Aqa A Level Biology- Model Answers Study Guide Rated A+

Resting Potential in a Neurone {Ans: The volatge-gated channels are closed. Na+ pumped out by sodium carrier proteins. Higher concentration of Na+ outside than inside neurone. Inside negative compound to outside as 3Na+ out and 2K+ in (-65mV)}Reduction in Genetic Diversity {Ans: Reduced variety of different alleles in new population. •Founder effect- few individuals from population become isolated to from colonies. •Genetic bottlenecks- significant fall in tissue of population •Selective breeding- using organisms with particular characteristics}Role of Bacteria Making Carbon Available to Plants {Ans: Decomposers release enzymes and digest dendritus. Absorb products of digestion. Respire and carbon dioxide released. used by plants in photosynthesis}Natural Selection {Ans: Individuals have different alleles. Predation, disease and competition create struggle to survive. Some better adapted than others. Those who survive and reproduce and pass on their advantageous allele to generation to generation. Next generation more likely to survive, reproduce. Frequency of beneficial alleles in gene pool increases}Muscle Relaxation {Ans: When not stimulated, sarcoplasmic reticulum actively transport Ca2+ back into it using energy from hydrolysis of ATP. Lack of Ca2+ means tropomyosin can establish Its original position (blocking actin filament). Myosin can no longer bind to actin and so contraction