acids are joined by peptide bond. - The first tRNA then leaves and a third tRNA binds to the next codon on mRNA. - This process continues producing a chain of linked amino acids (polypeptide chain), until it reaches a stop codon on mRNA. - The polypeptide chain moves away from ribosome and translation is complete. 12. PCR - To amplify DNA. - A reaction mixture consisting of the DNA sample, free nucleotides, primers and DNA polymerase is set up. - The mixture is heated to 95oC to break the hydrogen bonds between DNA strands. - Then it is cooled down to 55oC so that primers can bind to the strand. - After that, it is heated to 72oC for DNA polymerase to work. - Free nucleotides are lined alongside each template strand via complementary base pairing. - Two new copies of DNA are formed. - The cycle continues. 13. DNA Profiling - A fluorescent tag is added to all DNA fragments to be viewed under UV light. - Gel electrophoresis is used to separate the DNA fragments. - DNA is placed into a well in a slab of gel and covered in a buffer solution that conducts electricity. - An electrical current is passed through the gel. - Short DNA fragments move faster and travel further. - DNA fragments appear as bands under UV light.

14. Sequence and symptoms of AIDS - HIV attaches to CD4 receptor on cell surface (such as T helper cell) - Viral and cell membranes fuse so virus enters cell - Virus coat breaks down so genes and enzymes are released - Reverse transcriptase transcribes viral RNA to DNA - Viral DNA is integrated into host cell DNA using integrase enzyme - Host cell produces many copies of viral particles - Release of particles kills host cell - Virus particles now infect other susceptible cells

- high rate of mutation in genes that code for antigen proteins, form new strains of virus, antigenic varation

Stage 1: Fevers, headache, tiredness Stage 2: Virus replicates, infects CD4 T helper cells, but keep in check by T killer cells Stage 3: Immune system starts to fail. Number of T helper cells falls greatly. Weight loss, fatigue, diarrhoea, night sweats. Stage 4: Major weight loss, brain cells infected, cancers, TB. Then death.

- To prevent, treatment: : inhibitors of viral enzymes (AZT inhibits reverse transcriptase) : no smoking, alcohol : safe sexual practices : no sharing needles

15. Sequence and symptons of Tuberculosis (TB) - Caused by mycobacterium tuberculosis. - Attaches to mucous membranes - Picked u by white blood cells (neutrophils and macrophages) in alveoli - Resistant to digestive enzymes produced by white blood cells - Multiply in white blood cells - Infected cells are surrounded by other cells of immune system to form a granuloma - Disrupts antigen presentation in infected cells, so prevent immune system cells from recognising and killing infected phagocytes

Symptoms: - prolonged cough, chest pain, coughing up blood - weight lost, appetite lost, pale skin

16. Inflammation - A local, non-specific response to tissue damage - Pathogen enters the body. - Immune system cells recognise foreign antigens on surface and release molecules that trigger inflammation. - Immune system cells release histamine. - Cause vasodilation to increase blood flow, more immune system cells arrived - And increases the permeability of blood vessels -Neutrophils undergo phagocytosis.

- Cells that are infected with virus produces interferons. - Activate cells involved in SPECIFIC immune response, (T helper cells, B cells) - Promote inflammation

17. Phagocytosis of pathogens - Phagocytes: neutrophils, macrophages - Recognise antigens on pathogen - Cytoplasm of phagocyte moves around pathogen, engulfing it - Pathogen is now contained in a phagocytic vacuole. - Lysosome fuses with phagocytic vacuole and releases lysosyme. - Lysosyme breaks down pathogen. - Phagocyte then presents the pathogens antigen on the surface, forming antigenpresenting cell.