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AQA BIOL 2 - A Few Questions

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    (Original post by Booyah)
    The spotted owl was a member of a food chain as prey, this reduced the number of predators in the population as their food source decreased. Something like that when you look at species diversity whenever it is plants there are habitats and food to consider, in the place of animals however it is important to consider possible predators i.e. the owl may be hunted by pissed off mice with nuclear warheads...
    Haha! Awesome, thanks.
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    (Original post by Booyah)
    Well I can answer 3 for you... The Casparian strip has 1 entry point that water MUST go through, this is because it is coated in a waxy substance and there is only one access point, this is because the Casparian strip controls WHAT is going into the Xylem, if the plant had no control of water intake it can quite easily flood all the cells causing them to burst, or something along those lines...

    Hope that helped... revising for this myself
    The casparian strip only forces water into the cytoplasm of the epidermal cells (from the apoplastic pathway) not into the xylem.. it gets into the xylem by osmosis, but for that it needs a water potential gradient, which is made through the epidermis actively transporting mineral ions into the base of the xylem. This whole process causes root pressure, which helps in the transpiration cycle but not as much as cohesion tension.
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    (Original post by George_)
    The spotted owl is a bird. Numbers of spotted owls have decreased over the past 50 years. Explain how this decrease may affect genetic diversity...

    I would probably say something like the reduced numbers of the species means that there's a smaller gene pool available, and any variation within the species is now limited, which also limits genetic diversity... Then id probably throw something in about genetic bottlenecks and how a change in the environment is likely to wipe them out...
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    (Original post by George_)
    Haha! Awesome, thanks.
    Oh yeh and Genetic Diversity is the amount of different alleles present in a species, so there is a reduction in the number of alleles making the owls less likely to adapt to environmental changes... 4 o clock revision sesh... WINNING!

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Updated: May 21, 2012
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