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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

maybe,

these haven't really appeared, so a few may:

- aspects of meiosis
- exchange in insects
- exchange in fish
- absorption in roots
- xerophytes
- conjugation

Omg what do we need to know about xerophytes?

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Reply 3221

dooobie_

Someone tell me about xerophytes? I completely forgot this was on ths spec! Oh gosh :frown:

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Reply 3222

VigneshSB

Original post by Scienceisgood

Water DOES NOT diffuse - only goes through osmosis!

No, it does diffuse in the gas phase. Go and look up your definition of osmosis (There's no membrane to pass through in the leaf air spaces)

Reply 3223

faddys123

7

can someone please desibribe the stages of meiosis and how they differ from mitosis ?

Reply 3224

username984585

20

Original post by Tee Logan x

Thank you

so basically in meiosis, homologous pairs line up alongside each other but in mitosis, there are no homologous pairs, all chromosomes just line up at the equator?

Yep thats correct!
Just remember that first their is interphase, for mitosis and meiosis.
And then for mitosis there is prophase, metaphase, anaphase and telophase.
For meiosis, there is meiosis 1 and meioses 2.
Then cell division occurs for both, 4 haploid cells produced in meiosis and 2 diploid cells produced in mitosis. :smile:

Reply 3225

TheGeneral95

2

Original post by Nav_Mallhi

Yep thats correct!
Just remember that first their is interphase, for mitosis and meiosis.
And then for mitosis there is prophase, metaphase, anaphase and telophase.
For meiosis, there is meiosis 1 and meioses 2.
Then cell division occurs for both, 4 haploid cells produced in meiosis and 2 diploid cells produced in mitosis. :smile:

Mitosis just remember it with the acronym "Play me another track".

Reply 3226

Tee Logan x

1

Original post by Nav_Mallhi

Yep thats correct!
Just remember that first their is interphase, for mitosis and meiosis.
And then for mitosis there is prophase, metaphase, anaphase and telophase.
For meiosis, there is meiosis 1 and meioses 2.
Then cell division occurs for both, 4 haploid cells produced in meiosis and 2 diploid cells produced in mitosis. :smile:

Thanks a lot! Good Luck :smile:

Reply 3227

DannyRedman

Original post by dooobie_

Someone tell me about xerophytes? I completely forgot this was on ths spec! Oh gosh :frown:

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Hey, basically xerophytes and leaves that are adapted to reduce water loss this is how:
Thick cuticle: this is to reduce the water losses from the open stomata on the top layer of the lead
Curved leaves: this is helpful because it traps the air just outside of the leaf therefore as water evaporates and diffuses out down the water potential gradient it water vapor is trapped there for a build up of this vapor reduced water potential gradient. Therefore less water lossed
The same goes for stomata in pits/grooves
hairy leaves: this is to trap a thin layer of moisture just outside of the stomata. Again which reduced the water potential gradient hope this helps

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Reply 3228

TheGeneral95

2

Original post by dooobie_

Someone tell me about xerophytes? I completely forgot this was on ths spec! Oh gosh :frown:

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Def-Plants adapted to living in dry conditions.

Thick cuticle-Larger waterproof barrier to prevent waterloss
Rolling up of leaves-Traps a region of still air that becomes saturated with water vapor so lowing the gradient.

Hairy leaves-Trap moist air

Stomata in pits - also trap moist air

Reduced Surface area to volume ratio- reduces rate of diffusion

Reply 3229

username853993

21

Good luck guys :smile:

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Reply 3230

DannyRedman

Original post by madmadmax321

Good luck guys :smile:

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You too

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Reply 3231

KaranbirBandesha

Can someone sum of gaseous exchange in plants and how gases get to the mesophyll cells please

Reply 3232

Suzanna5678

Someone please help ! How do we draw meiosis seriously panicking now

Reply 3233

dooobie_

Original post by DannyRedman

Hey, basically xerophytes and leaves that are adapted to reduce water loss this is how:
Thick cuticle: this is to reduce the water losses from the open stomata on the top layer of the lead
Curved leaves: this is helpful because it traps the air just outside of the leaf therefore as water evaporates and diffuses out down the water potential gradient it water vapor is trapped there for a build up of this vapor reduced water potential gradient. Therefore less water lossed
The same goes for stomata in pits/grooves
hairy leaves: this is to trap a thin layer of moisture just outside of the stomata. Again which reduced the water potential gradient hope this helps

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Thanks so much!

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Reply 3234

PoorLoser

2

Original post by Suzanna5678

Someone please help ! How do we draw meiosis seriously panicking now

1 cell with a homologous pair of chromosomes
divide into 2 cells with 1 chromosome each
which divides into 4 cells, in which are 1 chromatid from each of the chromosomes

at the end, you actually get 23 chromatids in the daughter cell (correct me if I'm wrong anyone!)

Reply 3235

pnaidu

3

hey, can someone please tell me why mono-zygotic twins are a better sample than
di-zygotic twins?

Reply 3236

meganburberry

2

Original post by Suzanna5678

Someone please help ! How do we draw meiosis seriously panicking now

You don't need to be able to draw meiosis, you just need to be able to identify it's stages and explain them. Don't worry, you'll be fine!

Reply 3237

PoorLoser

2

Original post by KaranbirBandesha

Can someone sum of gaseous exchange in plants and how gases get to the mesophyll cells please

O2 needed for respiration/CO2 needed for photosynthesis enters through stomata
waste products exit through stomata

isn't that it? what else is there?

Reply 3238

PoorLoser

2

to help everyone relax, last year you could lose nearly 10 marks and get full ums

and you could lose 22 marks (roughly) and still get an A

so basically, just answer a few HSW questions and you'll be fine!!

good luck all!

Reply 3239

Rumschpringe

11

Do we have to memorise the formula for index of diversity?

AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

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