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BIOL4 Biology Unit 4 Exam - 13th June 2011

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So who's panicking? I feel ive gone over everything but i read a HSW past paper question and think 'S***' !! :frown:
Reply 641
Avatar for Rickesh
Rickesh
Original post by FatalError
Lets do some questions people!

What are the differences between stabilising and directional selection?


Stabilising selection is where the mean (middle of the curve) is the highest, and where those in the mean of the curve are the most sucessful and more likeley to to reproduce, it occurs when the environment is constant, but directional selectiron is where the two extremes can survive depending on the conditions of the environment as they are changing????
Reply 642
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kingsmod1
Original post by Superlogon
So who's panicking? I feel ive gone over everything but i read a HSW past paper question and think 'S***' !! :frown:


HSW just depends on the day, some u cant and some u can

just read the Q carfefully and think from the very foundations... :P
Stabilising selection is when the abiotic features of an ecosystem favour the mean individuals of a population, thus preserving the observable characteristics and phenotype of the population.

Directional selection, on the other hand, favours individuals at the extremities of the population. This changes the observable characteristics of the population and so changes the phenotype.
Reply 644
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Abby :)
8
Im stopping revision now for the night! :smile: Gonna do a few hours in the morning... im all revisioned out. My brains dead!
What is a limiting factor?
Original post by kingsmod1
HSW just depends on the day, some u cant and some u can

just read the Q carfefully and think from the very foundations... :P


My method at attacking them is go right back to square one and run through the stages! if i still havent got it, go even further back!
Reply 647
Avatar for Rickesh
Rickesh
Original post by FatalError
Stabilising selection is when the abiotic features of an ecosystem favour the mean individuals of a population, thus preserving the observable characteristics and phenotype of the population.

Directional selection, on the other hand, favours individuals at the extremities of the population. This changes the observable characteristics of the population and so changes the phenotype.


What is speciation?
Reply 648
Avatar for kingsmod1
kingsmod1
Original post by Superlogon
My method at attacking them is go right back to square one and run through the stages! if i still havent got it, go even further back!


perfect, read the keywords and just try and match the mark scheme lol
What is speciation?


Speciation is the evolution of new species from existing species. This is due to some sort of geographical barrier isolating members of the two species, essentially forming two different populations. No interbreeding can occur between the members of the two populations and because different selection pressures and abiotic factors are present in both populations different alleles are favoured for survival. This will eventually lead to changes in allele frequency and eventually the gene pool. The two populations will now have different gene pools and if they were to unite they would not be able to breed to produce fertile offspring.
Reply 650
Avatar for Rickesh
Rickesh
Original post by FatalError
Speciation is the evolution of new species from existing species. This is due to some sort of geographical barrier isolating members of the two species, essentially forming two different populations. No interbreeding can occur between the members of the two populations and because different selection pressures and abiotic factors are present in both populations different alleles are favoured for survival. This will eventually lead to changes in allele frequency and eventually the gene pool. The two populations will now have different gene pools and if they were to unite they would not be able to breed to produce fertile offspring.


Perfect, your turn
Original post by Rickesh
when working out the gradient? Why?


In fact it gives the same answer ...400/(25-15) = 40
What is the enzyme that fixes CO2 into the calvin cycle?
Reply 653
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Rickesh
Original post by FatalError
What is the enzyme that fixes CO2 into the calvin cycle?


Ribulose bisphosphase?? Something like that...
Good luck everyone :smile:
Original post by FatalError
What is the enzyme that fixes CO2 into the calvin cycle?

You don't need to know.
Original post by FatalError
What is the enzyme that fixes CO2 into the calvin cycle?


Rubisco :smile:
Original post by FatalError
What is the enzyme that fixes CO2 into the calvin cycle?


Rubisco
Rubisco. You might need to it's not that hard lol. Ok your turn.
Original post by Rickesh
Ribulose bisphosphase?? Something like that...


It's not RuBP. The enzyme is used to join CO2 to RuBP.

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