The Phosphorus Cycle

okay so in this video we're going to

look at the phosphorous cycle now one

thing I want to mention is that even

though phosphorous cycles through the

environment there is no phosphorous in

the atmosphere so it's not like the

carbon cycle where there's carbon

dioxide in the atmosphere it's not like

the nitrogen cycle where there's

nitrogen in the atmosphere the

phosphorous cycle begins with rocks and

we're going to go through that in just a

moment well first of all why do we need

phosphorous well phosphorous if you

recall is one of the one of the atoms

that makes up the molecule called ATP

adenosine triphosphate in the picture

here here's a mitochondria and through

the process of cellular respiration the

mitochondria will make this molecule

adenosine triphosphate you can see there

are peas for phosphorus in the diagram

another important molecule that that

requires phosphorus is DNA and not just

DNA but RNAi nucleic acids so here's a

double helix now if we if we look at the

molecular structure of DNA remember that

DNA is made from small parts called

nucleotides and you can see the

nucleotide is a sugar molecule nitrogen

base and then a P the P stands for a

phosphate molecule the reason it's

called phosphate is there's phosphorus

in it and one nucleotide combined with

another with another with another like

you see in the picture makes up DNA a

nucleic acid so DNA the genetic heredity

the genetic molecule of life requires

phosphorus and a third reason why

phosphorus is really important in the

animation here we have a phospholipid

bilayer basically we have the cell

membrane of all of our cells

phospholipid phospho implies there's

phosphorus in the lipids that make up

the cell membrane well let's go ahead

and get on in to the stages of the cycle


so here we have on a rain cloud and it's

raining and so what we're going to show

you is really the first stage of the

phosphorous cycle and it comes from the

breaking down in the weathering of rocks

you know rocks are just lumps of

minerals and one of the minerals that

rocks are commonly made from is

phosphorous and so when it rains

phosphorus little chips of rocks break

off and crack and crumble and this is

what we mean by the weathering of rocks

and so phosphorous is released as rocks

weather and break down and erode and the

phosphorous has now entered the soil

well once the phosphorous is in the soil

now it becomes pretty straightforward

the flowers representing their producers

in this animation will absorb the

phosphorous through their roots and once

the phosphorous is in the roots of

plants I hope you can figure out how

animals can obtain the phosphorous

so now that the phosphorus is in the

plants the phosphorus simply moves up

the food chain in our animation we have

phosphorus going from the flowers to the

snail well that's because stales eat

leaves and flowers and plants in the

next part of the animation we have

phosphorus going from the snail into the

frog well that's because frogs can eat

snails phosphorus is simply moving up

the food chain and then we come to area

four represented by our mushrooms in the

animation it says decomposers will

obtain phosphorus as they feed on dead

remains in the animation there's a peak

coming from the flowers there's a pea

coming from the snail and there's a pea

coming from the frog and they're all

going to the mushrooms representing the

decomposers I'm not implying that

mushrooms hunt frogs and snails and

flowers but when frogs and snails and

flowers die they're dead remains which

still contain phosphorous are fed on by

default or such as fungus decomposers

such as bacteria well if we notice here

also there is a pee coming out of the

mushroom because again all organisms

give off waste and fungus and other

decomposers will give off phosphorous in

their waste and so if you just pause and

look at the animation we have a cycle

here we have a continuous loop of

phosphorous throughout the ecosystem

throughout the environment well there's

one little twist I want to add to this

before the video is finished

we have to focus on the human

contribution to the phosphorus cycle so

humans will often use fertilizers and

phosphorus is a very common ingredient

as well as nitrogen phosphorus and

nitrogen are very common to fertilizers

well we add fertilizers to help our

crops and plants grow better and so here

we have a picture of a farmer using a

tractor and pulling a trailer that is

dispensing fertilizers over their crops

and so the problem with this is that the

phosphorus when it's sprayed on the

crops will often run off with rain into

bodies of water

so in this picture right here you can

see that water is running off of this

farm and so often the fertilizers are

simply being carried away with this rain

water here

so in my animation here here we have a

farmer adding peas a bunch of peas for

phosphorus so the farmers adding

phosphorus to their crops to the plants

and so their fertilize the farm is

fertilizing the crops well unfortunately

the phosphorus that's accumulating in

the animation won't just stay there

often the phosphorus is carried with

weather and rain so when it rains when

it rains often the phosphorus is simply

carried downstream or downriver down

down the slope of the land and you can

see in the animation the phosphorus is

accumulating in this body of water well

this is going to lead to another problem

this often causes what are called algal

blooms an extreme growth of algae in the

animation you see the water in the pond

is turning green because of all the

algae that is now being stimulated to

grow from all the phosphorus phosphorus

is a fertilizer it stimulates the growth

of algae as well as stimulating the

growth of crops well why is this bad

well first of all before we address why

is that bad here's a couple photographs

of algal blooms you can see this watery

area is just as a layer of green slime

growing on it and here we have a lake or

a river that's completely been turned

green because of the extreme growth of

algae well what the problem that this

causes is something called

eutrophication off often and ultimately

what happens to this little body of

water it becomes a dead zone the algae

is so dense and so thick it will often

block sunlight to plants that live

deeper in the water and they start to

die often oh the next step that happens

is the algae themselves will begin to

die and bacteria will feed on the dead

remains of the algae

well the bacteria are using all of the

oxygen in the water to break down and

decompose the algae that the the water

almost becomes action oxygen lists

becomes void of oxygen because the

bacteria are using it all

so therefore snails die fish die

organism other animals that live in this

water begin to die because there's no

oxygen the extreme growth of algae often

causes the pH of the rivers and the

lakes to change and so that's another

reason why the lake can become a dead

zone so the point is is that the

phosphorus cycles out of balance and you

know human contributions are some of the

reasons for that so if you're if you

have a bit of a green thumb at home and

you're interested in landscaping and

gardening you know perhaps you can go

down to you know the local supply store

and look for safer non-chemical ways to

perhaps fertilize your lawn and

fertilize your garden

so here we go that was the there we go

that was the phosphorous cycle go ahead

and pause this video it's a very quick

practice quiz then the video was pretty

quick so go ahead and pause the video

answer these questions if you're in my

class I'd be happy to check them for

accuracy before school or after school

good luck