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OCR A-level Biology A Biological diversity - 13th June 2019 Unofficial Markscheme

Define osmosis : the process by which water moves across partially permeable membranes down a water potential gradient

Why is osmosis important for the shape of plants

Water moves into cells down a water potential gradient this Increases hydrostatic pressure on cell wall in cell maintaining turgidity. This allows stomata to open only when turgid. Without osmosis plant cells would be flaccid and would not keep the plants shape.

Solution level increased inside capillary tube X . What can be said about the composition of tube X and Tube Y and explain why?

Tube Y is hypotonic (more dilute and higher water potential than X. Therefore water moves in by osmosis down a diffusion gradient into X as X is hypertonic (lower water potential less dilute than Y ) until equilibrium is met.

Explain different levels in biodiversity or something
Species diversity
Habitat biodiversity
Genetic diversity
Go on to talk about species evenness and the effects of low species evenness , few dominant species , specific adaptations , lower genetic diversity resulting in a lesser ability to adapt to environment. Visa Versa

Explain the process of coppicing and how it increases biodiversity

Cut trees low down but do not remove them from the ground provides a sustainable way on obtaining timber etc etc Rotational coppicing
More light to the ground of woodland more access to light more photosynthesis . Plants grow this provides more habitats this increases habitat diversity and species biodiversity of plants . Habitats becomes more available so more species move in increasing species diversity as there are more places to live. This in turn increases genetic diversity leading to more resistance to disease etc etc

Importance of water density for living organisms
- insulating layer as when water freezes it’s less dense than liquid
- temperature buffer - high specific heat capacity
- coolant high latent heat of evaporation.

DNA purification forgot to revise lol


Last Q about try tryglycerides
2 marks explain hydrolysis
Tryglycerides has 1 glycerol
3 fatty acids with ester linkages
Hydrolysis reactions breaks the ester linkages using water to produce 3 fatty acids and 1 glycerol

Why did they use percentage change
Because they kept surface area the same that does not necessarily mean the same mass
. Makes results more comparable.

How did tourists increase biodiversity
Increase funding for conservation groups and local people to contribute to the ecosystem.
Funding allows them to restore ecosystems and therefore increase habitat and species biodiversity

Why is dolly the sheep not the same as the tadpole

- embryo is implanted into surrogate mother
- here it just becomes a tadpole then a frog

0.69 for simpsonis, and 45.3% for hardy weinberg

Why does gene therapy not work to cure Huntington’s disease
Gene therapy does not work for Huntington’s Huntington’s disease in genetically inherited, in order to cure it germ line therapy must take place which is illegal

Addition of a gene would alter other genes

A gene could be inserted into another gene making the original gene non functioning

Control variable of pregnancies

- type of mouse , monkey , sheep should be the same As the have different reproductive potential
Same conditions for each individual within each type of animal ie same heat food water
- same number of original pregnancies

6 marker on plant fertilisation validity

- Control temperature , ph of soil , light exposure , humidity,
- Keep the concentration of fertiliser the same and add equal volumes at regular intervals over a period of time
- Repeat the process at least 3 times this allows us to identify anomalies and disregard them and calculate a mean and therefore a statistical test such as the T test
- Make sure both plants have the same surface area of leaves at first to reduce affect of transpiration


Which one has the highest sucrose concentration
Courgette as the concentration of sucrose increases from 0 to 0.7. The percentage change in mass decreases the least. This means that water is moving via osmosis down a water potential gradient into courgette at the slowest rate or something like that I’m weird lol

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Please write the answers to the question you remember! OCR PAPER 2
(edited 4 years ago)
Original post by Sara saeed
Please write the answers to the question you remember!


What exam board is this for?
Original post by Evil Homer
What exam board is this for?


OCR
Reply 4
What did people put for cloning/vegetative propagation?
Cut from shoot tip - explant
Sterelise to kill micro organisms
Grows into a callus
Seperate and Re plant into greenhouse
Original post by 12kirn
What did people put for cloning/vegetative propagation?
It never asked about the process for that it asked about the advantages. It asked about the process for plant cuttings.
Original post by Rosiepointon5
Cut from shoot tip - explant
Sterelise to kill micro organisms
Grows into a callus
Seperate and Re plant into greenhouse
Original post by KaasimAnwarr
It never asked about the process for that it asked about the advantages. It asked about the process for plant cuttings.

Nope. The first question was how to carry out the process and the advantages question was after that.
The advantages for vegetative propagation I put were that you get many clones per plant and that you can choose desirable characteristics.

The process for plant cuttings is cutting a section off the plant (I.e. stem- I also mentioned that you cut between leaf joints). Then dip the base in rooting hormone/powder. Root grows and plant develops, etc
Original post by KaasimAnwarr
It never asked about the process for that it asked about the advantages. It asked about the process for plant cuttings.
I don’t remember that, does anyone else?
Original post by y.u.mad.bro?
Nope. The first question was how to carry out the process and the advantages question was after that.
what did you guys get for the multiple choice question on hox genes, i wasn't sure between the two options. One said that the sequence varies between taxonomic levels, produced transcription factors and mutations were random, the other said that the sequence was similar between animals, produced polypeptides and caused lethal mutations. Am not sure which one
I think I wrote about it being lethal
Original post by nicholasflee
what did you guys get for the multiple choice question on hox genes, i wasn't sure between the two options. One said that the sequence varies between taxonomic levels, produced transcription factors and mutations were random, the other said that the sequence was similar between animals, produced polypeptides and caused lethal mutations. Am not sure which one
Well ticked that one, not wrote about it😅
Original post by KaasimAnwarr
I think I wrote about it being lethal
Reply 13
Yhh that question was there
Original post by KaasimAnwarr
I don’t remember that, does anyone else?
What did it ask exactly? I’m sure there was one on plant cuttings because people from my college remembered it too. I’m don’t remember the exact question?
Original post by Kodyyy
Yhh that question was there
I*
Original post by KaasimAnwarr
What did it ask exactly? I’m sure there was one on plant cuttings because people from my college remembered it too. I’m don’t remember the exact question?
Original post by KaasimAnwarr
I think I wrote about it being lethal

don't hox genes make transcription factors?
Did anyone else get 0.6 something for Simpsons Diversity index and 45.3 (D I think) for hardy Weinberg??
What did everyone get for the hardy Weinberg Mcq
I wasn’t confident about that so I might’ve gotten it wrong tbh

Original post by nicholasflee
don't hox genes make transcription factors?

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