In today's video, I'm going to be answering this specimen paper.
It's an Edexcel 9-1 Biology Paper 2 specimen, and we're going to be doing a complete walkthrough,
so I'll be writing the answers.
(reading visual aid 1a.i)
So, if you don't know the answer straight away, let's start by labelling the various chambers.
So this is going to be the left atrium ...
because remember, it's switched around to the way in which you think is.
This is going to be the left ventricle.
That's my cat apparently geting her own food.
This is the right atrium.
And this is the right ventricle.
And just remember for me that the right-hand side deals with deoxygenated blood.
So it receives the deoxygenated blood from the body -
so here ...
And then it takes that deoxygenated blood to the lungs for oxygenation.
And then looking on the other side,
we can see that Z will be receiving oxygenated blood ...
from the lungs ...
and it will be taking that oxygenated  blood around the body.
So that's a brief summary of the heart.
So, vessel X, we can see -
I've said it's the right-hand side, which means it's deoxygenated,
and it's going to the lungs.
So which option is that? Well, it's B.
And I'm just going to make my nib a bit fatter because that's a bit skinny.
(reading visual aid 1a.ii)
And as you can see from my diagram -
we can see that the left ventricle is going to deposit ...
blood into the aorta, which travels around the body
delivering oxygenated blood, which means that the left ventricle has to pump at a high pressure
in order to deliver that blood around the body,
whereas if you compare the wall of the right ventricle over here -
well, that blood's only going to the lungs,
and the heart sits very close to the lungs, so the blood doesn't have to travel as far.
So really, the left ventricle is thicker so it can pump the blood further and at higher pressure.
(reading visual aid 1a.iii)
So they've shown us where the bicuspid valve is; it sits here.
So, can you see that blood which should be travelling upwards to the aorta, which is vessel Y,
around the body,
that blood won't be stopped from going backwards into the atrium,
so it'll end up with the blood basically shunting backwards ...
and therefore less oxygenated blood would be pumped around the body?
So that would be quite disastrous.
So, first of all, state that blood would flow backwards.
And state exactly where it travels to and from.
(reading visual aid 1b)
So hopefully you can see that this is a cross-section.
This middle chunk is the lumen, which is where the blood travels through.
Here you have thick muscle and elastic fibre walls.
Now, because the lumen is fairly narrow,
especially when compared with the thick walls,
this means that it must be an artery.
So when it comes to answering the question
'Explain how the structure of this blood vessel is related to its function',
talk about the narrow lumen,
talk about the fact that it has thick muscle and elastic fibre walls
to withstand the high pressure of the blood found within.
(reading visual aid 1c)
So, as you look at it, you can see that it has a single ventricle and a single atrium,
whereas the diagram before showed the human heart as a structure containing two ventricles and two atria,
so our hearts are much more complicated.
We also have a double circulatory system,
which means that the blood travels twice into the heart for every once around the body.
Here you can see it -
just simply, the blood keeps circulating round and round through the capillaries to the heart,
through the capillaries and to the heart.
It also doesn't have any separation between the deoxygenated and oxygenated blood.
Obviously, the left-hand side of the human heart deals with oxygenated blood;
the right-hand side deals with deoxygenated blood.
So lots of differences to state.
So let's first of all state that the fish heart ...
has two chambers ...
whereas the human heart -
(cat meowing)
Lyra.
has four.
More detail - means that the fish heart ...
has one ventricle.
You can come in.
Come in.
Has one ventricle and one atrium ...
whereas ...
the human heart ...
has two ventricles ...
and two atria.
In the human heart ...
the oxygenated blood and deoxygenated blood is separated.
And then for the final point, state that human circulatory systems ...
are double ...
compared with the fish one, which is single.
That's a lot of detail here.
(reading visual aid 2)
So, with person 1, we can see after they fasted that their blood glucose levels have dropped to 5.4,
and then two hours after drinking 75 grams of glucose, they have a blood glucose level of 6.4.
With person 2, after drinking glucose, their blood glucose levels rocket to nine.
and then person 3 generally has elevated blood glucose levels.
(reading visual aid 2a.i)
So you're looking at these two numbers here,
and you can see that they're pretty similar ...
with person 2 having an only slightly higher blood glucose level.
(reading visual aid 2a.ii)
So make sure, again, we're looking at the right thing.
And you can see person 3 basically has almost double the amount of blood glucose.
So, really you're just saying what you see in the table.
Just make sure you're looking at the right numbers.
(reading visual aid 2a.iii)
Well, the hormone responsible for reducing blood glucose levels is insulin.
And type 1 diabetics are lacking the ability to actually meet this insulin.
(reading visual aid 2b.i)
So, describing means that we again look at what we can see in the table and just state it;
we don't need to explain it.
So, as you look at the table, you can see that the levels remain low up until day 14,
whereby they start increasing dramatically ...
and then they continue to rise to day 23, before dropping off at day 24.
So, progesterone levels ...
remain low ...
until day 14 ...
and then increase.
They continue to rise ...
up to day 23 ...
before dropping at day 24.
(reading visual aid 2b.ii)
And it's because ovulation will have occurred.
When ovulation occurs, it means that you have an egg released into the fallopian tube,
and it also means that you have the kind of husk left over from the egg being released,
which is called the corpus luteum.
And the corpus luteum is ...
responsible for producing the progesterone needed to maintain the uterus lining.
So, quite a lot of detail needed here.
So, first of all, state that at day 14 ...
ovulation occurred, which is the release of an egg.
The corpus luteum ...
produced ...
progesterone ...
in order to maintain the uterus lining.
So, you want to thicken the uterus lining, or maintain it, in order to support a potential pregnancy.
(reading visual aid 2b.iii)
Now, the reason I know this woman isn't pregnant is because between days 24 and 28,
her progesterone levels decrease.
Now, if she was pregnant, those progesterone levels would need to stay high
in order to make sure that that uterus lining stayed thick so it could actually support the growing embryo.
So the fact that it drops means that the uterus lining has been shed
due to a lack of fertilization.
So, we know this because the progesterone ...
levels ...
fall after day 23 ...
indicating ...
that no fertilization ...
has occurred ...
so there is no need ...
to maintain ...
the uterus lining.
(reading visual aid 3)
So, A and B, we're looking at 500 grams of compost, whereas C and D, we doubled the amount of compost.
Then we measured the volume of water retained,
and then we measured the mass of the compost after the water was added.
(reading visual aid 3a.i)
So we're looking here.
Remember, when we're doing percentage change ...
you need to do the change in mass -
you need to learn this equation -
over the original mass ...
and then because it's a percentage, we need to multiply our number by 100.
So, if you look at compost B, you can see that the original mass was 500 grams,
the final mass was 529 grams, so obviously that change is 29 grams.
The original mass was 500, and then we multiply it by 100 in order to turn it into a percentage.
So when you do 29 divided by 5, you get 5.8%.
(reading visual aid 3a.ii)
The crucial thing here is it's a hot summer, which means that transpiration rates -
so that's water loss from the leaves of the strawberry plant -
will be high.
So effectively, you want a compost which retains its moisture.
Now, you can't just look at these numbers and decide which compost has retained its moisture the best.
It's really annoying, but you're actually going to have to work out the percentage change
for every single compost.
So obviously we just did it for B and worked out that it was 5.8%.
If you were to do the same calculation for A ...
you'd be doing the change in mass -
so that would be 15 -
over the original mass, which is 500, and then times it by 100, and you'd get a percentage ...
which is 3%.
Do the same calculation for the numbers with C, and that would be 4.5%.
And for D, that would be 3.4%.
So as you actually look at these numbers,
you can see that the compost B held on to the most amount of water.
So let's say that now.
Compost B -
this is an awful lot of work for two marks  -
would be the best ...
as it retained ...
the highest percentage of water.
This is necessary ...
due to transpiration rates ...
being very high ...
in the hot sun.
(reading visual aid 3a.ii)
And really, the reason we had to calculate the percentage change in mass here
was because we weren't using the same starting masses for A, B, C, and D compost,
and how can you make a valid comparison if you're not comparing the same starting point?
So basically, you just need to write here: Use the same starting mass of compost.
(reading visual aid 3b.i)
So, when answering this question,
you need to fundamentally understand that all living organisms require water,
and that includes microorganisms.
The bacteria actually use the water to help dissolve their food.
So obviously, if you reduce the water content,
then you'll reduce the microorganism growth,
and that will help reduce the decay process and will ensure that the jam is preserved.
(reading visual aid 3b.ii)
So, that's heating to a very high temperature, and that's in order to kill pathogens.
It's the same reason why UHT works.
So that's ultra-high treated milk;
it's the stuff that sits in the supermarket that doesn't need to be in the fridge.
Because it's been heated to such a high temperature, those pathogens all get killed.
(reading visual aid 4a.i)
Let's have a look at these conditions.
'A was placed in a window with light from one direction only.'
This means that the seedlings will bend towards the light.
'B was placed in a cupboard with no light,' so they'll show poor growth ...
as they haven't been able to photosynthesize properly.
'Pot C was placed with light from above,' so you'd expect good growth in an upwards direction.
'Label the pots.'
Okay. So let's have a look at what agrees with what I just said.
So I said A would bend, which is why this one is A.
I said that B would show poor growth.
That's that one.
C would be growing well because the light's from above.
(reading visual aid 4a.ii)
So, in Pot A, they're bending towards the light, which means the tropism has to involve photo -
photo meaning light.
And it's a positive response to light; they're actually bending towards the light.
So it's positive phototropism.
That's D.
As with always these questions,
I always try and work out the answer before I confuse myself by looking at all the options.
(reading visual aid 4a.iii)
Those are auxins - simply a word you're going to have to remember.
(reading visual aid 4b)
At school, your teacher ought to have told you about Darwin's experiments with coleoptiles.
So, what he got were these coleoptiles, which are little wheat seedlings ...
and then he put them in different conditions.
So, some were allowed to grow ordinarily.
Some had a unidirectional light source, which meant they bent towards it.
And with other ones, he actually chopped off the tip ...
and dipped them in various substances, replaced the tip, and saw if there was any change in how the tip grew.
And so, really, we're trying to summarize that here.
So start by saying, remove ...
the tip ...
from a plant shoot.
And because we're making a comparison, we need to keep the second plant shoot intact.
And then lastly, measure the changes ...
in growth ...
and direction.
So see if these actually bent at all.
(reading visual aid 4c.i)
So, do try and remember for me that the waxy cuticle is there to prevent transpiration.
And remember, transpiration is water loss.
And fruits, such as lemons and oranges, which grow in particularly hot countries have very thick, waxy cuticles
to minimize water loss.
Also, use this diagram to help you and notice that the waxy cuticle actually surrounds the whole leaf.
So that will actually prevent water loss further.
(reading visual aid 4c.ii)
So, here are our transport vessels, phloem and xylem.
Xylem transports water, and that goes from the root upwards always like this.
Phloem transports sugar ...
and that's from the leaves ...
to everywhere else in the plant, so that's up and down the plant.
And this process of moving sugar is known as translocation.
So again, let's try and second-guess this answer.
So 'method of transport of sucrose through the plant' -
I know we're looking straight away at C and D.
And 'structure through which sucrose is transported' -
I just said that it was the phloem, which is why the answer here is D.
(reading visual aid 5a.i)
Using the equation they've given us then, so light intensity ...
equals 1 over (d squared) ...
which is therefore 1/25 centimetres squared.
When you put that into your calculator, you get a value which is 0.0016.
And make sure that it makes sense in terms of its size compared with all the other answers up here.
(reading visual aid 5a.ii)
So, describing, you're saying what you see.
So from the table,
you can see that as light intensity increases, the rate of photosynthesis increases.
And then as you actually get above 20 centimetres' distance away ...
if we have a look at the number of oxygen bubbles produced,
which will obviously be produced as a result of photosynthesis taking place,
the altering the light intensity doesn't really affect the amount of photosynthesis that takes place.
(reading visual aid 5a.iii)
So you could describe a piece of apparatus here which actually measures light intensity,
and that is called a light meter.
Pretty basic name, really.
(reading visual aid 5a.iv)
Yeah, this scientist, he's sensible, really,
because if you think about bubbles, some will be small some will be big,
and you're counting them as if they're all equal.
So really, you want a better, more accurate way of measuring volume.
What do you use in chemistry?
Well, you tend to use the gas syringe.
So, collect ...
oxygen bubbles ...
using a gas syringe ...
to give a more accurate ...
measurement of volume.
(reading visual aid 5b)
So, yeah, if you compare it to the table,
we're talking about a light intensity which is much lower than the ones we've seen in the experiment.
Now, light is essential for photosynthesis,
so if you remove that light, then you're really going to reduce the rate of photosynthesis ...
and therefore, fewer oxygen bubbles would be released.
(reading visual aid 6a)
First of all, a water bath is a great way of controlling the temperature,
because after all, our independent variable is the type of pea; it shouldn't be the temperature.
So we need a water bath to control the temperature.
Secondly, there are lots of enzymes involved in the process of respiration ...
and we need to try and provide them with the optimum temperature to actually ...
carry out the reactions involved in respiration.
So, a water bath ...
ensures that the temperature's kept constant.
And secondly, 25° provides the optimum temperature ...
for the enzymes involved in respiration.
(reading visual aid 6b)
So, for A ...
after 10 minutes, we have 0.8ml lost;
after 20 minutes, we have 1.6 ml lost;
after 30 minutes, we have (-2.4) ml,
so 2.4 ml lost.
Then we have the same for B's, but different set of results.
And then C, there were no changes in the oxygen levels.
'Complete the table for these results.'
This is quite a hard little task.
Let's start by listing the various different experiments,
so that's experiment A, experiment B, experiment C.
And then if you have a look here, we're comparing the oxygen levels ...
after 10 minutes, 20 minutes, and 30 minutes.
So let's write here, oxygen used up in ml -
so it's good to have the unit -
after 10 minutes.
Let's do the same,
so oxygen used up in ml after ...
20 minutes.
Final row, oxygen used up ...
in ml after 30 minutes.
So for A, we can see after 10 minutes that it was 0.8 ...
after 20 minutes, it was 1.6 ...
and after 30 minutes, it was 2.4.
For B, after 10 minutes, it was 0.1 ...
20 minutes, 0.1 ...
30 minutes, 0.1.
And then 0.0 for C.
So notice, there are no units in the table.
You should never have the milliliters within the table.
So it should never read 0.8 ml because that looks really sloppy.
(reading visual aid 6b.ii)
Now, it doesn't matter which of these numbers you use.
In fact. the answer will all end up being the same.
So what you want to do is take a value -
let's take 0.8 for example -
and then divide it by the time that the experiment was run for, which was 10 minutes,
but because it needs to be per second, we need to multiply those number of minutes by 60.
And you get a value which is 0.0013.
(reading visual aid 6b.iii)
So, let's have a look, again, at what's going on in A.
So A contained germinating peas,
which means that they are respiring, therefore, using up oxygen ...
using up glucose in order to produce carbon dioxide and water and obviously their energy.
B contains peas that are not germinating, so they're basically dead.
C is a control because it contains glass beads.
So, A has the highest rate of oxygen consumption because the peas in A are germinating ...
and using up oxygen ...
in their respiration ...
in order to release energy for growth.
(reading visual aid 6c)
Quite frankly, this is just soda lime;
it's a substance which absorbs carbon dioxide.
(reading visual aid 7)
Just want to highlight the key bits here.
(reading visual aid 7a.i)
So, first of all, we need to work out how many grams of carbohydrate he ate,
so we need to add up these numbers here ...
and that gives you a total of 156 grams.
So he ate 156 grams of carbohydrates.
And then if you look at my highlighted portion above, it says he needs to inject one unit for every 10 grams,
so just work out how many units that would be by doing 156 divided by 10,
which is 15.6.
So he effectively needs 15.6 units of insulin, but they probably don't do it to the nearest 0.6,
so you just want to go one up to the next integer, the next whole number,
so that would be 16 units.
(reading visual aid 7a.ii)
Now, insulin lowers blood glucose concentrations
by converting glucose into an insoluble storage compound called glycogen ...
which gets stored in the liver.
And that would mean that his blood glucose levels would fall extremely low,
and this is known as being hypoglycemic.
So, an increase in insulin ...
would cause more -
you need to be nice and detailed here -
would cause more ...
glucose ...
to be converted into glycogen ...
for storage in the liver.
This would result ...
in his blood glucose levels ...
becoming very low ...
which is known as hypoglycemia.
(reading visual aid 7b.i)
So, BMI is given by mass ...
divided by height squared.
So learn this equation for me.
His mass is 120 kilograms.
His height is 1.9, which we need to square.
When you put that into your calculator,
you get this value, which is therefore option B.
(reading visual aid 7b.ii)
So, an in-depth knowledge, really, of what the thyroid gland does -
so the thyroid gland produces thyroxine,
and what that does is it regulates the metabolic rate.
And metabolism is all to do with how quickly chemical reactions take place.
So basically, low levels of thyroxine would reduce the metabolic rate ...
meaning that there's less energy available for tasks,
and effectively, more fat is stored, so the person gains in body mass.
Six marks though, so we need to make six separate points, if possible.
(reading visual aid 8a.i)
So, we know that there's 2.1 times 10 to the 4 J of energy in the stonefly larvae.
And then we know that 90% of that will be lost ...
by the water beetle stage, and then another 90% will be lost here.
So we need to work out, first of all, how much energy goes into the water beetles.
And the way in which you do that is you do -
because 90% is lost, all that will go through is 10%,
and because it's a percent, you divide it by 100, and then times it by that original number.
That means of the original 2.1 times 10 to the 4 J,
by the water beetle stage, they'll only have 2,100 joules of energy.
And then another 90% of that energy is lost going into the birds, so we need to find 10% again ...
but this time of the new number ...
and that gives a measly 210 J of that original 2.1 times 10 to the 4.
(reading visual aid 8.ii)
Hopefully, you can see that this number is reducing hugely from one stage to the next.
So, basically, there just isn't enough energy left for a longer food chain;
effectively, the energy runs out, meaning that the length of the food chain is severely limited.
(reading visual aid 8b.i)
So, we're looking at stream A only, so make sure you're looking at the right column.
And the ones indicating clean water are these three here ...
as we've been told.
So we need to work out their total,
and once you've done that, you get a number which is 107.
And you need to compare it to the total number of organisms in stream A,
so that means you need to add up everything else in stream A,
which gives you a total number of organisms in stream A of being 153.
And then it's a matter of doing 107 divided by 153, times by 100,
because we're being asked to calculate the percentage,
and to two significant figures, that is 70%.
Be careful with your sig figs.
(reading visual aid 8b.ii)
I mean, as you look at the table, you can see that stream B has hardly any of the clean water indicators;
it's only got one stone fly larvae, so we can see that stream B is way more polluted.
And actually, if you look, they've got a huge number of the gross things,
so the water louse, the bloodworm, and the sludge worm, which are all indicators of pollution, really.
I hate the names; it sounds so gross.
(reading visual aid 8c)
This should be screaming eutrophication at you ...
which is a process whereby excess fertilizers ...
sewage, et cetera, gets into streams and basically causes overgrowth of plants,
leading to their mass death and a huge increase in bacteria,
so that fewer fish and aquatic animals can survive.
So effectively, we're just going to write out the perfect answer of eutrophication.
So start by saying that algal bloom occurs -
seeing as we actually need to start here because it's asking us about algal growth -
meaning that ...
many ...
algae die ...
due to competition for light.
Basically, they block out the light for each other.
Because there's a huge increase in the dead material, it means that microorganisms will thrive.
So, microorganisms feed upon the dead algae ...
and use up ...
all the oxygen ...
in aerobic respiration.
When all the oxygen has been used up, we call this anoxic.
These anoxic conditions ...
make it ...
impossible ...
for fish ...
and aquatic animals to survive ...
so biodiversity within the stream is reduced.
(reading visual aid 9)
So cute.
(reading visual aid 9a)
Water -
the word you're looking for is osmo -
controls -
another word for that is regulates.
So if you shove those words together, you get osmoregulation.
So, let's look down. Yeah, that's C.
D thermoregulation - regulating temperature.
Diffusion is a process whereby particles move from a high concentration to a low concentration.
And osmosis, which you might have been tempted to tick, is just movement of water,
but it doesn't actually control the water levels in the body.
(reading visual aid 9b.i)
So if I draw a really terrible diagram here of the Bowman's capsule -
has the glomerulus, which is the blood vessel coming in.
And at the Bowman's capsule, ultrafiltration takes place ...
which is when ...
ions and water and glucose and things enter the Bowman's capsule.
So once they've entered ...
they pass along the proximal convoluted tubule down to the loop of Henle ...
distal convoluted tubule ...
and then lastly, the collecting duct here.
And urine gets produced down here.
So in terms of processes that take place, you've got ultrafiltration taking place at the Bowman's capsule,
and then selective reabsorption takes place here.
So basically, let's convert this horrible diagram into an answer that will actually get you marks.
So state, first of all, that ultrafiltration ...
occurs ...
at the glomerulus.
Sodium ions and water ...
enter the Bowman's capsule.
Selective reabsorption ...
takes place ...
at the proximal convoluted tubule -
which I can't write out because I'm running out of space -
and then lastly, urine ...
is made ...
in the collecting duct.
And because I don't want to be incomplete with this, let's spell proximal convoluted tubule up here ...
because good spelling is key in science ...
and really everywhere.
(reading visual aid 9b.ii)
And that's because if you look at the beginning part of the question,
it tells us that the kangaroo rat lives in the desert,
which means it needs to retain as much water as possible.
Because water is reabsorbed in the loop of Henle,
a longer loop, therefore, provides a larger surface area for water absorption.
(reading visual aid 9b.iii)
Remember, ADH is a hormone ...
and that high levels of it ...
mean that you basically urinate less ...
because more water is reabsorbed.
Anyway, 'Figure 17 shows the average results for 500 kangaroo rats.'
So, we have a look at the amount of sodium they've been fed.
So we're increasing.
And then we look at the volume of ADH stored in the pituitary gland.
So as the concentration of sodium chloride increases, we can see that the volume of ADH stored decreases.
'Explain how ADH helps to control the levels of water and sodium ions in the bloodstream.'
So, our answer needs to be in two parts.
It's worth 6 marks altogether.
So try and do an even split between how ADH controls water and how it controls sodium ions.
So, let's start with water.
So start by saying that increased ADH ...
causes ...
the walls of the collecting duct ...
to be more permeable to water ...
so more water ...
is reabsorbed into the bloodstream ...
and less urine is produced.
This helps prevent dehydration.
If we now take the sodium ions,
use the table here, and as you can see from the table,
as the sodium ion concentration increases, the levels of stored ADH decrease.
You could state some numbers.
So you could say,
at 0.25 moles, the ADH stored reduces by 5 arbitrary units.
Pull out more numbers by looking at high concentrations of sodium chloride ions, so here.
Look further down the table, and as you can see,
when the sodium chloride concentration gets really high,
we can see that the amount of stored ADH remains pretty stable at eight.
And that's really to ensure that the maximum amount of water can be reabsorbed,
and thus helps prevent dehydration.
And sodium levels are high.
So let's make a really bland comment, first of all, by saying that as sodium ions ...
increase in concentration ...
the levels ...
of ADH stored decrease.
At 0.25 moles of sodium chloride -
by the way, write it out in full if you prefer; I'm just using the chemistry way of writing sodium chloride -
the ADH stored ...
reduced by five arbitrary units.
The volume of ADH stored ...
remains stable ...
at eight arbitrary units ...
causing maximum amount of water to be reabsorbed.
This, therefore, prevents dehydration ...
when sodium levels are high.
Yay! Question 10.
(reading visual aid 10)
'The pH level of water in a tropical fish tank needs to be maintained between 6.6 and 7.4' -
so, slightly acidic -
'for the fish to survive.'
Although, obviously, at 7.0, it's neutral.
(reading visual aid 10)
Weirdly, this is bringing back all kinds of memories;
this is exactly what I had to do for my GCSE, and we had to know these bacterial names.
Anyway ...
'Nitrosomonas bacteria are an example of' -
Let's go through these different types of bacteria, just to show you what they all do.
Nitrogen fixing bacteria are the ones found on the roots of legumes ...
such as peas and beans,
and they take nitrogen in the air and turn it into a nitrate ...
source for the plants.
Nitrifying bacteria are also good because they take ...
ammonia ...
and nitrites and convert them to nitrates.
Denitrifying bacteria are bad ...
because they take nitrates,
which are great in the soil because they add fertility to the soil,
and convert them to nitrogen, which is rubbish.
The air is full of nitrogen; we don't need any more of that.
Helicobacter bacteria - that's so funny.
That's nothing; that's neither here nor there.
That's to do with stomach ulcers.
So literally has nothing; total curveball.
So in terms of Nitrosomonas bacteria, what are they examples of?
Well, it says here that they convert ammonia into nitrites,
which I've just said is this one here, the nitrifying bacteria,
which is why B is the answer.
'Explain why Nitrosomonas and Nitrobacter bacteria are needed in tropical fish tanks.'
So, basically, pull out the information given in the question.
So state that these bacteria convert the ammonia into nitrites and then nitrates, thus maintaining the pH.
And why is it so essential that we maintain pH?
Because of little proteins called enzymes,
which are found pretty much in all living organisms.
And if these enzymes do not experience the correct pH, basically, they denature ...
and they don't catalyze chemical reactions which take place in the fish, meaning that the fish would die.
So the bacteria
convert the ammonia into nitrites and then nitrates ...
thus maintaining the pH.
And as I said, that was all in the question itself.
Now, this is the bit where we need to use our biology brain,
so state an optimum pH is required ...
to prevent the fish enzymes ...
from denaturing ...
which would kill the fish, fundamentally.
That noise, by the way, is my washing machine.
(reading visual aid 10a.iii)
It's asking you, how does a plant, in general, absorb, mineral ions?
And this is actually - is it osmosis, is it diffusion, or is it active transport?
So if we draw a rubbish aquatic plant -
okay, it looks like a Christmas tree; this is so bad.
Here are its roots.
And the aquatic plant is really greedy, and it actually has lots of mineral ions inside its roots,
and actually, there are only a few nitrate ions surrounding,
so I'm hoping that you can see that these nitrate ions are moving from an area of low concentration ...
to an area of high concentration.
This requires energy, so ATP ...
and, therefore, is an example of movement via active transport.
'Leguminous plants' -
yay, I've already mentioned that; that makes me happy -
'have nodules on their roots that have colonies of nitrogen-fixing bacteria.'
So hopefully, that's what I was trying to tell you here:
the nitrogen-fixing bacteria belong on leguminous plants.
(reading visual aid 10b)
So, a quadrat is this, like, grid.
It's really boring.
I don't know if you've had to do it at school.
And basically, you have to place this grid - this quadrat - in a very random manner.
So, chucking it over your shoulder does not count as random, by the way;
you need to use a random number generator ...
because, effectively, you split up your field -
so if this is your field, you split it up into a grid so it actually looks like a quadrat,
and then you list each grid -
it has a reference, like, one, two, three, A, B, C.
And if you use a random number generator, it might tell you to place your quadrat in space A3 ...
which would be this one here, so that's where you could place your quadrat.
So it's so important that you place it randomly.
And actually I'm going to write about that now.
And obviously you need to place that quadrat quite a few times
in order to get a reasonable representation of how much clover there is there.
So ...
Oh, no, the washing machine is so loud.
Place the quadrat randomly.
(reading visual aid 10c)
So, yeah, we love clover because they're basically natural fertilizers, and really you could do crop rotation.
So if the actual plan you were really after -
because clover isn't that useful; you can't really sell it.
Say you wanted to grow wheat.
Well, you could grow it for three years ...
and we harvest it to help us produce our bread.
Then you do crop rotation, which means you plant clover for the next year.
It goes and adds all of those nitrates to the soil, making it nice and fertile,
meaning that you can then grow wheat the following year ...
meaning that you fundamentally don't need to add loads of artificial fertilizers to your soil.
So start by saying that clover could be used in crop rotation.
Wheat is planted - or any crop really, any useful crop - for two years ...
or three years, doesn't really matter ...
followed by ...
a year in which clover is planted.
The nitrogen-fixing bacteria on the clover ...
add nitrates to the soil, increasing its fertility ...
meaning that there's no need for artificial fertilizers.
And that is done.
I really hope you found this paper helpful, guys.
That was quite a mission.
But yeah, don't forget to like and sub and tell your friends if they're not already following my channel.
Thanks, guys.
(music)
