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    (Original post by ibysaiyan)
    What buzzes you about sliding filament model? Just remember the bands.. and what happens when active potential passes through post-muscular membrane =]

    Here's what happens:
    Sodium ions start to increase in conc. near the pre- end from there they stuck onto the post receptors in doing so as that side gets polarized (i.e changes in potential difference) Calcium ions start to flux in from the sarcoplamisc reticulum,these Calcium ions bind onto the tropomyosin causing them to detach from the actin myosin filament,in this manner troponin chain moves...

    Correct me if I am mistaken.. I did this months ago
    it seems so much easier when it's broken down. My problem is that our teacher kinda skipped the whole 3rd and 4th modules (literally taught the 4th one in a day)..so i'm self-teaching all of that, and the first time you read those spreads they're a bit 'in-ya-face' lol.
    anyway good luck with your exams less than two weeks :eek4:
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    (Original post by sillysal)
    can someone explain the species concept to me please? i don't understand the whole phylogenetic concept with all that monophyletic, cladistics marlarky
    You going on about the definitions?

    Well the biological species concept- a group of similar organisms that can breed to form fertile and offspring and are isolated from other such groups. This is known as biospecies.

    Whereas the phylogenetic species concept- a group of organisms similar to each other in physiology, biochemistry, embyology, behavioural and ecological and this forms the basis of classification and showing phylogenetic lineage called a clade. DNA sequencing is needed to show lineage.

    However it excludes organisms that produce asexually, we only have a preserved specimen for and fossil evidence of organism.
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    (Original post by J DOT A)
    Same!
    You NEED full marks?! That's gotta be a lot of pressure ...
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    (Original post by slacker07906)
    You going on about the definitions?

    Well the biological species concept- a group of similar organisms that can breed to form fertile and offspring and are isolated from other such groups. This is known as biospecies.

    Whereas the phylogenetic species concept- a group of organisms similar to each other in physiology, biochemistry, embyology, behavioural and ecological and this forms the basis of classification and showing phylogenetic lineage called a clade. DNA sequencing is needed to show lineage.

    However it excludes organisms that produce asexually, we only have a preserved specimen for and fossil evidence of organism.
    thankyou so much! i don't quite get the cladistics hierachy system or the monophyletic/paraphyletic...what's the difference? really confusing me!
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    (Original post by sillysal)
    thankyou so much! i don't quite get the cladistics hierachy system or the monophyletic/paraphyletic...what's the difference? really confusing me!
    Do we need to know that? :s I aint come across it!
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    do we need to know about dna fingerprinting souther blotting etc coz my teacher went through it but it isn't on the syllabus. please help me!
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    (Original post by slacker07906)
    Do we need to know that? :s I aint come across it!
    its in the heinemann book page 143
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    (Original post by kabolin)
    do we need to know about dna fingerprinting souther blotting etc coz my teacher went through it but it isn't on the syllabus. please help me!
    No am pretty sure we don't. All you need to know is that the techniques of PCR and electrophoresis aid in genetic fingerprinting. I wouldn't worry about it too much. As long as you know the process of PCR, electrophoresis. Automated chain termination and replica plating then that's the main thing.
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    Which revision guide is worth getting do you think guys? Or would you say just reading the textbook again and again?
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    plant responses

    Plants respond to their environment in order to avoid predation and abiotic stress such as water shortage.

    Tropism: a directional growth response in which the direction of the response is determined by the direction of the external stimulus.

    Tropisms can be either positive or negative.

    positive- growing towards the direction of the stimulus.
    negative- growing aways from the direction of the stimulus.

    Phototropism shoots grow towards the light to increase rate of photosynthesis.
    Geotropisms- shoots grow upwards and roots grow downwards towards the pull of gravity
    Chemotropisms- pollen tubes grow towards the chemicals given off by the ovary in a flower
    Thigmotropism- plants respond by touch by growing around other plants

    Plants divide by mitosis in the meristem and then the cells elongate to bring about growth.

    meristematic tissue: growing parts on a plant where immature cells are still capable of dividing by mitosis.

    Plant hormones: coordinate plant growth. They are produced in one part of the plant then transported to target cells by active transport and diffusion in the xylem and phloem.

    The need for hormones- obviously, it is recognised that plants don't have a nervous system, and therefore to bring about a response they need these hormones. Without them the plant would lose its natural advantage and denature.

    There are several types of hormones:

    Cytokinins- promotes cell division (mitosis) in the meristem.
    Auxins- promote cell elongation in shoots. Inhibit growth of lateral buds. Inhibit leaf fall.
    Gibberellins- promotes elongation of stems
    Abscisic acid- stimulates production of ethene. Causes stomatal closure when the plant becomes stressed by low water avaliablity.
    Ethene- stimulates leaf fall and the ripening of fruit.

    REMEMBER: plant hormones are like any other hormones. They have a specific shape. Bind to complementary shaped receptors on target cells (plasma membrane). This is synoptic.
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    (Original post by slacker07906)
    No am pretty sure we don't. All you need to know is that the techniques of PCR and electrophoresis aid in genetic fingerprinting. I wouldn't worry about it too much. As long as you know the process of PCR, electrophoresis. Automated chain termination and replica plating then that's the main thing.
    Whats automated chain termination? I don't recognise the name...


    (Original post by sillysal)
    thankyou so much! i don't quite get the cladistics hierachy system or the monophyletic/paraphyletic...what's the difference? really confusing me!

    (Original post by slacker07906)
    Do we need to know that? :s I aint come across it!
    I haven't come across this either
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    (Original post by twelve)
    Whats automated chain termination? I don't recognise the name...
    Automated gene sequencing? Involving the tagged/marked free DNA nucleotides?
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    (Original post by sportycricketer)
    Automated gene sequencing? Involving the tagged/marked free DNA nucleotides?
    Ohhh yepp, just hadn't heard that name for it Wanted to make sure I hadn't completely missed something off the specification haha.
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    (Original post by .r.)
    it seems so much easier when it's broken down. My problem is that our teacher kinda skipped the whole 3rd and 4th modules (literally taught the 4th one in a day)..so i'm self-teaching all of that, and the first time you read those spreads they're a bit 'in-ya-face' lol.
    anyway good luck with your exams less than two weeks :eek4:
    Same to you too although I have sat my f215 in january, got an A =]
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    (Original post by sportycricketer)
    Which revision guide is worth getting do you think guys? Or would you say just reading the textbook again and again?
    Id definitely say don't bother yourself with tons of books, the biology text book has all the information in it sometimes even extra, so concentrated on that and just keep reading it,
    Ive kinda finished revising biology 5, but got to go over it all again to ensure its screwd in cuz it worries me when i hear random stuff i have forgotten :eek:
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    Why does small population size increase chance of rapid evolutionary change???????
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    Can someone explain epistasis? Meiosis and Variation is my weakest topic and I've got a horrible feeling it's going to be worth big marks.
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    (Original post by nif1boy)
    Why does small population size increase chance of rapid evolutionary change???????
    This is genetic drift, which is caused by a random event that changes the allele frequency within a population due to the narrowing of the gene pool. So as a result some allelels will get passed on while others will be phased away. This causes some phenotypic traits to be more common than others.
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    Guys, whats the difference between Primary and secondary metabolites.... and why is it that the production of primary metabolites is nearly nsync with the population growth of microorganism in a closed culture?
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    (Original post by J DOT A)
    Guys, whats the difference between Primary and secondary metabolites.... and why is it that the production of primary metabolites is nearly nsync with the population growth of microorganism in a closed culture?
    Primary metabolites are substances produced during the normal/essential functioning of a cell for instance during respiration as for secondary metabolite they are made at a certain period during the life-cycle of a micro-organism.
    -ibysaiyan
 
 
 
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