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[imqt]

can anyone please help me with the whole chromosome/gamete/crossing over/meiosis thing? or tell me where i can find some handy info that is easy to understand.
I have no idea what this stuff is on about cept for the fact it provides variation within a species or something...help pleaseee

hye i had the same problem with meosis...im on youtube now..http://www.youtube.com/watch?v=R_LUJSqeSrI&feature=related

this is an excellent demonstration! highly recommended! made it much easier for me

this is how i now understand meosis (correct me whereever i'm wrong please)

- individual chromosomes duplicates (connected by a centrometer?)
- homologous pairs come together
- crossing over may occur where homologous chromosomes exchanges sections = this leads to new alleles and combinations of genes
- then the homologus chromosomes line up in the centre of the cells and segregate, in the 2nd cell division...two new cells formed
- they further split to form 4 haploid cells (gametes) which each contain different chromosomes from each parent in random assortment

does this all sound right? anything else i need to know?

 

[imqt]

hey, thanx for that

no problem

 

[dolbinau]

hye i had the same problem with meosis...im on youtube now..http://www.youtube.com/watch?v=R_LUJSqeSrI&feature=related

this is an excellent demonstration! highly recommended! made it much easier for me

this is how i now understand meosis (correct me whereever i'm wrong please)

- individual chromosomes duplicates (connected by a centrometer?)
- homologous pairs come together
- crossing over may occur where homologous chromosomes exchanges sections = this leads to new alleles and combinations of genes
- then the homologus chromosomes line up in the centre of the cells and segregate, in the 2nd cell division...two new cells formed
- they further split to form 4 haploid cells (gametes) which each contain different chromosomes from each parent in random assortment

does this all sound right? anything else i need to know?

Centromere* But I think that's right.

 

[imqt]

Centromere* But I think that's right.

oh oops thanks

 

[dolbinau]

identify some responses of plants to temperature change (named examples please)

 

[Undermyskin]

Guys! Q27 (2007):

Scientists at a climate research unit estimate that global land areas have warmed at an average rate of 0.07 C/ decade from 1901 to 2000.

Analyse the possible effects of temperature change on Aus plants and animals with regard to the short-term survival of individuals and long term survival of species.

PS: plants' responses:
- thick, waxy cuticle to reflect heat (banksia)
- leaves vertically hung --> decrease surface area exposed to sunligh (eucalyptus)
- deciduous in cold climate to prevent heat loss and energy to leaves (Nothofagus)
etc

 

[AvieT]

Tell the difference between passive and active vaccinations.
Good luck every one.

 

[Undermyskin]

Active: immunization with antigen

Passive: immunization with antibodies of another organisms that responded to the disease.

A is better than P as P has risk of rejection of foreign blood protein, short term effect tho very effective in case emergency. I'm nor sure which organisms (other human's) but maybe they use sharks' antibodies. Well, they are very very close to those of human's anyway but much more resilient.

EDIT: forgot to add, antigens can be attenuated pathogens, debris of killed pathogens, their capsules or toxoids rendered harmless.

 

[boony3]

thanks for all your help people, i will go check out that youtube thing now

 

[dolbinau]

In the marking guidelines they often mention how unnecessarily long some people write some answers (especially option> for the 7 mark questions). How long would be appropriate for a 7 mark question?

 

[Undermyskin]

I think... the whole page or even more.

Anyone? Q27 2007, please!

 

[lil-monkey]

In the marking guidelines they often mention how unnecessarily long some people write some answers (especially option> for the 7 mark questions). How long would be appropriate for a 7 mark question?

good question. im not realy sure.
all i know is make sure you stay directly on what the question is asking and remember that if it is a 7 mark q it is asking for 7 things.
(after i have written an answer i go and see how many points i have written down and see if it adds up to the total mark of the question- it has worked so far...why not for the HSC lol)

 

[bekmay]

In the marking guidelines they often mention how unnecessarily long some people write some answers (especially option> for the 7 mark questions). How long would be appropriate for a 7 mark question?

the amount of lines provided, normally a page i think. although they often don't leave enough space for the necessary amount of information needed, especially if you have big writing. sooo i guess maybe a lil tiny bit over, couple of lines. the markers would prolly get the shits if you go wayy over cos that often means it isn't precise enough and the person is just waffling. i always start these questions with large writing cos i think i won't have enough info to fill up the space and it just keeps getting smaller and smaller once i realise i actually need more space LOL.

 

[AvieT]

Guys! Q27 (2007):

Scientists at a climate research unit estimate that global land areas have warmed at an average rate of 0.07 C/ decade from 1901 to 2000.

Analyse the possible effects of temperature change on Aus plants and animals with regard to the short-term survival of individuals and long term survival of species.

PS: plants' responses:
- thick, waxy cuticle to reflect heat (banksia)
- leaves vertically hung --> decrease surface area exposed to sunligh (eucalyptus)
- deciduous in cold climate to prevent heat loss and energy to leaves (Nothofagus)
etc

• tempreature rise will mean death to some species who cannont cope with the warming of tempreatures.
• plants and animals will have a adpat quickly- eg becoming nocturnal, less movement to conserve energy. ( not too sure about plants)

yeahh thats all i got right now off the top of my head hahhaha.

 

[gloworm14]

hye i had the same problem with meosis...im on youtube now..http://www.youtube.com/watch?v=R_LUJSqeSrI&feature=related

this is an excellent demonstration! highly recommended! made it much easier for me

this is how i now understand meosis (correct me whereever i'm wrong please)

- individual chromosomes duplicates (connected by a centrometer?)
- homologous pairs come together
- crossing over may occur where homologous chromosomes exchanges sections = this leads to new alleles and combinations of genes
- then the homologus chromosomes line up in the centre of the cells and segregate, in the 2nd cell division...two new cells formed
- they further split to form 4 haploid cells (gametes) which each contain different chromosomes from each parent in random assortment

does this all sound right? anything else i need to know?

thats a pretty clear demonstration, thanks.

hey i finished studying and looking over my notes LOL

 

[dolbinau]

the amount of lines provided, normally a page i think. although they often don't leave enough space for the necessary amount of information needed, especially if you have big writing. sooo i guess maybe a lil tiny bit over, couple of lines. the markers would prolly get the shits if you go wayy over cos that often means it isn't precise enough and the person is just waffling. i always start these questions with large writing cos i think i won't have enough info to fill up the space and it just keeps getting smaller and smaller once i realise i actually need more space LOL.

Do we have allocated space for the option? In past exams It's all been just writing booklets. I'm not sure how it would work for all the different options .

 

[boony3]

can someone please show me an example of how to construct a table listing the possible genotypes and expected frequency for a cell containing 3 pairs of chromosomes just prior to a meiotic division.
thanks

 

[Undermyskin]

• tempreature rise will mean death to some species who cannont cope with the warming of tempreatures.
• plants and animals will have a adpat quickly- eg becoming nocturnal, less movement to conserve energy. ( not too sure about plants)

yeahh thats all i got right now off the top of my head hahhaha.

But the total one is just a rise of 0.7 degree! How can it kill anything? Or is it a typo they made and it should be 0.7/decade instead?

OK, should I give two possible scenarios that Aus has increased or decreased temperatures?

 

[adnan91]

Do we have allocated space for the option? In past exams It's all been just writing booklets. I'm not sure how it would work for all the different options .

nah booklets and u can have as many as u want

 

[AvieT]

can someone please show me an example of how to construct a table listing the possible genotypes and expected frequency for a cell containing 3 pairs of chromosomes just prior to a meiotic division.
thanks

i dont know, but just prior to meiotic division, isnt there just like 1 chromosome in the cell? and then it meets up with the other and crosses over and what not? you can do a table of possible genotypes with punnet squares and 2 Alleles. i dont know if im right hahaha. whered you get the question?