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OCR Biology A Exam Thread (Breadth - May 26, 2016 and Depth - June 7, 2016)

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Ahh, I'm sure you will be fine. I hope they dont ask some stupid 6 marker about a biosensor or how to use colorimetry to find out how much glucose there is in a solution :frown:

We still have a good 2 hours maybe go over it.. Heck I just learnt the cardiac cycle today thanks to the help of users on here :smile:

Reply 1201

KappaRoss

i wonder how easy it is so cheat in a exam :3. i have never tried

Reply 1202

SultanOE

Can someone explain the T-Test for me please? I get the values of x1, s1 and n1 but no idea how to achieve x2, s2 and n2

Reply 1203

Carrot_Cake_13

@4nonymous

Ahh wait you were talking about the left side of the heart right. So that the blood is pushed out of the ventricle thru the semi lunar valves to the aorta and then into the arteries.

Reply 1204

KappaRoss

Original post by SultanOE

Can someone explain the T-Test for me please? I get the values of x1, s1 and n1 but no idea how to achieve x2, s2 and n2

im pretty sure this is standard deviation. in that case the formula can vary, use the one they give you in the exam.
if you have the purple OCR endorsed text book turn to page 312 it has an example there you might find useful

Reply 1205

4nonymous

Original post by Carrot_Cake_13

@4nonymous

Ahh wait you were talking about the left side of the heart right. So that the blood is pushed out of the ventricle thru the semi lunar valves to the aorta and then into the arteries.

No it applies to both left and right. I'm explaining it in reply to your other post just give me a sec.

Reply 1206

4nonymous

Original post by Carrot_Cake_13

@4nonymous Sorry to be more of a hassle.. Could you explain the blood flows into the arteries and out of the heart bit. I remember something on the pulmonary artery being the only vessel to carry deoxygenated blood? Idk whether that's true though..

The pulmonary artery is the only ARTERY that carries deoxygenated blood.

Here's what you need to know:
In general Arteries carry oxgygenated blood, veins carry deoxygenated blood
The only exception is the pulmonary artery and pulmonary vein which are the opposite to this rule
Arteries carry blood away from the heart. Veins carry to the heart.
Capillaries is where gas exchange takes place so can be oxygenated or deoxygenated

During diastole, blood enters the atria from the pulmonary vein(left side of heart) and vena cava (right side of heart. there are 2 of these - inferior and superior). These are both veins.
The vena cava carries deoxygenated (remember the rule) as blood is coming from the body to the heart.
The pulmonary vein carries oxygenated blood as blood is coming from the lungs back to the heart so has got oxygen (this is one of the exceptions I mentioned above)
Notice how both of these carry blood to the heart as they are veins.

During ventricular systole blood flows into the aorta (left side) and pulmonary artery (right side). These are both arteries.
The aorta carries oxygenated (again remember the rule) and carries it out of the heart to the rest of the body.
The pulmonary artery carries deoxygenated(other exception to the rule) as the blood has come from the vena cava and is deoxygenated do the pulmonary artery takes it AWAY from the heart to the lungs.

Hope this helps :smile:

Ask if you're still confused.

Reply 1207

Carrot_Cake_13

Thank you once again!! I understand the complete cycle now. Erm for meiosis is the independent assortments just the crossing over of the bi-valent chromosomes?

Reply 1208

mahmzo

Hello! Fellow Biology students. I am an OCR A Physics student and was wondering after your exam has finished. Could tell me how the depth paper was compared to the breadth. (Were there repeated topics, how many experiments.) and in general if it was harder or easier.

Kind regards,

From the other side of Science :P

Good luck guys!!!!

Reply 1209

bluesandgreens

Original post by alevelnerd123

Is transpiration this?

Transpiration is the loss of water from the stomata. Water is able to enter the plant as the plant has a higher solute concentration than the surrounding dirt, meaning the dirt will have a higher water conc compared to plant and the water can move in by osmosis. Once in the plant, it will move through either the apoplast pathway (cell walls and intercellular spaces) or by the symplast pathway (continuous cytoplasm) either way once the pathway's reach the endodermis there is a layer of suberin (casparian strip) which blocks the water from entering the xylem in the apoplast. So water in apoplast moves to symplast. There is a continuous flow of water going UP the xylem due to the strong cohesive forces between water molecules. Once the water evaporates from the mesophyll layer the water will leave the plant through the stomata, lowering the water potential meaning water can continuously move by osmosis into the mesophyll cell. And then I would talk about the stomato being open more in the day-time etc..

Or have I gone into too much detail?

It's not necessarily from the stomata its from the surface of the plant and dont forget its a side effect of gas exchange

(edited 7 years ago)

Reply 1210

username1292215

Differences between meiosis and mitosis?

Reply 1211

Desouza123

Original post by SuperHuman98

Differences between meiosis and mitosis?

-2 daughter cells produced in mitosis, 4 in meiosis
-daughter cells are genetically identical to parent cells in mitosis whereas cells produced in meiosis show genetic variation
-Daughter cells are genetically identical to each other in mitosis whereas in meiosis they show variation

Reply 1212

4nonymous

Original post by Carrot_Cake_13

Thank you once again!! I understand the complete cycle now. Erm for meiosis is the independent assortments just the crossing over of the bi-valent chromosomes?

No they are 2 different things.
Crossing over of the bi-valent chromosomes shuffles the alleles.
Independent assortments is the random distribution of the maternal and paternal chromosomes of each pair.

Also, for the cardiac cycle I forgot to mention as a tip its probably a good idea to mention the blood vessels through which blood enters and leaves the heart.

Reply 1213

lubna1998

Can anyone explain how you'd interpret results from a t test please? As in how you'd compare it with the p value and when you'd reject the null hypothesis etc.

Original post by mahmzo

Thanks for the luck :smile:

PM me later so I don't forget to say how it went :tongue:

Reply 1214

4nonymous

Original post by lubna1998

Can anyone explain how you'd interpret results from a t test please? As in how you'd compare it with the p value and when you'd reject the null hypothesis etc.

When you have an answer for t you want to compare it in the given table. You need to always look at the p value of 0.05 (just ignore the others, IDK why but for biology you use this). Then you want to calculate the degrees of freedom= (n-1)+(n-1) where n is the number of data that you have. This will also be in the table and then you choose the value which is equal to both of those values. So for example, if your degrees of freedom is 26 and p=0.05 look across here and see where they meet. Then using that value there and your answer you can work out if the null hypothesis should be rejected.

If your t value is much greater then the two areas/habitats (whatever is being tested) are significantly different due to a biological factor and not due to chance
In this case you reject the null hypothesis.

Thats all you need to know.

Reply 1215

Rectum_resizer

Is the exam tomorrow or what?

Reply 1216

4nonymous

Original post by rectum_resizer

is the exam tomorrow or what?

lol its today

Reply 1217

sugi10

Original post by JStebz

Tachycardia is when your heart rate is too fast (eg 100bpm)
Bradycardia is when your heart rate is too slow
Ectopic heart beats are when the heart beats too early, followed by a long pause
Fibrillation is when there is an irregularly timed heart beat

and that's all you need to know

Thank you so much