- Hello lovely kittens.
This is a video covering
everything you need
for your second biology exam for Edexep.
If you want to follow everything along,
get loads and loads of keywords,
'cause there are so many in biology,
get loads and loads of crosswords
for you to help sort stuff out,
you can do that by getting
my free written guide,
which you can download from my website.
(upbeat, happy music)
Photosynthesis is going to take
water,
carbon dioxide,
and turn it into
oxygen
and glucose.
We can take light and we can
put it above the equation,
but do not put it in the equation,
because it is not a reactant.
It's just a condition that's needed.
You also need to know
the symbols for these,
so water is H20, plus carbon
dioxide, which is CO2,
goes to oxygen, O2, plus glucose,
which is C6H12O6.
This needs to be balanced, but it's the
most easy one to balance
because it is six, six, six.
So you can just remember
that it's six, six, six.
And when you're writing out your formula,
make sure your numbers are little and
are in the correct place,
because if you write this,
that's wrong,
that's wrong, and you will lose the marks.
In photosynthesis we are
taking energy from here,
we're taking energy from light,
and we are locking it up in glucose.
This is an endothermic reaction.
It takes in energy.
There are certain requirements
of photosynthesis.
First of all, we are
going to need chlorophyll.
That is our green pigment in leaves.
We're going to need water
and carbon dioxide, because they are our
reactants, and then we're
going to need sunlight.
And the levels of these can greatly affect
how much photosynthesis takes place.
The rate of photosynthesis
is going to depend
on the percentage level of carbon dioxide.
As the percentage level of
carbon dioxide increases,
so the rate of photosynthesis
is going to increase,
but only up to a point.
After this point there are going to be
other limiting factors.
Past this point we need
to increase something
like the water, light, or the temperature
if we want more
photosynthesis to take place.
We could easily switch this out to be
percentage level of water and
the graph would look the same.
When plants are very, very cold,
everything acts very, very slowly.
Not a lot happens.
It slowly increases into a nice point
where the enzymes are happy and
there's lots and lots of
photosynthesis going on,
until it gets too hot and they
start to be denatured, and then the
rate will fall off very rapidly.
So we have our rate of reaction increasing
with temperature and
our optimal temperature,
and our enzymes getting denatured.
It's really important that you remember
that the enzymes are denatured,
they are not killed, they are denatured.
Light intensity is important
for the rate of photosynthesis.
When it is nighttime, when it is dark,
we do not have lots of
photosynthesis going on.
As we get further through the day,
as we get more light intensity,
the rate of photosynthesis will increase
until we get to a point
where it was no longer
the limiting factor, and other things
like the reactants or
temperature need to be increased.
After this point we need to think
about increasing other things.
Now even though the graph is flat here,
it looks like it might
have stopped, it hasn't.
There is still a steady
rate of photosynthesis.
It's just not increasing as
much as it was down here.
It's just a steady rate.
The actual rate of photosynthesis that
takes place is much more complicated
than depending on just one thing.
It's going to depend on
lots of different things
all at once.
The glucose from photosynthesis
is going to be stored as starch.
The most obvious example of
starch is going to be potatoes.
Here we have a cross section of a
typical leaf, our palisade mesophyll where
photosynthesis is going to take place,
cuticle, which is the waxy layer,
upper and lower epidermis,
which cover the plants,
spongy mesophyll, which is
the space for gas exchange,
and the guard cell and stomata,
which is where transpiration takes place.
Inside the plant we have
the xylem and the phloem.
The phloem is going to carry water
that is generally going
to be in upwards direction
from the roots where its collected
to the leaves where it can be used
for photosynthesis, and the
phloem, which carries ions
and food, and this is generally
in a downwards direction
from the leaf where food can
be made in photosynthesis
to the roots where it can be stored
in, for example, potatoes.
There are several factors that affect
the rate of transpiration,
and transpiration
not only involve water
moving out of the stomata,
but also moving up through the xylem.
So if we have bright light
that is going to lead
to more transpiration.
More light means more photosynthesis,
which means there's going to need to be
more water brought up into the cell.
If we have a high temperature,
that is going to lead
to more transpiration,
because the rate of reaction's
going to happen faster.
If we have high wind
that is going to lead
to more transpiration,
because wind is going to be brushing
against the leaf, or flowing against
the leaf, moving things out of the way,
so diffusion is going to play a part here.
And if we have high humidity
this is going to lead
to lower transpiration.
Water is going to
struggle to leave the leaf
because there is a very high concentration
of water, its very humid, outside.
Here we have the male and
female endocrine system.
The pituitary gland is in the brain,
thyroid is in the neck,
the adrenal glands on the kidneys,
pancreas is hiding behind the stomach,
ovaries are kind of like hip level,
and testes hang below the penis.
The testes produce testosterone,
which has the effects of growing muscles,
making the balls and penis
drop and grow larger,
increasing the rate of hair growth.
Estrogen is produced in the ovaries.
That's responsible for the maturation
of eggs and the menstrual cycle.
The pancreas produces insulin,
which is important for
regulating blood glucose levels.
The adrenal glands produce adrenalin,
which is part of our
fight or flight response.
The thyroid produces thyroxine, which is
important in regulating our metabolism.
The pituitary gland is very busy.
Among other things, it
produces follicle stimulating
hormone, FSH, and leutinizing hormone, LH.
One of the reasons periods feel so rubbish
is because your hormones are
literally all over the place.
Starting with follicle
stimulating hormone,
it rises, peaks, and its job is to make
the small egg grow up to a
larger egg and then be released.
Leutinizing hormone is only active
for a very, very short period.
It's job is to release the egg.
Estrogen builds up until it
stimulates leutinizing hormone.
Progesterone builds up slowly as it
builds up the lining of the uterus
And if there is no egg, if there is no
embryo implanted in it, that will decrease
and the lining of the
uterus will break down.
There are a number of different methods
of contraception, some
hormonal, some non-hormonal
that will stop you getting pregnant.
But not all of these will protect
against sexually transmitted diseases,
so it's always very, very
important that you wear a condom.
This is a barrier method of contraception.
This will stop the sperm
getting the woman pregnant
and it will also stop any nasties
that are being transmitted
from her to him or from him to her.
The pill and the coil
IUD, intraruterine device,
are hormonal methods of
stopping getting pregnant.
They are going to stop
the egg being released
or the egg being implanted.
The diaphragm is a barrier method
because it will stop
sperm entering the vagina,
but the semen will still be transferred
into the vaginal entrance, so you can
still get sexually
transmitted diseases this way.
If you're sure that you
don't want to have children
you can go to be sterilized, you can have
a vasectomy, you could
have your tubes tied,
which would mean that no sperm will get
from the testes out to the penis,
or for the woman, no egg will be released.
Around one in six people find themselves
in the unfortunate position where
they can't have children naturally,
but half of this is due
to male-related reasons
and half this is due to
female-related reasons.
As you can see, I am one of those people,
and last year, 2016, we did IVF
and this is my massive bump.
So the obvious advantages for IVF are
you get a baby out at the end of it,
and if you've been in the situation where
you can't have something
that you really, really want,
you know it's very, very sad and affects
your mental health quite a lot,
so having a baby is going to be good for
people that want to have the
baby, that mental health.
However, the disadvantages
are that you have to take
a large, large number of drugs for a
very, very long period of time.
These have very nasty side effects,
as well as the daily injections,
which leave you horribly bruised.
There are long-term consequences for these
because taking these IVF drugs
increases your chance of various
different types of cancer.
It's very, very expensive.
I had to have it twice.
That's twice as expensive.
It doesn't always work.
There is about a 40%
success rate with IVF,
with each round of IVF costing a minimum
of 5,000 pounds, with a
40 percent success rate.
Here are all the large number of
drugs that I had to take day by day.
It's a very costly, time
consuming, painful process.
We are about halfway
through, well done guys,
we can keep going, we can do this.
I do want to say thank you to a few people
who have supported me, helped
me to add captions to the DVD,
captions are gonna make your
revision so much easier.
Beth, Hannah, and Nicola
have been fantastic in
their support and Narinder and Izzy are
awesome, awesome teachers who
are supporting me as well.
Homeostasis is the
maintenance of a constant
internal environment.
And to keep your body
functioning properly we
need to control our blood glucose levels,
our water levels and our temperature.
The brain is the control center.
And that's gonna be sending signals
to various parts of the body.
For example, to the pancreas which
is responsible for producing insulin.
Effectas muscles are gonna do things like
moving, for example, shivering.
And then glands are going to be
responsible for the
production of our hormones.
Control of blood glucose
is very complicated.
After a meal has been
eaten, blood glucose levels
start to rise, this is
picked up by the pancreas.
The pancreas produces insulin which
is sent out into the blood.
The insulin in the blood
stream is gonna cause
the body cells to start to
remove insulin from the blood.
Liver and muscle cells
can take the glucose
and convert it into glycogen and store it.
Removing glucose from the blood will
cause blood glucose levels to fall.
If blood glucose levels get too low,
it's also picked up by the pancreas.
The pancreas will start to produce glugon.
The glucose that's
previously been stored in
muscle and liver cells starts
to return to the blood.
The most complicated part
of this is getting all
the names right, the
stored form of glucose
is glycogen, glucogon with
convert that into glucose
and this returning to the glucose will
cause blood glucose levels to rise again.
There are two different types of diabetes,
type one and type two.
In type one diabetes the
pancreas doesn't work properly.
So it doesn't produce the
right amount of insulin.
In type two diabetes cells start to become
insensitive to insulin.
Symptoms for both are
going to be loss of weight,
an increased need to wee,
being very thirsty,
blurry vision,
fatigue, so being very sleepy, and hunger.
Treatment for type one diabetes is
going to involve insulin injections.
Type two diabetes it's gonna
be controlling diet, exercise.
When we're talkin' about diffusion we
are talkin' about things moving from
a high concentration down the diffusion
gradient to an area of low concentration.
This could be things moving from an area
inside a cell where they've been made
to an area, or it could be
things moving out of a cell.
For example, it could be happening
in the lungs, the alveoli, the air spaces
and this is the capillary
traveling around it.
These very very thin
walls only one cell thick
and carbon dioxide is going to diffuse
from the blood into the lungs so it
can be breathed out and oxygen is going
to diffuse from the lungs into the
blood so it can be taken around the body.
Or this can be in the
gut, these are the villas
of the gut, this is the gut cavity here
and you notice again
they are one cell thick
and just like the alveoli have
a very large surface area.
We're going to get digested
food moving from the gut cavity
into the blood so that it can be
taken around the rest of the body.
So diffusion is the
movement of gasses or any
particles that dissolved in solution
moving down a concentration gradient from
a high concentration to an
area of low concentration.
Blood is made up of several components.
The actual color of
blood is this pale yellow
color, this is the serum, that's the
liquid component of the blood.
The cells give it its actual color.
Red blood cells, the cells
that give blood its color,
have no nuclei, and this is so they
have more space to carry oxygen
which is their main function.
White blood cells are
part of the immune system.
And platelets are fragments of cells
and they are important
for things like clotting.
Arteries have a very thick walls
because they are carrying
blood under high pressure,
which means they have a thin lumen,
that's the gap in the middle.
Capillaries are very, very small.
They are only one cell thick, or
very very thin I should say.
They're only one cell thick,
this is to allow for diffusion.
They generally go around
in this kind of like
mesh network around things like the gut,
or in the villa in the gut, around the
alveoli in the lungs, so they
have a large surface area.
They veins carry deoxygenated blood.
They carry it back to the
heart so they have valves
and they have thin walls and a thick lumen
because they're carrying
blood under low pressure.
Here we have our respiratory system.
Air goes in through the mouth or the nose,
down into the trachea which
is also known as the windpipe.
Then into the bronchus which
is a branch of the trachea.
Into the bronchiole which
is a branch of the bronchus.
And into the little grape or cauliflower
shaped alveoli, this is
where gas exchange happens
and they have incredible
large surface area.
Your diaphragm moves up and
down to bring air in and out.
The heart pumps blood around the body.
The intercostal muscles
allow the ribcage to expand.
And the ribs, the last part that makes up
everything protects the lungs.
Here we have a cardiovascular system
and it is a double system.
The blood get pumped from the heart to the
lungs, goes back to
the heart and then gets
pumped around the rest of the body.
If you see a picture of a heart the
first thing you do is write
right and left on there.
We have our vena cava
where the blood enters.
It goes into the right atrium,
down through a valve
into the right ventricle.
From the right ventricle it goes up and to
the lungs via the pulmonary artery.
It comes back into the heart
via the pulmonary vein.
Into the left atrium,
into the left ventricle,
and then it's pumped to the rest of
the body via the aorta.
If you want to check you have the path
of blood right, then you need to be
looking at capital letters,
it goes through the vena cava,
the atrium, the ventricle,
then the artery,
back through the vein, into the atrium,
to the ventricle, and then the aorta.
So it goes vena cava, atrium, ventricle,
artery, vein, atrium, ventricle, aorta.
VAVAVA, if you don't have that
pattern you've made a mistake somewhere.
Other features of the
heart you need to know are
here these are valves, they will only
allow blood to to flow,
and this side has a much
larger muscle than this side.
The right side only needs to pump blood
to the lungs which aren't very far away.
But this side has to pump blood to the
rest of the body, a much longer distance.
The majority of the time, veins carry
deoxygenated blood
apart from the pulmonary
vein which carries oxygenated
blood back into the heart.
And the majority of the time
arteries carry oxygenated
blood apart from the
pulmonary vein which carries
deoxygenated blood from
the heart to the lungs.
If the heart isn't functioning properly
pace makers, artificial pace makers can be
introduced to help the heart keep time.
Or if somebody has cardiovascular disease
then these tubes can get blocked up.
You are doing such fantastic work,
well done for making
it this far we're just
gonna take another little mind pause,
another little break for you to gather
yourself, refresh yourself,
and then we'll start again.
For respiration we are
going to take glucose
add it to oxygen and come out with water
and carbon dioxide.
You need to know the symbols for these,
so oxygen is O2, water
H2O, carbon dioxide CO2
and glucose C6H12O6.
This needs to be balanced
but it's not an easy one.
Six, six, six, you have to make sure
your numbers are in the right
format and the right place.
So these ones needed to be little numbers
and these ones need to be little numbers.
Respiration is an exothermic reaction.
Which means energy is given out.
The best example we can
see of respiration is
screaming jelly baby demo.
Where we take potassium
chlorate, that's our liquid
oxygen, add in our glucose,
that's our jelly baby,
and you can see the massive amount
of energy that comes off it.
Anaerobic means without oxygen.
So for anaerobic
respiration we take glucose
and we turn it into
energy and lactic acid.
Not as much energy as aerobic respiration.
Because the glucose isn't
fully breaking down.
The lactic acid is going
to build up in muscles
causing an oxygen debt.
This buildup is gonna be quite painful
so you'll get it when you're doing things
like sprinting or when
you've run out of oxygen.
So after you've finished
sprinting, after you've
finished running to get
rid of this oxygen debt,
you're going to need to
breathe really, really hard
that's why you pant, you keep breathing to
pay that oxygen debt get the blood flowing
to remove the lactic
acid from your muscles.
Anaerobic respiration can
also take place in yeast.
So yeast will take the glucose and will
convert it into carbon
dioxide and ethanol.
Ethanol is used in drinks
and cleaning products.
And carbon dioxide is used
for a variety of things.
What we're talking about
in the context of yeast
that's what's going to make
your cakes or your bread rise.
An ecosystem are the
animals, plants, everything
living within a certain area.
The community are the plants
and animals that live there.
And they're all dependent upon one another
they cannot survive without each other.
For example the animals eat the plants,
they can't survive without doing that.
And the plants rely on the animals
to distribute their seeds.
To survive and reproduce
a species needs food,
water, air, and sometimes
but not always a mate.
Abiotic and biotic factors are things
that are going to affect any organism.
Abiotic are non living factors,
such as light intensity,
temperature, water levels,
pH, iron levels, wind,
carbon dioxide levels, and oxygen levels.
Biotic factors are going
to be living factors
such as food, predators, and pathogens.
An increase or reduction
or removal or introductions
of any of these factors
can have a dramatic impact
on a community.
For example, the introduction
of a new predator
or a new pathogen could
wipe out a community.
An increase or a decrease
in the temperature
could mean that an organisms
food source could be gone or an
organism can't survive
in that environment.
And plants and animals
aren't going to survive
without sufficient levels of
carbon dioxide and oxygen.
If you want to investigate
what grows in a field
you can used a quadrat
which is going to be
a meter square, you
throw that on the ground
and count what is in there.
Randomly moving it around the field
so you get a wide coverage.
You're going to need to
estimate the size of the
field so you will can work out how much
of an area there is, work
out your plant population
per area that you've measured and then
multiply that up to
cover the entire field.
A transect is a bit more ordered.
You start at a point and take a line
and then take measurements and then take
measurements at every single
point along that line.
This could be say from a hedge moving
away so you are varying things like light
intensity or distance from water.
All food chains start in the same place,
with the sun providing energy.
And then from this energy
things are going to grow.
Mainly plants, and they
get eaten by other things.
Whether it's grass being eaten by cows
and then going on to be eaten by us
or we eat the plants
directly or the plants
here the corn is being
turned into corn syrup
which is used in ketchup.
Whether we eat them
directly or process them
we are a top consumer whereas other things
like cows are gonna be herbivores
'cause they just eat plants.
The directional arrow is really
important in food chains.
Direction of the arrow means eaten by.
Biodiversity is the range of plants
and animals that live within a habitat.
Humans have a massive
impact on biodiversity.
Whether it is chopping
down loads of natural
fields so that we can plant the same type
of crop over and over again,
reducing the biodiversity
of that environment
because we are replacing type of crop.
Or whether we are chopping down fields
forests so we can replace it with cities.
Microorganism are part
of the system of biotics
and abiotic factors that
break down old things,
for example old food
so that the components
can be recycled back through the system.
So for the carbon cycle I'll be referring
a lot to organic compounds.
And if you haven't heard this phrase
before it can be a bit confusing.
Organic compounds are just any compound
that has carbon in it.
And just to remind you a compound is two
or more elements that are
chemically bonded together.
So here are the different
locations that carbon can be.
There can be carbon dioxide in the air
or carbon dioxide can
be dissolved in oceans,
it can be as organic compounds in plants
or in animals, these
organic compounds can also
be present in the dead plants and animals
and they are in fossil fuels.
Now you need to know the
various different ways
that they change from all these different
locations and what the
processes are called.
So let's start with fossil fuels.
When we have fossil
fuels, we can burn them
so that the carbon in
them goes into the air
and the fancy name for this is combustion.
When the carbon dioxide is in the air
it can be taken up by plants and this
is the process of photosynthesis.
And the opposite can occur as well because
plants will also undergo respiration.
Plants get eaten by animals
and then plants and animals both die.
From the organic compounds that are in the
dead plants and animals they can turn into
fossil fuels by either being
buried or being sedimented
or they can just go straight back up
into the air by the process of decay.
And then lastly all animals are
also undergoing respiration.
So carbon isn't a static thing.
It is constantly moving
around from carbon dioxide
in the air to carbon
compounds that are in animals
plants, in dead animals,
and then being turned
into fossil fuels which can then be burnt
and put the carbon
dioxide back in the air.
This is very, very
complicated involved process
that happens over millions of years
and you need to know all of these steps.
The water cycle is much more complicated
than you think it is going to be.
Heat and energy from the sun comes down
warms the surface of
the water on the earth
and this is gonna cause
the water to evaporate.
As water evaporates it's gonna become less
dense, it's gonna rise up and then
it's gonna condense when
it starts to cool down.
This is when we're going
to get clouds formed.
When the clouds are heavy, when the water
is accumulated so much it is going to
start to rain and the fancy
word for rain is precipitation.
After it's rained the water is going to do
a number of things, it
can go into the mountains
where it will sink in or percolate,
deep into the mountains where it's then
gonna pick up stuff like irons, salts,
which is gonna affect the
taste and the chemistry
of the water.
This will then come out
somewhere as a stream
and go into the river.
Some of it's going to go into the soil.
Moving slowly back towards a river or
a lake as through flow.
Some of the water will go
straight onto the ground.
If the rock or the mud
is already saturated,
if it is full of water or
the rock is impermeable,
then that will just run off into the
nearest river or stream
or lake or reservoir.
All of it ending up at some point
in a large collection of water whether
that is in the sea again or whether it's
in a reservoir or whether it's in a lake.
Some of that water will
get taken up by plants
and used in photosynthesis.
It will also come out of plants
in a process of transpiration.
And then go up into make clouds
and then the cycle starts all over again.
The air is about 78 percent nitrogen
but is really, really unreactive.
So getting it to do anything is tricky.
We need to convert the
nitrogen into nitrates.
This can happen by lightening,
by the harbor process which
we'll cover in chemistry,
the harbor process is
used to make fertilizers.
Which are then put on the
ground by nitrofying bacteria.
And these nitrofying bacteria are going
to be in the root nodules of legumes.
So peas, sweet peas, we have here peanuts
and stuff like that.
These plants then get eaten by animals.
The animals can then release
the nitrogen compounds
in either urine or feces, poo.
And eventually death as well.
We are then gonna have
denitrifying bacertia
which will take the
nitrate compounds which are
in the soil from the urine
the poo or the death,
turn it back into nitrogen gas,
and release it into the air.
Well done guys, excellent
work for making it this far.
The rest is biology only.
So if you're doing
combined science well done,
you can go and have a relax or try some
quick trial questions or go
through the revision guide.
Phototropism means something is
gonna grow towards the light.
Geotropism or gravitropism means something
is gonna grow towards gravity.
Meaning your roots are
always gonna go downwards
and your shoots are
always gonna go upwards.
Gibberellins are important for growth,
ethene is important for ripening plants
and auxins are important for
growth in the right direction.
Body temperature is going to be regulated
by the thermoregulatory
center in the brain.
If you are too cold, the hairs
on your body will stand up.
This is to trap a layer of air
you're going to stop sweating.
Vasoconstriction will start,
so your blood vessels will constrict
so that they are further
away from the skin.
Less blood is going to flow close to the
surface of the skin so less
heat is going to be lost from it
and your muscles are
going to start to shiver
and movement is gonna produce energy.
If you are too hot your
hairs are going to lie flat
so they're not trapping any air.
You're going to start
sweating and the water
is going to evaporate leading
to heat and energy loss.
And your blood vessels
are going to undergo
vasodilation meaning they are going to
get wider so blood can flow closer
to the surface of the skin
so that heat can be lost.
The kidneys have three functions.
They remove urea, they
control the iron content,
and they control the water
content of the blood.
There are three ways we can
lose water from our body.
In urine in sweat, and
when we breathe out.
It's important to control the level
of water in the body because there is
too much water taken
up by cells by osmosis
they might pop or if there's not
enough water then the
enzymes, the functions,
the reactions won't be able to take place.
There are three steps to the
way that the kidneys function.
Ultrafiltration, reabsorption
and then the release.
Blood enters the kidneys
under high pressure
and water, ions, urea, and sugar are gonna
be squeezed out into the capsule which is
at the start of the nephron.
As this all flows along the nephron useful
things are reabsorbed.
All of the sugar is going to
reabsorb by active transport.
Some ions, the amount of
ions that we need, the type
of ions that we need are gonna be
reabsorbed by active transport.
And enough water that we need
is going to be reabsorbed.
The hormone that controls how much water
is going to be absorbed is
ADH, antidiuretic hormone.
And then anything that isn't reabsorbed
is going to come out as wee.
If the kidneys aren't working properly
a person can undergo kidney dialysis.
The dialysis machine will take over the
function of the kidneys but it is very
tie consuming, takes about four hours
and has to be done three times a week.
So this has a huge
impact on someone's life
and is not a lot of fun.
An alternative to dialysis
could be a kidney transplant.
But these come with
very long waiting lists
and there is always the risk of rejection.
When we are looking at food chains
we can also think about
constructing pyramids.
Either pyramids of numbers
or pyramids of biomass.
Each of these are trophic levels
and when we're doing numbers you just need
look at the number of things
that eat the thing below it
and biomass we need to take into account
the number and the mass of
the stuff that's being eaten.
As we jump between trophic levels
roughly 10 percent of
energy is transferred
from one to the other.
It is going to be lost in
a number of different ways.
Respiration, waste as in urea and feces,
movement, running around, jumping,
doing normal animal things.
Food security is how
sure that we are going
to have food on our tables.
How sure we are that our supermarkets
are going to be full of things to buy.
If as a country we don't
produce much of our own food
we have to buy it in from other places.
Which means we depend on other countries,
other people's climates, trade agreements
with these other countries
and transport arrangements,
getting the food across borders.
Increasing our own food
production in this country
will help to ensure our food security if
we are producing our own food, we're
not reliant on other people.
We need to take into account
ways to increase yield,
for example using
fertilizer, but then we also
need to take into account
the impact that will have
on the wider environment.
And we need to take into
account production methods.
Are they land intensive, are they good
for the environment or not.
As we are an island
sustainable fishing is one
way we can help to
secure our food security.
But we need to take into account things
like net size, are we catching fish before
they are too old, before they
have had a chance to reproduce
are we catching too
many, do we need to move
to line caught fish so we
don't catch endangered species
and we need to look at fisheries quotas.
We can also look at new
ways of developing food.
For example culturing microorganisms which
we can use as a food source.
Decay and decomposition are
breaking down of organic matter.
This generally happens by microorganisms.
And microorganisms are alive and this is
what we need to think
about when we are looking
at how temperature, water, and oxygen
affect the levels of decay.
They are not going to work at
very very low temperatures.
They are going to have a rather narrow
set of temperatures which
they're going to want to work in.
They rely on enzymes to break things down.
They are going to slowly be increasing how
well they work as the
temperature increases.
But then at a certain point the enzymes
are gonna nature so it's gonna come
quite steeply down and if it gets too hot
the whole thing is gonna catch on fire.
Very similar with the level of water
it's gonna be slowly increasing as it gets
wetter and then past a certain point
the bacteria just aren't
going to be able to cope.
They need to have oxygen, they need
to be able to respire, and if there's
too much water they just can't do that.
Oxygen, there is a very narrow amount
of oxygen that they will be able to use.
Without oxygen they can't do anything
and too much oxygen then
it starts to become toxic.
In the garden, gardeners
can compost things
so they can get rid of
their unwanted things
and then take the nutrients, the goodies
in there and put them
back onto the garden.
Compost is gonna get rather hot as this
goes on and it's gonna get rather smelly
and gas is going to be released.
And this gas can be harvested and used.
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