Edexcel GCE Biology Unit 4 6BI04 June 2013

Hello, we only need to know about the following experiments:

11 Describe how to carry out a study on the ecology of a habitat to produce valid and reliable data (including the use of quadrats and transects to assess abundance and distribution of organisms and the measurement of abiotic factors, eg solar energy input, climate, topography, oxygen availability and edaphic factors).

17 Describe how to investigate the effects of temperature on the development of organisms (eg seedling growth rate, brine shrimp hatch rates).

18 Describe how to investigate the effect of different antibiotics on bacteria.

"From the Edexcel SNAB Specification"

okay guys please start asking some hard questions now

Im liking that idea!

How does the HIV virus lead to someones death?

can somebody summarise the whole HIV mechanism leading to death?

I've just been reading people thoughts and predictions about tomorrows exam and I've got some more extra ones which I haven't seen in the last couple of exams:

-the way bacteria reproduce - asexual and binary fission
-the way some bacteria are able to transfer genes between each other -
a) transformation, which is when a small piece of DNA is released by the donor and actively taken up by a recipient. ( this only happens in certain types of bacteria).
b) transduction, when a small amount of DNA is transferred from one bacterium to another by a bacteriophage(a virus that infects bacteria)
c) (most common but still rare) Conjugation, genetic information is transferred from one bacterium to another by direct contact.
-the way viruses infect host cells - lysogenic pathway, which is when they insert their DNA into the host DNA so it replicates every time the host cell divides(this is called a provirus). and Lytic pathway, which is the genetic material is replicated independently of the host DNA straight after entering the host.
-what are retroviruses - viruses which have genetic RNA and reverse transcriptase.

**obviously I'm not saying this will come up for certain, but I think that they are some topics/questions which haven't been asked in recent papers Good Luck everyone

I've just been reading people thoughts and predictions about tomorrows exam and I've got some more extra ones which I haven't seen in the last couple of exams:

-the way bacteria reproduce - asexual and binary fission
-the way some bacteria are able to transfer genes between each other -
a) transformation, which is when a small piece of DNA is released by the donor and actively taken up by a recipient. ( this only happens in certain types of bacteria).
b) transduction, when a small amount of DNA is transferred from one bacterium to another by a bacteriophage(a virus that infects bacteria)
c) (most common but still rare) Conjugation, genetic information is transferred from one bacterium to another by direct contact.
-the way viruses infect host cells - lysogenic pathway, which is when they insert their DNA into the host DNA so it replicates every time the host cell divides(this is called a provirus). and Lytic pathway, which is the genetic material is replicated independently of the host DNA straight after entering the host.
-what are retroviruses - viruses which have genetic RNA and reverse transcriptase.

**obviously I'm not saying this will come up for certain, but I think that they are some topics/questions which haven't been asked in recent papers Good Luck everyone

lol should I call it a coincidence? :P okay u explain it to me?

Brad0440 explained it really well:

There are three stages that follow the initial infection:

The acute phase:
-HIV antibodies appear in the blood (after 3-12 weeks)
-The virus enters and destroys T-helper cells to replicate, causing a net loss of T-helper cells and an increase in HIV
-A few weeks after the initial infection, the T-killer cells recognise and destroy infected T-helper cells

The chronic/latent phase:
-The action of T-killer cells keeps in check the number of HIV in the body, but cannot completely eliminate them
-During this phase, opportunistic diseases (like TB) can reactivate and other illnesses like colds can take longer to get over than normally, due to a decreased immune system

The disease phase:
Eventually, the number of HIV in the body overwhelms the immune system and causes the T-helper cell count to drop dramatically, severely damaging the immune system and indicating the onset of AIDS

what exam board are you doing?
whatever you've mentioned has NOTHING to do with the edexcel syllabus

I completely agree

thank you! i got so worried and then realized i actually have nothing to worry about.
i have NEVER seen that in the past papers or in any past syllabus!
STOP SCARING ME RIGHT BEFORE MY EXAM

This is a good basic explanation but what i was looking forward was explaining in detail the whole mechanism including receptors and bacteria involved and how HIV invade the normal cell?

Do you know where i can find some past paper questions from old syllabuses? Ive done all the past papers twice

tbh, i've only done new syllabus papers. i would advise you not to do past ones as they might be slightly different and you don't want to get confused end minute.
and if you've gone through them twice, that's fine... don't stress last minute!

Do you know where i can find some past paper questions from old syllabuses? Ive done all the past papers twice