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  1. Hey there! I beg any of you to help me with the three questions regarding the evolution option. 1. How does actually polyploidy lead to speciation? Is it because a e.g. tetraploid plant cannot interbreed with a diploid plant? I understand that the nucleus contains >2 sets of chromosomes, but not why that leads to speciation. 2. Is the process of adaptive radiation just; many similar but distinct species evolve rapidly from a single species? Isnt that the same as divergent evolution, or is divergent evolution a type of adaptive radiation? Thank you!!
  2. Hey Feels like I'm starting a new topic here everyday but you guys are much help. I have small questions regarding the exagerrated traits and altruism. Regarding the traits.. (lets talk about the peacock's tail), is the problem that the tail becomes too large or is the problem that very many of the peacock's get this large tail because they inherit it from the male which mates the most because the females are attracted to the large tail? The altruism question...I don't need help with the examples, but I don't really understand if "kin selection" and "reciprocal altruism" are types of altruism
  3. Hello! I need help with the effect of THC on the brain, in terms of synaptic transmission. I don't understand if the THC binds to presynaptic receptors and block the release of anandamide into the synaptic cleft, or if it binds to receptors on the postsynaptic neurone, blocking the binding of anandamide. What I understand from the book and the study guide is that it binds to presynaptic receptors (cannabioid receptors) and so block the release of anandamide (excitatory neurotransmitter) and so the postsynaptic neurone is not stimulated. But the book also says that THC causes the postsynaptic
  4. I thought I'd use this topic again, now a question regarding ultrafiltration. The basement membrane prevents large molecules e.g. proteins and blood cells to become part of the filtrate. What I don't really understand is the function of the fenestrated capillaries, is their function solely to let some substances such as amino acids, glucose and water through to become part of the filtrate? (these will later be reabsorbed). Is there another function relevant for the IB syllabus? Or is it just that they "allow" substances to become part of the filtrate due to the high pressure in the glomerulus
  5. Hello I am just wondering, if I take a retake in a course where I got a 6 in May exams, and I get a 5 in the November exams, which grade will count, the highest or the lowest?
  6. Hello I am retaking biology HL because I got a 4 in it, and I am not happy with that at all. What I wonder is, what IF, I get a 3 now in November, will that be my new grade or will still the "highest" = 4 counts? If the highest counts, does this apply for all courses? Take care
  7. I have one more small question; is vaccination active or passive immunity? Cannot find an answer to that. I suppose it is active since the body still reacts to the weakened antigen and produces antibodies and memory cells to kill it?
  8. Aah..yes, I confused selection with expansion, but now I get it Sometimes you guys are better than the teachers, thank you!
  9. Hey guys! I am not sure whether it is allowed to create topics regarding just one small question in the book so let me know if it isn't. I have a question regarding Human health and physiology II (HL) - defence against infectious disease. Principles of immunity involve challenge and response (immune system challenged by an antigen which produces a response which involves macrophages etc etc until memory cells are produced). Memory cells then respond quickly to the secondary infection so we don't have to get sick. I get that. But when it comes to "clonal selection" I am a bit confused. I under
  10. Hey I just wonder how much paper 3 counts when getting a final grade in Biology HL. Sorry if the information is around but I could not find it. Say I get 4 on paper 1, 4 on paper 2 and 6 on paper 3, will my final grade be 5 if my IA-grade is 4 as well? I know the grades vary and one cannot say with 100% confidence that yes the grade will be 5, but approximately. Best wishes, kentpop
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