Wrong Qs- L6th EOY Flashcards
(13 cards)
Describe an explains one other process (not a mutation) which may result in an increase in genetic diversity (4 marks):
- species may interbreed with one another to produce offspring which may result in variation
- independent segregation of homologous chromosomes
- crossing over of chromatids
- random fertilisation of gametes- produces a new combination of gametes
Descibr an explain the processes that occur during meiosis that increase genetic variation (5 marks):
- Homologous chromosomes pair up
- Independent segregation of chromosomes
- Maternal + paternal chromosomes are shuffled into any combination
- Crossing over leads to exchange of parts of non-sister chromatids between homologous chromosomes
- Both create new combinations of alleles
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the right aorta (5 marks):
- Atrium has a higher pressure than the ventricles- causing AV valves to open
- Ventricle has higher pressure than atrium, causing AV valves to close
- Ventricle has higher pressure than aorta, causing SL valves to open
- higher pressure in aorta than ventricle causing SL valves to close
- Muscle contraction causes increase in pressure
Describe the role of haemoglobin in the loading, transport and unloading of oxygen (5 marks):
- He loads/ binds to oxygen in the lungs
- At high partial pressure of oxygen
- Binding of an oxygen molecule to Hb makes binding of another molecule of oxygen easier
- Oxygen transported as oxyhemoglobin in red blood cells
- Hb unloads/ dissociates oxygen in respiring cells/ tissues
- At low partial pressures of oxygen
Explain of tissue fluid is formed and how it may be returned to the circulatory system (6 marks):
- Hydrostatic pressure of blood high at arterial end
- Fluid/ water soluble molecules lass out
- Proteins/ large molecules remain
- Lowers the water potential/ becomes more negative
- Water moves back into venous end of capillary by osmosis/ diffusion
- Lymph system collects any excess tissue fluid which returns to blood/ circulatory system
Describe and explain 4 ways in which the structure of a capillary is adapted for its function (4 marks):
- permeable capillary wall/ membrane
- single cell thick- reduces diffusion distance
- flattened endothelial cells, reduces diffusion distance
- fenestrations- allows large molecules through
Describe how populations of Nm can become resistant to antibiotics (4 marks):
- Mutation occurs
- Results in cell with allele for resistance to antibiotic
- Cell survives and passes the allele for resistance to offspring
- Process repeated with different genes conferring resistance to each of the other two antibiotics
Describe what happens to chromosomes in meiosis (6 marks)
- Chromosomes condense
- Chromosomes associate in their homologous pairs
- Crossing over can occur
- Join spindle fibres
- At equator
- By centromere
- Homologous chromosomes move to opposite poles
- Separation of pairs of sister chromatids in 2nd division
How to reduce uncertainty (1 mark):
Use an instrument with smaller increments
Why would a calorimeter improve repeatability? (1 mark)
Standardises the method
Why is it not possible to determine the identity of the structures labelled x using an optical microscope? (2 marks)
- wavelength of light too long
- not a high enough resolution
Describe the role of one named organelle in digesting bacteria (3 marks):
- lysosomes
- fuse with vesicles
- release hydrolytic enzymes
What is a null hypothesis?
No significance between observed and expected data, results are down to chance
