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    Could anyone explain the difference between monophyletic and paraphyletic groups? Thank you
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    (Original post by Elchar)
    I don't know how to revise for F215 now because my previous method got me an A at AS but it failed me with f214 I need an A overall for uni and will be so gutted if I don't make it because of the irrelevant questions the examiners threw at us on Monday. Does anyone have any revision advice to help with f215? I badly need an A on this paper to salvage my grade
    Look through as many past papers as u can! And learn all the definitions as stated in the book, also make sure you know all the processes

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    (Original post by EspDe97)
    Could anyone explain the difference between monophyletic and paraphyletic groups? Thank you
    Monophyletic means it contains the ancestor and *all* descendants. Paraphyletic groups contain some but not all descendants of a common ancestor (which may or may not be included).

    Here's the most accurate diagram I've come across: https://www.dropbox.com/s/zppvhld303...%2048.jpg?dl=0
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    [QUOTE=HeyThereHarry;56932043]Monophyletic means it contains the ancestor and *all* descendants. Paraphyletic groups contain some but not all descendants of a common ancestor (which may or may not be included).

    Here's the most accurate diagram I've come across: https://www.dropbox.com/s/zppvhld303...l=0[/QUOTE]

    Thank you so much! That's really helpful. Do we need to know polyphyletic too or is that not in the spec?
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    (Original post by jessicadanby1996)
    The study of the evolutionary history of groups of organisms. All evolve from common ancestors, the more closely related two species are, the more recently their last common ancestor will be. Problems with this are that there is no cut off as to when two organism are classed as different/same species. 94% of human and chimpanzee DNA is the same for example, but we are classed as different species
    Thank you!, that made it a lot clearer....Kept getting confused
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    Hi can someone please explain how the best male offspring is chosen when selectively breeding cattle, as the mother of all the offspring is the same so how would you figure which male cow has the most desirable characteristic?
    All I can think of is that other characteristics are selected for instead in the males?
    Thank you in advance☺️


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    Can someone please tell me if I am right in the thinking/understanding of this:

    homeotic genes have regions called homeobox sequences that code for a homeodomain that can act as a transcription factor. It can bind to parts of DNA causing or preventing the transcription and translation of certain developmental genes like the maternal effect genes, segmentation genes and homeotic selector genes?
    Please correct me if I am wrong! Thanks in advance
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    (Original post by GXO)
    Hi can someone please explain how the best male offspring is chosen when selectively breeding cattle, as the mother of all the offspring is the same so how would you figure which male cow has the most desirable characteristic?
    All I can think of is that other characteristics are selected for instead in the males?
    Thank you in advance☺️


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    i think you would mainly test the progeny of the bulls so which ones produce the daughter cows with the greatest milk yield. The sperm can then be obtained and used to artificially inseminate the cows
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    Can any explain to me the answer of q5D) in june 2011??? Thank you!!!
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    Also can someone give me the advantages of behaviours of innate and learning so classical operant habituation and innate reflexes kinesis and taxes??
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    (Original post by ktdogan)
    Can someone please tell me if I am right in the thinking/understanding of this:

    homeotic genes have regions called homeobox sequences that code for a homeodomain that can act as a transcription factor. It can bind to parts of DNA causing or preventing the transcription and translation of certain developmental genes like the maternal effect genes, segmentation genes and homeotic selector genes?
    Please correct me if I am wrong! Thanks in advance
    Do we need to know the ins and out of that spread (I feel like I've misinterpreted the spec point again)?
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    (Original post by Student23478)
    Can any explain to me the answer of q5D) in june 2011??? Thank you!!!
    Is that the question about the triplet codons?
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    (Original post by Student23478)
    Can any explain to me the answer of q5D) in june 2011??? Thank you!!!
    Just to check - you mean "Using the information in Fig. 5.1, list the three triplet codons that would cause termination of a polypeptide chain (stop codons) and explain why these codons have this effect."

    The three triplet codons are just the ones that code for "stop" - so following the diagram, this is UAA, UAG, and UGA (read from the diagram).

    They code for a "stop" because, whilst there is a tRNA with the complementary anticodon, there is no associated amino acid on the tRNA. This means the amino acid on the previous tRNA has nothing to create a peptide bond with, and the whole chain breaks away from the tRNA and therefore forms the primary structure.
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    Help... My biology teacher stated that OCR does not accept the role of Nitrogen Fixing Bacteria as converting atmospheric nitrogen to nitrates and that it has to be atmospheric nitrogen to ammonia/ammonium ions/ammonium compounds. I don't understand then what I have to learn as the specification for ecosystems states 'describe how microorganisms recycle nitrogen within ecosystems. (Only Nitrosomonas, Nitrobacter and Rhizobium need to be identified by name).' However, Rhizobium is used for the nitrogen fixation process (by nitrogen fixing organisms).
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    (Original post by missEA)
    Help... My biology teacher stated that OCR does not accept the role of Nitrogen Fixing Bacteria as converting atmospheric nitrogen to nitrates and that it has to be atmospheric nitrogen to ammonia/ammonium ions/ammonium compounds. I don't understand then what I have to learn as the specification for ecosystems states 'describe how microorganisms recycle nitrogen within ecosystems. (Only Nitrosomonas, Nitrobacter and Rhizobium need to be identified by name).' However, Rhizobium is used for the nitrogen fixation process (by nitrogen fixing organisms).
    Nitrogen fixation is atmospheric nitrogen to ammonium ions (Rhizobium used). The nitrification is the conversion of the ammonium to nitrites (nitrosomonas) and nitrites to nitrates (nitrobacter). They are two different processes.
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    (Original post by missEA)
    Help... My biology teacher stated that OCR does not accept the role of Nitrogen Fixing Bacteria as converting atmospheric nitrogen to nitrates and that it has to be atmospheric nitrogen to ammonia/ammonium ions/ammonium compounds. I don't understand then what I have to learn as the specification for ecosystems states 'describe how microorganisms recycle nitrogen within ecosystems. (Only Nitrosomonas, Nitrobacter and Rhizobium need to be identified by name).' However, Rhizobium is used for the nitrogen fixation process (by nitrogen fixing organisms).
    I think they may be trying to state that Rhizobium converts atmospheric nitrogen to ammonium ions whilst Nitrosomonas Bacteria converts these ammonium ions to nitrites and nitrobacter bacteria these nitrites to nitrates (the latter two are involved in nitrification and known as nitrifying bacteria collectively)
    Thus, stating that rhizobium converts nitrogen to nitrates would not be an accurate statement as you'd miss mentioning the roles of the latter two bactera
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    (Original post by EvasiveRose)
    Do we need to know the ins and out of that spread (I feel like I've misinterpreted the spec point again)?
    I think we just need to know the basic idea of the homeobox sequences and how they control the development of the body plan. I don't think we need to know the drosophila example, but it will probably help to have a rough idea of it.
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    Have a feeling a good proportion of this paper is going to be on all that ecosystems/timber/behaviour stuff, rest most likely consist of qwc on sequencing genome and standard genetic diagram, then experimental stuff and data analysis.
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    Can someone summarise the main points about the DRD4 receptor for me please. I don't really get what we need to know about it.
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    (Original post by domcandrews)
    Have a feeling a good proportion of this paper is going to be on all that ecosystems/timber/behaviour stuff, rest most likely consist of qwc on sequencing genome and standard genetic diagram, then experimental stuff and data analysis.
    Do you have a model answer for sequencing a genome as people are on about BACs even though its in none of my textbooks nor in te spec

    Thanks In advance !
 
 
 
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