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