AQA Biology Unit 2 18th January

how prepared is everyone for this exam?

you have your exam tomorrow?

Not overly prepared but not under. I've done a decent amount.

You?

Independent segregation were the daughter cells can have any combination of maternal and paternal chromosomes.

Crossing over when the chromosomes arrange themselves into homologous pairs and bits of chromatids swap over they still code for the same gene but different combinations of alleles.

Can have crossing over and independent segregation.
Parts of the chromatids break off and swap with another chromatid.
Chromosomes are randomly put into the middle so randomly pulled apart into different poles of the cell.
I suck at the brief description

Can someone explain to me the difference between apoplastic pathway and symplastic pathway...and eventually the water travels the symplastic pathway anyway?

Mostly right
but just remember to clearly state independent segregation of HOMOLOGOUS CHROMOSOMES

If a cell has 3 pairs of homologous chromosomes. How many possible combinations are there when indepenent segregation of homologous chromosomes occurs ?

There must be an equal pair of chromosomes so homologous pairs can pair up to undergo meiosis, correct? So if there is an odd number of chromosomes, meiosis cannot take place as the homologous chromosomes are not able to pair up?

Correct.

The apoplastic pathway is the pathway for water to move into cell walls. However, the apoplastic pathway reaches the endodermis (I believe) which has the casparian strip which is a waterproof cuticle so forces water to go through the symplast instead which is the cytoplasm. The water moves by osmosis down a water potential gradient

Thank you

Did my cohesion/root pressure make sense?

There was a diagram on June 2010 paper with a question like that, I did not understand it It said in the examiner report it was a tough question - not to figure it out

There must be an equal pair of chromosomes so homologous pairs can pair up to undergo meiosis, correct? So if there is an odd number of chromosomes, meiosis cannot take place as the homologous chromosomes are not able to pair up?

NP

What's the features of xerophytes to reduce water loss?

Ok look at this question, first fill in the sperm cell - which is half the chromosomes as it is a gamete. If it has half the chromosomes, it will have 1/4 of the mass of DNA. I'll explain this after I'm finished with the Telophase bit.

Look back at the concept of mitosis...what is it? It's the cell division which produces TWO IDENTICAL cells as the SAME number of CHROMOSOMES. So the chromosome number is 26. BUT the mass of the DNA halves as that one parent cell (at stage of prophase) splits equally into TWO so it halves.

Going back to the mass of the DNA of the sperm cell, the telophase is talking about TWO cells. The sperm cell only comes from ONE of those TWO cells so the mass of DNA also is halved again from the telophase one.

Hopefully that helps

xerophytes have
1) thick cuticles to reduce evaporation
2) Reduced number of stomata
3) Smaller and fewer leaves to reduce surface area

these are the only 3 i could think of, if there are any more please let me know

xerophytes have
1) thick cuticles to reduce evaporation
2) Reduced number of stomata
3) Smaller and fewer leaves to reduce surface area

these are the only 3 i could think of, if there are any more please let me know