OCR A-Level Biology Paper 3 17th June 2019 - Unified Biology [Unofficial Markscheme]

i got that too i think

I couldn't find a thread for today's paper and I am really curious what y'all put for your answers.

Tbh for the 6 marker I wrote that environmental factors that lead to a weaker immune response are things like immune suppressant drugs, HIV, diet. Strong immune response would be things like vaccination.

For genetics I wrote about inherited illnesses e.g cystic fibrosis, ethnicity, diabetes I.

Plant Cell - Air Gaps and Nucleus
Diagram - Don't Shade and Connect Lines?

Immune System effected by genes and environment -
Genes:
- Sickle Cell Anemia prevents Malaria
- Autoimmune Disease?
Environment:
-Social factors can effect transmission of communicable diseases like HIV, can be prevented by good healthcare and education
- Living conditions, TB can infect alot of people crowded together in small spaces
- Climate, Malaria ideal in tropical regions as ideal for mosquitoes which are malaria vectors.

Advantages of Microorganisms -
- Can grow in waste making helping environment and cheap source of food for the microorganisms
- Animals take alot of resources and time, Microorganisms don't
- Take up less space for more produce
- Vegitarian option?

Cells Calc. - 50
Fill Gaps - Vectors and Spores

The first answer was Permanent vacuole.

For the radius question do you not have to times by 2 to get the diameter

For the 6 marker on immunity. I believe you are supposed to talk about natural and artificial, active and passive immunity. So for example natural, passive immunity is only determined by genes and leads to individual being immune to disease due to inheritance of antibodies directly from mother via breastfeeding. Artificial passive immunity is determined only be environment. Artificial active immunity (vaccines) is determined by both environmental and genetic factors. As environmental cuz you are receiving it not naturally. But genetic due to body natural response to produce memory cells.

I did. I got 1.6 and no

I said something about hypothermia below optimum conditions for enzymes so less heat generated and therefore body continues to cool down.

Think there will be a wide variety of answers. some people just talked about humoral vs cell-mediated which is completely wrong.

Lol when people are talking about what answer they got for the dilution and arguing between 5 and 50 and you got 174. Smashed it.

Question 1: Permanent vacuole, Nucleolus, x14000, Magnification not stated, use continuous lines only, no title, no shading etc.
Some other questions I remember
Staining question.
Naked moles body temp is similar to the environment, not the same for most mammals,

Using the mean is more valid because it takes into account the extreme values. Median and mode disregard extreme values and so not all of the data is used hence not as accurate? (Not entirely sure)

Use Unpaired Students T Test to compare the means and see if the difference between the values is significant or not.
Anitbodies usually have 2 binding sites not 3, antibodies have 2 light polypeptide chains not 3? (not sure about the 2nd point)
0.79 for the length of the cell which is < 1 so the organism can rely on diffusion alone.

50 colonies (not sure if its 50 or 5)
Second to last question: Suggest why the student's estimate of the colonies is inaccurate or something?
Last question: Vector, Spores

I did. I got 1.6 and no

I'm so glad it did that felt the questions was too easy to make it 0.8

For the mean one I put the mode. Using the mean didn't seems right because the result for the same temperature was measured 5 times. Yet there was such a huge difference between the lowest and highest. I assumed that was due to mistakes the student made.