BIOL4 Biology Unit 4 Exam - 13th June 2011

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Could someone outline eutrophication for me(and for yourself as revision of course)

What I got down here is;

1. Leaching of inorganic fertiliser into lake/river
2. Algae grows rapidly
3. Algae die but there's so much of it that bacteria strive as they decompose the algae
4. Bacteria use up oxygen in water, oxygen concentration decreases
5. Fish and aerobic organisms die due to low oxygen concentration
6. bacteria decompose detritus, reducing the oxygen concentration even more
7. random thought 'anaerobic bacteria infest the water possibly?'

I would go with :

1) Leaching of water-soluble inorganic fertiliser allows algae to grow. Algal blooms occur.
2) This blocks out sunlight, thus not allowing plants to photosynthesise and they die.
3) Saprobiotic micro-organisms or decomposers digest on this dead material, and to do they need energy and so respirate. They use up o2 dissolved in the water
4) Fish die, and anaerobic micro-organisms then can survive, releasing toxins/hydrogen sulfide which kills more fish/plants.

Hope that helps :smile:

Reply 501

INeedToRevise

Original post by Stratos

Could someone outline eutrophication for me(and for yourself as revision of course)

What I got down here is;

1. Leaching of inorganic fertiliser into lake/river
2. Algae grows rapidly
3. Algae grow at the surface and so become densely populated killing plants and algae at lower levels because of lack of lightAlgae die but there's so much of it that bacteria strive as they decompose the algae
4. Leads to an increase in saprobiotic microorganics which feed on dead material however they create a demand for oxygenBacteria use up oxygen in water, oxygen concentration decreases
5. Fish and aerobic organisms die due to low oxygen concentration
6. bacteria decompose detritus, reducing the oxygen concentration even more
7. random thought 'anaerobic bacteria infest the water possibly?'Yeah, anaerobic bacteria increase due to less competition from aerobic bateria but they decompose releasing more nitrates and toxic waste making water putrid.

Made a few corrections in bold.

Reply 502

Rickesh

Out of 75 what is roughly an A?
Let's get some questions rolling....
What is meant by co-dominance?

Reply 503

SK-mar

Original post by Stratos

- soluble nitrates from fertiliser are leached into nearby water source (eg. pond or river)
- nitrates stimulate algal growth and an algal bloom occurs on the surface of the water
- this prevents light from reaching plants below, so they die as they are not able to photosynthesis
- microorganisms digest the dead organic matter and in doing so aerobically respire, removing oxygen from the water
- the increase in respiring microorganisms leads to a decrease in the dissolved oxygen levels in the water
- fish and other aquatic organisms cannot respire sufficiently due to the lack of dissolved oxygen and so die
- anaerobic organisms increase as there is no competition. they feed on the dead matter and in doing so produce nitrates and toxic waste.

Reply 504

Stratos

Thanks for the corrections guys I feel confident on eutrophication now ^__^.

Reply 505

kingsmod1

Original post by Thepupil

If it asks about population or genotype then its p or q squared. Think it as the genotype/population have the alleles already and say R/r is your alleles. RR = p squared and rr = q squared.

If it's asking about allele frequency its on about p + q = 1 and it is not squared.

If they ask about genotype/populations its going to ask about heterozygous genotypes :smile:

cheers mate

Reply 506

kingsmod1

chap 8 i find the hardest, dont kno about u lot?

Reply 507

INeedToRevise

Original post by Rickesh

Out of 75 what is roughly an A?
Let's get some questions rolling....
What is meant by co-dominance?

Alleles are equally dominant and both are present and expressed in the phenotype..

Question: Describe nitrogen fixation :smile:

Reply 508

BioFurMatPhyStudent

Original post by Rickesh

Out of 75 what is roughly an A?
Let's get some questions rolling....
What is meant by co-dominance?

http://store.aqa.org.uk/over/stat_pdf/AQA-A-LEVEL-GDE-BOUND-JAN11.PDF
http://store.aqa.org.uk/over/stat_pdf/AQA-A-LEVEL-AND-AS-NEW-GDE-BOUND-JAN10.PDF

Hope this helps :smile:

Codominance - both alleles are expressed in the phenotype

Reply 509

SK-mar

Original post by Thisisj

hi can you please explain 5b on the jan 2011 paper :smile:

pleaseeeeeeeeeeeeeeeeeeeeeee

use the equation:

net = gross - respiratory losses

then re-arrange to get, gross = net + respiratory losses.

on the graph the net rate for medium light intensity at 20 degrees is around 2.4

then look at the straight line below the light intensity lines (this refers to the respiration rate) ..... now read off the graph its value at 20 degrees, but remember to read from the left hand sides graduations as they are the ones relevant to respiration. it should read around 0.35 .... so the anwer is around 2.75

Reply 510

SK-mar

Original post by INeedToRevise

Alleles are equally dominant and both are present and expressed in the phenotype..

Question: Describe nitrogen fixation :smile:

nitrogen fixing bacteria (eg. rhizobium) convert nitrogen gas in the atmosphere into ammonia. they form a mutualistic relationship with plants by providing them and the ecosystem with usable nitrogen, and in turn the plants give them carbohydrates.

Reply 511

kingsmod1

Original post by SK-mar

knew the formula, still flopped it

i hope hardy equation comes up again lol

Reply 512

tehsponge

Original post by Rickesh

Out of 75 what is roughly an A?
Let's get some questions rolling....
What is meant by co-dominance?

Probably no more than 60% raw marks, but that depends on the paper really.
Codominance- when neither allele is dominant or recessive, so both are expressed in the phenotype usually as a mixture e.g. pink flowers from codominant red and white colour alleles.

Reply 513

SK-mar

Original post by kingsmod1

knew the formula, still flopped it

i hope hardy equation comes up again lol

don't worry i flopped it the first time too, its frustrating when you realise how you went wrong though! Yeh i hope hardy comes up, but i hope its a decent question. i sometimes get confused with hardy but fingers crossed for tomorrow!

Reply 514

Abby :)

Hoping hardy weinberg equation dosnt come up again, i can NOT do it to saave my life. Hahahaha

Reply 515

Stratos

Questions I want to come up; photosynthesis, respiration, succession, carbon cycle, nitrogen cycle, anything to do with genetics and eutrophication, If I get those questions it will be a guarantee A, anything to do with the more annoying part of ecology= :colonhash:

Reply 516

proud nd luvin it

Original post by INeedToRevise

Alleles are equally dominant and both are present and expressed in the phenotype..

Question: Describe nitrogen fixation :smile:

Nitrogen fixation is a way that nitrogen in the atmosphere becomes available to plants. Nitrogen fixing bacteria in the soil, convert the nitrogen in the atmosphere into ammonium ions. These are subsequently oxidised by nitrifying bacteria to nitrites, and again to nitrates, which can be actively transported into the plants' roots.

Alternatively, some plants, such as legumes, have nitrogen-fixing nodules on their roots, allowing the plants to get the nitrates they require :smile:

Reply 517

Thisisj

Original post by SK-mar

Yhh i got this wrong in jan .. i get it now though , thankyou.

Reply 518

tehsponge

Original post by Stratos

Apart from succession, same for me. I find succession so fiddly to talk about. If chapter 5 comes up, I'll cry my way through the questions.

Reply 519

Rickesh

Nitrogen fixation is when the nitrogen in the atmosphere is converted into, firstly nitrite ions by an oxidatio reaction, then into nitrate ions again through oxidation. The nitrifying bacteria do this reaction, in aerobic conditions. Or some bacteria live in the roots of plants in nodules, they give the plant nitrate ions, for growth and the plant must give the bacteria carbohydrates in a mutualisitc relationship.
Is that right?