AQA BIOL4 ~ 11th June 2013 ~ A2 Biology

Can someone summarise chapter 8.6 Selection for me please

Are enzymes involved in light dependent?

Questions!

Name the products of 1 krebs cycle (3)
When a field floods, nitrate concentration in the soil decreases, explain why (2)
Explain why a farmer may choose to use a pesticide rather than a biological agent (2)
Explain why modern farming practices increase productivity (5)
What is the equation for mark, release, recapture (1)
Name 2 methods of conservation (2)
State and explain the two types of succession (4)
Explain why increasing the temperature will have little effect on the light dependent reaction (2)
XNPT is a drug that inhibits ATP synthase explain why less ATP was produced when XNPT was used (2)
Describe and explain two processes that can reduce genetic diversity (4)
Explain why CO2 concentration is higher in the night(2)
Name a process in which CO2 is released into the atmosphere (1)


Out of 30! Go :-)

Selection = Process where better adapted organisms survive and breed, thus passing on favourable alleles to the next generation

Directional Selection = Selection towards one extreme of a phenotype, usually when something happens in the environment
So like longer fur is selected for due to a decrease in temperature

Stabilising Selection = Favours mean of phenotype, usually when environment is constant
So of a population of mice, the mean of ear size is 5 cm, if the environmental conditions are constant there will be more mice with this ear size and less mice with the longest and shortest ear size - stabilising usually makes the extremes, less extreme :P

just always remember to talk in terms of alleles being passed on that are responsible for a favourable phenotype (allele is usually needed in the answer from the latest mark schemes)

Selection = Process where better adapted organisms survive and breed, thus passing on favourable alleles to the next generation

Directional Selection = Selection towards one extreme of a phenotype, usually when something happens in the environment
So like longer fur is selected for due to a decrease in temperature

Stabilising Selection = Favours mean of phenotype, usually when environment is constant
So of a population of mice, the mean of ear size is 5 cm, if the environmental conditions are constant there will be more mice with this ear size and less mice with the longest and shortest ear size - stabilising usually makes the extremes, less extreme :P

just always remember to talk in terms of alleles being passed on that are responsible for a favourable phenotype (allele is usually needed in the answer from the latest mark schemes)

Hey, could anyone tell my why plant growth would decrease at higher temperatures? Thanks in advance

So I realise this has been asked before but: Advantages and disadvantages of artificial fertlisers? Might as well throw in natural too.

So with natural there is less leaching and it aerates the soil/acts as a soil conditioner, has a wider range of elements and is cheaper to produce (as is produced on-site by animals excreting etc). However it takes a long time to break down and release its nutrients (is that right?) and what else? is it less efficient as it is less concentrated?

Artificial fertilisers the only disadvantages I can think of is that they are expensive and cause leaching and eutrophication...what else? And what are the advantages?

edit: oh yeah reduced species diversity with nitrogen fertilisers too as it favours the growth of rapidly growing species like grasses and nettles

Name the products of 1 krebs cycle (3)
Reduced NAD; ATP and CO2 (also a-ketoglutaric acid which is an important intermediate molecule from which plants can synthesise amino acids)

When a field floods, nitrate concentration in the soil decreases, explain why (2)
Nitrates dissolve in the rainwater and are leached from the soil
Anaerobic conditions allow denitrifying bacteria to convert nitrates to atmospheric nitrogen

Explain why a farmer may choose to use a pesticide rather than a biological agent (2)
Pesticides are quicker acting
Biological control does not completely remove the pest species

Explain why modern farming practices increase productivity (5)
Animals are kept indoors in heated environments to reduce the amount of energy they have to expend in maintaining their body temperature, increasing the amount of energy converted into biomass; movement may be restricted so as to reduce the rate of respiration; animals fed concentrate diets which are more easily digested to reduce the amount of energy lost in the faeces; animals and plants selectively bred for maximum productivity/genetically modified; fertilisers applied to plants to provide nitrates for protein synthesis; fields irrigated so as water availability is not a limiting factor in photosynthesis; pest control removes species which eat or harm the crop, increasing productivity; herbicides remove weeds which compete with the crop and reduce the resources available to the crop.

What is the equation for mark, release, recapture (1)
Number in 1st sample * Number in second sample / Number of marked in second sample
Name 2 methods of conservation (2)
Grazing
Mechanical removal of invasive species

State and explain the two types of succession (4)
Primary succession occurs when an area has not previously been inhabited; a pioneer species is the first species to become established and changes the environment, making it more favourable to more species.
Secondary succession occurs when an area has been previously inhabited but the habitat has been destroyed such as by fire, removing all species.

Explain why increasing the temperature will have little effect on the light dependent reaction (2)
The light dependent reactions are not enzyme mediated and so temperature has no effect

XNPT is a drug that inhibits ATP synthase explain why less ATP was produced when XNPT was used (2)
As ATP synthase was inhibited less enzyme-substrate complexes formed between ATP synthase and ADP/Pi, as a result less ATP was produced per unit time

Describe and explain two processes that can reduce genetic diversity (4)
A genetic bottle-neck such as a natural disaster which kills most of the individuals of a species will reduce genetic diversity as few organisms remain to reproduce, and so the gene pool is small.
Selective breeding of a plant or animal will reduce the genetic diversity as certain traits are selectively bred for, reducing the frequency of phenotypes and therefore genotypes.

Explain why CO2 concentration is higher in the night(2)
At night no photosynthesis occurs as it is dark, so no CO2 is absorbed by plants, however plants and animals continue to respire, producing CO2, therefore the concentration of CO2 increases.

Name a process in which CO2 is released into the atmosphere (1)
Respiration

Are enzymes involved in light dependent?

please please please can you help explain what the difference between gross production, gross productivity, net production, and net productivity is?? :'(

Had anyone worked out what has come up in the past papers and therefore what won't/will come up?
Would be interesting!

Yes, ATPase

Dis: too much in concentration cause osmotic damage to plants?

Yes, ATPase

Ah yeah that's a good one cheers!

Anybody got anything for the advantages of artificial fertilisers?

It's almost impossible to predict, but looking at January's paper, neither succession nor the carbon cycle came up, so perhaps expect those. Also in general they haven't really asked much about global warming or conservation management, so those topics could come up, too

P.S. sorry for the multiple posts, I couldn't work out how to multi-quote! :\